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Item Open Access Struktuur en sintese van metaboliete uit rooibostee (Aspalathus linearis): fisiologiese aktiwiteit en biomimetiese model vir die fermentasieproses(University of the Free State, 1995) Marais, Charlene; Steenkamp, J. A.; Ferreira, D.In die huidige ondersoek is nie alleen op die isolasie en karakterisering van wateroplosbare metaboliete uit rooibostee gefokus nie, maar is daar gepoog om 'n profiel van die fisiologiese aktiwiteit van sodanige verbindings daar te stel ten einde wetenskaplike stukrag te verleen aan aansprake oor die heilsame invloed van rooibostee wat reeds oor dekades heen gemaak word.Item Open Access A crystallographic investigation of multidentate ligand hafnium(IV) halido complexes(University of the Free State, 2021-11) Viljoen, Johannes Augustinus; Roodt, Andreas; Visser, Hendrik G.Hafnium, the chemical element with atomic number 72 in the titanium-triad on the periodic table, was first discovered by Dirk Coster and George von Hevesy in 1923 by analysing X-Ray spectra of Norwegian zircon samples (sea sand). Hafnium is considered relatively abundant and comprises about three parts per million by weight of the earth's crust. Unfortunately, hafnium only occurs naturally in zirconium ores at an approximate ratio of 1:50 and has almost identical general chemical properties to that of zirconium. Zirconium has a very desirable application in the nuclear industry as a cladding material for nuclear fuel rods due to its low affinity for thermal neutrons. However, for zirconium to be used as a cladding material in nuclear reactors, it must be virtually hafnium free since hafnium has a 600 times larger affinity for thermal neutrons than that of zirconium, turning it into a “poison” in zirconium cladding materials. However, this high affinity for thermal neutrons is exactly why pure Hf makes an excellent shielding material. Therefore, for hafnium and zirconium to be utilised in the nuclear industry, it is apparent why the effective and economically viable separation of these metals to their pure chemical state is vital. The principle aim of this study is focused on studying the solid-state and solution behaviour of hafnium(IV), with various N- and O-donating multidentate ligand systems, in order to obtain valuable new data that could potentially be used to compare to zirconium(IV) to evaluate if metal separation is feasible for industrial applications. Therefore, in this study, the solid-state and solution behaviour of novel hafnium(IV) and zirconium(IV) coordination compounds, obtained from a systematic range of N- and O- bi- and multidentate ligands, is investigated. A detailed description of the synthesis of the hafnium(IV) and zirconium(IV) complexes containing different N,O- and O,O’-bidentate ligand systems as well as N,O,O,N- and N,N’,N’,N-tetradentate ligands are reported and characterised by means of IR, UV/Vis and NMR (1H and 13C) spectroscopies. Moreover, it is clearly illustrated by this study that it is possible to synthesise hafnium(IV) and zirconium(IV) complexes under simple bench-top aerobic conditions. Furthermore, the solid-state structural characterisation by means of single crystal X-Ray Diffraction studies of ten of these synthesised complexes is described in detail. Thus, six novel hafnium(IV)-oxinato complexes containing a systematic range of substituents on the outer periphery of the ligand are firstly presented: (1) [Hf(Ox)4]·2(C7H8), (2) [Hf(5-ClOx)4]·2(C7H8), (3) [Hf(diMeOx)4]·2(DMF), (4) [Hf(diClOx)4]·3DMF, (5) [Hf(diBrOx)4]·3DMF and (6) [Hf(diIOx)4]·DMF and described. The complexes contain non- and substituted 8-hydroxyquinoline (OxH) ligands [with (5-ClOxH) = 5-chloro-8-hydroxyquinoline, (diMeOxH) = 5,7-dimethyl-8-hydroxy-quinoline, (diClOxH) = 5,7-dichloro-8-hydroxyquinoline, (diBrOxH = 5,7-dibromo-8-hydroxyquinoline, (diIOxH) = 5,7-diiodo-8-hydroxyquinoline], and are discussed and compared with regard to the intimate geometric environment around the hafnium(IV) metal centre. It is clearly illustrated by this study that tetrakis-(oxinato)hafnium(IV) complexes prefer the square-antiprismatic coordination geometry in the D2-corner clipped isomer form. It is further shown that all the hafnium(IV) -and zirconium(IV) oxine complexes are very similar with relation to bond lengths, angles and packing modes. Secondly, two new hafnium(IV)-β-diketonato complexes – (7) [Hf(dbm)4] and (8) [Hf(OH)(tfba)3]2·2DMF – are structurally evaluated and described [where (dbmH) = dibenzoylmethane and (tfbaH) = 4,4,4-trifluoro-1-phenyl-1,3-butanedione]. Focus is placed on the influence of ligands when increasing the metallocycle from five (oxine-type ligands) to six (acac-type ligands) and using acac-type ligands containing different electron-donating properties. The effect of electron-withdrawing substituents on the ligand backbone with regards to coordination mode and coordination geometry. These examples show and conclude that hafnium-β-diketonato complexes also prefer a square-antiprismatic coordination geometry in the D2-corner clipped isomer form. Moreover, all the hafnium(IV)- and zirconium(IV)-β-diketonato complexes are very similar with respect to their general geometry and corresponding bond lengths, angles and packing modes. Similar to the oxine-type complexes, this suggests that hafnium(IV) and zirconium(IV) has a certain preference for the chelation sites of the coordinating atoms, regardless of the steric or electronic properties of the ligands as a whole. Thirdly, a novel hafnium(IV) and zirconium(III) complex containing a N,O,O,N- and N,N’,N’,N-tetradentate ligand, respectively – (9) [Hf(salophen)2·2(C7H8), (10) [Zr(pbp)(H2O)2]2NO3·(MeOH) – are structurally evaluated and compared with regard to the intimate geometric environment around the metal centres [where (salophen) =N,N'-bis(salicylidene)-1,2-phenylene-diamine & (pbpH) = N,N'-(1,2-phenylene)bis-(pyridine-2-carboxamide)]. It was found that the eight coordinated hafnium(IV) complex favours a square-antiprismatic coordination polyhedron. However, the six coordinated zirconium(III) complex formed a distorted octahedron as coordination polyhedron around the metal centre, as expected for many six coordinated metal complexes. Finally, preliminary liquid-liquid extraction experiments are described herein, and it is concluded to in principle be considered a preliminary proof-of-concept for separation. The preliminary extraction investigation reported includes liquid-liquid extractions of zirconium- and hafnium-oxine complexes from methanol into dichloromethane and competition extractions, as qualitatively evaluated by (I) UV-Vis spectroscopy and (II) inductively coupled plasma optical emission spectroscopy.Item Open Access Struktuur en sintese van prorobinetinidien- en prosianidientipe gekondenseerde tanniene(University of the Free State, 1992-02) Cronje, Annemarie; Steynberg, J. P.; Ferreira, D.; Brandt, E. V.Afrikaans: Die wye kommersiële toepassing van die 'Mimosa' ekstrak van die tannienryke bas van Acacia mearnsii het as stimulus vir die eerste fitochemiese ondersoek van die fenoliese komponente in die nywerheidsgedroogde bas gedien. Toepassing van uitgebreide verrykings- en skeidingstegnieke lewer benewens die bekende mono-, di- en trimeriese voorlopers, die flavan-3-ol, epirobinetinidol, prorobinetinidien biflavanoïede met 3,4-cis relatiewe konfigurasie, (-)-robinetinidol-(4β,8)-(+)-gallokatesjien en (-)-robinetinidol-(4β,8)-(+)-katesjien, 'n A-tipe prorobinetinidien, (-)-robinetinidol-(2β - 7; 4β - 8)-(+ )-katesjien en 'n C-gealkileerde profisetinidien, (-)-fisetinidol-( 4α,8)-6-metiel-(+)-katesjien. Hierdie metaboliete word deur 'n reeks unieke prorobinetinidienverwante ringgeïsomeriseerde tanniene vergesel. Struktuurbepaling is gedoen deur benutting van hoe resolusie 'H k.m.r. n.O.e. tegnieke, sirkulere dichroïsme (SD), massaspektrometrie (MS) en is waar moontlik deur sintese, d.i. die basisgekataliseerde omskakeling (pH 10) van biflavanoïedvoorlopers, bevestig. Weens die vatbaarheid van biflavanoïede vir C-2-epimerisasie en herrangskikking via kinoonmetiede onder basiese kondisies is die 3',4'- en 4'-O-metieleterderivate (E-ring) van die biflavanoiedvoorlopers geselekteer vir 'n studie van hul basisgekataliseerde herrangskikking. Die piraanherrangskikkingsreaksie van (-)-robinetinidol-(4β,8)-(+)-katesjien mono-O-metieleter lewer 'n A-tipe prorobinetinidien, (-)-robinetinidol-(2β - 7; 4β - 8)-(+)-katesjien, met spektroskopiese data identies aan die van die natuurproduk. Hierdie verteenwoordig nie slegs die eerste A-tipe van die 5-deoksi (A-ring) oligoflavanoïede nie, maar ook die eerste in die klas van proantosianidiene met 'n 3,4-cis relatiewe konfigurasie van die C-ring. Die omskakeling van 'n B-tipe proantosianidien na 'n A-tipe analoog word in terme van die oksidatiewe verwydering van 'n hidriedioon by C-2( C) verklaar. Die rol van atmosferiese suurstof in hierdie oksidatiewe transformasie blyk duidelik uit 'n vergelykende basisgekataliseerde reaksie waarin spesiale voorsorgmaatreëls getref is om suurstofvrye kondisies te skep. Stereoselektiewe isomerisasies asook herrangskikking waartydens die pirogallol B- en A-ringe omruil t.o.v. die posisies in die 'normale' isomere, lewer die verwagte ringgeïsomeriseerde produkte en slegs klein hoeveelhede van die A-tipe analoog. Die 'H k.m.r. spektrum van die A-tipe proantosianidien met 3,4-cis relatiewe konfigurasie (C-ring) toon identiese koppelingskonstantes (J3,4 3.5 Hz) in vergelyking, met die van analoe met 3,4-trans stereochemie. Hierdie waarneming kan aan die konformasionele starheid van die bisikliese sisteem wat tot identiese dihedriese hoeke tussen 3-H(C) en 4-H(C) aanleiding gee, toegeskryf word. 'n Metode gebaseer op die hoogs selektiewe 'H n.O.e. assosiasie van 3-H(C) is ontwikkel waarvolgens die 3,4-trans en 3,4-cis isomere ondubbelsinnig onderskei kan word. Die basisgekataliseerde piraanherrangskikkingsreaksie van die 'beskermde' triflavanoïed voorloper, (4α,8: 4(α,6)-bis-(-)-ro binetinidol-(+)-katesjien di-O-metieleter lewer na 'n kort reaksietyd slegs die intermediere, 10-flavaniel[2,3f]- chromeen. Hierdie flobatannien is uit die kommersiële A. mearnsii-ekstrak geïsoleer en ontstaan via 'n enkele hoogs stereoselektiewe ringisomerisasie. Die basisgekataliseerde C-ring isomerisasies is ook uitgebrei om 'n reeks piranochromene verwant aan (-)-fisetinidol-(-)-epikatesjien biflavanoïede in te sluit. Die natuurlike voorkoms van 'n reeks flobatanniene met beide (+)- en (-)-epikatesjien sowel as (+)- en (-)-katesjien as tenninale eenhede, tesame met die waarneming dat die koppelingskonstantes (J2,3 ca. 1.0 en ca. 7.0 Hz onderskeidelik) vir die heterosikliese protone differensiasie bemoeilik, het die noodsaaklikheid van sintese beklemtoon. Die strukture van 'n reeks natuurprodukte uit Guibourtia coleosperma, Colophospermum mopane en Baikiaea plurijuga is aldus volgens hierdie protokol bevestig. Ondersoek is verder ingestel na reduktiewe degradasietegnieke ten einde die probleme rakende die struktuurbepaling van A-tipe proantosianidiene en veral die bepaling van die stereochemie van die terminale flavan-3-ol eenhede van hierdie klas van proantosianidiene uit te klaar. Vanwee verskeie kompliserende faktore byvoorbeeld die reduksie van die vry fenol, sou die geredelik beskikbare A-tipe proantosianidien uit Arachis hypogea L., (+ )-epikatesjien-(2α - 7; 4α - 8)-(+)-katesjien verkieslik as fenoliese metieleter aan die reduktiewe reaksiekondisies blootgestel word. Metilering met diasometaan lewer gevolglik 'n mengsel van die heksametiel- en heptametieleterderivate. Die beperkte toeganklikheid van diasometaan by 5-0H(A) kan aan die waterstofbinding tussen die betrokke hidroksisubstituent en O-1(F-ring) toegeskryf word. Blootstelling van die heptametieleter van (+)-epikatesjien-(2α - 7; 4α - 8)-(+)- katesjien aan diisobutielaluminiumhidried (DIBAL) lewer twee produkte wat as gevolg van splyting van aromatiese metieleterbindings