Structural and thermal properties of three novel alkaline earth metal coordination polymers based on 5-hydroxylsophthalate ligand

Three novel coordination polymers [Ca(5-OH-BDC)(H2O)(3)] - H2O (1), [Sr(5-OH-BDC)(H2O)(4)] - H2O (2) and [Ba(5-OH-BDC)H 10)31 (3) were obtained by self-assembly of the corresponding alkaline earth metal chlorate with a ligand, 5-hydroxyisophthalic acid (5-OH-H2BDC), and their structures were determined by X-ray crystallography. The results revealed that complexes 1, 2 and 3 have two-dimensional network with (6,3) topology observed in the be plane. Moreover, the two-dimensional layers can be assembled into three-dimensional supramolecular architectures via intermolecular hydrogen bonds. The two carboxylate groups of 5-OH-BDC2- ligand adopt the same coordination mode in complex 1 as that in 2: a mu 3-eta 2: eta 1 mode and a chelated mode while in complex 3 they coordinate to Ba(II) ions in a mu 3-eta 2:eta 1 mode and a monodentate mode, which is not observed in previous reports. The constant-volume combustion energies, Delta cU, of these complexes were determined by a precise rotating-bomb calorimeter at 298.15 K, then their standard enthalpies of combustion, Delta H-c(m)0, and the standard enthalpies of formation, have been calculated. (c) 2007 Elsevier B.V. All rights reserved.