The reactions of ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen center dot H2O) by hydrated lanthanide chlorides in the presence of absolute ethanol yield two novel lanthanide derivatives represented with the empirical formula RE(PDC)(3)(phen) (RE = Eu, Tb). The resulting compounds were characterized by elemental analysis, TG-DTG and i.r. spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Delta H-r(m)0 (1), and the molar heat capacities of the compounds, c(m), were determined at T = 298.15 K by using an RD496-III heat conduction microcalorimeter, which were (-22.21 +/- 0.08) kJ center dot mol(-1) and (61.68 +/- 0.65) J center dot mol(-1) center dot K-1 for Eu(PDC)(3)(phen) and (-21.04 +/- 0.05) kJ center dot mol(-1) and (67.74 0.60) J center dot mol(-1) center dot K-1 for Tb(PDC)(3)(phen), respectively. On the basis of the appropriate thermochemical cycles and other auxiliary thermodynamic data, the enthalpy changes of formation of the compounds from the reactions of the regents in solid phase, Delta H-r(m)0(s), were calculated as being (54.53 +/- 0.31) kJ center dot mol(-1) for Eu(PDC)(3)(phen) and (40.20 +/- 0.36) kJ center dot mol(-1) for Tb(PDC)(3)(phen). The thermodynamics of reactions of formation of the compounds were investigated by the reactions in ethanol. Fundamental parameters, the activation enthalpy (Delta H-not equal(0)), the activation entropy (Delta S-not equal(0)), the activation free energy (Delta G(not equal)(0)), 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 of the thermochemical data of the reaction and kinetic equations with the data of thermokinetic experiments. (c) 2006 Elsevier Ltd. All rights reserved.