Synthesis, Characterization, and Thermodynamic Study of the Solid State Coordination Compound Ca(Nic)(2)(s) (Nic = Nicotinate)

A novel compound, anhydrous calcium nicotinate Ca(Nic)(2)(s) (Nic = nicotinate), was synthesized by the method of room-temperature solid phase synthesis. FTIR, chemical, and elemental analyses and an X-ray powder diffraction technique were applied to characterize the structure and composition of the complex. Low-temperature heat capacities of the solid coordination compound have been measured by a precision automated adiabatic calorimeter over the temperature range from T = 78 K to T = 400 K. The experimental values of the molar heat capacities in the temperature regions of (78 similar to 400) K were fitted to one polynomial. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the sample relative to the standard reference temperature 298.15 K were calculated and tabulated at intervals of 5 K. In accordance with Hess' law, a thermochemical cycle was designed; the enthalpy change of the solid phase reaction of nicotinic acid with calcium hydroxide was determined to be Delta H-r(m)degrees = -(9.121 +/- 0.336) kJ.mol(-1) by use of an isoperibol solution-reaction calorimeter; and the standard molar enthalpy of formation of the complex Ca(Nic)(2)(s) was calculated to be Delta H-f(Ca)degrees(Nic)(2) = -(1113.17 +/- 1.87) kJ.mol(-1) by use of the enthalpies of dissolution and other auxiliary thermodynamic quantities