EPR, Resonance Raman, and DFT Calculations on Thiolate- and Imidazole-Bound Iron(III) Porphyrin Complexes: Role of the Axial Ligand in Tuning the Electronic Structure

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• 作者：Pradip Kumar Das ; Sudipta Chatterjee ; Subhra Samanta ; Abhishek Dey
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：October 15, 2012
• 年：2012
• 卷：51
• 期：20
• 页码：10704-10714
• 全文大小：664K
• 年卷期：v.51,no.20(October 15, 2012)
• ISSN：1520-510X

文摘

Iron(III) porphyrin complexes bearing covalently attached imidazole and thiolate axial ligands are investigated using resonance Raman, electron paramagnetic resonance, and cyclic voltammetry. The thiolate ligand stabilizes a low-spin ground state in solvent-bound six-coordinate species, weakens the Fe鈥揘_pyr bonds, and shifts the Fe^III/II potential more negative by 500 mV relative to an imidazole-bound species. Density functional theory calculations reproduce the experimental observation and indicate that the covalent charge donation from thiolate to iron reduces the Z_eff on the iron. This increases the Fe_3d orbital energies, which changes the bonding interaction present in these complexes significantly. In particular, the increase of the Fe_3d energies activates an iron-to-porphyrin 蟺*-back-bonding interaction not present in the imidazole-bound complex.