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

Abstract

Two novel mononuclear lanthanide complexes, [Ln(2,4-DClBA)3(terpy)(H2O)]·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 Ln3+ ion is nine coordinated adopting a distorted monocapped square antiprismatic molecular geometry. Mononuclear complexes 1–2 are stitched together via Cl–π 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.