Nonlinear optical material of a low-dimensional coordination polymer: Synthesis, structure, NLO and fluorescence properties

Employing unsymmetrical 2-mercapto-5-methyl-1,3,4-thiadiazole and 2,2??-bipyridine as mixed ligands, a new low-dimensional coordination polymer Zn(MMTA)₂(2,2??-bipy)]n (MMTA = 2-mercapto-5-methyl-1,3,4-thiadiazole, 2,2??-bipy = 2,2??-bipyridine), as been synthesized under solvothermal condition and characterized by single crystal X-ray diffraction. This compound crystallizes in the noncentrosymmetric space group C _c, with cell parameters: a = 8.291(4) ?, b = 15.483(9) ?, c = 15.620(6) ?, ?? = 96.00(5)°, V = 1994.1(2) ?³, and Z = 4. The mixed ligands link the zinc center into a mononuclear unit, which is futher linked by weak C-H??N and C-H??S hydrogen bonds into a three-dimensional noncentrosymmetric framework. The compound exhibits intense photoluminescence and distinct NLO properties at room temperature. The intensity of the green light produced by the powder sample of the compound is about 3.2 times that produced by KDP powder. On the basis of the results of TG analysis, the structure is thermally stable up to ??260 °C.