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.