Catalytic isomerizations of double bonds typically occur through chemical modification of the bond, such as the reversible addition of a metal hydride. By contrast, peptidylprolyl isomerases (PPIases) catalyze the cis/trans isomerization of proline residues in proteins through stabilization of the twist amide transition state, with no chemical modification to the isomerized bond. Although the catalytic isomerization of C=C double bonds is prevalent in the literature, the catalytic isomerization of N=N double bonds is significantly less studied. Here, we report the catalytic isomerization of Z-azoarenes by a dinuclear nickel catalyst through stabilization of the N=N torsional transition state using a flexible Ni-Ni active site. High-performance azoarenes with highly Z-enriched photostationary states (PSS) and long thermal half-lives are shown to readily isomerize at low catalyst loadings. The mechanism of the catalyst-induced bond rotation is probed through analysis of crystalized azoarene complexes, reaction kinetics, molecular orbital interactions, and DFT models.

Transition metal catalyzed N=N bond rotation

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