Photolysis of Zn(8-quinolinolate)2(H2O)2 in non-aqueous solution. Photoactivation of hydrolysis

The octahedral complex Zn(8-quinolinolate)2(H2O)2 in non-aqueous solvents (e.g. chloroform, cyclohexane) undergoes a photolysis: Zn(8-quinolinolate)2(H2O)2 → Zn(OH)2 + 2 8-quinolinole. It is suggested that this photohydrolysis is facilitated by hydrogen bonding. The irradiation (λ > 340 nm) is absorbed by the ligand chromophore. The IL excitation is associated with a charge shift from the coordinated phenolate to the nitrogen of the pyridine ring. As a consequence, the phenolate loses its coordinating ability. The subsequent deactivation is accompanied by the reversal of the charge shift. The regenerated phenolate may now undergo protonation from an adjacent water ligand in competition with the re-coordination to Zn2 +. This system represents a simple model for activation of water which is coordinated to zinc(II). In distinction to the enzymatic function the hydrolysis in our system is initiated by a light switch.