Standard Molar Enthalpy of Formation of the Solid State Coordination Compound Cu(Nic)2·H2O(s) (Nic = nicotinic acid)

A novel compound - monohydrated cupric nicotinate was synthesized by solid phase synthesis at room temperature. FTIR, chemical and elemental analyses, and X-ray powder diffraction technique were applied to characterize the structure and composition of the complex. Enthalpies of dissolution of {Cu(Ac)2 H2O(s)} and {HAc(l)} in 0.1 M HCl solution, {Nic(s)} in 0.1 M HCl solution containing certain amounts of monohydrated cupric acetate, and {Cu(Nic)2 H2O(s)} in 0.1 M HCl solution containing certain amounts of acetic acid at T = 298.15 K were determined by means of an isoperibol solution-reaction calorimeter: DsHCu(Ac) H O o2 2 = -(6.234 ± 0.187) kJ mol-1, DsHHAc o = -(1.788 ± 0.008) kJ mol-1, Ds HNico± = (10.337 ± 0.393) kJ mol-1, and DsHCu(Nic) H Oo2 2 = -(6.801 ± 0.130) kJ mol-1. In accordance with Hess law, a reasonable thermochemical cycle was designed, the enthalpy change of the solid phase reaction of monohydrated cupric acetate with nicotinic acid was determined to be DrHmo = (24.817 ± 0.818) kJ mol-1, and the standard molar enthalpy of formation of the title complex was found to be -(891.463 ± 2.139) kJ mol-1.