Computational, structural and electrochemical properties of metal (III) tris-betadiketonato complexes

[摘要] English: A series of MnIII(β-diketonato)3 complexes (β-diketonato = acac, ba, dbm, tfaa, tfth, tffu, tfba and hfac) were synthesized and characterized with the aid of mass spectroscopy, elemental analysis, X-ray diffraction (crystallography) and melting point measurements. The electrochemical study (cyclic voltammetry) showed that for MnIII(β-diketonato)3 complexes with more electron withdrawing R and R' groups on the β-diketonato ligands (RCOCHCOR')-, the redox potential of the [MnIII(β-diketonato)3] + e- [MnII(β-diketonato)3] redox reaction was found to shift to more positive potentials. The reduction potential of the the MnIII/MnII couple was correlated to electronic parameters (acid dissociation constant (pKa) of the uncoordinated b- diketones (RCOCH2COR'), the total group electronegativities [Σ(cR + cR')] and total Hammett sigma meta constant [Σ(σR + σR')] of the R and R' side groups of the b-diketonato ligands (RCOCHCOR') and the calculated electron affinity of Mn(β-diketonato)3 complexes. DFT computational studies were done on the Mn(acac)3 and Mn(dbm)3 complexeto understand the Jahn-Teller distortion that that MnIII(β-diketonato)3 complexes undergo. Electrochemical (cyclic voltammetry) studies were done on M(acac)3 complexes where M = V, Cr, Mn, Fe and Co. The reduction potential of the MIII/MII couple was correlated to electronic parameters such as the metal electronegativity (cPauling and cMulliken), calculated electron affinity and LUMO energy. DFT computational studies were done on the symmetry of V(acac)3 to investigate the Jahn-Teller distortion of the V(acac)3 complex. A DFT computational study was used to illustrate the d-orbital occupations of the M(acac)3 complexes ( M = V, Cr, Mn, Fe and Co).

[发布机构] University of the Free State