Influence of the solvent, structure and substituents of ruthenium(II) polypyridyl complexes on their electrochemical and photo-physical properties

• The pending group nature influences the physical–chemical behavior of the complexes.
• Photo-physical behavior was modulated through vibrational coupling with the solvent.
• An interaction with a water molecule was highlighted for the pip bent complex 6.

This work highlights the relative importance between structural issues, longer range interactions and solvent effects for a series of ruthenium compounds on their electrochemical and photochemical properties. To study these effects, eight complexes of general formula [Ru(bpy)2(L)]2+ have been synthesized and characterized, where L represents substituted phenyl-imidazophenanthrolines (pip), dipyridophenazines (dppz) and pyrazinophenanthrolines (pzp). This experimental work supported by an important theoretical investigation has pointed out that the electrochemical and the photo-physical behavior of these types of molecular systems depends mainly of the close environment around the photosensitizer. A relation between the ditopic ligand structure (aromatic central part and/or the distal substituents) and the absorption properties have been observed, along with the lower reduction potential of dipyridophenazine and pyrazinophenanthroline moieties. This study points out the influence of the nature of the distal substituents, as well as the significant impact of the solvent nature and the interaction with water molecules, on the photo-physical properties of these ruthenium compounds.

The relation structure–properties of a series of eight ruthenium complexes integrating ditopic polypyridyl ligands of three different families was studied using UV–Vis and 1H NMR spectra, DFT and TD-DFT calculations, and photo-physical and electrochemical measurements.Figure optionsDownload as PowerPoint slide