Hydrothermal syntheses and characterizations of three coordination polymers based on mixed organic ligands

Three new coordination polymers, namely {[Cu2(bptc)(4,4′-bpy)(H2O)2]·2H2O}n (1), {Cu2(bptc)(bpe)(H2O)6}n (2), and {[Mn(H2bptc)(H2O)4]·2bpe}n (3) [H4bptc = 3,3′,4,4′-biphenyltetracarboxylic acid, 4,4′-bpy = 4,4′-bipyridine, bpe = trans-1,2-bis(4-pyridyl)ethene], were rationally designed and hydrothermally synthesized at different pH values. Their structures were determined by X-ray diffraction on single crystals. Compound 1 exhibits a 3D network with 1D open channels that contain free solvent water molecules, and two kinds of chiral, helical, hydrogen-bonded chains exist in the neighboring holes. Both compounds 2 and 3 show a 3D supramolecular network that is connected through hydrogen bonds. Compound 2 also shows weak Cu···O semicoordinated interactions that are based on 1D chains. Importantly, bptc reveals three different coordination modes in these compounds: the four carboxylic groups combine with metal ions by bis(monodentate) and bis(chelate) fashions in 1, whereas only two carboxylic groups are bis(monodentate) in 2 and 3, respectively, and the 4,4′-carboxylic groups are protonated in 3. The elemental analysis, IR spectra, UV/Vis spectra, and TG analysis for compounds 1, 2, and 3 are discussed. Additionally, the XRPD is also studied for compound 1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)