op die 4-posisie van die B- en E-ringe onderskeidelik, ontstaan. Die benutting van natriumsianobóorhidried in trifluoroasynsuur (NaBH3CNj CF3COOH) het egter tot die suksesvolle bepaling van die stereochemie van die terminale eenheid in die A-tipe proantosianidien gelei. Die reeks produkte wat via piraanring- en interflavanielbindingsplyting ontstaan, kan meganisties verklaar word in terme van die suurgekataliseerde vorming van 'n karbokatioon wat herrangskikking na 'n intermediere kinoonmetied ondergaan. Nukleofiele aanval van die hidriedioon lewer die tetrahidropirano[2,3-h]chromene en brokstukke afkomstig vanaf beide die 'boonste' en 'terminale' eenhede. Bevestiging vir die voorgestelde meganisme volg uit die reaksie van die heptametieleterderivaat van die A-tipe proantosianidien met CF3COOH. In die afwesigheid van 'n hidrieddonor word slegs klein hoeveelhede (+)-katesjien, geëpimeriseerde uitgangstof en hoofsaaklik polimeriese materiaal verkry. Die voorkoms van die reeks C-ring gei"someriseerde verbindings in nywerheidsgedroogde A. mearnsii-bas, dra waarskynlik by tot die kommersiële sukses van wattelbasekstrak. Die 'vrystelling' van 'n nukleofiele resorsinolring in flobatanniene verhoog waarskynlik die reaktiwiteit teenoor formaldeheid en dra aldus by tot die suksesvolle benutting van wattelbasekstrak in die koudsettende kleefstofbedryf. Die relatief planere sentrale CDF trisikliese sisteme in die dimeriese en CDFI tetrasikliese sisteme in trimeriese C-ring geïsomeriseerde verbindings, behoort verder tot verhoogde affiniteit vir kollageensubstrate by te dra en verklaar waarskynlik die uitgebreide benutting van wattelbasekstrak in die leerlooibedryf.Item Open Access Sintese en konformasie van natuurlike flobatanniene: die meganisme van basisgekataliseerde piraanherrangskikkings(University of the Free State, 1988-12) Steynberg, Jan Petrus; Ferreira, D.; Brandt, E. V.; Young, D. A.Afrikaans: Guibourtia coleosperma (Rhodesian copalwood) is bekend as 'n harde en duursame houtsoort wat opvallend weerstand teen verrotting bied. Die onlangse isolasie van unieke bi- en triflavanoïede gebaseer op leukoguibourtinidiene (4',7-dihidroksiflavan-3,4-diole) en fenoliese stilbene, bekend vir antifungiese eienskappe, het as stimulus gedien vir 'n herondersoek van die fenoliese metaboliete. Uitgebreide verrykings- en skeidingstegnieke lewer, benewens bekende (E)-stilbeen monosiede, die unieke 4',5-dimetoksi- en 3',5-dihidroksi-4'-metoksi-3-[O-α-L-rhamnopiranosiel-(1 - 6)-β-D-glukopiranosieloksil stilbeenbiosiede. Die lae konsentrasie van hierdie verbindings het 'n nuwe benadering ten opsigte van identifikasie genoodsaak. Ontwikkeling van 'n elegante metode waar die aard en posisie van interglikosidiese-sowel as glikosied-aglikoon bindings met behulp van n.O.e. tegnieke ('H k.m.r.) gekarakteriseer word, voorsien 'n waardevolle bydrae tot identifisering van glikosiede. Hierdie metode het veral meriete waar alternatiewe spektroskopiese en chemiese metodes deur die beskikbaarheid van voldoende materiaal aan bande gelê word. Die stilbeenglikosiede word in G. coleosperma vergesel deur flobatanniene, 'n unieke klas van ring-geïsomeriseerde tanniene. Hierdie verbindings verteenwoordig die produkte van stereospesifieke ring-isomerisasie van 2,3-trans-3,4-trans- en stereoselektiewe isomerisasie van 2,3-trans-3,4-cis-(-)-fisetinidol eenhede in konvensionele (4,8)-bi- en (4,6:4,8)-triflavanoïede. Fisiese data soos massaspektroskopie, sirkulêre dichroisme maar veral hoë resolusie 1H k.m.r. n.O.e. tegnieke, lei, op enkele uitsonderings na, tot volledige struktuuropklaring van die gefunksionaliseerde tetrahidro-2H,8H-pirano [2,3-h]-, [2,3-f]- en [2,3-g] asook heksahidro-2H,6H,10H-dipirano[2,3-f:2',3'-h] chromene. Eenduidige struktuurbewys vir die nuwe klas van gekondenseerde tanniene volg uit piraanherrangskikkings van die waarskynlike biflavanoiedvoorlopers onder milde basiese kondisies (pH1O) . Die vatbaarheid van biflavanoiede onder basiese kondisies vir epimerisasie en herrangskikking via kinoonmetiede kompliseer egter die reaksieverloop. Om dus newereaksies geassosieer met 'n E-ring kinoonmetied uit te skakel, is die 4-0-metieleterderivate (E-ring) van die biflavanoiede aan die basiese reaksiekondisies blootgestel. Terwyl biflavanoiede met 2,3-trans-3,4-trans-flavan-3-ol "boonste" eenhede vatbaar is vir relatief stadige maar stereospesifieke C-ring isomerisasie, ondergaan die analoë 2,3-trans- 3,4-cis isomere stereoselektiewe isomerisasies teen 'n verhoogde tempo. Laasgenoemde analoë is verder vatbaar vir herrangskikkings na tetrahidropiranochromene waar die pirokatekol B- en resorsinol A-ringe omgeruil is relatief tot die posisies daarvan in die "normale" isomere. Hierdie ringomruilings geskied via 1,3-flavanielmigrasie in intermediêre kinoonmetiede en gaan gepaard met die inversie van die absolute konfigurasie by die ekwivalent van 3-C (C-ring) in die biflavanoied voorloper. Opvallend is dat sommige van hierdie "ringomgeruilde " analoë ook in Baikiaea plurijuga aangetref is wat vermoedelik dui op die funksionering van 'n meganisme in die natuur soortgelyk as dié voorgestel in hierdie ondersoek. Benewens die voorsiening van eenduidige struktuurbewys vir die volledige reeks natuurlike flobatanniene, is 'n aanvaarbare meganistiese verklaring vir die verloop van die basisgekataliseerde piraanherrangskikkings ontwikkel. Die benadering van selektiewe beskerming van 4-OH(E), het verder afdoende bewys verskaf dat die waargenome flavanielmigrasies by die "onbeskermde" analoë via 'n E-ring kinoonmetied verloop. In teenstelling met "beskermde" biflavanoïede waar slegs die C-ring aan isomerisasie onderworpe is, kan beide die C- en I-heterosikliese ringe van 'n triflavanoïed piraanherrangskikking ondergaan. Behandeling van die (4α,8:4α,6)-bis-(-)-fisetinidol-(+)-katesjien as prototipe vir trimeriese profisetinidiene met basis het inderdaad die heksahidro-2H,6H,lOH-dipirano[2,3-f:2' ,3'-h] chromeen wat dui op 'n dubbele ringisomerisasie asook isomerisasie-intermediêre 6-flavaniel-[2,3-h]- en 1O-flavaniel-[2,3-f] chromene waar slegs een heterosikliese ring isomerisasie ondergaan het, gelewer. Die 10-flavaniel-[2,3-f] chromeen is ook uit G. coleosperma geïsoleer terwyl die dipirano[2,3-f:2' ,3'-h'] chromeen uit Colophospernum mopane geïsoleer is. Ten spyte van intensiewe ondersoeke na kommersiële basisgekataliseerde reaksies van prosianidiene met die oog op benutting van kommersiële ekstraksie van "loblolly pine" bas onder basiese kondisies, bestaan geen getuienis van C-ring isomerisasies by hierdie kommersieel-belangrike klas verbindings nie. Behandeling van prosianidien B-3, 'n tipiese prosianidien biflavanoïed, met milde basis lei tot 'n tetrahidropirano[2,3-h] chromeen met "omgeruilde" floroglusinol A- en pirokatekol B-ringe asook analoë 4-ariel-2- flavaniel bensopirane d.w.s. analoë waarin die 4-C (+)-katesjienen die 2-C pirokatekoleenheid "uitruil". Terwyl die tetrahidropiranochromeen vorm deur 1,3-flavanielmigrasie in 'n intermediêre kinoonmetied, ontstaan die 4-ariel-2-flavanielbensopirane deur 1,3-migrasie van 'n "vrygestelde" floroglusinoleenheid in dieselfde kinoonmetied intermediêr. Onder hierdie milde basiese kondisies kon geen bewyse vir omskakeling na "catechinic-acid" tipe produkte verkry word nie. Hierdie verbindings is bekend vir buitengewone suurheid en lae reaktiwiteit teenoor aldehiede en het die suksesvolle toepassing van alkaliese ekstraksie van natuurlike prosianidiene tot dusver gekortwiek. Die huidige ondersoek bewys dus dat met die versigtige seleksie van kondisies hierdie probleme grootliks oorbrug kan word. Die afwykende 1H k.m.r. en SD data van tetrahidropiranochromene met trans-trans C-ring konfigurasie en die omgekeerde Cotton-effek van [2,3-h] chromene met 2,3-trans F-ring konfigurasie, het die toekenning van absolute konfigurasie by sekere verbindings gekompliseer. So toon die SD spektra van die produkte met "omgeruilde" resorsinol A- en pirokatekol B-ringe 'n sterk negatiewe Cotton-effek in teenstelling met 'n verwagte positiewe Cotton-effek deur toepassing van die aromatiese kwadrantreël. Die teenstrydige chiroptiese gedrag word aan die konformasionele mobiliteit van die F-ring toegeskryf en is in 'n poging om die probleem te oorbrug die volgende benaderings benut. Die geredelike-beskikbare 4-arielflavan-3-ole is in modelreaksies gebruik om ondubbelsinnig te bewys dat ringomruiling tydens die isomerisasiereaksie met inversie van die absolute konfigurasie by die chirale sentra van die C-ring gepaard gaan. Laastens is die konformasionele gedrag van die flobatanniene teoreties met rekenaargesimuleerde molekulêre meganika bestudeer en kon deur die SD data met teoreties voorspelde voorkeurkonformasies in verband te bring die afwykende chiroptiese gedrag van sekere flobatanniene sinvol verklaar word. Uit Dreidingmodelle blyk dit duidelik dat 'n dominante A-konformasie, soos deur MM-berekenings bevestig, by tetrahidropiranochromene met alles-trans C-ring konfigurasie tot 'n "omgekeerde" Cotton-effek sal lei. Die konformasionele mobiliteit van die F-ring by tetrahidropiranochromene met 2,3-trans F-ring konfigurasie word inderdaad deur MM-berekenings bevestig (E:A konformeerverhouding, + 50:50). Uit die oogpunt van die kommersiële benutting van gekondenseerde tanniene is bogenoemde C-ring isomerisasie met gepaardgaande "vrystelling" van 'n resorsinoleenheid van fundamentele belang. Die vrygestelde resorsinolring behoort tot die aktivering van die basiese tannienskelet, veral vanaf die triflavanoiedvlak, vir reaksie met bv. formaldehied te lei om aldus aanleiding te gee tot beter benutting van tanniene in die koudsettende kleefstofbedryf.Item Open Access Modelverbindings in tanniensintese: die konformasie van vryfenoliese eenhede(University of the Free State, 1980-12) Pretorius, Pierre Johann; Roux, D. G.; Ferreira, D.Afrikaans: Die basiese doelwitte van hierdie studie is essensieel tweërlei van aard naamlik: (i) fragmentering van die heterosikliese eterbinding in 'n flavan-3-ol, as model vir die fundamentele bousteen van tanniene, gevolg deur die koppeling van 'n hidrofobiese tipe nukleofiel om sodoende enersyds die molekule te aktiveer ten opsigte van nukleofiliteit vir reaksie met formaldehied en andersyds wateroplosbaarheid te verlaag en (ii) die koppeling van fenoliese eenhede met bensiliese oksigenering onder milde suurkondisies aan die C4-karbokatioon van flavan-3,4-diole, as modelreaksie vir die sintese van biflavonoïede met terminale 3,4-diol funksionaliteit en ter bestudering van die konformasie van die heterosikliese ring van 4-ariel-/ -flavanielflavan-3-ole. Reaksie van (+)-katesjien met natriumsianied lewer 'n basisgekataliseerde herrangskikkingsproduk, katesjiensuur. Hierdie produk ontstaan deur onverwagse opening van die heterosikliese ring onder invloed van elektronvrystelling deur die 4-fenolaatioon en herrangskikking via In 1,6-tipe Michael addisie van C8 van die A-ring en die intermediêre kinoonmetied. Onder relatief drastiese kondisies reageer (+)-katesjien met swaeldioksied om uitsluitlik 'n dimeriese kondensasieproduk te lewer. Struktuurbewys hiervoor bevestig vir die eerste keer die postulaat van Freudenberg rakende die selfkondensasie van flavan-3-ole. Suurgekataliseerde koppeling van (+)-mollisacacidien en floroasetofenoon lewer beide die 3,4-trans- en 3,4-cis-4-arielflavan-3-oIe. Soortgelyke koppeling van (+)-mollisacacidien en (+)-taksifolien lei tot vorming van die 4,β-gekoppelde alles trans isomeer in uiters lae opbrengs. Onder dieselfde en selfs meer drastiese kondisies kon egter geen koppeling tussen (+)- mollisacacidien en (+)-fustien verkry word nie. Die KMR-spektra van sommige van die vryfenoliese 3,4-cis-4-arielflavan-3-ole dui op 'n abnormale klein koppelingskonstante tussen H2 en H3. Hierdie lae waarde word geïnterpreteer op grond van 'n afwyking van die normale vyfpunt-koplanêre konformasie van die heterosikliese ring as gevolg van die neiging van beide C2- en C4-fenielsubstituente om 'n ekwatoriale posisie in te neem en sodoende die heterosikliese ring in 'n verwringde bootkonformasie te forseer. Dit blyk dus dat verdere verfyning van reaksiekondisies waarskynlik sou kon lei tot sintese van biflavanolede met terminale diolfunksionaliteit terwyl 'n groter reeks vryfenoliese 4-arielflavan-3-oIe benodig word ten einde die konformasie van die heterosikliese ring finaal vas te stel.Item Open Access Profisetinidiene: die eerste sintese van tetraflavanoiede: bi- en triflavanoiede met terminale diolfunksie(University of the Free State, 1984-01) Young, Desmond Austin; Roux, D. G.; Ferreira, D.Afrikaans: Chemici in die flavanoiedveld leun swaar op spektroskopiese metodes ter ontrafeling van die komplekse strukture van bi- en hoëre flavanoiede. Die kragtigste van hierdie tegnieke naamlik ultra-hoë resolusie 1H en 13C kmr-spektrometrie gaan egter mank aan sekere inherente tekortkomings op veral die tetraflavanoiedvlak vanweë veral die abnormale hoë temperatuurvereistes (>200'C) om vinnige rotasie om die onderskeie interflavanoiedbindings en aldus skerpgedefinieerde spektra te induseer. Hierdie probleme het die behoefte aan sintetiese toegang tot oligomeriese tanniene beklemtoon en verteenwoordig hierdie studie dus primêr 'n ekskursie ten opsigte van die bepaling van koppelingsvolgorde en stereochemie van tetraflavanoiede deur middel van sintese. 