Design, crystal growth, characterization, and second-order nonlinear optical properties of two new three-dimensional coordination polymers containing selenocyanate ligands

Two new second-order nonlinear optical coordination polymers, zinc cadmium tetraselenocyanate ([ZnCd(SeCN)(4)](n), 1) and cadmium mercury tetraselenocyanate ([CdHg(SeCN)(4)](n), 2), have been synthesized by reactions of self-assembly. Their structural, optical, and physicochemical properties were characterized by X-ray diffraction, infrared and Raman spectroscopy, electronic spectra, and thermal analyses. Structure analyses reveal that they belong to the tetragonal system M space group. The cell dimensions for 1: a = 11.3420(l), b = 11.3420(1), c 4.6326(1) angstrom, V = 595.94(1) angstrom(3), Z = 2, D-c = 3.331 g(.)CM(-3), R-i 0.0411, wR(2) = 0.1058; for 2: a = 11.6579(7), b = 11.6579(7), c 4.5109(4) angstrom, V = 613.06(8) angstrom(3), Z = 2, D-c = 3.970 g(.)cm(-3), R-1 = 0.0432, wR(2) = 0.1031. The structural features of 1 and 2 are Cd-Se=C=N-Zn and Hg-Se=C=N-Cd bridges, respectively, which lead to the formation of an infinite three-dimensional (31)) network. Consistent with their polar structures, compounds 1 and 2 exhibit powder second harmonic generation (SHG) responses much stronger than urea, indicating quite a promising application potential as useful nonlinear optical (NLO) materials. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).