Synthesis, structures and photoluminescence of thiocyanate bridged metal-organic polymers containing functional imidazole ligand

Abstract

Three new coordination polymers, [Cd(SCN) 2L 2] n ( 1), [CdHg(SCN) 4L 2] n ( 2) and [MnHg(SCN) 4L 2] n ( 3) have been prepared by the self-assembly of L with the corresponding metal salts and NaSCN (L is a new functional rigid imidazole ligand, trans-4-imidazolyl-4′-( N, N-diethylamino)stilbene). The crystal structures of the coordination polymers have been determined by single crystal X-ray diffraction analysis. [Cd(SCN) 2L 2] n ( 1) crystallizes in the triclinic crystal system with space group P 1 ¯ . Adjacent Cd II ions are bridged by SCN − ligands to form infinite chains with the remaining two positions of six-coordinated Cd II ion being occupied by two imidazole ligands. [CdHg(SCN) 4L 2] n ( 2) crystallizes in the triclinic crystal system with space group P 1 ¯ . Cd II and Hg II centers are bridged by SCN − ligands to form two-dimensional framework sheets. Cd II and Hg II ions are coordinated by six nitrogen atoms and four thiocyanate sulfur atoms, respectively. [MnHg(SCN) 4L 2] n ( 3) crystallizes in the monoclinic crystal system with space group P2 1/ c. Each Mn II ion is in a N 6 distorted octahedral geometry, and each Hg II ion is in a S 4 distorted tetrahedral geometry, which exhibit similar coordination mode to that of 2. Mn II and Hg II ions are linked by bridging NCS − groups to form two-dimensional sheets. The electronic spectra and solid-state luminescence properties of complexes 1, 2 and 3 have been studied at room temperature.