Treatment of hydrate rare-earth （RE=La, Pr, Nd, Sm-Lu） chloride with ammonium pyrrolidinyldithiocarboxylate （apdtc） and 1,10-phenanthroline （phen） gave rise to thirteen complexes with an empirical formula RE[（pdtc）3（phen）]. The enthalpies of solution of hydrate rare-earth （RE= Sm-Ho, Tm-Lu） chloride, apdtc and phen in ethanol were measured by an RD-496 Ш microcalorimeter at 298.15 K, along with the mixing enthalpy of ethanol solution of APDC and that of phen and the enthalpies of reaction of formation of the title complexes in ethanol. The enthalpies of reaction of formation of the title complexes in solid were available through a rationally thermochemical cycle. Using an RD-496 Ш microcalorimeter, a model was developed for calculating the specific heat capacity and the responding specific heat capacity of the complexes were determined. The thermochemical properties, including the enthalpies of solution of hydrate rare earth chloride in ethanol, the enthalpies of reaction of formation of the title complexes in ethanol, the enthalpies of reaction of formation of the title complexes in solid, the special heat capacities at room temperature, the standard molar enthalpies of combustion and the standard molar enthalpies of formation for this series of complexes versus the atomic numbers of rare earth, presented triplet effect, which is representative of certain covalent bond between RE and the ligands and the result of 4f electron not shielded fully by 5sSp.
Four solid complexes of Ln(Me2dtc)3(phen) (Ln=Eu, Gd, Tb, Dy) were synthesized in anhydrous ethanol by the reaction of lanthanide chloride low hydrate with the mixed ligands of sodium dimethyldithiocarbamate and 1, 10-phenanthroline·H2O (abbreviated as phen·H2O), and characterized by elemental analysis, IR spectroscopy, TG-DTG and X-ray diffraction techniques. Combining with the crystal structures, the complexes are identified as the general formula of Ln(Me2dtc)3(phen). TG-DTG with X-ray powder diffraction showed that these compounds could decompose to lanthanide sulfides under relatively lower temperature, which indicated that the title complexes could be ideal precursors to prepare lanthanide sulfides.
A ternary solid complex Lu(Et2dtc)3(phen) has been obtained from the reaction of hydrated lutetium chloride with sodium diethyldithiocarbamate (NaEt2dtc), and 1,10-phenanthroline (o-phen·H2O) in absolute ethanol. IR spectrum of the complex indicates that Lu3+ binds with sulfur atom in the Na(Et2dtc)3 and nitrogen atom in the o-phen. The enthalpy change of liquid-phase reaction of formation of the complex, △CHM- (l), was determined to be (-32.821 ± 0.147 ) kJ·mol-1 at 298.15 K by an RD-496 Ⅲ type heat conduction microcalormeter. The enthalpy change of the solid-phase reaction of formation of the complex, △CHM- (s), was calculated to be (104.160 ± 0.168) kJ · mol-1 on the basis of an appropriate thermochemistry cycle. The thermodynamics of liquid-phase reaction of formation of the complex was investigated by changing the temperature of liquid-phase reaction. Fundamental parameters, such as the activation enthalpy (△HM-), the activation entropy (?驻SM-), the activation free energy (△GM-), the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A) and the reaction order (n), were obtained by combination the reaction thermodynamic and kinetic equations with the data of thermokinetic experiments. The molar heat capacity of the complex, cm, was determined to be (82.23 ± 1.47) J·mol-1·K-1 by the same microcalormeter. The constant-volume combustion energy of the complex, ΔcU, was determined as (-17 898.228 ± 8.59) kJ·mol-1 by an RBC-Ⅱtype rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, △CHM-, and standard enthalpy of formation, △CHM-, were calculated to be (-17 917.43 ± 8.11) kJ·mol-1 and (-859.95 ±10.12) kJ·mol-1, respectively.
