Tyrosinase is an oxygen‐activating enzyme and thus, functional model complexes are of high interest. The most prominent model complexes, the bis(µ‐oxido) as well as the µ‐η 2 :η 2 ‐peroxido dicopper species, show catalytic activity toward phenolic substrates. Herein, we present a kinetic and mechanistic study of the electron transfer reaction of reducing agents with two bis(µ‐oxido) dicopper complexes. As ligands, the bis(guanidine) 2‐(2‐(((bis(dimethylamino)methylene)‐amino)methyl)‐phenyl)‐1,1,3,3‐tetramethylguanidine (TMG 2 tol) and the hybrid guanidine 2‐(3‐(dimethylamino)propyl)‐1,1,3,3‐tetramethylguanidine (TMGdmap) were chosen since previous studies showed that the dicopper species with these ligands are relatively stable at −80°C and at the same time have a fast formation. We determine full kinetic and thermodynamic parameters of the electron transfer reaction. With the help of spectroscopic kinetic analysis, we show that the electron transfer step is a reaction containing two independent steps. Moreover, density functional theory studies reveal the intriguing electronic structure of the reduced Cu 2 O 2 complexes. This study highlights the ability of Cu 2 O 2 species to cope with reducing equivalents.
Schmidt et al. (Mon,) studied this question.