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

Abstract

AbstractOver the years, phosphate ester hydrolysis catalyzed 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 the hydrolysis of this compound hydrolysis. Herein, we report preparing and characterizing three mononuclear iron(III) complexes (1, 2, and 3) and their hydrolase‐like activity. Complexes 2 and 3 have benzimidazole (BIMZ) moieties and were strategically designed to separate the BIMZ moiety from the first coordination sphere, and complex 1 (without BIMZ) 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, thus showing higher catalytic rates (kcat). Moreover, a longer carbon chain led to a higher hydrolysis rate but less interaction with substrate. These findings provide background for further investigations and the development of efficient catalysts for agrochemical degradation.