Phosphate Triester Hydrolysis by Mononuclear Iron(III) Complexes: The Role of Benzimidazole in the Second Coordination Sphere

Abstract

Over the years, phosphate ester hydrolysis promoted by coordination compounds has attracted extensive research on developing new bioinspired compounds. However, the literature lacks sufficient examples displaying activity toward phosphate triesters specifically, limiting the understanding of efficient strategies for its hydrolysis. Herein, we report the preparation and characterization of three mononuclear iron(III) complexes (1, 2, and 3) and their hydrolase‐like activity. Complexes 2 and 3 contained benzimidazole (BIMZ) moieties and were strategically designed to separate the BIMZ moiety from the first coordination sphere, and complex 1 was used as a reference. Several techniques provided structural information, including spectrophotometry, spectrometry, electrochemistry, elemental analysis, and 57Fe Mossbauer. Density functional theory (DFT) revealed distorted octahedral geometries due to the presence of the BIMZ groups. These groups also directly affected the protonation equilibria and catalytic activity. The phosphate triester diethyl‐2,4‐dinitrophenylphosphate (DEDNPP) hydrolysis was enhanced at least 27 times compared to the uncatalyzed reaction, with complexes 2 and 3, containing the BIMZ moiety showing higher catalytic rates (kcat). Moreover, a longer carbon chain led to a higher hydrolysis rate but less interaction with substrate. These findings provide a foundation for further investigations and developing into efficient catalysts for agrochemical degradation.