'n Herondersoek van die komplekse fenoliese mengsel van die kernhout van A. mearnsii het verskeie 'nuwe' produkte gelewer. 'n Pienk band vanaf sellulose kolomme (lae mobiliteit met water as eluant) het onder andere 'n nuwe dioksaantipe bifisetinidol met 2,3-trans-3,4-trans:2,3-trans-3,4-cis stereochemie gelewer. Sintese van die dioksaantipe biflavanoied is vanaf tri-O-metiel-(+)-mollisacacidien met BF3 as katalisator uitgevoer. Die sintese het, benewens die genoemde isomeer, die bekende 3,4-alles-cis dioksaan biflavanoied as hoofproduk gelewer tesame met 'n 2,3-cis-3,4-cis:2,3-trans-3,4-cis analoog en twee [4,6]-C-C-gekoppelde triflavanoied dioksane waarvan die stereochemie van die 6-flavanieleenhede as 3,4-trans en 3,4-cis onderskeidelik bepaal is. Uit dieselfde fraksie is 'n nuwe 3,8,9-trihidroksidibenso-a-piroon, 3,9,1o-trihidroksidibenso-a-piroon en 'n komplekse dibenso-a-piroon identies aan dié uit Umtiza Zisterana vir die eerste keer uit A. mearnsii verkry. Die isolasie van laasgenoemde reeks verbindings beklemtoon opnuut die kompleksiteit van die metaboliese poel van Acacia mearnsii. Om insae te kry in sommige aspekte van die meganisme van flobafeenvorming, is die [4,8]-3,4-trans(-)-fisetinidol-(+)-katesjien biflavanoied in asynsuur/monochloorasynsuur/etanol vir 24 uur onder stikstof gerefluks. Bewyse vir splyting van die interflavanoïedbinding is verkry deur isolasie van(+)-katesjien, [4,6] -trans- en cis-biflavanoïede (1,3-flavanielmigrasie) en twee angulêre triflavanoiede. Hierdie produkte word vergesél deur twee verbindings waarin die heterosikliese ring van die (-)-fisetinidoleenheid herrangskikking ondergaan het. Herrangskikking vind plaas deur aanval van O7 van die (+)-katesjieneenheid op C2 van die O-geprotoneerde C-ring om verbindings van beide retensie en inversie van konfigurasie op die betrokke koolstof te lewer. Hierdie herrangskikking het effektief die 'vrystelling' van die resorsinol A-ring van die (-)-fisetinidoleenheid tot gevolg met gepaardgaande verhoogde nukleofiliteit en aldus verhoogde dryfkrag vir kondensasie na onoplosbare en hoogsgekondenseerde tanniene (ekwivalent van flobafeenvorming). 'n Noukeurige herondersoek na die kondensasiereaksie van (+)-katesjien met (+)-mollisacacidien het al vier moontlike isomere gelewer wat die vermoede bevestig dat die [4.6]-cis produk in 'n vorige ondersoek oor die hoof gesien is. 1H kmr (80MHz) spektra (σDMSO 150'C) het spesifieke diagnostiese patrone aangedui. naamlik dat ∆σH H 2 - 3 vir die F-ring (+)-katesjieneenheid) groot is (0.61) vir [4.8]-cis koppeling en klein (0.14) vir [4.8]-trans koppeling. Uitbreiding hiervan na die angulêre triflavanoiede uit A. mearnsii bevestig hierdie waarneming en dui daarop dat soortgelyke parameters ook vir hoër oligomere geldig is. Reaksie van (+)-katesjien met die vryfenoliese triflavanoied fraksie uit A. mearnsii het drie produkte gelewer waarvan twee [4. 6] en [4, 8] -gekoppel, in ooreenstemming is met verwagte strukture gebaseer op 3,4-cis:3,4-trans:3,4- trans-stereochemie van die diol triflavanoied. Die derde produk dui daarop dat 'n tweede diol triflavanoied met 'n 3,4-trans:3.4-trans-interflavanoied stereochemie waarskynlik in bogenoemde fraksie teenwoordig is. Weens gebrek aan materiaal kon die struktuur van die kondensasie produkte egter slegs gedeeltelik bepaal word. Om as modelle te dien vir hoër oligomere, is (+)-katesjien aan die diolbiflavanoiede gekoppel. Dit is opmerklik dat 3,4-ois interflavanoied stereochemie van die diolbiflavanoïede uitsluitlik 3,4-trans aansluiting met (+)-katesjien en 3,4-trans interflavanoied stereochemie, 3,4-cis aansluiting tot gevolg gehad het. Hierdie waarneming kan slegs gedeeltelik verklaar word aan die hand van die rigtende invloed deur die A-ring van die [6]-flavanieleenheid op koppeling van (+)-katesjien aan die elektrofiele C4-sentrum. Struktuurbepaling van tetraflavanoiede uit A. mearnsii het tekortkominge in kmr-tegnieke blootgelê, aangesien die koppelingspunt van die bifisetinidoleenheid aan die ten volle gesubstitueerde A-ring van die (+)-katesjieneenheid nie bepaal kan word nie en vanweë die hoë temperatuurvereistes om vinnige rotasie en dus 'skerp' kmr-spektra te bewerkstellig. Sintese van tetraflavanoïede is dus aangepak om die strukture van die geïsoleerde analoë te bepaal. Toegerus met kennis van stereochemie via sintese, kon 80MHz kmr sinvol benut word om karakteristieke kmr-patrone te identifiseer en sodoende redelik volledig kmr-interpretasie moontlik te maak. SD-spektra van die meerderheid van die hoëre oligomere het getoon dat die stereochemie van die koppelingspunt aan (+)-katesjien in die lineêre tri- en tetraflavanoiede die teken van die lae golflengte hoë-intensiteit Cotton-effek bepaal. Vir meeste van die 'angulêre' tetraflavanoiede het dit geblyk dat die stereochemie van die Ca koppelingspunt van (+)-katesjien soortgelyk die teken van die Cotton-effek bepaal. Hoewel normale koppelingskonstantes waargeneem word, is uitsonderings egter verkry wat daarop wys dat die SD-metode met huidige korrelasies nie op hoër oligomeriese vlak met dieselfde vertroue as op biflavanoied vlak toegepas kan word nie. 13C kmr-spektrometrie van sommige profisetinidiene dui daarop dat C4-kwasi-aksiale-(3,4-cis)-lavanielgroepe 'n Y skermende effek op C2 relatief ten opsigte van die ongesubstitueerde koolstof uitoefen, terwyl C4-kwasi-ekwatoriale groepe 'n y ontskermende effek uitoefen. Op die vryfenoliese (-)-fisetinidol-(+)-katesjien profisetinidiene kan die koppelingspunt aan (+)-katesjien afgelei word. Koppeling aan 'n spesifieke koolstof het ontskerming van daardie koolstof tot gevolg met 3,4-trans stereochemie wat 'n groter mate van ontskerming as in die geval van die 3,4-cis analoog veroorsaak. Op die metieleterdiasetaatvlak word 13C kmr-spektra egter ook gekompliseer deur beperking op rotasie om die interflavanoiedbinding en word studies by verhoogde temperatuur benodig alvorens sinvolle interpretasie en ekstrapolering na hoër oligomere moontlik is.Item Open Access Development of bionanocomposites based on PCL/PBS double crystalline blends and carbon nanotubes(University of the Free State, 2018) Gumede, Thandi Patricia; Luyt, A. S.; Muller, A. J.𝑬𝒏𝒈𝒍𝒊𝒔𝒉 The main purpose of this research was to use commercially available crystalline biobased polymers, namely poly(ε-caprolactone) (PCL) and poly(butylene succinate) (PBS), and introduce polycarbonate (PC)/multi-walled carbon nanotubes (MWCNTs) masterbatch into these polymers in order to provide additional functionalities, especially those associated with electronic applications. All the samples were prepared through melt- mixing in a twin-screw extruder. According to our results, the PCL/PBS blends showed a sea-island morphology with discrete droplets of the minor phase within the matrix of the major phase, indicating immiscibility. The introduction of the PC/MWCNTs masterbatch to PCL, PBS and the PCL/PBS blends showed partial miscibility, where PC-rich, PCL-rich and PBS-rich phases were formed. A number of MWCNTs diffused from the PC-rich phase to the PCL- rich and the PBS-rich phases, although the MWCNTs were mostly agglomerated in the PC-rich phases. However, the extent of partial miscibility was different for each system. The polar component surface energy, interfacial tension and isothermal crystallization results suggested that the MWCNTs would preferably diffuse into the PBS-rich phase, rather than the PCL-rich phase. Standard DSC measurements for the PCL/PBS blends, PCL/(PC/MWCNTs) and PBS/(PC/MWCNTs) nanocomposites demonstrated nucleation effects. In the PCL/PBS blends, nucleation was ascribed to (1) transference of the impurities from the PCL phase to the PBS phase, and (2) since the PBS crystallizes first, the PCL droplets may have crystallized by surface induced nucleation on the interface with the PBS crystallized matrix and nucleate at the interphase. In the case of the nanocomposites, the nucleation effect was attributed to the MWCNTs that diffused from the PC-rich to the PCL-rich and PBS-rich phases, even though the nucleating efficiency was lower than reported in the literature, which probably was due to the limited phase mixing between the PC-rich, the PCL-rich and PBS-rich phases. For the PCL/PBS/(PC/MWCNTs) nanocomposites, there was a decrease in the Tc values. This was due to the competition between two effects: (1) the partial miscibility of the PC-rich with the PCL-rich and PBS-rich phases, and (2) the nucleation effect of the MWCNTs. The decrease in the Tc values indicated that miscibility was the dominating effect. Isothermal crystallization experiments performed by DSC showed an increase in the overall crystallization rate of PCL with increases in MWCNTs contents, which was the result of their nucleating effect. However, for the PBS/(PC/MWCNTs) nanocomposites, the crystallization rate increased up to 0.5 wt% MWCNTs, while further increases in MWCNTs loading (and also in PC content) resulted in progressive decreases in crystallization rate. The results were explained through increased MWCNTs aggregation and reduced diffusion rates of PBS chains, as the masterbatch content in the blends increased. In the case of the PCL/PBS/(PC/MWCNTs) nanocomposites, the overall crystallization rates decreased as a result of the competition between the nucleating effect and miscibility. Since the PC-rich phase is partially miscible with the PCL-rich and PBS-rich phases, the PC probably immobilized the PCL and PBS chains and inhibited the rate of crystallization. The thermal conductivities and mechanical strengths of the nanocomposites were generally enhanced compared to those of the neat material. The nanocomposites prepared in this work could be used in applications where electrical conductivity, as well as low weight and tailored mechanical properties, are required. ___________________________________________________________________Item Open Access Analysis of zirconium containing materials using multiple digestion and spectrometric techniques(University of the Free State, 2014-10) Lotter, Steven James; Purcell, W.; Nel, J. T.English: The preparation of pure zirconium metal for nuclear applications is difficult due to the non-reactivity of zirconium minerals, such as zircon. The ability to accurately analyse zirconium-containing materials across the whole beneficiation chain is of crucial importance to the zirconium industry as a whole. The development of such an analytical technique is problematic, however, as the very properties which make these materials desirable also make quantification of their components extremely difficult. Certified reference materials