Metalloenzyme active sites provide great inspiration for the design of new types of catalysts for the activation and selective conversion of inert substrate molecules. In this lecture I will first give a brief overview of various facets of my group's fundamental research that addresses key small molecule transformations relevant to sustainable energy schemes (see Scheme). This often follows a bioinspired approach using complexes of earth abundant metals, it mostly requires the orchestration of proton-coupled electron transfer (PCET) steps, and it includes photo- and electrocatalytic scenarios.
In one of our priority lines of research we have exploited the use of compartmental pyrazolate-based ligand scaffolds for preorganizing two metal ions at tunable distances to enable metal-metal cooperativity, to enforce constrained substrate binding modes, and to emulate bioinorganic reactivity and isolate key intermediates. The focus of this lecture will be on such systems that use H2 release from dinuclear nickel hydride complexes to provide the required reducing equivalents for the binding and subsequent transformation of ubiquitous molecules such as O2, H2O, NO, or N2. The pyrazolate-based dinickel platform also allows for the stabilization of unusual radical species such as N2∙− or S∙− within the bimetallic pocket and the study of their PCET reactivity. Spectroscopic and kinetic investigations as well as DFT calculations for these systems are revealing electronic structure contributions to reactivity, and are providing important mechanistic insight.