Crystal structures, topologies and luminescent properties of three Zn(ii)/Cd(ii) coordination networks based on naphthalene-2,6-dicarboxylic acid and different bis(imidazole) linkers

Abstract

Three new mixed-ligand metal–organic coordination networks based on naphthalene-2,6-dicarboxylic acid and different bis(imidazole)s, [Cd(bmimb)_0.5(ndc)]·1.5H₂O (1), [Zn(bibp)(ndc)]·H₂O (2), [Zn(bip)(ndc)]·2H₂O (3), (bmimb = 1,4-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene, bibp = 1,1′-(2,5-dimethyl-1,4-phenylene)bis(1H-imidazole), bip = 1,4-di(1H-imidazol-1-yl)benzene, H₂ndc = naphthalene-2,6-dicarboxylic acid), have been synthesized under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, infrared spectroscopy (IR), elemental analyses, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). These complexes display different types of entanglements. Topological analysis reveals that 1 features a 3-fold interpenetrated pcu network constructed from paddle-wheel secondary building units. Complex 2 exhibits a normal mode of a 5-fold diamondoid interpenetrating net, while complex 3 is a 3D 4-connected coordination network with an extremely rare (6⁵·8)-hxg-d-4-Cccm topology. These results suggest that both naphthalene-2,6-dicarboxylic acid and bis(imidazole) ancillary ligands influence the final resulting structures. Furthermore, luminescence properties and thermogravimetric properties of these complexes were investigated.