for the fluoride-containing Necsa zirconium process products were not available. Therefore in-house reference materials were created by crystallisation of several (cation)xZrF4+x compounds. Potassium catena di-μ-fluorido-tetrafluoridozirconate(IV), cesium hexafluoridozirconate(IV) and tetraethyl ammonium catena di-μ-fluorido-bis-(trifluoridozirconate(IV)) monohydrate were prepared and characterised by X-ray crystallography and qualitative XRD. Coordination numbers for the zirconium atoms in each of these crystals were found to be 8, 6 and 7 respectively. Bridging fluorine bond lengths were determined to be approximately 2.06 and 1.97 Å for the potassium and tetraethyl ammonium complexes while terminal bond lengths were found to be 2.17 (potassium), 2.007 (cesium) and 2.15 (tetraethyl ammonium) Å. ICP-OES lower limits of detection for zirconium in the 3.25% nitric acid matrix were found to be 1.6 ppb with lower limits of quantification being ten times this value. ICP-OES zirconium recoveries for these crystals were 101(1) and 100(2)% for the potassium and cesium crystals respectively. Dissolution of various commercial and Necsa process samples was problematic and thus several digestion methods were investigated. Sulphuric acid, ammonium bifluoride and hydrofluoric acid were all investigated along with microwave assistance. A microwave-assisted acid digestion method was developed capable of complete dissolution of all zirconium compounds with ICP-OES analytical recoveries of 102.0(9), 100(2) and 101(3)% for 99.98% zirconium metal foil, ZrC and ZrH2 respectively. In order to circumvent the dissolution step a solid state GD-OES method was developed wherein sample powders were pressed into disks with a binder material, either copper or graphite. Initially instrument response across different samples was inconsistent but after optimisation of several instrument parameters, such as applied voltage and pre-burn time, a calibration curve with a R 2 value of 0.9805 was achieved using multiple sample materials. This was achieved using the radio frequency glow discharge source operating at 900 V applied voltage and 14 W applied power with a 5-minute pre-burn period. Results for Necsa process products were largely in line with those achieved by the ICP-OES method.Item Open Access Comparison of the influence of CeYAG and MCM-41 as nanofillers on the properties of polycarbonate and poly( methyl methacrylate)(University of the Free State (Qwaqwa Campus), 2016-01) Sibeko, Motshabi Alinah; Luyt, A. S.This study reports on the morphology of poly( methyl methacrylate) (PMMA) and polycarbonate (PC) filled with mesoporous silica (MCM-41) and cerium doped yttrium aluminum garnet (Ce:YAG) at contents in the range of 0.1 to 5 wt.%. The interactions between the polymer and fillers in these composites, and their thermomechanical, mechanical and thermal degradation properties were studied. The techniques used were small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), CP-MAS-NMR spectroscopy, X-ray diffraction (XRD), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), impact testing and luminescence spectroscopy. The samples containing more than 0.5 wt.% of filler were Jess transparent than those containing smaller amounts, due to the presence of agglomerates. MCM- 41 particles were well dispersed at low loadings, but formed agglomerates at higher loadings, while the Ce:Y AG particles were not too well dispersed in both polymers at low loadings. Mixing with PMMA and PC did not alter the pore dimensions in the MCM-41 structure, and it maintained its hexagonal structure, even though the polymer chains partially penetrated the pores during composite preparation. Both polymers have carbonyl groups that had hydrogen bond interactions with the silanol group (Si-OH) on the surfaces of the MCM-41 particles. In the case of Ce: Y AG the interaction was through electron donor-acceptor interaction between the carbonyl oxygen lone pair in the polymers and the yttrium cation (Y3+). PMMA, however, showed a stronger interaction than PC. The addition of MCM-41 and Ce:Y AG increased the storage and loss modulus of PMMA and PC above the glass transition temperature. In the presence of MCM- 4 I the increase in modulus was due to the interaction of the polymer chains with the porous filler which restricted the mobility of the polymer chains and increased the stiffness of the composites. The impact strength of the polymer increased with the addition of MCM-41 and Ce: Y AG, but the concentration corresponding to the maximum increase depended on the type of filler. The combination of blue LEDs with the PMMA/Ce:YAG composites loaded with 5 wt.% and PC/Ce:YAG composites loaded with 2 wt.% gave off light in the white region, making them suitable for applications in white light emitting diodes.Item Open Access Totaalsintese en toksisiteit van 'n nuwe 12a-O-metielrotenoied: fitochemie van verwante isoflavonoiede(University of the Free State, 1976-12) Oberholzer, Maria Elizabeth; Rall, G. J. H.Afrikaans: Hierdie proefskrif behels die chemiese ondersoek van 'n reeks verwante natuurprodukte, waaronder 'n aantal fisiologies aktiewe rotenoïede, uit die bol van Neorautanenia amboensis. Tydens die ondersoek is daar ook gepoog om 'n voorstelling, gebaseer op biogenetiese grondslag, van die onderskeie komponente daar te stel. Die relatiewe toksisiteit van sintetiese en natuurlike rotenoïede is bepaal deur die snelheid van inhibisie van sitochroom-c-reduktase te volg terwyl 'n moontlike korrelasie tussen giftigheid en struktuur bespreek word. N. amboensis behoort tot die Leguminosae plantfamilie wat in Suider Afrika verteenwoordig word deur sleg s 'n paar spesies, wat bekend is vanwee die gebruik as visgif van veral N. ficifolia en N. amboensis. Hierdie aktiwiteit het as stimilus gedien tot die chemiese ondersoek van die plant. Met die toenemende kommer oor besoedeling en die leemte wat ontstaan het met die verdwyning van gechlorineerde insektisiede van die mark, het die vraag na geskikte plaasvervangers, onder andere rotenoon, skerp gestyg veralomdat die toksisiteit van rotenoïede deur oksidatiewe prosesse heeltemal verdwyn na slegs enkele dae en dus geen besoedelingsgevaar inhou nie. Met behulp van tweedimensionele dunlaag- en papierchromatografie is bepaal dat die benseen- en metanolekstrakte van die plantmateriaal baie komplekse mengsels is en voorlopige skeidings is uitgevoer deur kolomchromatografie en 'n teenstroomverdeling. Die isolasie en struktuuropklaring van opties aktiewe (-)-(6aS, 12aS)-neobanoon en (-)-(6aS, 12aS)-12a-hidroksi-isomillettoon, twee 12a-gesubstitueerde rotenoïede, en die bevinding dat beide 'n hoë mate van toksisiteit teenoor Lucilia serieata vertoon, het daartoe gelei dat die sintese van neobanoon volgens 'n biogeneties georïenteerde roete (chalkoon→isoflavoon→rotenoïed 12a-gesubstituteerde rotenoïed) aangepak is. Die sintese van neobanoon verteenwoordig die eerste totaalsintese van 'n 12a-O-metielrotenoied. Tydens die sintese is 'n baie bruikbare bydrae gelewer in die vorming van komplekse chalkone deur die aanwending van "Crown" eters. Benewens die isolasie van struktuurvariante van isoflavone, pterokarpane en rotenoïede, het hierdie ondersoek ook gelei tot die identifisering van die eerste natuurlike opties aktiewe isoflavan-4-ol, (+)-ambanol. Aan die hand van PMR-spektroskopie is aangetoon dat ambanol die 3,4-cis konfigurasie besit. Die struktuur is bevestig deur totaalsintese en omskakelingsreaksies. Identifikasie van hierdie verbinding is van besondere belang, aangesien dit 'n sleutelrol vervul in die biosintese van pterokarpane en by die oksidatiewe interomskakelbaarheid van isoflavonoiede. Die bol van N. amboensis bevat ook drie lede van die seldsame groep 2S-5-deoksi-flavonoïede, naamlik (-)-3',4',7-trihidroksi-2,3-transflavan-3,4-cis-diol, (-)-3',4',7-trimetoksi-2,3-trans-flavan-3,4-cis-diol en (-)-3,3',4,4'7-pentametoksi-2,3-trans-3,4-cis-flavaan waarvan laasgenoemde ‘n nuwe natuurprodruk verteenwoordig. Die struktuur en stereochemie van laasgenoemde korreleer met spektrometriese analises en is bewys deur omskakeling van eersgenoemde twee verbindings na die pentametoksiderivaat. Die gesamentlike voorkoms van flavonoïede en isoflavonoïede in N. amboensis is van biogenetiese belang, aangesien hierdie verskynsel daarop dui dat flavonoïed en isoflavonoïed biosintese langs gelyksoortige weë kan geskied. Die pterokarpaanskelet en substitusiepatroon van (-)-(6aR, llaR)- neobanol, ‘n nuwe 12a-hidroksipterokarpaan, is bepaal met behulp van PMR- en massagegewens terwyl die chemiese omskakeling na ‘n pterokarpeen die struktuur onteenseglik vasgelê het. 2’7-Dimetoksisophorol en 2’-hidroksi-2-metoksi-4’,5’-metileendioksi- 6,7,4",5"-furanoisoflavanoon is twee nuwe isoflavanone waarvan laasgenoemde nie alleen die eerste 2-metoksi-isoflavanoon is nie, maar ook die eerste verbinding in hierdie klas verteenwoordig wat optiese aktiwiteit vertoon. PMR- sowel as MS-gegewens is in ooreenstemming met die voorgestelde strukture en bevestig die onderskeie substituente. Twee nuwe isoflavoonglikosides, daidzein-7-D-xilosiel-β-D-glukosied en genistein-7-D-xilosiel-β-D-glukosied, is in relatief hoë konsentrasies geïsoleer. Die aglikoongedeeltes is met behulp van PMR- en MS-spektrometrie gekarakteriseer terwyl die suikers deur middel van hul trimetielsilieleters gaschromatografies bepaal is. Buitengewoon eenvoudige metaboliete, 6-hidroksi-2,3-dihidrobensofuraan, α-OH, α:5(6-metoksi-2,3-dihidrobensofuraan)-etaan en p-metoksiasetofenoon, tot op hede onbekend in natuurlike bronne, is uit N. amboensis geïsoleer. Met betrekking tot die strukture bied hierdie bevindings geen nuwigheid nie, maar die natuurlike voorkoms daarvan mag wel belangrike biogenetiese implikasies inhou, aangesien p-metoksi-asetofenoon moontlik as voorloper tot retrochalkone kan dien. Nadat voorlopige toksisiteitsbepalings belowend geblyk het, is twaalf verskillende rotenotede getoets met betrekking tot inhibisie van die mitochondriële nikotienamiedadeniendinukleotied oksidasie in die asemhalingstelsel. Met behulp van kinetiese studies kon bepaal word dat rotenoon, natuurlike neobanoon en 12a-hidroksi-isomillettoon van vergelykbare toksisiteit is terwyl dit aan die lig gekom het dat die stereochemie van rotenoïede (6aS, 12aS) 'n bepalende faktor is ten opsigte van hul inhibisievermoë van die mitochondriële elektronvervoersisteem. Hierdie bevinding is gerugsteun deur die feit dat sintetiese, (±)-neobanoon 'n baie laer fisiologiese aktiwiteit as die natuurproduk toon, asook deur die verskynsel dat (-)-cis-12a-hidroksirotenoon die enigste isomeer van die vier 12a-hidroksirotenoondiastereoisomere is wat toksisiteit vertoon.Item Open Access Biflavonoied diastereo-isomere en hul biogenetiese voorlopers uit Berchemia SPP.: pogings tot sintese van analoe(University of the Free State, 1976-02) Volsteedt, Francois du Rouan; Roux, D. G.Afrikaans: Hierdie studie behels die struktuurondersoek, omskakelingsreaksies en pogings tot sintese van sommige van die mono- en biflavonoïede uit die kernhout van Berchernia zeyheri met 'n aanvullende studie op die kernhoutstowwe van die taksonomies notiverwante spesie; B discolor. Die verbindings uit B. zeyheri (rooi ivoor) kan in twee groepe geklassifiseer word, nl. mono- en biflavonoïede, almal op dieselfde 4' ,5,7- trihidroksi- (of sy ekwivalent) fenoliese patroon gegrond. Die eerste groep sluit die volgende in: maesopsin {2-(4-hidroksibensiel)-2,4,6-trihidroksibenso[b]furan-3(2H)-oon}; 7-metielmaesopsin (nnut); α,2’,4,4’,6’-pentahidroksicis- en trans-chalkoon; 2,3-trans-aromadendrin (3,4’,5,7-tetrahidroksiflavanoon); kaempferol (3,4’,5,7-tetrahidroksiflavoon); naringenin (4’,5,7-trihidroksiflavanoon) en 4,4’,6-trihidroksiauroon. Uit die beskikbare eksperimentele gegewens kon geen aanduiding van die struktuur van die rooi pigment wat verantwoordelik is vir die besondere voorkoms van die kernhout, verkry word nie. Die relatiewe hoë opbrengs van maesopsin het toegelaat dat