Crystal structures, luminescent properties and thermal decomposition kinetics of lanthanide complexes with 2-chloro-4-fluorobenzoic acid and 2,2′-bipyridine

A new family of lanthanide with the general formula [Ln(2-Cl-4-FBA)3bipy]2 (Ln = Nd(1), Sm(2), Eu(3), and Ho(4); 2-Cl-4-FBA = 2-chloro-4-fluorobenzoate; bipy = 2,2′-bipyridine) were synthesized and characterized by elemental analysis, molar conductance, and infrared, ultraviolet and luminescent spectroscopy, single-crystal X-ray diffraction, thermogravimetry and different thermogravimetry (TG–DTG) techniques. These compounds are iso-structural and the lanthanide ions are all nine coordinated via two bidentate chelating, two bidentate bridging and two bidentate chelating-bridging modes. Under excitation, the europium complex exhibited characteristic red fluorescence of Eu3+ ion at room temperature. The non-isothermal kinetics was investigated by using NL-INT and Popescu methods. The mechanism functions of the first decomposition step of the title complexes were determined. Meanwhile, the thermodynamic parameters (ΔG≠, ΔH≠ and ΔS≠) were also calculated.