Dinucleating N‐donor Ligands with 1,2‐Diethynylbenzene Backbone for the Copper‐Mediated Monooxygenation of Phenols

Abstract

AbstractNew dinucleating, tweezer‐like ligands with 1,2‐diethynyl‐benzene backbone containing three pyridines (Tw1), a combination of pyridine and pyrazole (Tw2) or pyridine and triazole (Tw3), respectively, have been synthesized and characterized spectroscopically and by single crystal structure determination. The ability of the derived copper(I) complexes CuTw1–3 to act as model systems for tyrosinase (Ty) was investigated by studying the reactivity toward monophenolic substrates. No dioxygen intermediate was detected at low temperatures, and CuTw1 was found to be inactive toward monoxygenation of phenolic substrate DTBP‐H. However, a crystal structure containing a μ‐hydroxo ligand, similar to the met‐form of Ty, underlines the ability of the complex to bind oxygen. In contrast, CuTw2 converts phenols to o‐quinones with moderate yield and this activity is even higher when using CuTw3. The observed differences in reactivity are discussed.