verskeie nuwe omskakelings op die tetra-O-metieleter uitgevoer kan word met die doel om soortgelyke reaksies op daardie biflavonoïede, met een of meer maesopsineenhede waarvan genoegsaam verkry kon word, te herhaal. Reduksie met LiA1H4 het die ooreenstemmende 3-ol gelewer; brominering die 7-broomderivaat; en fotolise die 2’-hidroksi-α-metoksi-cis-chalkoonanaloog sowel as 1-(2-hidroksi-4,6-dimetoksifeniel)-2,2-dimetoksi-3-(4-metoksifeniel)-propan-1-oon. 2-(α-Asetoksi-4-metoksibensiel)-2,4,6-trimetoksi- en 2-(4-metoksibensoïel)-2-asetoksi-4,6-dimetoksibesno[b]furan-3(2H)-oon is vir die eerste keer verkry deur oksidasie van sintetiese 2’-hidroksi-α-metoksi-trans-chalkoon met Pb(0Ac)4 in asynsuur. Die struktuur van die cis- en trans-α-hidroksiechalkone is deur sintese en fotolitiese omskakeling bevestig. Die struktuur van die “konvensionele” chalkoon is deur sintese van 2’-hidroksi-4,4’,6’-trimetoksi-trans-chalkoon bevestig. Oksidasie van laasgenoemde met Pb(OAc)4 en Tl(NO3)3 lewer onderskeidelik tri-0-metielauroon en –isoflavoon. Al die biflavonoïede is nuwe natuurprodukte en sluit die volgende opties onaktiewe verbindings in (slegs triviale name genoem): zeyherin en isozeyherin, beide enantiomere pare bestaande uit twee I-2,II-7-gekoppelde bensokumaranonieleenheid verbind en neo- en isoneoberchenin wat slegs verskil t.o.v. die I-3,II-5-interflavonoïedbinding van voorafgaande twee. Al vier is enantiomere pare. ‘n Verdere biflavonoïed, rhamnin, saamgestel uit ‘n naringenieleenheid en ‘n terminale α-hidroksichalkooneenheid (I-3,II-3’-gekoppel), lewer vir die eerste keer direkte bewys (met die moontlikheid van ringopening in ag geneem) van inkorporasie van ‘n α-hidroksichalkoon as biogenetiese voorloper. Die bestaan van die verbinding dui aan dat ringsluiting van die terminale eenheid by berchenin en isoberchenin na intermolekulêre koppeling plaasvind. Twee verdure biflavonoïede, laktoon A en B genoem, identies aan die zeyherins behalwe dat die terminale eenheid (maesopsin) ’n bensielsuuromskakeling onder die toestande van metilering ondergaan het en derhalwe nie as natuurprodukte beskou word nie, is as enantiomorfe mengsels verkry. Hul dien egter as ‘n indirekte bewys vir α-hidroksichalkone as biogenetiese voorlopers, en dat siklisering by die zeyherins soos in die geval van berchenins moontlik eers na intermolekulêre koppeling geskied. Geeneen van die pare biflavonoïede ondergaan onderlinge omskakeling by ca. 150° (ontbinding) nie, sodat hul nie rotasie isomere verteenwoordig nie, maar wel diastereoisomere. Bibensokumaranonielmetaan, moontlik ‘n rotameriese mengsel volgens duplisering van seine in die KMR-spektrum van die 0-metieleter, bestaan uit twee maesopsineenhede, unike I-5,II-7 oor ‘n CH2-brug verbind. ‘n Verbinding verwant aan laasgenoemde, n. 2,7-bi(4-hidroksibensiel)-2,4,6-trihidroksibenso[b]furan-3(2H)-oon is ook geïsoleer. Al die biflavonoïede is uniek in die opsig dat hul 5-ledige heterosikliese ring(e) of ‘n α-hidroksichalkoon as eenhede bevat. As gevolg van ‘n gebrek aan material is slegs enkele omskakelings op sommige van die biflavonoïede uitgevoer. Reduksie van 0-metielzeyherin met KBH4 skakel slegs die karbonielgroep van die terminale eenheid na die alcohol om. Dieselfde resultaat is op die berchenins verkry. Fotolise van 0-metielzeyherin lei tot omskakeling van die terminale eenheid na ‘n ketalstruktuur soortgelyk as die verkry uit die fotolise van 0-metielmaesopsin. Deur die uitskakeling van suurtoestande en hitte is die 0-metieleters van maesopsin, zeyherin, isozeyherin, berchenin en isoberchenin na voltooiing van die ondersoek as opties aktiewe verbindings geïsoleer na metilering met diasometaan. In ‘n poging tot sintese van ‘n biflavonoïed is gevind dat wanneer ‘n gesubstitueerde fenol i.p.v. ‘n flavonoïedeenheid gebruik word onder toestande wat fenolkoppeling bevorder [alkalise K3Fe(CN)6], die reaksie van die verwagte afwyk deurdat koppeling in die β- i.p.v. die α-posisie van die chalkoon plaasvind. In die spesifieke geval koppel 2’,4-dihidroksi-4’,6’-dimetoksi-trans-chalkoon in die β-posisie met 3,5-dimetoksifenol in teenwoordigheid van K3Fe(CN)6 om vier diastereoisomere 2-[α-(4-hidroksi-2,6-dimetoksifeniel)-4-hidroksibensiel]-4,6-dimetoksiebenso[b]furan-3(2H)-one en 4’-hidroksie-4,6-dimetoksiauroon in goeie opbrengste te lewer. Die volgende verbindings is uit die kernhout van die verwante B. discolour geïsoloeer: maesopsin, alfitonien {2-(3,4-dihidroksibensiel)-2,4,6-trihidroksibenso[b]furan-3(2H)-oon}; α,2’,4,4’,6’-pentahidroksi- en α-2’,3,4,4’,6’-heksahidroksitrans-chalkoon (beide nuwe natuurprodukte); (-)-epi- en (+)-katesjien; kaempferol (3,4’,5,7-tetrahidroksiflavoon), kwersitien (3,3’,4’,5,7-pentahidroksiflavoon), 3,4’,5-trihidroksidihidrostilbeen, asook twee verbindings waarvan nog geen struktuurtoeseggings moontlik was nie. Fotolise van die heksametoksi-trans-chalkoon, derivaat van bogenoemde α-heksahidroksichalkoon, het die cis-isomeer gelewer. Slegs ‘n ketalanaloog is na die foto-oksidatiewe omskakeling van penta-0-metielalfitonien geïsoleer, in teenstelling met die addisionele cis-α-metoksichalkoon verkry by die fotolise van tetra-0-metielmaesopsin. Skrille kontras bestaan dus tussen die inhoudstowwe van die twee spesies. Benewens ‘n aanvullende katekoloksigeneringspatroon is die opvallendste egter die afwesigheid van die verwagte biflavonoïede by B. discolour op grond van taksonomiese verwantskap. Alhoewel twee α-hidroksichalkone in die kernhout voorkom dui die afwesigheid van biflavonoïede in teenstelling met die geval van B. zeyheri moontlik op ‘n verskil in die redokspotensiaal van die twee spesies se ensiemsisteme en/of dat ‘n α-hidroksichalkoon slegs tesame met ‘n “konvensionele” chalkoon, soos in die geval van rooi ivoor, as biogenetiese voorlopers vir biflavonoïede optree. Die aanwesigheid van α-hidroksichalkone en verwante hemiketale in hoë konsentrasie dui op ‘n chemotaksonomiese verwantskap tussen twee spesies.Item Open Access Structural and chemical relationships in metal phosphine complexes relevant to homogeneous catalysis(University of the Free State, 2010-03) Ndula, Bungu Peter; Otto, Stefanus; Roodt, AndreasEnglish: The aim of this research work was to improve the fundamental understanding of the role selected tertiary bicyclic and conventional phosphine ligands play in modified cobalt-catalyzed hydroformylation. Selected bicyclic ligands were synthesized by radical addition of 1-alkenes to the 2° phosphines shown in Figure 1 (see in full text PDF). The following ligands were synthesized in this way: Phoban-Q (Q = CH2CH3 (C2), (CH2)4CH3 (Cs), (CH2)3N(CH3)2 (C3NMe2), Lim-Cs, VCH-Cs and PA-Cs. Phoban-Cy was made from the reaction between a diene and a 1° phosphine, H2PCy, with a radical initiator at 100°C. the second set ranging from PnBu3 to the Lim family with hydrogenation ranging from 9 - 15% respectively. Crystal structures of the cobalt dimers of the following ligands; Phoban[3.3.1]-C21 Phoban[3.3.1]-C5, Phoban[3.3.1]-C3NMe2, Phoban[3.3.1]-Cy, PA-C5, PCy3, and PCp3 were obtained and characterised by X-ray crystallography. A series of [Rh(acac)(CO)(P-Ph)] complexes where P-Ph = Phoban[3.3.1]-Ph, Phoban[4.2.1]-Ph, a mixture of 4R, 8S- and 4S, 8S-Lim-Ph, a mixture of VCH[3.3.1]-Ph and VCH[3.2.2]-Ph and PA-Ph were successfully synthesized and characterised by NMR and IR spectrophotometers. The crystal structures of [Rh(acac)(CO)(4R, BS-Lim-Ph)] and [Rh(acac)(CO)(PA-Ph)] were obtained and characterised by X-ray crystallography. The oxidative addition and CO-insertion reactions of the rhodium complexes of these ligands were carried out and the results indicate that the Lim-Ph systems were the most active among the bicyclic ligands included in the study. The general reactivity trend for the oxidative addition was found to be: 4S, 8S-Lim-Ph > 4R, 8S-Lim-Ph > VCH-Ph > Phoban[3.3.1]-Ph > Phoban[4.2.1]Ph> PPh3 - PCy3 >PA-Ph. The overall reactivity trend for the CO-insertion reaction was determined as 4S, 8S-Lim-Ph > 4R, 8S-Lim-Ph > Phoban[4.2.1]-Ph > VCH-Ph > Phoban[3.3.1]-Ph > PA-Ph.Item Open Access Computational and characterization studies of homogeneous and heterogeneous tris(beta-diketonato) complexes with catalytic applications(University of the Free State, 2017-06) Gostynski, Roxanne; Conradie, J.; Erasmus, E.English: Nine [Mn(β-diketonato)3] [β-diketonato = dipivaloymethanato (dpm), 1; acetylacetonato (acac), 2; benzoylacetonato (ba), 3; dibenzoylmethanato (dbm), 4; trifluoroacetylacetonato (tfaa), 5; thenoyltrifluoroacetonato (tfth), 6; trifluorofuroylacetonato (tffu), 7; trifluorobenzoylacetonato (tfba), 8 and hexaflouroacetylacetonato, 9] complexes were synthesized by adapted methods from literature. An attempt was made to graft [Mn(β-diketonato)3] complexes 2-9 onto two dimensional (2-D) Si-wafer supports (S5-S12) via a silane linker. The X-ray photoelectron spectroscopy (XPS) Mn:F atomic ratio results of fluorine containing [Mn(β-diketonato)3] complexes grafted onto amino-functionalized Si-wafer (S9-S12) gave an indicaton that the [Mn(β-diketonato)3] complexes decomposed during the grafting process. Studying Mn2O3 on the hydroxylated Si-wafer surface by the use of XPS, it was confirmed that the Mn 2p photoelectron lines observed for S5-S12 consist mostly of Mn2O3 that has no interaction with the silane linker. Eight [Mn(β-diketonato)3] complexes 1-8 was wet impregnated onto various three dimensional (3-D) solid supports (S12- S28) to form [Mn(β-diketonato)3] model catalysts. Additionally a selection of [M(acac)3] complexes ([Co(acac)3], 12; [Rh(acac)3], 13, and [Ir(acac)3], 14) were grafted onto two dimensional (2-D) Si-wafer supports (S29-S31). While [M(acac)3] complexes ([Cr(acac)3], 10; [Fe(acac)3], 11; [Co(acac)3], 12; [Rh(acac)3], 13, and [Ir(acac)3], 14) were wet impregnated onto various three dimensional (3-D) solid supports (forming S32-S36). The model 2-D and 3-D catalysts were studied and characterized by the means of XPS, TGA and computational chemistry calculations. Selected model 2-D (S5, S7, S8, S12 and S29-S31) and Mn(acac)3 immobilized onto SiO2 (3-D catalysts, S14 as is and heat treated at 100, 130, 250 and 350 °C) were tested for the catalytic self-solvating reaction between ethanol and hexamethylenediisocyanate (HDI) to form hexamethylenediurethane (HDU) to mimic the industrial production of polyurethane. The model 2-D [Mn(β-diketonato)3] (S5, S7, S8 and S12) catalysts showed that as the total group electronegativity, 3(R + R'), increase a general decrease in turnover frequency (TOF) was observed. The model 2-D [M(acac)3] catalysts (S29-S31) showed that with an increase in the metal centre’s Pauling electronegativity a general increase in TOF was observed. The catalytic test on the Mn(acac)3 immobilized onto SiO2 showed that the sample heat treated at 100°C before hand has the highest TOF, which is most probably due to the loss of only one -diketonato ligand making it more active. The chromium(0) Fischer carbene complexes (Cr-FCCs) ([Cr(CO)4(PPh3)=C(OEt)(Fu)], C1; [Cr(CO)5=C(NHCy)(Fu)], C2; [Cr(CO)5=C(NHCy)(Th)], C3 and [Cr(CO)5=C(OEt)(ThTh)], C4) study was in collaboration with the research group of Dr. M Landman at the University of Pretoria. The four Cr(0) FCCs, were obtained and characterized by electrochemistry, XPS and computational chemistry calculations in this study. Penta-carbonyl Cr-FCCs [Cr(CO)5=C(OEt)(Fu)], C5, and [Cr(CO)5=C(OEt)(Th)], C6, were also supplied and anchored onto an amino-functionalized Si-wafer to create an immobilized Cr-FCCs C7 and C8. XPS results showed that the Cr(CO)5=C(OEt)(Fu)], C5, and [Cr(CO)5=C(OEt)(Th)], C6, was successfully anchored onto an amino-functionalized Si-wafer (C7 and C8). The electrochemical study of C1-4 showed that the oxidation potential (Epa) is influenced by the varied substituents on different sites of the Cr-FCCs. The oxidation order of the Cr-FCCs is: [Cr(CO)5=C(OEt)(ThTh)], C4 > [Cr(CO)5=C(NHCy)(Th)], C3 > [Cr(CO)5=C(NHCy)(Fu)], C2 > [Cr(CO)4(PPh3)=C(OEt)(Fu)], C1. The reduction followed the same trend except for the [Cr(CO)4(PPh3)=C(OEt)(Fu)], C1, complex that is reduced at a higher potential than the aminocarbene complexes, [Cr(CO)5=C(OEt)(ThTh)], C4 > [Cr(CO)4(PPh3)=C(OEt)(Fu)], C1 > [Cr(CO)5=C(NHCy)(Th)], C3 > [Cr(CO)5=C(NHCy)(Fu)], C2. The electronic energies of the different conformations obtained by the computational study showed that certain conformations are preferred over others. The computational results were in good agreement with experimental characterization method results. Computational study of HOMO and LUMO orbitals of the Cr- FCCs confirmed that the oxidation process is metal based and the reduction is based across the carbene ligand. The correlation of the oxidation potential (Epa) of the Cr0/Cr+1 redox couple and reduction potential (Epc) of the ligand based reduction with the HOMO energy (EHOMO) and LUMO energy (ELUMO) respectively, showed that with decreasing molecular orbital energy (HOMO and LUMO) an increase to more positive Epa and Epc potentials are obtained.Item Open Access Flammability studies on biopolymers and their blends(University of the Free State, 2016) Mngomezulu, Mfiso Emmanuel; John, M. J.; Luyt, A. S.; Jacobs, N. V.