Temperature-dependent Time-resolved Fluorescence Study of Cinchonine Alkaloid Dication

Photo induced excited state dynamical processes of cinchonine alkaloid dication (C⁺⁺) have been studied over a wide range of temperature using steady state and nanosecond time-resolved fluorescence spectroscopic techniques. The temperature-dependent fluorescence studies of C⁺⁺ clearly indicate the existence of two distinct emitting species having their own characteristic decay rates. The shorter-lived species shows a usual temperature dependence with increasing non-radiative deactivation at higher temperatures, while the longer-lived species show features resembling to the excited state solvent relaxation process with a large solvent relaxation time (τ _r ∼ 6 ns). The species emitting in the lower energy side, having longer decay time is found to be more sensitive towards chloride ion quenching and has a charge transfer character. Further, concentration quenching with decrease in τ _r of long lived species shows the possibility of energy migration along with solvent relaxation in C⁺⁺.