Preparation, luminescence and thermal properties of lanthanide complexes with 2-chloro-4-fluorobenzoic acid

Three new solid ternary lanthanide complexes of [Ln(2-Cl-4-FBA)3phen]2 (Ln = Eu3+(1), Tb3+(2), Ho3+(3), 2-Cl-4-FBA = 2-chloro-4-fluorobenzoate, phen = 1,10-phenanthroline) were synthesized and characterized by means of elemental analysis, IR and UV spectra and XRD. The complexes 1 and 2 emit bright red and green luminescence respectively under the excitation ultraviolet light at room temperature. Thermal analyses of the three complexes were discussed by TG–DTG and IR techniques. The heat capacities of the complexes were measured from 259.15 to 493.02 K by means of Differential scanning calorimetry (DSC). The relationship of the molar heat capacities varying with the reduced temperature (x) (x = [T − (Tmax + Tmin)/2]/[(Tmax − Tmin)/2]) was fitted to a polynomial equation with the least-squares method for each complex. Finally, the derived thermodynamic functions (HT − H298.15), (ST − S298.15) and (GT − G298.15) of the complexes relative to the standard reference temperature 298.15 K were also obtained on the base of the fitted polynomials and thermodynamic relationships.

► We have synthesized firstly and characterized three new lanthanide complexes [Ln(2-Cl-4-FBA)3phen]2. ► The heat capacities of the complexes were measured from 259.15 to 493.02 K by means of DSC. ► The thermodynamic parameters were also obtained on the base of the fitted polynomials. ► Thermal analyses of the three complexes were discussed by TG–DTG and IR techniques.