Computational Mechanistic Insights on the NO Oxidation Reaction Catalyzed by Non-Heme Biomimetic Cr-N-Tetramethylated Cyclam Complexes

Superoxide to Peroxide Interconversion in Ni-TMC Complexes: The Significance of Structure and Spin States

A deeper comprehension of the characteristics of metal-superoxide and metal-peroxide chemical species is imperative, considering their pivotal functions in oxygen transport, enzymatic activation, and catalytic oxygenations. O2 activation is mediated by the interconversion of superoxide and peroxide species. Even though there are multiple studies on metal-superoxide and -peroxide intermediates, robust examples of their interconversion processes are scarce synthetically. For example, Ni-superoxide/peroxide complexes have been characterized with N-Tetramethylated Cyclam (TMC) ligands with different ring sizes, i.e., Nickel(II)-superoxide complex is characterized with 14-TMC while Nickel(III)-peroxide complex with 12-TMC. Later, both complexes were obtained with 13-TMC ligand by employing different bases; interestingly, no evidence of interconversion between them was identified. What are the factors influencing these processes and why is this preference? We attempt a computational analysis of this issue and provide arguments based on our conclusions. 2-dimensional potential energy scan is performed on the 12-TMC, 13-TMC, and 14-TMC systems to identify the reaction path connecting superoxide and peroxide species. Analyses indicate that structure and spin states play a significant role in determining the probability of interconversion. The superoxide-peroxide interconversion process appears to be bound by their propensity for distinct structural features and spin states.

Dehydrogenation of Formic Acid to CO2 and H2 by Manganese(I)–Complex: Theoretical Insights for Green and Sustainable Route

In this work, a detailed computational study on a recently synthetized Mn(I)-dependent complex [(tBuPNNOP)Mn(CO)2]+ is reported. This species promotes the dehydrogenation of formic acid to carbon dioxide and hydrogen. The here proposed catalytic cycle proceeds through the formation of stabilized adduct between [(tBuPNNOPtBu)Mn(CO)2]+ and formate and the progressive release of CO2 and H2, mediated by the presence of trimethylamine. In order to evaluate the influence of the environment on the catalytic activity, different solvents have been taken into account. The computed barriers and the geometrical parameters account well for the available experimental data, confirming the robustness of the complex and reproducing its good catalytic performance. Outcomes from the present investigation can stimulate further experimental works in the design of new more efficient catalysts devoted to H2 production.

The Generation of the Oxidant Agent of a Mononuclear Nonheme Fe(II) Biomimetic Complex by Oxidative Decarboxylation. A DFT Investigation

The oxidative decarboxylation of the iron(II) α-hydroxy acid (mandelic acid) complex model, biomimetic of Rieske dioxygenase, has been investigated at the density functional level. The explored mechanism sheds light on the role of the α-hydroxyl group on the dioxygen activation. The potential energy surfaces have been explored in different electronic spin states. The rate-determining step of the process is the proton transfer. The oxidative decarboxylation preferentially takes place on the quintet state.