Construction of two novel lanthanide complexes supported by 2-bromine-5-methoxybenzoate and 2,2′-bipyridine: Syntheses, crystal structures and thermodynamic properties

Abstract

Two novel lanthanide complexes with the general formula [Ln(2-Br-5-MOBA)3(2,2′-DIPY)]2 (Ln=Pr(1), Dy(2); 2-Br-5-MOBA=2-bromine-5-methoxybenzoate; 2,2′-DIPY=2,2′-bipyridine) have been successfully synthesized and characterized. The complexes 1 and 2 are isostructural and nine-coordinated with distorted monocapped square antiprismatic coordination geometry by the single-crystal X-ray diffraction analyses. Two complexes are all assembled into the 1D, 2D, 3D supramolecular structures by CH⋯O hydrogen bonding and π–π stacking interactions. The thermal decomposition mechanism for title complexes were obtained by TG/DSC-FTIR technology. The molar heat capacities of the complexes 1 and 2 are measured by a DSC instrument over the temperature range from 263.15K to 365.15K. On the basis of the fitted polynomial and thermodynamic equations, the smoothed values of heat capacities and thermodynamic functions (HT-H298.15K), and (ST-S298.15K) of the two complexes are calculated. In addition, the fluorescence spectra indicate that the complex 2 exhibits the characteristic emission of Dy(III) ion (4F9/2→6H13/2–15/2).