𝑬𝒏𝒈𝒍𝒊𝒔𝒉 The effect of commercial expandable graphite (EG) on the flammability and thermal decomposition characteristics of two systems based on poly(lactic acid) (PLA) and poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blend was investigated. Furthermore, the morphology, structure, melting and crystallization behaviour as well as the dynamic mechanical properties of flame retardant PLA/EG and PLA/PCL/EG composites were also studied. The flame retardant PLA/EG and PLA/PCL/EG composites were prepared by melt-mixing using the Brabender-Plastograph and were melt-pressed using the electrical hydraulichot melt press. The samples were characterized for their flammability performance and thermal stability via cone calorimeter and thermogravimetric analyser (TGA), respectively. They were also characterized for their volatile pyrolysis products during thermal degradation using simultaneous TGA-Fourier transform infrared spectroscopy (TGA-FTIR). The char residues obtained after combustion by cone calorimeter were further analysed with environmental scanning electron microscopy (ESEM). Furthermore, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to elucidate the structure and morphology of the flame retardant PLA/EG and PLA/PCL/EG composite systems. Their thermal behaviour (i.e. melting and crystallization) as well as their thermo-mechanical properties were respectively analysed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques. For the PLA/EG composite system, the thermal decomposition stability of the composites was improved in the presence of EG. However, the char content was less than expected as per the sum of the wt.% EG added into PLA and % residue of PLA after thermal decomposition. The flammability performance of the PLA/EG composites was improved, especially at 15 wt.% EG content, due to a thick and strong worm-like char structure. The peak heat release rate (PHRR) was improved by 74%, the total smoke production (TSP) was improved by 40% and the specific extinction area (SEA) by 55%. These improvements were due to the ability of EG to exfoliate at increased temperatures during which three effects occurred: i) cooling effect due to an endothermic exfoliation process; ii) dilution effect due to the release of H2O, SO2 and CO2 gases and iii) formation of a protective intumescent char layer. However, both the CO and CO2 yields were found to be unfavourably high due to the presence of EG. The graphite layers still existed in an aggregate structure with poor filler dispersion and lack of interfacial adhesion between EG and the PLA matrix. The presence of EG micro-particles: i) did not favour the crystallization of PLA, ii) increased the glass transition temperature and iii) showed a reduction in the crystallinity of the composites. The composites showed enhanced storage and loss moduli, especially at high EG contents (i.e. 10 and 15 wt.%). The glass transition from the loss modulus and damping factor varied inconsistently with the EG content. The use of commercial expandable graphite as filler in PLA could preserve the thermal properties of injection molding grade Cereplast PLA, while improving the fire resistance of PLA/EG flame retardant composites. In the case of PLA/PCL/EG flame retardant composite system, the thermal degradation stability of the composites was improved and the char content was found to have increased. Although the char content of the composites increased generally with EG loadings, the combined % residue from both the blend and wt.% EG initially added into the blend was higher than the observed % residue because of the thermal degradation mechanism that favoured the formation of CO and CO2 volatile gases rather than carbon. The flammability performance results indicated that the PLA/PCL blend was successfully modified with the EG micro-filler that resulted in fire resistant composites, especially at high filler loadings, due to the formation of intumescent carbonaceous char. This was confirmed by reductions of up to 64% in both the peak heat release rate (PHRR) and the total smoke release (TSR) and 54% in the specific extinction area (SEA). This was due to the EG acting mainly through a physical mode by cooling and fuel dilution and through the formation of an intumescent char layer. However, the effective heat of combustion (EHC) and carbon monoxide (CO) yields did not favourably improve. It was found that the melt mixing process could not separate the graphite layers, which existed as aggregate structures (i.e. EG layered stacks and/or lumps). In the composites, PCL was favoured to crystallize mainly on the surface of the microspheres and EG. The PLA/PCL blend showed an immiscibility feature, even in the presence of EG filler. Incorporation of EG in PLA/PCL blend influenced the melting and crystallization behaviour of PCL than that of the PLA component. Both the PCL and EG hindered the crystallization of the PLA component. From DSC and DMA, the glass transition of the composites occurred at high temperatures, suggesting that PLA polymer chains were immobilized in the presence of EG micro filler. The storage and loss moduli values were low for the composites when compared to PLA/PCL. The results suggest that the PLA/PCL/EG flame retardant composites have low thermal and thermo-mechanical properties due to the aggregation of EG and lack of interfacial adhesion between EG lumps and the polymer blend matrix. ___________________________________________________________________Item Open Access Properties evaluation of electrospun alginate-based nanofibrous membranes for filtration applications(University of the Free State (Qwaqwa Campus), 2016-12) Mokhena, Teboho Clement; Jacobs, N. V.; Luyt, A. S.This study entails the electrospinning of a sodium alginate (SA) natural polymer with the aid of an electrospinnable synthetic polymer, polyethylene oxide (PEO), in order to develop nanofibrous-based membranes for wastewater treatment. The two most abundant natural polymers (i.e. cellulose and chitosan) were also incorporated in order to improve the selectivity and antifouling of the membrane. In order to improve the antibacterial activity of the membrane, chitosan was used to synthesize silver nanoparticles (AgNPs). The membranes were characterized under different conditions, depending on their intended wastewater treatment application. The electrospinnability of the alginate/PEO blend was dependent on the storage time, with 10 days being the minimum duration to obtain smooth defect-free nanofibres. The adsorption capacity of the electrospun alginate nanofibres was studied under different concentrations, pH, and temperature using copper (Cu2+) as a model heavy metal. The maximum adsorption was approximately 15.6 mg g-1 at 25 °C and a pH of 4, and it maintained a reasonable metal adsorption over 5 recycling intervals. The adsorption capacity for chromium of the membrane based on the electrospun alginate nanofibres coated with cellulose nanowhiskers was 78 mg g-1 at a pH of 11. Complete removal of nanoparticles and a high retention of oil/water (>98%) was obtained. This was as a result of the pore size, the functional groups, and the inherited hydrophilic character of the membrane. In the case of the antibacterial alginate electrospun nanofibre membranes, the fibres were coated with silver nanoparticles and the susceptibility of gram negative and gram positive bacteria was also investigated using diffusion and kinetic methods. Spherical silver nanoparticles were obtained after 12 hours of heating at 95 °C using chitosan as a capping and reducing agent. The composite membrane was potent to gram negative and gram positive bacteria due to the presence of the AgNPs. The complexation between alginate and chitosan illustrated the possibility of the controlled release of AgNPs into wastewater streams. Further analyses were carried out on the silver nanoparticles containing chitosan as selective barrier in a three-tier membrane. The electrospun nanofibres (middle layer) was double-crosslinked by using calcium and glutaraldehyde in order to reduce the swelling behaviour of the alginate in an aqueous medium. The membrane displayed a larger than 98% rejection of nanoparticles (10-35 nm) and a larger than 93% retention of oil emulsions retention. It was found that the presence of AgNPs in the barrier layer did not affect the membrane performance.Item Open Access The constitution of oligomeric benzofuranoids(University of the Free State, 1999-05) Bekker, Riaan; Brandt, E. V.; Ferreira, D.English: Berchemia zeyheri is known for its unique red heartwood, a property that was probably responsible for the first phytochemical investigation into the flavonoid content of this tree. The heartwood contains a unique series of biflavonoids with one of more benzofuranoid moieties. These are usually found in diastereomeric mixtures, the biogenetic origin and stereochemistry of which have hitherto been unknown. This investigation thus represents a renewed effort to solve some of the intricate problems associated with these compounds. The high concentration of maesopsin in the heartwood made extensive enrichment and fractionation by the use of Craig countercurrent distribution techniques and Sephadex LH- 20 gelchromatography necessary. The two diastereomers of 4',5, 7-tri-O-methylnaringenin-(3a~ 7)-2,4,4',6-tetra-Omethylmaesopsin were, for the first time, successfully isolated and separated. Reduction of these diastereomers with Na(CN)BH3 gave two enantiomeric pure fragments. The conformations of the heterocyclic rings of these fragments were established by molecular mechanics (MMX and GMMX) and semi-empirical methods (AMI). These results allowed the absolute configuration of the fragments to be deduced from CD-curves of the compounds by application of Snatzke's rule for a,~-unsaturated five-membered cyclic rings. A n.O.e. correlation observed for one of the diastereomers only, correlates the stereocenter of the maesopsin moiety, of known absolute configuration, with a specific configuration of the naringenin unit, thus defining the absolute configuration of the dimer. These results also allowed the determination of the absolute stereochemistry of two regioisomers of the above dimers, 4',5, 7-tri-O-methylnaringenin-(3a~5)-2,4,4',6-tetra-Omethylmaesopsin and its epimer. The 13CNMR spectra of these related dimers were also studied and fully elucidated by means of HMQC and HMBC experiments. The structure and stereochemistry of two novel isoflavanone-benzofuranone biflavonoids, 4',5,7-tri-Omethyldihydrogenistein-fêcc-» 7)-2,4,4',6-tetra-O-methylmaesopsin and its epirner, were similarly determined. Resolution of maesopsin, the main metabolite in the heartwood, by means of HPLC using a chiral column, for the first time gave access to the two enantiomers of this benzofuranoid. 