PNNL

Abstract

Ru-complexes are widely studied because of their use in biological applications and technologies, such as photocatalysis and solar energy conversion. In this work, we reveal novel insights into the chemical bonding of a series of Ru(II)- and Ru(III)-complexes by leveraging recent advances in high-energy-resolution tender x-ray spectroscopy and the- oretical calculations. We perform Ru 2p4d resonant inelastic x-ray scattering (RIXS) to probe the valence excitations in dilute solvated Ru-complexes. Combining these experiments with a theoretical approach based on time-dependent density functional theory, we assign the spectral features and quantify the metal-ligand bonding interac- tions. The valence-to-core RIXS features uniquely identify the metal-centered, ligand- centered, and charge transfer states and allow extracting the ligand-field splitting for all the complexes. The combined experimental and theoretical approach described here is shown to reliably characterize the ground and excited valence states of Ru complexes, and serve as a basis for future investigations of ruthenium, or other 4d metals active sites, in biological and chemical applications. Project acknowledged by PNNL authors: KC-030105172685 (D.R.N., N.G.)