[Pt(mesBIAN)(tda)]: A near-infrared emitter and singlet oxygen sensitizer

Abstract

The synthesis and subsequent photophysical investigation of [Pt(mesBIAN)(tda)], where mesBIAN is bis(mesitylimino)acenaphthene and tda is tolan-2,2′-diacetylide, reveal excited-state characteristics best described as triplet charge transfer (³CT) in nature upon visible light excitation. Large ground-state dipole moments are apparent as the absorption spectrum dramatically red-shifts with decreasing solvent polarity. The ³CT excited state is significantly lower in energy than the ligand-centered ³tda excited-state, as confirmed by steady-state and time-resolved techniques. Singlet oxygen sensitization studies demonstrate that ¹O₂ production occurs by diffusive quenching from the photo-excited ³CT state (Φ_Δ = 0.24, λ_max∼1270 nm) in oxygen-saturated dichloromethane.