Photoactivated artificial metalloesterases

A photoactivated metalloesterase has been developed. The alcohol is masked as an ester that is covalently attached to either a bi- or tridentate ligand. Yields of alcohol of up to 86% are achieved upon photolysis at λ > 350 nm. The masked alcohol undergoes cis–trans photoisomerization that brings the ester carboxyl into proximity with a Lewis-acidic metal ion. The metal ion catalyzes the hydrolysis of the ester bond, resulting in release of an alcohol and a coordinated carboxylate. The presence of a metal cation is sufficient to drive the cis–trans photostationary state completely to the cis (coordinating) isomer, in contrast to the 1:1 cis:trans ratio formed at the photostationary state in the absence of metal. The photorelease of the alcohol is most efficient when only one ligand is bound to the metal. The synthesis, characterization and photochemistry of the ligands are described and the implications of metal–ligand equilibria on the reaction is discussed.