Endogenous Arene Hydroxylation Promoted by Copper(I) Cluster Helicates

A novel neutral triple-stranded hexanuclear copper(I) cluster helicate [CuI 6L3]·2CH3CN derived from a thiosemicarbazone ligand could be synthesized and crystallographically characterized. The MALDI mass spectrum of this complex suggests that the tetranuclear copper(I) cluster helicate [CuI 4L2] is also present in solution. These copper(I) cluster helicates are capable, in the presence of O2, of hydroxylating the arene linker of their supporting ligand strands. The resulting dinuclear complex [CuII 2L’(OH)] is formed by two copper(II) centers, a new ligand arising from the hydroxylation reaction, and one hydroxide group. The magnetic investigation of this compound shows a strong antiferromagnetic coupling between the two CuII centers. The kinetic studies for the hydroxylation process show values of DH=70 kJmol1, similar to those mediated by the tyrosinase enzymes.