4,4',6- Tri-O-methyl-2-deoxymaesopsin-(2~ 7)-2,4,4',6-tetra-O-methyl-maesopsin and its epimer, consist of two benzofuranoid constituent units. An X-ray crystal structure was obtained for the one diastereomer, but due to the presence of a symmetric Pbea point group, only the relative configuration could be determined. After the racemic nature of each of the diastereomers was determined, each epimer was resolved with HPLC into its constituent enantiomers. The information obtained from the CD curves and crystal structure allowed the determination of the absolute stereochemistry of each of the enantiomers. Four further epimeric biflavonoids were isolated as the hepta-O-methyl ethers. Evidence obtained from 13C NMR data suggested the presence of a y-lactone functionality in the upper benzofuranoid moiety, identifying the dimers as the epimers of 4,6-dimethoxy-3-( 4- methoxy-benzyl)benzo[b ]furan-2(3H)-one-(2~5)-2,4,4',6-tetra-O-methylmaesopsin and the (2~ 7)-coupled regio-isomer. In order to supplement the above data, an asymmetric synthesis of maesopsin was attempted. The first attempt involved the oxidation of 2-( 4-methoxybenzyl)-4,6- dimethoxybenzo[b ]furan-3(2H)-one, obtained by reduction of the corresponding aurone, with AD-mix-a, a stereoselective catalyst, or chiral oxaziridine. The former afforded the desired product in low yield but no stereo selectivity while the latter method realized a much-improved yield, but still with no selectivity. This lack of selectivity is attributed to equilibrium of the product with the a-diketone. Attempts to prevent the formation of this equilibrium product were unsuccessful. A second synthetic attempt involved benzylation of 2,4,6-trimethoxybenzo[b]furan-3-(2H)-one with (-)-sparteine as chiral auxiliary, but again resulted in high yields but no stereo selectivity.Item Open Access New ring closing metathesis based methodology for the synthesis of monomeric flavonoids(University of the Free State, 2017-02) Pieterse, Tanya; Bezuidenhoudt, B. C. B.; Marais, C.Although the physiological activity of flavonoids stimulated investigations into more efficient synthetic methods for the preparation of these compounds, many of these routes entail multiple steps and require the utilization of stoichiometric and often poisonous reagents. Known methodologies are also hampered by difficulties around the isolation of the desired product and often lead to inseparable mixtures, low yields, and tedious synthetic processes. To circumvent these problems and to bring the synthesis of flavonoids in line with modern synthetic methodologies, it was decided to embark on a process of preparing the different classes of flavonoids through the application of a catalytic process, like ring closing metathesis (RCM), as key step in the methodology. Developing this methodology would have the added advantage that all the different classes of flavonoids would be reachable from readily available starting materials and the application of basically a single catalytic reaction in the final process step. For entry into the first class of flavonoids, i.e. compounds with a 2-phenylchromane skeleton, the preparation of flav-2-enes were investigated as key intermediate. In this regard, allyl phenyl ethers, prepared via Williamson etherification [K2CO3 (2.0 e.q), CH3CN, reflux], were subjected to Claisen rearrangement in a neat microwave assisted process to obtain the substituted allyl benzenes, 1-allyl-2-hydroxy-4-methoxybenzene and 1-allyl-2-hydroxy-4,6- dimethoxybenzene, in 44% and 88% yields, respectively. Subsequent esterification of the allyl phenols with substituted benzoyl chlorides [aq. NaOH (2.0 M, 40.0 mL) or 4- dimethylaminopyridine (0.2 eq.), dry pyridine (1.0 eq.), dichloromethane, reflux] afforded a series of the benzoates, i.e. 2-allylphenyl benzoate, 2-allylphenyl 4-methoxybenzoate, 2- allylphenyl 3,4-dimethoxybenzoate, 2-allylphenyl 3,4,5-trimethoxybenzoate, 2-allyl-5- methoxyphenyl 3,4-dimethoxybenzoate, 2-allyl-5-methoxyphenyl 3,4,5-trimethoxybenzoate, 2-allyl-3,5-dimethoxyphenyl 3,4-dimethoxybenzoate and 2-allyl-3,5-dimethoxyphenyl 3,4,5- trimethoxybenzoate in 68 – 98% yield. During methylenation of these esters through utilisation of the Tebbe reagent, it was found that the reaction is largely dependent on the concentration of the substrate, as well as reaction time and temperature. High yields (71 – 94%) were obtained with an increase in concentration of the ester and a brief period at elevated temperature (80 – 90°C). While a series of substituted diaryl vinyl ethers could be prepared, methylenation of substrates containing a phloroglucinol-type substitution pattern on what was to become the A-ring of the flavonoid failed. Ring closing metathesis of all the vinyl ethers in hand under standard metathesis conditions [Grubbs II, dichloromethane, reflux] led to the formation of flav-2-ene, 4'-methoxyflav-2-ene, 3',4'-dimethoxyflav-2-ene, 3',4',5'-trimethoxyflav-2-ene, 3',4',7-trimethoxyflav-2-ene and 3',4',5',7-tetramethoxyflav-2- ene in 41 – 96% yields. Attempts at the epoxidation of flav-2-ene with m-CPBA with and without a base (NaHCO3), did not yield any of the desired product. Construction of the isoflavonoid nucleus was first attempted through preparation of the isoflav-2-ene analogue via the deoxybenzoin intermediate, which could be prepared by phenylmagnesium bromide addition to the corresponding phenyl acetate. Although the phenyl acetates (methyl 4-methoxyphenyl acetate, methyl 4-trifluoromethylphenyl acetate, methyl 3-methoxy-4-trifluoromethanesulfonyloxyphenyl acetate and methyl 3,5- dimethoxyphenyl-4-trifluoromethanesulfonyloxyacetate) could be prepared in excellent yields (80 – 99%) via ozonolysis of the substituted allyl benzenes, the transformation of these compounds into the required deoxybenzoins was hampered by the inability (even at temperatures as low as -78 °C) to stop the reaction of the Grignard reagent with the substrate at the ketone stage. The methodology for the preparation of isoflavenes was therefore adapted to the synthesis of the isoflav-3-ene analogues, which could be constructed through a one-pot reaction of the substituted benzaldehyde with substituted α-bromoacetophenones followed by Wittig reaction with methyltriphenylphosphonium bromide to afford vinyl benzene intermediates, 4-methoxy-2-[(2-phenylallyl)oxy]-1-vinylbenzene, 1,5-dimethoxy-3-[(2- phenylallyl)oxy]-2-vinylbenzene, 1-{[2-(4-methoxyphenyl)allyl]oxy}-2-vinylbenzene, 4- methoxy-2-{[2-(4-methoxyphenyl)allyl]oxy}-1-vinylbenzene and 1,5-dimethoxy-3-{[2-(4- methoxyphenyl)allyl]oxy}-2-vinylbenzene, in 61 – 89% yield. Subsequent ring closing metathesis of the 7- and/or 4' substituted vinyl benzenes proceeded smoothly over Grubbs II catalyst in refluxing DCM and gave the isoflav-3-enes, (7-methoxyisoflav-3-ene, 4'- methoxyisoflav-3-ene and 4',7-dimethoxyisoflav-3-ene) in 57% to quantitative yields. RCM of the vinyl benzenes with a phloroglucinol-type substitution pattern, however, required elevated temperatures (refluxing toluene) and/or the addition of 1,4-benzoquinone in order to form the isoflav-3-enes, 5,7-dimethoxyisoflav-3-ene and 4',5,7-trimethoxyisoflav-3-ene, in decent yields (67 and 65%, respectively). Subsequent epoxidation of 7-methoxyisoflav-3-ene with m-CPBA and NaHCO3 in dichloromethane again failed to give any of the desired isoflavene epoxide. Although the neoflavonoid nucleus could be reached through Claisen rearrangement of 1- cinnamyloxybenzenes followed by vinylation of the phenolic hydroxy entity or Wittig mediated methylenation of 2-allyloxybenzophenones, followed by ring closing metathesis, this methodology was not viewed as being appropriate for application to oxygenated substrates as a number of process steps would be required to obtain oxygenated starting materials. It was therefore decided to follow a process where the appropriate acetophenones would be converted into the substituted styrenes by a Grignard reaction-dehydration process. Since electron-rich acetophenones are notorious for being lousy substrates in Grignard reactions the addition of aluminium triflate to the reaction mixture to enhance the reactivity of the reactant was investigated and it was found that the addition of Al(OTf)3 to the reaction mixture had a significant effect on the reaction of 4-methoxyphenylmagnesium bromide and 2-allyloxy-4-methoxyacetophenone. Not only did the presence of the Lewis acid increase the reaction rate, but it also led to the direct formation of the substituted styrene in 66% yield. Extending this reaction to the addition of phenylmagnesium bromide to 2-allyloxy-4,6- dimethoxyacetophenone and the addition of 4-methoxyphenylmagnesium bromide to 2- allyloxy-4,6-dimethoxyacetophenone and 2-allyloxy-4,5-dimethoxyacetophenone gave the substituted styrene products in moderate to high yields (52 – 94%). When 3,4- dimethoxyphenylmagnesium bromide was utilised in reactions with 2-allyloxy-4- methoxyacetophenone and 2-allyloxy-4,5-dimethoxyacetophenone, however, the analogous alcohols were obtained in 50% and 4% yields, respectively. When employing standard Grignard conditions (THF, -60 °C) i.e. without Al(OTf)3 activation, the tertiary alcohol products could be obtained 60% and 80% yields, respectively. Subsequent CuSO4-mediated dehydration of the alcohols yielded the desired styrenes (75% and 65%, respectively). Ring closing metathesis of all the styrene intermediates in hand proceeded smoothly and yielded the series of neoflav-3-enes, (4',7-dimethoxyneoflav-3-ene, 5,7-dimethoxyneoflav-3-ene, 4',5,7-trimethoxyneoflav-3-ene, 4',6,7-trimethoxyneoflav-3-ene, 3',4',7-trimethoxyneoflav-3- ene and 3',4',6,7-tetramethoxyneoflav-3-ene) in excellent yields (67% – quant.). Since it was shown that aluminium triflate had an enhancing effect on the addition of Grignard reagents to the acetophenones required for the synthesis of neoflavenes and that the styrenes could be obtained in a one-step process, it was decided to explore the scope of this novel process towards other ketones. During this investigation it was determined that the addition of Grignard reagents like phenylmagnesium bromide, benzylmagnesium bromide and ethylmagnesium bromide, to electron-rich ketones, i.e. 4-methoxyacetophenone, 2,4- dimethoxyacetophenone, 2,4-dimethoxypropiophenone and 4-chromanone, led to the formation of respective alkenes in 46 – 97% yields, while no product formation was observed for the less activated substrates like 4-chloroacetophenone and α-tetralone. It was furthermore observed that for the reaction of 4-methoxyacetophenone with ethyl - and benzylmagnesium bromide only the E-isomers of the product was formed, while only the Z-isomer was obtained during the addition of ethylmagnesium bromide to 2,4-dimethoxyacetophenone. The reaction of 2,4-dimethoxypropiophenone with phenylmagnesium bromide, on the other hand, yielded both geometric isomers in a 1:1 ratio. The stereoselectivity found during the reactions of 4- methoxy- and 2,4-dimethoxyacetophenone with ethyl - and benzylmagnesium bromide is probably explicable in terms of an E2 elimination process involving the preferred sterically less hindered gauche conformation of the transition state. Extending the reaction to the addition of phenylmagnesium bromide to α,β -unsaturated systems, like chalcone, indicated Al(OTf)3 to also have an activating effect in this regard, albeit to a marginal extent, since only an 8% increase in the yield of the 1,4-addition product was observed. Finally, indications were also found that Al(OTf)3 may also be utilized in catalytic quantities for this reaction when p-methoxy-1-phenylstyrene could be prepared in 82% yield by utilising Al(OTf)3 in 10 mol%; thus rendering the new methodology the first Grignard based Lewis acid catalysed process for the direct synthesis of alkenes.Item Open Access Encapsulation of selected metallated phthalocyanines in aluminium aminoterephthalate framework, NH₂-MIL-101(Al), with heterogeneous catalytic and hydrogen storage applications(University of the Free State, 2017-01) Peens, Frederick Hermanus; Langner, E. H. G.English: The amine-functionalised metal organic framework (MOF), NH2-MIL-101(Al) was successfully synthesised and optimised with a benchtop method. A newly developed activation method to evacuate the pores of the MOF, achieved a larger BET surface area (3192 ± 57 m2g-1) than those currently reported in literature. 