Work

Photophysical and Biological Properties of Diprotic Ruthenium(II) Complexes with Extended π-Systems

Year: 2026

Type: article

Abstract: Ruthenium(II) polypyridyl complexes can be harnessed for photodynamic therapy. In this work, diprotic ligands which can be deprotonated to change the metal complexes from dicationic to neutral are combined with extended π systems for light absorption at longer wavelengths. Herein, the diprotic ligands are 4,4′-dhbp = 4,4′-dihydroxybipyridine or 4,7-dhphen = 4,7-dihydroxy-1,10-phenanthroline and the π-expanded ligands are bphen = bathophenanthroline, dppz = dipyrido[3,2- a:2′,3′- c ]phenazine, and dppn = benzodipyrido[3,2- a:2′,3′- c ]phenazine. This report describes the synthesis and characterization of [(bphen) 2 Ru(4,4′-dhbp)]Cl 2 ( 1 A ), [(dppz) 2 Ru(4,4′-dhbp)]Cl 2 ( 2 A ), [(dppn) 2 Ru(4,4′-dhbp)]Cl 2 ( 3 A ), [(bphen) 2 Ru(4,7-dhphen)]Cl 2 ( 4 A ), [(dppz) 2 Ru(4,7-dhphen)]Cl 2 ( 5 A ), and [(dppn) 2 Ru(4,7-dhphen)]Cl 2 ( 6 A ). Single crystal X-ray diffraction data are reported for 1 A, 2 A, and two known precursor compounds: [(η 6 - p -cymene)RuCl(diprotic ligand)]Cl ( P1, P2 where diprotic ligand = 4,4′-dhbp and 4,7-dhphen, respectively). Compounds 1 A – 6 A have been studied for their photocytotoxicity vs breast and melanoma cancer cells, lipophilic vs hydrophilic properties, thermodynamic acidities (p K a values), singlet oxygen quantum yields, and luminescence which is heavily influenced by the nature of the π expanded ligand. Four compounds (bearing bphen and dppn ligands) have promising photocytotoxicity including activity with green light and one compound has a phototherapeutic index (PI) as high as 145.

Source: Organometallics

DOI: 10.1021/acs.organomet.5c00305