1,2,4,5-Benzenetetracarboxylic Acid And 4,4 '-Bipyridine As Ligands In Designing Low-Dimensional Coordination Polymers

The combined use of 1,2,4,5-benzenetetracarboxylic acid (H(4)bta) and 4,4'-bipyridine (bpy) as ligands with Mn-II and Co-II ions afforded two polymeric compounds with the formulae [Mn(Hbta)(Hbpy)(H2O)(2)] (1) and [H(2)bpy][Co(bta)(bpy)(H2O)(2)] (2). 1 and 2 were prepared under hydrothermal conditions (145 degreesC, 3 h) and characterized by elemental analysis, IR spectroscopy, TG-DTA analysis and single-crystal X-ray diffraction methods. 1 exhibits a novel double chain structure growing along the b axis where the manganese atoms are linked by tris-monodentate Hbta(3-) ligands. The values of the manganese(...)manganese intrachain separations are 7.627(2) Angstrom [Mn(1)Mn-...(1c); c = -x + 1/2, y - t/2, -z] and 9.274(4) Angstrom [Mn(1)Mn-...(1d); d = x, y + 1, -z]. Adjacent double chains in I are further linked through hydrogen bonds between the NH fragment of the Hbpy(+) cation and one of the carboxylate groups of the Hbta(3-) anion along the a axis, resulting in a sheetlike structure. 2 exhibits a rectangular grid arrangement of cobalt atoms bridged by bis-monodentate bta(4-) and bpy ligands in the bc plane, the cobalt(...)cobalt separations across them being 6.228(2) and 10.074 (2) Angstrom, respectively. The metal atoms in 1 and 2 are six-coordinate with two water molecules in trans positions (1 and 2), three (1)/two (2) carboxylate oxygen atoms and one (1)/two (2) pyridyl nitrogen atoms forming a distorted octahedral environment, The varying nature of the divalent metal ions [Mn 1 and Co 2] along with the differing degrees of protonation of the tetracaboxylate [Hbta(3-) 1 and bta(4-) 2] and bipyridyl [Hbpy(+) 1 and bpy and H(2)bpy(2+) 2] species account for the structural differences between 1 and 2. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.