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Ligand Noninnocence in Iron Corroles: Insights from Optical and X‐ray Absorption Spectroscopies and Electrochemical Redox Potentials
Author(s) -
Ganguly Sumit,
Giles Logan J.,
Thomas Kolle E.,
Sarangi Ritimukta,
Ghosh Abhik
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201702621
Subject(s) - corrole , chemistry , ligand (biochemistry) , xanes , substituent , absorption (acoustics) , crystallography , electrochemistry , redox , spectrochemical series , spectroscopy , stereochemistry , photochemistry , inorganic chemistry , ligand field theory , materials science , ion , organic chemistry , physics , biochemistry , receptor , electrode , quantum mechanics , composite material
Two new series of iron meso ‐tris( para ‐X‐phenyl)corrole (T p XPC) complexes, Fe[T p XPC]Ph and Fe[T p XPC]Tol, in which X=CF 3 , H, Me, and OMe, and Tol= p ‐methylphenyl ( p ‐tolyl), have been synthesized, allowing a multitechnique electronic–structural comparison with the corresponding FeCl, FeNO, and Fe 2 ( μ ‐O) T p XPC derivatives. Optical spectroscopy revealed that the Soret maxima of the FePh and FeTol series are insensitive to the phenyl para substituent, consistent with the presumed innocence of the corrole ligand in these compounds. Accordingly, we may be increasingly confident in the ability of the substituent effect criterion to serve as a probe of corrole noninnocence. Furthermore, four complexes—Fe[TPC]Cl, Fe[TPC](NO), {Fe[TPC]} 2 O, and Fe[TPC]Ph—were selected for a detailed XANES investigation of the question of ligand noninnocence. The intensity‐weighted average energy (IWAE) positions were found to exhibit rather modest variations (0.8 eV over the series of corroles). The integrated Fe‐K pre‐edge intensities, on the other hand, vary considerably, with a 2.5 fold increase for Fe[TPC]Ph relative to Fe[TPC]Cl and Fe[TPC](NO). Given the approximately C 4 v local symmetry of the Fe in all the complexes, the large increase in intensity for Fe[TPC]Ph may be attributed to a higher number of 3d holes, consistent with an expected Fe IV ‐like description, in contrast to Fe[TPC]Cl and Fe[TPC](NO), in which the Fe is thought to be Fe III ‐like. These results afford strong validation of XANES as a probe of ligand noninnocence in metallocorroles. Electrochemical redox potentials, on the other hand, were found not to afford a simple probe of ligand noninnocence in Fe corroles.