Crystal structures, thermal properties, and luminescent properties of two novel mononuclear lanthanide complexes with 2,4-dichlorobenzoic acid and 2,2′:6′,2-terpyridine

Two novel mononuclear lanthanide complexes, [Ln(2,4-DClBA)(3)(terpy)(H2O)]center dot H2O (Ln = Dy(1), Er(2)); 2,4-DClBA: 2,4-dichlorobenzoate; terpy: 2,2':6',2 ''-terpyridine; have been synthesized and characterized by single-crystal and powder X-ray diffraction. The results reveal that complexes 1-2 are isomorphous, and each Ln(3+) ion is nine coordinated adopting a distorted monocapped square antiprismatic molecular geometry. Mononuclear complexes 1-2 are stitched together via Cl-pi and hydrogen bonding interactions to form the 1D, 2D, 3D supramolecular structures, which the 3D is rarely observed. Thermal decomposition mechanism is determined by TG/DSC-FTIR, and the 3D stacked plots for the FTIR spectra of the evolved gases were recorded. Heat capacities of complexes 1-2 were measured, and the derived thermodynamic functions (H-T - H-298.15), (S-T - S-298.15) and (G(T) - G(298.15)) of the complexes relative to the standard reference temperature 298.15 K were obtained. The activation energy E values of the first decomposition stage for title complexes were calculated by integral isoconversional nonlinear (NL-INT) and Starink methods. Complex 1 shows the characteristic emission of Dy3+ with strong yellow emission.