2(3),9(10),16(17),23(24)-Tetra-tert-butylphthalocyanine (2HPctBu4) was successfully synthesised by either the lithium method or the hydroquinone method. The latter was superior since it is a solventfree synthesis, with a 60% higher yield than the lithium method. Successful metallation of 2HPctBu4 with the acetate salts of Zn2+ and Ni2+, gave single Q-bands at ~670 nm during UV-Vis absorbance measurements, while double Q-band maxima were observed at 660 nm and 690 nm for the metal-free 2HPctBu4. Four tetracarboxymetallophthalocyanines (MPc(COOH)4) with Zn2+; Fe3+; Co2+ or Ni2+ as central metal cations were synthesised in a two-step cyclotetramerisation method. Their aggregation behaviour was determined by UV-Vis spectroscopy. For concentrations up to 180 μM, only NiPc(COOH)4 showed aggregation from 5 μM, whereas ZnPc(COOH)4, FeClPc(COOH)4 and CoPc(COOH)4 showed little to no aggregation. Two different methods were used to encapsulate the MPcs in the pores of NH2-MIL-101(Al): templating, as well as customised solution phase infiltration. In both procedures MPctBu4 was encapsulated by the MOF via physical interaction, while all MPc(COOH)4 derivatives could covalently bind to the NH2-MIL-101(Al) structure via amide bonds. Encapsulation in the pores of the MOF would eliminate aggregation of the MPc molecules. DRS-UV-Vis showed that solution phase infiltration led to a higher loading of MPc in the MOF than when templating was used. This correlated with ASAP and PXRD results showing that all solution phase infiltration products, except for NiPc(COOH)3-CONH-MIL-101(Al), had smaller BET surface areas (between 244 cm3g-1 and 89 cm3g-1) due to their high loadings of MPcs. Hydrogen storage capacities of CoPc(COOH)3-CONH-MIL-101(Al) and NiPc(COOH)3-CONH MIL- 101(Al) were measured as 0.47 wt% (at 16 bar) and 1.5 wt% (at 128 bar) respectively. A trial test showed that CoPc(COOH)3-CONH-MIL-101(Al) catalysed the photo-oxidation of ciscyclooctene to cis-cyclooct-2-enol with a 5% conversion. For both MPctBu4 derivatives, liquid state cyclic voltammetry showed four Pc ring-based redox processes in DCM. With MPc(COOH)4 derivatives in DMSO , three redox couples were observed. For the Co2+-containing MPc, two metal-based redox processes (E°′ = -738 mV and -289 mV vs. ferrocene) and for the Fe3+-containing MPc, only one metal-based couple (E°′ = -88 mV vs. ferrocene) was observed. With solid state cyclic voltammetry of all MOF-encapsulated MPcs only one redox couple (near 200 mV vs. ferrocene) was detected, with the exception of ZnPc(COOH)3-CONH-MIL-101(Al) which gave an additional redox couple (E°′ = 1158 mV vs. ferrocene) and with NiPc(COOH)3-CONH-MIL- 101(Al) two additional couples (E°′ = 1146 mV and 1383 mV vs. ferrocene) were present. These processes were mostly electrochemically and chemically irreversible, but showed that the MOF’s matrix had a conductive effect on the flow of electrons during oxidation and reduction of the encapsulated MPcs.Item Open Access Methanol carbonylation via platinum group metal complexes(University of the Free State, 2010-11) Kotze, Philippus Daniel Riekert; Roodt, AndreasThe aim of this study, firstly, involved the synthesis of a range of S,O-functionalized thiourea ligands with systematically changing electro-steric properties and investigate these ligands coordination modes to rhodium complexes in an attempt to primarily synthesize a range of [Rh(S,O-thioureato)(CO)2] and [Rh(S,O-thioureato)(CO)(PR1R2R3)] complexes. Moreover, the aim also included the synthesis of [Rh(diphosphine)(CO)2]+ complexes using a range of diphosphine ligands. These complexes were then to be used to synthesize the corresponding Rh(III)-acyl complexes via iodomethane oxidative addition and study the carbonylation/hydrogenation of methanol to ethanol by investigating the kinetic and activation parameters of the iodomethane oxidative addition as well as reductive elimination/hydrogenation of acyl iodide/acyl species. Several S,O-functionalized thiourea ligands were successfully synthesized and characterized from which the X-ray crystallographic structures for several of the ligand systems are reported: N-benzoyl-N' -(2,4,6-trimethylphenyl)thiourea (Triclinic P 1, R1 = 5.60 %), N-benzoyl-N' -(2,6-dibromo- 4-fluorophenyl)thiourea (Triclinic P 1, R1 = 3.76 %), N-benzoyl-N' - (pentafluorophenyl)thiourea (Monoclinic C2/c, R1 = 3.69 %), N-benzoyl-N -(phenethyl)thiourea (Monoclinic P21/n, R1 = 3.91 %), N-benzoyl-N' -(naphthalene-1-ylmethyl)thiourea (Monoclinic C2/c, R1 = 5.37 %), N-benzoyl-N '-(cyclohexyl)thiourea (Triclinic P , R1 = 2.10 %) and Nbenzoyl- N' -(isopentyl)thiourea (Triclinic P , R1 = 5.06 %). It was established that these ligands exhibit a keto conformation in the solid state, where the carbonyl oxygen is trans to the sulphur atom and is stabilized by a hydrogen bond interaction with the terminal nitrogen atom of the thiourea moiety. The keto conformation was also confirmed in solution by NMR spectroscopy. Furthermore, hydrogen bond interactions exist between neighbouring molecules in the solid state, which leads to either dimer or polymer formation in the crystal packing of these thiourea compounds. The [Rh(diphosphine)(CO)2]+ complexes could not be successfully synthesized, however, during several attempts one synthetic route led to the formation of a cationic A-frame complex of the type [Rh2(µ -Cl)(diphosphine)2(CO)2]BF4. The X-ray crystallographic structure of [Rh2( µ-Cl)(dppm)2(CO)2]BF4 (Monoclinic P21/n, R1 = 8.84 %) is reported. Several [Rh(S,O-thioureato)(CO)2] complexes were synthesized and characterized, however, these complexes were unstable outside of solution. Several attempts were made to synthesize [Rh(S,O-thioureato)(CO)(PPh3)] complexes, which led to the isolation of rhodium thiourea complexes where the thiourea ligands exhibit S,O-, S- and N,S-coordination modes. The X-ray crystallographic structures of the following complexes are reported: [Rh(N,S-(N- 4h2mPT))(CO)(PPh3)2] (Triclinic P , R1 = 2.75 %), [Rh(N,S-(N-PT))(S,O-(N-PT))(PPh3)2] (Triclinic P , R1 = 4.44 %), [Rh(COD)(Cl)(S-(N-PTH))] (Triclinic P , R1 = 3.18 %), [Rh(COD)(Cl)(S-(N-tmPTH))] (Monoclinic C2/c, R1 = 6.74 %). [Rh(N,S-(N- 4h2mPT))(CO)(PPh3)2] is analogous to typical Vaska-type complexes, where the coordinated thiourea ligand is trans to the carbonyl ligand and the two PPh3 are trans to each other on the rhodium centre. [Rh(N,S-(N-PT))(S,O-(N-PT))(PPh3)2] is a Rh(III) species with an octahedral arrangement around the rhodium centre, where one of thiourea ligands coordinated in its enol conformation. In both [Rh(COD)(Cl)(S-(N-PTH))] and [Rh(COD)(Cl)(S-(N-tmPTH))] the preferred orientation of the free ligands translated to the orientation of the coordinated ligands. These complexes were also stabilized by hydrogen bond interactions between the chlorido ligand and the internal nitrogen atom of the thiourea moiety. A range of [Rh(S,O-(N-diPT))(CO)(PR1R2R3)] complexes were successfully synthesized using N-benzoyl-N' ,N' -(diphenyl)thiourea and a range of phosphine ligands with systematically changing electro-steric properties (PPh3, PPh2Cy, PPhCy2, PCy3). The X-ray crystallographic structures of the following complexes are reported: [Rh(S,O-(N-diPT))(CO)(PPh3)] (Monoclinic P21/c, R1 = 6.86 %), [Rh(S,O-(N-diPT))(CO)(PPh2Cy)] (Monoclinic P21/c, R1 = 6.32 %), [Rh(S,O-(N-diPT))(CO)(PCy3)] (Monoclinic P21/c, R1 = 6.86 %). The respective first order coupling constants (1JRh-P) and the carbonyl stretching frequencies ( VCO) were obtained, from which the expected order of electronic effects of the phosphine ligands was established. The effective cone angles ( E) for the different phosphine ligands were also calculated, which correlated well with the expected steric congestion of the ligands on the rhodium centre. The reactivity of the [Rh(S,O-(N-diPT))(CO)(PR1R2R3)] complexes towards the iodomethane oxidative addition was investigated. In general the reaction rate of the individual reactions increased in the order of [Rh(N-diPT)(CO)(PPhCy2)] < [Rh(N-diPT)(CO)(PCy3)] < [Rh(N-diPT)(CO)(PPh3)] < [Rh(N-diPT)(CO)(PPh2Cy)]. This order of reactivity was ascribed to a combinative effect of both the steric and electronic properties of the phosphine ligands. The activation parameters calculated for the individual reactions were found to be similar. The proposed mechanism for the iodomethane oxidative addition to complexes of the type [Rh(S,O-thioureato)(CO)(L)], where L = CO/PR1R2R3, is depicted in Scheme I. (Find scheme 1 on full text) The electro-steric effects of phosphine ligands in catalytic processes were further investigated by studying these effects in the phosphine exchange reactions of Vaska-type complexes [Rh(Cl)(CO)(PR1R2R3)2] with the corresponding PR1R2R3 ligand via NMR techniques. The reaction rate for the exchange reaction was almost two orders of magnitude faster for PPh3 than for PPh2Cy. Both exchange processes exhibited a large negative ∆ S≠ and a small ∆H≠ , which suggested an associative activation, where a stable 5-coordinated transition state is formed.Item Open Access Modification of nano-sized zinc zeolitic 2-methylimidazolate frameworks (zif-8) by solvent assisted ligand exchange and post-sythetic modification to enhance functionality towards catalysis, gas storage and drug delivery(University of the Free State, 2017) Tsai, Chih-Wei; Langner, E. H. GEnglish: Zeolitic Imidazolate Framework-8 nanoparticles (nZIF-8) were successfully synthesized during isothermal benchtop reactions, with different reagent concentrations in methanol. At an optimal concentration, an average particle size of 22 nm was achieved for nZIF-81500 with an external surface area of 320 m2 g-1. Addition of triethylamine (TEA) in different molar ratios during synthesis, increased the yield of nZIF-8 from 40 to 85 %. Particle sizes decreased to 16 nm at high TEA concentrations. Time resolved Solvent Assisted Ligand Exchange (SALE) of nZIF-8 with 2-mercaptobenzimidazole, 2-aminobenzimidazole, 2-phenylimidazole and presynthetic modified benzimidazole-thioesters, resulted in a ~13% exchange of the 2-methylimidazolate linkers of nZIF-8. Following an identical SALE procedure, the exchange with imidazole and 2-nitroimidazole, both without any attached benzene rings, reached a maximum exchange of 86 and 66 %, resulting in new zni and frl topologies respectively. All the SALE processes gave particle sizes below 100 nm, except when 2-mercaptobenzimidazole and 2-nitroimidazole were used. All nZIF-8 materials with SOD topologies remained microporous throughout the SALE process. Four different post synthetic modification (PSM) techniques were developed for aminoand ester functionalised nZIF-8 particles. PSM of lithiated SALEM-2 with (PPh3)2PdCl2, gave a 1.2 wt % Pd content, with an improved BET surface area (100 m2 g-1 larger). An iron content of 8.3 wt % was achieved via amidation of amino functionalised nZIF-8 with ferrocenecarboxylic acid. Sebacoyl chloride and polyacrylic acid were successfully anchored to the surface of amino functionalised nZIF-8. The SALE products of nZIF-8 were screened for catalysis of the Knoevenagel condensation between ferrocenecarboxaldehyde and malononitrile. Amine-containing nZIF-8 gave a lower TOF than nZIF-81500, suggesting a different catalytic pathway via an imine route. CO2 adsorption of nZIF-8 was doubled to 77 cm3 g-1, after SALE with imidazole derivatives containing NO2 and SH electron withdrawing groups. H2 uptake of all nZIF-8 derivatives was on par with the Chahine rule, with SALEM-216h-Pd adsorbing 3.07 wt % of H2 at 77 K.