Endogenous Arene Hydroxylation Promoted by Copper(I) Cluster Helicates

A novel neutral triple-stranded hexanuclear copper(I) cluster helicate [(Cu6L3)-L-I]center dot 2CH(3)CN derived from a thiosemicarbazone ligand could be synthesized and crystallographically characterized. The MALDI mass spectrum of this complex suggests that the tetra-nuclear copper(I) cluster helicate [(Cu4L2)-L-I] is also present in solution. These copper(I) cluster helicates are capable, in the presence of O-2, of hydroxylating the arene linker of their supporting ligand strands. The resulting dinuclear complex [(Cu2L)-L-II'(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 Cu-II centers. The kinetic studies for the hydroxylation process show values of Delta H not equal=-70 kJ mol(-1), similar to those mediated by the tyrosinase enzymes.