Research Articles (Chemistry)

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Browsing Research Articles (Chemistry) by Author "Fourie, Eleanor"

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    Octakis(dodecyl)phthalocyanines: influence of peripheral versus non-peripheral substitution on synthetic routes, spectroscopy and electrochemical behaviour
    (MDPI, 2022) Swart, Glendin; Fourie, Eleanor; Swarts, Jannie C.
    Non-peripherally octakis-substituted phthalocyanines (npPc’s), MPc(C12H25)8 with M = 2H (3) or Zn (4), as well as peripherally octakis-substituted phthalocyanines (pPc’s) with M = Zn (6), Mg (7) and 2H (8), were synthesized by cyclotetramerization of 3,6- (2) or 4,5-bis(dodecyl)phthalonitrile (5), template cyclotetramerization of precursor phthalonitriles in the presence of Zn or Mg, metal insertion into metal-free phthalocyanines, and removal of Mg or Zn from the phthalocyaninato coordination cavity. The more effective synthetic route towards pPc 8 was demetalation of 7. npPc’s were more soluble than pPc’s. The Q-band λmax of npPc’s was red-shifted with ca. 18 nm, compared to that of pPc’s. X-ray photoelectron spectroscopy (XPS) differentiated between N–H, Nmeso and Ncore nitrogen atoms for metal-free phthalocyanines. Binding energies were ca. 399.6, 398.2 and 397.7 eV respectively. X-ray photoelectron spectroscopy (XPS) also showed zinc phthalocyanines 4 and 6 have four equivalent Nmeso and four equivalent N–Zn core nitrogens. In contrast, the Mg phthalocyanine 7 has two sets of core N atoms. One set involves two Ncore atoms strongly coordinated to Mg, while the other encompasses the two remaining Ncore atoms that are weakly associated with Mg. pPc’s 6, 7, and 8 have cyclic voltammetry features consistent with dimerization to form [Pc][Pc+] intermediates upon oxidation but npPc’s 3 and 4 do not. Metalation of metal-free pPc’s and npPc’s shifted all redox potentials to lower values.
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    Substitution reactivity and structural variability induced by tryptamine on the biomimetic rhenium tricarbonyl complex
    (Royal Society of Chemistry, 2021) Jacobs, Frederick J. F.; Venter, Gertruida J. S.; Fourie, Eleanor; Kroon, Robin E.; Brink, Alice
    A series of seven fac-[Re(CO)3(5Me-Sal-Trypt)(L)] complexes containing tryptamine on the N,O 5-methylsalicylidene bidentate ligand backbone and where L is MeOH, Py, Imi, DMAP, PPh3 coordinated to the 6th position have been studied, including the formation of a dinuclear Re2 cluster. The crystallographic solid state structures show marked similarity in structural tendency, in particular the rigidity of the Re core and the hydrogen bond interactions similar to those found in protein structures. The rates of formation and stability of the complexes were evaluated by rapid time-resolved stopped-flow techniques and the methanol substitution reaction indicates the significant activation induced by the use of the N,O salicylidene bidentate ligand as manifested by the second-order rate constants for the entering nucleophiles. Both linear and limiting kinetics were observed and a systematic evaluation of the kinetics is reported clearly indicating an interchange type of intimate mechanism for the methanol substitution. The anticancer activity of compounds 1–7 was tested on HeLa cells and it was found that all compounds showed similar cytotoxicity where solubility allowed. IC50-values between ca. 11 and 22 mM indicate that some cytotoxicity resides most likely on the salicylidene–tryptamine ligand. The photoluminescence of the seven complexes is similar in maximum emission wavelength with little variation despite the broad range of ligands coordinated to the 6th position on the metal centre.
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    Unexpected XPS binding energy observations further highlighted by DFT calculations of ruthenocene-containing [Irᴵᴵᴵ(ppy)₂(RCOCHCORc)] Complexes: Cytotoxicity and Crystal Structure of [Ir(ppy)₂(FcCOCHCORc)]
    (MDPI, 2024) Buitendach, Blenerhassitt E.; Erasmus, Elizabeth; Fourie, Eleanor; Malan, Frederick P.; Conradie, Jeanet; Niemantsverdriet, J. W. (Hans); Swarts, Jannie C.
    The series of iridium(III) complexes, [Ir(ppy)₂(RCOCHCOR′)], with R = CH₃ and R′ = CH₃ (1), Rc (2), and Fc (3), as well as R = Rc and R′ = Rc (4) or Fc (5), and R = R′ = Fc (6), ppy = 2-phenylpyridinyl, Fc = Feᴵᴵ(η⁵–C₅H₄)(η⁵–C₅H₅), and Rc = Ruᴵᴵ(η⁵–C₅H₄)(η⁵–C₅H₅), has been investigated by singlecrystal X-ray crystallography and X-ray photoelectron spectroscopy (XPS) supplemented by DFT calculations. Here, in the range of 3.74 ≤ ΣχR ≤ 4.68, for Ir 4f, Ru 3d and 3p and N 1s orbitals, binding energies unexpectedly decreased with increasing ΣχR (ΣχR = the sum of Gordy group electronegativities of the R groups on β-diketonato ligands = a measure of electron density on atoms), while in Fe 2p orbitals, XPS binding energy, as expected, increased with increasing ΣχR. Which trend direction prevails is a function of main quantum level, n = 1, 2, 3. . ., sub-quantum level (s, p, d, and f), initial state energies, and final state relaxation energies, and it may differ from compound series to compound series. Relations between DFT-calculated orbital energies and ΣχR followed opposite trend directions than binding energy/ΣχR trends. X-ray-induced decomposition of compounds was observed. The results confirmed good communication between molecular fragments. Lower binding energies of both the Ir 4f₇/₂ and N 1s photoelectron lines are associated with shorter Ir-N bond lengths. Cytotoxic tests showed that 1 (IC₅₀ = 25.1 μM) and 3 (IC₅₀ = 37.8 μM) are less cytotoxic against HeLa cells than cisplatin (IC₅₀ = 1.1 μM), but more cytotoxic than the free β-diketone FcCOCH₂COCH₃(IC₅₀ = 66.6 μM).