Luminescent zinc and cadmium complexes incorporating 1,3,5-benzenetricarboxylate and a protonated kinked organodiimine: From a hydrogen-bonded layer motif to thermally robust two-dimensional coordination polymers

Hydrothermal treatment of zinc chloride, 1,3,5-benzenetricarboxylic acid (H3BTC), and 4,4'-dipyridylamine (dpa) afforded two different complexes depending on reaction conditions, which were characterized by single-crystal X-ray diffraction, infrared spectroscopy, and elemental analysis. Under acidic conditions, a discrete neutral molecular species with formulation [Zn(HBTC)(2)(Hdpa)(2)] (1) was isolated, which aggregates into two-dimensional hydrogen-bonded layers. Under more basic conditions, the two-dimensional layered coordination polymer [Zn(BTC)(Hdpa)] (2) is obtained, which manifests covalent linkage of [Zn(BTC)(Hdpa)] serpentine chain motifs into 3-connected undulating 4. 8(2) topology 2-D layers. Both 1 and 2 possess tetrahedral coordination at Zn. Use of cadmium nitrate in the synthesis resulted in [Cd(BTC)(H2O)(Hdpa)] (3), which displays a similar layer topology as 2 but with significant adjustments imparted by octahedral coordination at Cd. In all cases, supramolecular hydrogen bonding promoted by Hdpa ligands provide an important assistive structure-directing role. All materials display blue luminescence upon excitation with ultraviolet light, ascribed to intraligand transitions. Crystallographic data: 1: monoclinic, C2/c, a = 25.389(6)angstrom, b = 9.811(2)angstrom, c = 17.309(4) angstrom, and 128.957(3)degrees, 2: monoclinic, P2(1/c), a = 13.212(17)c, b 17.15(2) angstrom, c = 7.506(10)angstrom, and beta = 93.71(2)degrees, and 3: monoclinic, C2/c, a = 14.241(6) angstrom, b = 15.218(6) angstrom, c = 17.976(7) angstrom, and beta = 109.330(6)degrees. (c) 2007 Elsevier Inc. All rights reserved.