Two-photon-excited fluorescence of zinc(Ⅱ),cadmium(Ⅱ) complexes containing phenothiazine ligand

Two new ligands, S-benzyl-β-N-10-ethylphenothiazine-3-methylene] dithiocarbazate (HL1), S-methyl-β-N-10-ethylphenothiazine-3-methylene] dithiocarbazate (HL2), and their complexes which exhibit intensive two-photon excited (TPE) fluorescence at 800 nm laser pulses in the femtosecond regime, are synthesized and fully characterized. The measured power dependence of the fluorescence signals provides a direct evidence for TPE. All of them exhibit a large two-photon absorptive crosssection. The two-photon-excited fluorescence spectra of them are compared and contrasted with the corresponding results obtained from the one-photon excitation. Emission peaks of the ligands and their complexes are observed mostly at the region 550-595 nm in the TPE fluorescence spectra.