Studies on preparation, crystal structure, thermal properties and fluorescence properties of rare earth complexes composed of 2-chloro-4-fluorobenzoic acid and 2,2':6′,2″-terpyridine

Abstract

Four new 2D complexes namely [Ln(2-Cl-4-FBA)3(terpy)H2O] (Ln=Er(1),Ho(2)); [Eu(2-Cl-4-FBA)3(terpy)H2O]·1.5H2O(3); [Tb(2-Cl-4-FBA)3(terpy)H2O]·2H2O (4); (2-Cl-4-FBA=2-chloro-4-fluorobenzoate,terpy=2,2':6′,2 ″-terpyridine) were synthesized at normal temperature. The structures of complexes were determined by single-crystal X-ray diffraction. The results show that the two complexes 1-2 are isomorphous and complexes 3-4 are isostructural. Four complexes are both assembled into the 1D and 2D supramolecular structures through the C-H⋯Cl hydrogen bond interactions. The thermal decomposition mechanism of complexes 1-4 was investigated by the technology TG/DSC-FTIR. FTIR spectra were obtained by analyzing the evolved gases in the thermal decomposition process of complexes 1-4. In addition, the differential scanning calorimetry was used to measure the average molar melting values of the complexes 1-2 in the temperature range of 259.15-343.15K by a specific heat comparison method, and the thermodynamic function values were obtained by calculation. The fluorescence tests of complexes 3 and 4 show that both of them have certain luminescent properties.