Low-temperature Heat Capacities and Thermodynamic Properties of the Solid State Complexes(C2H10N2)MCl4(s)(M=Cu and Cd)

摘要

The tetrachlorocuprate(Ⅱ)ethylenediammonium and tetrachlorocadmate(Ⅱ)ethylenediammonium were synthe-sized.Chemical analysis,elemental analysis,and X-ray crystallography were applied to characterize the composi-tions and crystal structures of the two complexes.The lattice potential energies and the radiuses of the anions of two complexes were calculated to be UPOT[(C2H10N2)CuCl4]=1810.19 kJ·mol-1,UPOT[(C2H10N2)CdCl4]=1784.39kJ·mol-1,r[(CuCl4)2]=0.308nm,and r[(CdCl4)2-]=0.321nm from the data of the crystal structure,respectively.Low-temperature heat capacities of the two complexes were measured by a precision automatic adiabatic calorimeter with the small sample over the temperature range from 78 to 400K,respectively.Two polynomial equations of heat capacities against the temperatures were fitted by least square method:Cp,m[(C2H10N2)CuCl4,s]=213.553+118.578X-5.816X2+4.392X3+0.276X4 and Cp,m[(C2H10N2)CdCl4,s]=190.927+98.501X-7.931X2+0.657X3+3.834X4,in which X=(T-239)/161.Based on the fitted polynomial equations,the smoothed heat capacities and thermodynamic functions of the two complexes relative to the standard reference temperature 298.15 K were calculated at intervals of 5K.