# DFT‐Guided Synthesis, Electrochemical, and Photophysical Properties of Ruthenium(II) Polypyridyl Complexes Featuring Flavin‐Inspired π‐Extended Ligands

## TL;DR

This paper explores new ruthenium complexes with extended ligands for efficient light-driven electron storage, combining theory and experiments.

## Contribution

The study introduces new Ru(II) complexes with flavin-inspired ligands and validates their multielectron storage potential through DFT and experiments.

## Key findings

- Ru-Me2alloxB and Ru-Me2deazaalloxB showed promising electrochemical and photophysical properties.
- Theoretical predictions matched experimental results for Ru-Me2alloxB's behavior.
- Singly reduced complexes revealed insights into electronic distribution via EPR and spectroscopy.

## Abstract

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 synthesis. Two complexes, Ru‐Me2alloxB
and Ru‐Me2deazaalloxB
, 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‐Me2alloxB
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 underline the promising multielectron storage capacity of the newly designed π‐extended alloxazine ligand.

The photophysical properties as well as the multielectron storage capacity of a several ruthenium(II) polypyridyl complexes with flavin‐inspired π‐extended ligands are investigated in a joint synthetic‐spectroscopic‐theoretical approach.