Preparation and thermal properties of lanthanide complexes with 2,3-dichlorobenzoic acid and 1,10-phenanthroline

Three lanthanide complexes with a general formula [Ln(2,3-DClBA)3phen]2 (Ln(III) = Eu(1), Tb(2), Ho(3); 2,3-DClBA = 2,3-dichlorobenzoate; phen = 1,10-phenanthroline) were synthesized and characterized by elemental analysis, molar conductance, infrared and ultraviolet spectra and powder X-ray diffraction (XRD). The luminescent properties of the complexes 1 and 2 were studied. The thermal behaviors of the complexes were also discussed by thermogravimetric (TG), differential thermogravimetric (DTG) and infrared spectra (IR) techniques. The heat capacities of the complexes were measured from 259.15 to 493.02 K by means of Differential scanning calorimeter (DSC). The dependence of heat capacity on the reduce temperature x (x = [T − (Tmax + Tmin)/2]/[(Tmax − Tmin)/2]) was fitted to a polynomial equation with the least squares method for each complex. Furthermore, based on the fitted polynomial, the smoothed heat capacities and the derived thermodynamic functions (HT − H298.15 K), (ST − S298.15 K) and (GT − G298.15 K) in the measured temperature range were obtained with an interval of 10 K.