Pyridine- and imidazoledicarboxylates of zinc: Hydrothermal synthesis, structure, and properties

The reaction of hetrocyclic dicarboxylic acids, such as pyridine-2,5-dicarboxylic acid and imidazole-4,5-dicarboxylic acid, under hydrothermal conditions in the presence of an appropriate zinc salt yields three new zinc coordination polymers (0)(infinity)[{Zn-2(H2O)(4)}{C5H3N(COO)(2)}(2)] (1), (1)(infinity)[{Zn(C12H8N2)}{C5H3N(COO)(2)}center dot 0.5H(2)O] (2), and (1)(infinity)[{Zn(C12H8N2)}{C3HN2(COO)(2)}] (3). While 1 forms with a zero-dimensional molecular rectanclular box structure, 2 and 3 have zig-zag one-dimensional chain structures. The Zn 21 ions are coordinated by both the carboxylate oxygen atoms and also by the nitrogen atoms of the heterocycles. The 1,10-phenanthroline molecules in 2 and 3 act as a secondary ligands and occupy the inter-chain spaces. The moderate hydrogen-bond interaction energy in 1 and the pi(...)pi interactions in 2 and 3 appear to play an important role for the structural stability. The structures of 2 and 3 appear to be related, even though they are formed with different carboxylic acids. All three compounds exhibit photoluminescence at room temperature. (c) Wiley-VCH Verlag GmbH & Co.