One- and two-photon excited dual fluorescence properties of zinc(II) and cadmium(II) complexes containing 4-dipropylaminobenzaldehyde thiosemicarbazone

A new ligand, 4-dipropylaminobenzaldehyde thiosemicarbazone (HL) and its complexes (ZnL2, CdL2), which exhibit intense two-photon excited (TPE) dual fluorescence using 800 nm laser pulses in the femtosecond regime, were synthesized and fully characterized. The measured power dependence of the fluorescence signals provides direct evidence for TPE. The two-photon excited dual fluorescence spectra were compared and contrasted with the corresponding results obtained from one-photon excitation. Emission peaks of the ligand and its complexes were assigned with the aid of PM3 calculations.