Infinite chains constructed from flexible bis(benzimidazole)-based ligands

Two neutral ligands, L-1 center dot 2H(2)O and L-2 center dot H2O, and seven complexes, [Cu(pmb)(2)(L-1)] (1), [Cu(pmb)(2)(L-2)] (2), [Cu(Ac)(2)(L-2)] center dot 4H(2)O (3), [Cu(4-aba)(2)(L-2)] (4), [Ag(4-ts)(L-1)(H2O)](5), [Ag-2(epes)(2)(L-1)] center dot 2H(2)O (6), [Ag(1,5-nds)(0.5)(L-2)] center dot 0.5C(2)H(5)OH center dot H2O (7) [where L-1 = 1,1'-(1,4-butanediyl)bis(2-methylbenzimidazole); L-2 = 1, 1'- (1,4-butanediyl)bis(2-ethylbenzimidazole), pmb = p-methoxybenzoate anion; Ac = acetate anion; 4-aba = 4-aminobenzoate anion; 4-ts = p-toluenesulfonate anion; epes = N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonate) anion; 1,5-nds = 1,5-naphthalenedisulfonate anion], have been synthesized and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. The L-1 and L-2 ligands in compounds 1-7 act as bridging ligands, linking metal ions into chain structures. The chains in compounds 3, 4 and 6 interlace with each other by hydrogen bonds to generate 3D supramolecular structures. In compound 5, pi-pi interactions between adjacent L-1 ligands hold the chains to a supramolecular layer. In compound 7, the sulfonate anions act as counterions in the framework. The thermal stabilities of 3, 6 and 7, and the luminescent properties for 5-7 in the solid states are also discussed. (C) 2008 Elsevier Ltd. All rights reserved.