Dimethyl Dithiocarbamate And Phenanthroline And The Thermodynamic Properties Of Rare Earth Complexes

1.Thirteen ternary solid complexes,Ln(Me₂dtc)₃(phen)(Ln=La,Pr,Nd,Sm～Lu),have been prepared from the reactions of hydrous lanthanide chloride,sodium dimethyldithiocarbamate(NaMe₂dtc)and 1,10-phenanthroline.H₂O(o-phen.H₂O)in anhydrous ethanol.They were characterized by means of elemental analysis,IR spectroscopy,TG-DTG,X-ray powder diffraction and X-ray diffraction analysis.The experimental results revealed that sulfur atoms in dithiocarbamate coordinated to lanthanides in a didentate manner.The thermal decomposition behaviors of the complexes have been performed by TG-DTG.The complexes were decomposed into sulfur chalcogenides in one step at the low temperature(close to 400℃),indicating that the complexes are potential single-source precursors to lanthanide chalcogenides materials based on the X-ray powder diffraction pattern.2.The enthalpy changes of the liquid-phase reactions of formation,△_rH_m^θ(1),are determined at 298.15 K by an improved RD496-Ⅲtype microcalorimeter,and the enthalpy changes of the solid-phase reactions of formation,△_rH_m^θ(s),are calculated on the basis of a thermochemical cycle.The enthalpies of reactions in absolute ethanol are of negative values that benefit the proceeding of the reactions and thus provide a thermodynamic reason for the occurrence of the reactions,while the enthalpies of reactions in solid are of positive values that not favorable for the occurrence of the reactions,which represent the preparation ideology that changing the route of reaction aims at lowing the energy of reaction.The thermokinetic investigation for the preparation reactions of the complexes indicated that the activation energies of the formation of the reactions in ethanol are close to 63 kJ·mol^-1at which the reaction occurs instantaneously at room temperature,which provide a thermokinetic support for the instantaneous reactions of formation of the complexes.The values of△G_≠^θare approximately the same,indicating that xanthates is the key to this kind of reaction. 3.The molar heat capacities of the title complexes were determined using an improved RD496-Ⅲtype microcalorimeter according to two reference substances at 298.15 K.4.The plots of the related thermochemical data against the lanthanide atom numbers exhibit triplet effect.