Photoresponsive Nitric Oxide Release from Aggregation-Induced Emission-Based Ruthenium–Nitrosyl Complexes and Their Anticancer Activity through In Situ Formation of Peroxynitrite

Nitric oxide (NO) is recognized as a gaseous chemical mediator that regulates various physiological functions. Two naphthalene-appended terpyridine-based mononuclear ruthenium–nitrosyl complexes with the molecular framework [1.Ru2+(L)NO](PF6)3 (L = 2,2′-bipyridine (bpy) or phenanthroline (phen) and 1 = 4′-(anthracene-9-yl)-2,2′:6′,2″-terpyridine), named 1.Ru(bpy)NO and 1.Ru(phen)NO, were reported for NO delivery. The introduction of ancillary ligands (bpy and phen) to the Ru-center led to the noticeable variations of photophysical properties and aggregation behavior in aqueous solution, which helps to modulate the NO release. Both the complexes facilitate the photocleavage of the Ru–NO bond on exposure to either blue (410 nm) or green light (525 nm) in CH3CN and CH3CN-H2O (20/80, v/v) mixture. The photo release kinetics of 1.Ru(bpy)NO and 1.Ru(phen)NO have been studied in detail and confirmed by IR studies, the Griess assay, and the DAF assay. The interaction of photoinduced NO and singlet oxygen (1O2) and thereby formation of peroxynitrite (ONOO–) were confirmed by the emission assay. The cytotoxicity MTT assay of these complexes with human neuroblastoma cancerous cells with or without green light irradiation was also investigated. Notably, the in situ formation of ONOO– on cells produces potent anticancer effects that originated from NO and 1O2 in an aqueous solution.