Hydrophobic Interactions of Ru-bda-Type Catalysts for Promoting Water Oxidation Activity

Abstract

The catalytic activity of the bimolecular reaction was affected by many parameters. Although many efforts have been dedicated to investigate the influence of secondary interactions in pre-organizing catalysts, the hydrophobic effect on Ru-bda-type water oxidation catalysts remains unclear as a result of the lack of an ideal catalytic model. In this work, four catalysts 1–4 with variable hydrophobicity have been synthesized, and cerium­(IV)-driven water oxidation results showed that the hydrophobic complexes 3 and 4 outperformed the hydrophilic complex 2. Steric mapping, nuclear magnetic resonance, and differential pulse voltammogram studies indicated that the increase in activity has no correlation with electronic and steric effects but has correlation with hydrophobicity. Molecular dynamics have shown that the modifications of the hydrophobicity on the axial pyridine ligands of the Ru-bda type of catalysts can improve the water oxidation catalytic activity by stabilizing the pre-reactive catalyst dimer.

The impact of secondary coordination sphere engineering on water oxidation reactivity catalysed by molecular ruthenium complexes: a next-generation approach to develop advanced catalysts

“…23). 35 To study the hydrophobic effect exclusively, the axial ligand modifications in 19–20 were done judiciously so that the para -substituents did not create much electrostatic repulsions and steric hindrances, as well as avoiding π extensions. The crystal structure of 20 , as shown in Fig.…”

Ligands modification strategies for mononuclear water splitting catalysts

“…Complex 1a , complex 12 , and complex 13 WO catalysts are good examples of this phenomenon. The hydrophobic modification on ligands improves the WO catalytic activity of Ru-bda from 22 s −1 to 146 s −1 ( Liu et al, 2021 ). The octyl substituent in the carbene ligand of triazolylidene Cp*Ir-complexes induces the association of the iridium species, leading to a ∼10-fold increase of TOF (101 min −1 ) comparing with their methyl counterparts (TOF = 9.9 min −1 ), shown in Figure 5A ( Corbucci et al, 2015 ).…”

2021 Pioneers in Energy Research: Vivian Yam

“…A titanium−oxy single-atom site leads to the longest lived charge-separated (CS) species compared to cobalt and nickel in a similar arrangement, proving guidance in designing MOF-based catalytic systems for photocatalysis and solar fuel production. On the basis of results from experiments and molecular dynamics simulations, Sun and co-workers 39 have demonstrated a clear structure−activity relationship of the hydrophobic effect on Ru-bda-type water oxidation catalysts.…”