Electronic spectroscopic study of complexation of a ketocyanine dye in the ground and excited state with lithium and magnesium ions

Electronic absorption and emission spectral characteristics of a ketocyanine dye have been studied in acetonitrile solution in presence of perchlorate salts of lithium and magnesium. Absorption spectral studies indicate complex formation between metal ions and the dye in the ground state. The value of equilibrium constant has been determined for the dye cation interaction. The energy of maximum fluorescence shifts towards red with the addition of perchlorate salts. Steady-state emission band of the dye in presence of salts can be expressed as a sum of two Gaussian bands. Studies point to the existence of two emitting species viz, the solvated and the complexed dye in equilibrium. The values of spectroscopic and thermodynamic parameters for the complexation process involving the S0 and S1 states of the dye have been determined and compared with those of the corresponding symmetric ketocyanine dye.