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 I $\bar {4}$ space group. The cell dimensions for 1 : a = 11.3420(1), b = 11.3420(1), c = 4.6326(1) Å, V = 595.94(1) Å 3 , Z = 2, D c = 3.331 g · cm –3 , R 1 = 0.0411, wR 2 = 0.1058; for 2 : a = 11.6579(7), b = 11.6579(7), c = 4.5109(4) Å, V = 613.06(8) Å 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 (3D) 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)