Enhancing the photophysical properties of Ru(II) complexes by specific design of tridentate ligands

Artificial photosynthetic systems can collect and transform solar energy into chemical energy. Inspired by natural photosynthesis, molecular artificial systems are commonly composed of a light harvesting complex or photosensitizer (PS) and a reaction center or catalyst. Ru(II) tris-2,2'-bipyridine [Ru(bpy)(3)](2+) and its analogues are widely studied for the application as PS in both photocatalytic water oxidation and reduction. However, this class of compounds lacks stereo specificity. The use of ligands with tridentate 2,2':6',2-terpyridine (tpy) metal ion receptors on the other hand leads to achiral complexes and allows for linear polynuclear structures. However, these [Ru(tpy)(2)](2+) complexes generally exhibit poor photophysical properties, which makes them unattractive for the use as PS. Nevertheless, by introducing different substituents, other N-heterocycles, or employing polynuclear designs, the photophysical and electrochemical properties of these tridentate metal ion receptors can be modified to make them more attractive in artificial photosynthesis. In this review, we discuss different strategies currently used to tune the photophysical and electrochemical properties of Ru(II) polypyridine type complexes of tridentate ligands. (C) 2021 Published by Elsevier B.V.

Automated summary

Artificial photosynthetic systems use molecular complexes to convert solar energy into chemical energy, but improving the photophysical and electrochemical properties of these complexes is crucial for their efficiency and effectiveness in photocatalytic reactions.