Synthesis, crystal structure and thermochemical behaviour of a barium complex [Ba(5-OH-BDC)(H2O)3] [5-OH-H2BDC = 5-hydroxyisophtalic acid]

A novel complex Ba(5-OH-BDC)(H₂O)₃] 5-OH-H₂BDC = 5-hydroxyisophtalic acid] was synthesized and characterized by X-ray crystallography. The complex is Monoclinic P2₁/c, a = 11.1069(4), b = 14.8192(6), c = 6.5005(2) Å, β = 103.465(3)° and Z = 4, which exhibits a three-dimensional framework formed by linkage of adjacent two-dimensional (6, 3) layers via intermolecular hydrogen bonds. The title complex has been studied by IR spectrum and TG-DTG. The constant-volume combustion energy of the complex, Δ_cU, was determined as being (−3210.45 ± 1.41) kJ mol⁻¹ by a precise rotating-bomb calorimeter at 298.15 K. The standard enthalpy of combustion, , and the standard enthalpy of formation, , were calculated as being (−3207.97 ± 1.41) and (−1922.80 ± 1.76) kJ mol⁻¹, respectively. A calculation model for determining the specific heat capacity of the complex with an improved RD496-III microcalorimeter is also derived. The specific heat capacity of the complex was (6158.387 ± 0.187) J mol⁻¹ K⁻¹.