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)(3)phen](2) (Ln = Eu(3+) (1), Tb(3+) (2), Ho(3+) (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 - (T(max) + T(min))/2]/[T(max) -T(min))/2]) was fitted to a polynomial equation with the least-squares method for each complex. Finally, the derived thermodynamic functions (H(T) - H(298.15)), (S(T) - S(258.15)) and (G(T) - G(298.15)) 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. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.