DFT-Guided Synthesis, Electrochemical, and PhotophysicalProperties of Ruthenium(II) Polypyridyl Complexes FeaturingFlavin-Inspired π-Extended Ligands

Light-driven electron transfer and subsequent multielectron storage is among the key aspects of photochemical reactions in artificial photosynthesis and molecular electronics. Following our previously introduced design and characterization of Ru(II)-based photosensitizers, four new Ru complexes with π-extended ligands featuring a flavin-inspired subunit were investigated via density functional theory in order to evaluate their electrochemical properties ahead of a time and resource-demanding syn-thesis. Two complexes, Ru-Me2 alloxB and Ru-Me2 deazaalloxB, with a bent ligand architecture, were identified as promising candidates for application in light-driven charge accumulation and subsequently synthesized. The electrochemical characterization of Ru-Me2 alloxB confirmed the theoretical predictions and its photophysical properties were investigated using UV/Vis absorption, resonance Raman, time-resolved emission, and time-resolved absorption spectroscopy in combination with quantum chemical simulations. Furthermore, first insights into the electronic distribution in the singly reduced complex were modelled computationally and obtained by EPR and UV/Vis absorption spectroscopy and spectroelectrochemistry. These results under-line the promising multielectron storage capacity of the newly designed π-extended alloxazine ligand.