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)(H 2 O) 2 ] ( 1 ) and [H 2 bpy][Co(bta)(bpy)(H 2 O) 2 ] ( 2 ). 1 and 2 were prepared under hydrothermal conditions (145 °C, 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) Å [Mn(1) ··· Mn(1c); c = − x + 1/2, y − 1/2, − z ] and 9.274(4) Å [Mn(1) ··· Mn(1d); d = x , y + 1, − z ]. Adjacent double chains in 1 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) Å, 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 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)