Mononuclear iron(III) complexes derived from tridentate ligands containing non‐innocent phenolato donors: Self‐activated nuclease, protease, and phenoxazinone synthase activity studies

Abstract

The tridentate ligands HPhimpH, OCH3PhimpH, CH3PhimpH, tBuPhimpH, and NO2PhimpH have been synthesized and characterized. These tridentate ligands having non‐innocent phenolato function, Npy and Nim donors upon deprotonation bind to iron(III) center resulting in a series of novel iron complexes, namely, [Fe(HPhimp)2](ClO4) (1), [Fe(OCH3Phimp)2](ClO4) (2), [Fe(CH3Phimp)2](ClO4) (3), [Fe(tBuPhimp)2](ClO4) (4), and [Fe(NO2Phimp)2](ClO4) (5). Complexes were characterized by elemental analysis, IR, and UV–visible, and electrospray ionization mass spectral (ESI–MS) studies. Molecular structure of complex 2 was determined by single‐crystal X‐ray diffraction study. Electrochemical studies depicted Fe(III)/Fe(II) couple in the range of −0.50 to −0.65 V versus Ag/AgCl. Theoretical calculation using density functional theory (DFT) was also performed to optimize the geometrical and structural parameters. Time‐dependent DFT (TD‐DFT) was also optimized to observe the electronic properties, and data obtained were found to be consistent with experimentally observed values. Representative complex 4 exhibited nuclease and protease activities in the absence of external agents. Complex 4 was found to cleave the DNA and protein via self‐activated mechanism. Complexes 1–5 were utilized to optimize oxidation of o‐aminophenol in methanol. Complexes were found to be efficient in the oxidation of o‐aminophenol. Kinetic experiments were also explored to gain better insight into the oxidation process.