Synthesis, crystal structures and third-order nonlinear optical properties of 4-formylpyridine Schiff base of thiosemicarbazide, and its dinuclear copper(I) and silver(I) complexes

A novel thiosemicarbazide ligand L and its dinuclear complexes M2(dppm)2L(NO3)2 [where dppm = bis(diphenylphosphino)methane, M = Cu(I) (1), Ag(I) (2)] were designed, synthesized and characterized by 1H NMR spectroscopy, elemental analysis, IR, MALDI-TOF mass spectroscopy, and single crystal X-ray diffraction analysis. The third-order nonlinear optical (NLO) properties of the metal complexes were determined by the open/close aperture Z-scan technique. The results reveal that the complexes possess much larger third-order nonlinear susceptibility and two-photon absorption cross sections than that of its free ligand L in the near IR region, especially for complex 2. The photophysical properties of them were investigated and interpreted on the basis of theoretical calculations (TD-DFT).