Investigation on photophysical and photochemical properties of Ir and Ru complexes featuring sulfurated pyridine-1,2,3-triazole based ligands

In this study, we developed novel pyridine-triazole hybrid ligand scaffolds using the copper-catalyzed azide-alkyne cycloaddition (CuAAC) approach, followed by the incorporation of methylthio functionalization. These ligands were then employed to synthesize ruthenium(II) and iridium(III) complexes, which were comprehensively characterized by NMR spectroscopy, optical spectroscopy, electrochemistry, and single-crystal X-ray diffraction (sXRD). The introduction of a methylthio group in the triazole backbone led to significant anodic shifts in the reduction potentials of the ancillary ligands, attributed to LUMO + 2 stabilization as confirmed by DFT calculations. Ruthenium complexes demonstrated photochemical reactivity, with a low-lying ³MC (metal-centered) state facilitating thermally accessible non-radiative deactivation via photo-induced ligand release, indicating their potential for photoactivated chemotherapy. In contrast, the iridium complexes exhibited structured emission bands, with triplet excited states localized on the ³LC state and long luminescence lifetimes (∼1.5 μs), making them promising candidates as phosphors for advanced light-emitting devices. Notably, the dual methylthio groups offer further versatility, including potential for disulfide bond formation under reductive conditions and surface anchoring applications, underscoring the multifunctionality and broad applicability of this ligand design.