Axial Ligand Effects of Ru‐BDA Complexes in the O–O Bond Formation via the I2M Bimolecular Mechanism in Water Oxidation Catalysis

Abstract

A detailed computational investigation of the mechanistic aspects of the water oxidation catalysis (WOC) for ruthenium‐based catalysts [Ru(bda)(isoq)2] (H2bda = 2,2′‐bipyridine‐6,6′‐dicarboxylic acid; isoq = isoquinoline). Density functional theory (DFT) calculations describe the kinetics by means of the energy barrier that leads to the O–O coupling, the rate‐limiting step for WOC. To test the effect of the axial ligand environment, we investigated bda complexes with para‐substituted isoquinolines, phthalazines and pyridines. Since previous screening analyses of the potential energy surface revealed a face to face orientation of metal‐oxo species to be best for facilitating the O–O bond formation, this paper probes the deeper role of the axial ligands that saturate the Ru(bda) based complexes from a computational point of view.

Phenoxylation of Alkynes through Mono‐ and Dual Activation Using Group 11 (Cu, Ag, Au) Catalysts

“…NCI plots computed by the NCIPLOT package, confirmed the significant additional non‐covalent interactions due to the aromatic rings of the IPr* ligand, whereas only the ones between the phenoxide and one of the aryl rings on the diphenylacetylene for the IMe based system (see Figure ). The plot for the IPr ligand is placed in between, and it confirms the effect of the substitution of phenyl by methyl groups, with much less favourable π‐π staking interactions . Thus, NCI plots and EDA analyses here unveil why the sterically more hindered IPr* ligand ends up showing less unfavourable kinetics and thermodynamics than expected for the C–O bond formation.…”

“…The plot for the IPr ligand is placed in between, and it confirms the effect of the substitution of phenyl by methyl groups, with much less favourable π-π staking interactions. [60][61][62][63][64] Thus, NCI plots and EDA analyses here unveil why the sterically more hindered IPr* ligand ends up showing less unfavourable kinetics and thermodynamics than expected for the C-O bond formation.…”

Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation

“…[10][11][12][13] Among those, ruthenium-based catalysts 12,13 particularly Ru(bda) WOCs (bda: 2,2 0 -bipyridine-6,6 0 -dicarboxylic acid) 14,15 have attracted much attention as some of these catalysts exhibit activities comparable to those of the oxygen-evolving complex of photosystem II. 16,17 During the last decade, some insightful studies have been performed on the effect of substituents at axial [18][19][20][21][22][23][24][25] and equatorial [26][27][28] ligands on the catalytic performance of monomeric Ru(bda) WOCs. Hereby, uncomplicated manipulations of the axial ligands have enabled the synthesis of a plethora of catalysts within the family of mononuclear Ru(bda) WOCs.…”

Structural Effects on Dioxygen Evolution from Ru(V)−Oxo Complexes

“…[16] Poater and coworkers have shown from DFT studies that auxiliary ligand substituents also affect the OÀ O coupling kinetics and thermodynamics via the I2M pathway. [24] Entropic effects related to the effective collisions of RuÀ oxo complexes can also have a significant impact on the energetics of the I2M coupling step. [25] Outside of RuÀ oxo coupling, little attention has been given to characterizing the post-coupling OER intermediates, e. g. dioxygen complexes, and the factors influencing the energetics of their interconversion.…”