Design and characterization of novel pyridylbenzimidazole-based ruthenium(II) complexes, and their evaluation in singlet oxygen generation

Six new ruthenium(II) polypyridyl complexes incorporating pyridinyl, quinolinyl, or isoquinolinyl-benzimidazole ligands were synthesized to investigate the influence of π-conjugated mono- and bis-chelating ligands on their photophysical and electrochemical properties, and compared to the frontrunner [Ru(bpy)₃]2PF 6 . Their evaluation reveals that ligand π-extension modulates the ILCT and MLCT transitions, leading to red-shifted absorption and tunable excited-state redox potentials. The mononuclear complexes were further evaluated as visible-light photocatalysts through reactive oxygen species (ROS) generation and a model α-arylation reaction. These findings demonstrate that benzimidazole-based ligand engineering provides an effective strategy to tune the excited-state properties and photocatalytic behavior of ruthenium complexes.