Syntheses, crystal structures, thermodynamic and fluorescent properties of dinuclear lanthanide complexes constructed with 2-fluorobenzoic acid and 5,5′-dimethy-2,2′-bipyridine

Abstract

2-fluorobenzoic acid and 5,5′-dimethy-2,2′-bipyridine were used to construct two novel isostructural lanthanide complexes [Ln(2-FBA)3(5,5′-DM-2,2′-bipy)]2 (Ln = Eu(1), Tb(2); 2-FBA = 2-fluorobenzoate; 5,5′-DM-2,2′-bipy = 5,5′-dimethy-2,2′-bipyridine) by conventional solution method. They were characterized by infrared spectroscopy (IR), elemental analysis and single-crystal X-ray diffraction. The crystal description based on single-crystal X-ray diffraction data revealed that both of the complexes gave the triclinic crystal structure, belonging to the Pī space group. The two complexes were an infinite one-dimensional (1D) chain by hydrogen bonding (C–H…F) interactions to give a 2D supermolecular structure. Additionally, thermal behavior of the complexes was investigated by TG-DSC/FTIR technology in detail. The molar heat capacities of the two complexes in the temperature range of 278.15-423.15 K were determined by a DSC instrument, and their thermodynamic functions (HT-H298.15 K) and (ST-S298.15 K) were calculated. Beyond that, the fluorescence spectra and fluorescence lifetime of the complexes 1 and 2 were also evaluated.