An artificial enzyme of a polyoxometalate-supported cobalt complex for the oxidation of isochromans to isochromanones by activating O2

Abstract

The simulation of the coordination geometry and environment of the active metal center in metalloenzymes is highly valuable for activating O₂ to oxidize inexpensive bulk chemicals into high-value-added fine chemicals. In this study, we have selected the inorganic ligand phosphovanadomolybdate (PMoV) and the auxiliary ligand N-butylimidazole (bIM), which possess a long flexible alkyl chain, to jointly stabilize two types of triangular bipyramidal cobalt-based enzymatic complexes (PMoV-Co). The synthesis of PMoV-Co on a decagram scale is rare among coordination polymers based on polyoxometalates. The utilization of three distinct types of potential catalytic centers together facilitates the catalyst to activate O₂ for the subsequent oxidation reactions, converting isochromans into isochromanones. Catalytic results reveal that, under mild reaction conditions without any additives, the isolated yield of the target product isochromanones reaches 88%. Moreover, the catalyst has good substrate universality and cycling stability.