For decades, employing cyclic voltammetry for mechanistic investigation has demanded manual inspection of voltammograms. Here, we report a deep-learning-based algorithm that automatically analyzes cyclic voltammograms and designates a probable electrochemical mechanism among five of the most common ones in homogeneous molecular electrochemistry. The reported algorithm will aid researchers’ mechanistic analyses, utilize otherwise elusive features in voltammograms, and experimentally observe the gradual mechanism transitions encountered in electrochemistry. An automated voltammogram analysis will aid the analysis of complex electrochemical systems and promise autonomous high-throughput research in electrochemistry with minimal human interference.

We show that reduced rhenium bipyridyl carbonyl complexes are stable and selective catalysts for deoxygenation of nitrous oxide (N 2 O) in organic media in the presence of water. Mechanistic studies indicate that the Re complex is initially reduced to produce the activated species. Then N 2 O binds to labile position at the reduced metal and the resulting adduct is further reduced to trigger N-O bond breaking and release of N 2 . Proton donors are beneficial to enhance the catalytic rate and to reduce the energy required to generate potential limiting intermediate. These results open directions for N-O bond activation.

Homogeneous electrochemical catalysis of N2O reduction to N2 is investigated with a series of organic catalysts and rhenium and manganese bipyridyl carbonyl complexes. An activation-driving force correlation is revealed with...

Molecular catalysis of electrochemical reactions involving transition-metal complexes as catalysts requires getting a free metal coordination site to bind the substrate. It implies that the generation of a strong coordinating ligand as a product or coproduct of the reaction might be detrimental for an efficient catalysis because it can bind the metal center and block or slow down the catalytic process. This self-modulation phenomenon is revealed and illustrated via a thorough spectro-electrochemical investigation of the mechanism of the electrochemical reduction of nitrous oxide with rhenium bipyridyl triscarbonyl complexes [Re(bpy)(CO) 3 X] n+ (X = CH 3 CN, Cl − , n = 0 or 1) as a catalyst. We show that the bi-reduced [Re 0 (bpy •− )(CO) 3 ] − , electrogenerated from [Re(bpy)-(CO) 3 X] n+ , readily reacts with N 2 O and produces the hydroxo complex [Re I (bpy)(CO) 3 (OH)]. Because hydroxide, a product of the reaction, is a stronger coordinating ligand than acetonitrile or chloride, catalysis does not occur significantly at a potential where [Re 0 (bpy •− )(CO) 3 ] − is generated from [Re(bpy)(CO) 3 X] n+ . Substantial catalysis is only triggered at a potential corresponding to the second reduction of [Re I (bpy)(CO) 3 (OH)]. Nonetheless, we show that a slower innersphere reduction of N 2 O by the monoreduced [Re I (bpy •− )(CO) 3 X] (n−1)+ (X = CH 3 CN, Cl − ) occurs due to the lability of acetonitrile and chloride in these species. Because hydroxide is less labile and cannot be displaced to create an open coordination position for N 2 O, only an even slower outersphere reduction of N 2 O by the mono-reduced [Re I (bpy •− )(CO) 3 (OH)] − takes place. However, we finally show that an excess of free chlorides is able to displace hydroxide and then open the way for a faster innersphere process. This remarkable example emphasizes the critical role of ligand exchange in modulating molecular catalysis of electrochemical reactions with transition-metal complexes as catalysts, a likely general phenomenon.

In the context of molecular catalysis of electrochemical reactions, the competition between reduction of the substrate and deactivation of the catalyst by a cosubstrate is investigated. It is a frequent situation because proton donors are ubiquitous cosubstrates in reductive electrochemical reactions and molecular catalysts, either transition metal complexes or organic aromatic molecules, and are often prone to electrohydrogenation. We provide a formal kinetic analysis in the framework of cyclic voltammetry, and we show that the response is governed by two parameters and that the competition does not depend on the scan rate. From this analysis a methodology is proposed to analyze such systems and then illustrated via the study of N2O to N2 electroreduction catalyzed by 4‐cyanopyridine in acetonitrile electrolyte with water as proton donor. Incidentally, new insights into the mechanism of 4‐cyanopyridine radical anion protonation are revealed.