Synthesis, electrochemistry and density functional theory calculations on chrome and cobalt carbene and betadiketonato complexes
| dc.contributor.advisor | Conradie, J. | |
| dc.contributor.author | Liu, Renyuan | |
| dc.date.accessioned | 2015-09-22T09:18:59Z | |
| dc.date.available | 2015-09-22T09:18:59Z | |
| dc.date.copyright | 2014 | |
| dc.date.issued | 2014 | |
| dc.date.submitted | 2014 | |
| dc.description.abstract | English: Two series of metal(β-diketonato)3 complexes were synthesized: tris(β-diketonato)chromium(III) complexes (where β-diketonato = [R1COCHCOR2]- = acac, ba, dbm, tfba, tfth, tffu, tfaa, hfaa) and tris(β-diketonato)cobalt(III) complexes (where β-diketonato = acac, ba, dbm, tfba, tfaa). These paramagnetic complexes were characterized by mass spectroscopy, X-ray crystallography and melting point measurements. The electrochemical behaviour of tris(β- diketonato)chromium(III) complexes was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and square wave voltammetry (SWV). The reduction potentials of the CrIII(β-diketonato)3 → CrII(β-diketonato)3 process correlate linearly with the following electronic parameters: 1) the acid dissociation constant (pKa) of the uncoordinated β-diketonato ligands, 2) the total electronegativities (Σx) of the side groups (R1 and R2) on the β-diketonato ligands, and 3) the total Hammett sigma constant (Σσ) of the side groups (R1 and R2) on the β-diketonato ligands. DFT-calculations were done on both series of these metal(β-diketonato)3 complexes. Molecular geometry, spin state and respective population of possible isomers were calculated in this study. The understanding of crystal structures was complemented by using DFT-results. For CrIII(β-diketonato)3 complexes, linear dependence was found between their reduction potentials and electron affinity (EA), as well as between reduction potentials and the energies of the lowest unoccupied molecular orbitals (ELUMO). Electrochemical behaviour of chromium(0) carbene complexes was investigated by cyclic voltammetry. The difference in oxidation potential of fac/mer isomers was observed for the first time for chromium(0) carbene complexes and discussed in this study. DFT-calculations revealed the following linear relationships with the redox process of Cr(0) carbene complexes: 1) the linear dependence between the cathodic potential (Epc) and energies of the lowest unoccupied orbitals (ELUMO), and 2) the linear dependence between the anodic potential (Epa) and energies of the highest occupied orbitals (EHOMO). | en_ZA |
| dc.description.abstract | Afrikaans:Twee reekse metaal(β-diketonato)3 komplekse is in hierdie studie gesintetiseer: tris(β- diketonato)chroom(III) komplekse (met β-diketonato = [R1COCHCOR2]- = acac, ba, dbm, tfba, tfth, tffu, tfaa, hfaa) en tris(β-diketonato)cobalt(III) komplekse (met β-diketonato = acac, ba, dbm, tfba, tfaa). Hierdie paramagnetiese komplekse is gekarakteriseer deur massa-spektroskopie, X-straal-kristallografie en smeltpunt-bepalings. Die elektochemiese gedrag van die tris(β- diketonato)chroom(III) komplekse is ondersoek deur sikliese voltammetrie (CV), lineêre skandeer-voltammetrie (LSV) en reghoekige golf-voltammetrie (SWV). Die reduksie potensiale van die CrIII(β-diketonato)3 → CrII(β-diketonato)3 proses korreleer lineêr met die volgende elektroniese parameters: 1) die suur dissosiasie-konstante (pKa) van die ongekoördineerde β- diketonato ligand, 2) die som van die elektronegatiwiteite (Σx) van die end-groepe (R1 en R2) op die β-diketonato ligand, en 3) die som van die Hammett-sigma-konstantes (Σσ) van die endgroepe (R1 en R2) op die β-diketonato ligand. DFT-berekeninge is gedoen op beide hierdie metaal(β-diketonato)3 series. Die molekulêre geometrie, spin-toestand en populasie van die moontlike isomere is bereken in hierdie studie. DFT-berekeninge het die begrip van die kristalstrukture gekomplementeer. Vir CrIII(β-diketonato)3 komplekse is ‘n lineêre verband bepaal tussen hulle reduksie potensiale en elektron affiniteit (EA), sowel as tussen reduksie potensiale en die energieë van die laagste besette molekulêre orbitale (ELUMO). Elektrochemiese gedrag van chroom(0) karbeen komplekse is ondersoek deur sikliese voltammetrie. Die verskil in oksidasie-potensiaal van die fac/mer isomere, is in hierdie studie vir die eerste keer vir chroom(0) karbeen komplekse waargeneem en bespreek. DFT-berekeninge het die volgende lineêre verwantskappe met die redoks-prosesse van die Cr(0) karbeen komplekse getoon: 1) die lineêre verband tussen die katodiese potensiaal (Epc) en die energieë van die laagste ongeökkupeerde molekulêre orbitale (ELUMO), en 2) die lineêre verband tussen die anodiese potensiaal (Epa) en die energieë van die hoogste besette molekulêre orbitale (EHOMO). | af |
| dc.description.sponsorship | National Research Foundation | en_ZA |
| dc.description.sponsorship | University of the Free State | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/1269 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Electrochemistry | en_ZA |
| dc.subject | Chromium -- Synthesis | en_ZA |
| dc.subject | Metal complexes | en_ZA |
| dc.subject | CV | en_ZA |
| dc.subject | Fischer carbene complexes | en_ZA |
| dc.subject | DFT | en_ZA |
| dc.subject | tris(β-diketonato)metal complexes | en_ZA |
| dc.subject | Cobalt | en_ZA |
| dc.subject | Chromium | en_ZA |
| dc.subject | Dissertation (M.Sc. (Chemistry))--University of the Free State, [2014] | en_ZA |
| dc.subject | Cobalt compounds -- Synthesis | en_ZA |
| dc.title | Synthesis, electrochemistry and density functional theory calculations on chrome and cobalt carbene and betadiketonato complexes | en_ZA |
| dc.type | Dissertation | en_ZA |