A series of lanthanide complexes with 2-fluorobenzoic acid and 5,5′-dimethyl-2,2′-bipyridine: Synthesis, supramolecular structures, spectroscopy and thermal behaviour

A family of lanthanide-based self-assembling complexes constructed from 2-fluorobenzoic acid and 5,5 '-dimethyl-2,2 '-bipyridine have been successfully fabricated via conventional synthesis, namely, [Ln(2-FBA)(3)(5,5 '-DM-2,2 '-bipy)](2) (2-FBA = 2-fluorobenzoate, 5,5 '-DM-2,2 '-bipy = 5,5 '-dimethyl-2,2 '-bipyridine, Ln = La(1), Pr(2), Nd(3), Sm(4), Gd(5), Dy(6), Ho(7), Er(8)). The obtained complexes are investigated by means of elemental analysis, IR spectra, Raman spectra and single-crystal X-ray diffraction. Crystallographic results exhibit that each Ln(3+) ion of them is located in a distorted Muffin coordination sphere finished by seven oxygen atoms of 2-FBA ligands and two nitrogen atoms of 5,5 '-DM-2,2 '-bipy ligand. Interestingly, although complexes 1-6 and 7-8 have the same formula unit, the differences in hydrogen bond interactions lead to different supramolecular structures. Besides, the thermal decomposition mechanism of the complexes has been studied by TG/DSC-FTIR technology. The results show that these complexes are thermally stable up to 450 K. In addition, complexes 4 and 6 both exhibit the characteristic fluorescence of lanthanide ions, that is, complex 4 exhibits characteristic (4)G(5/2)-> H-6(J/2) (J = 5, 7, 9) transitions, and complex 6 shows characteristic F-4(9/2)-> H-6(J/2) (J = 15, 13) transitions.