New nitrogen-containing lanthanide complexes with novel structural, thermal, and fluorescence properties

Five new lanthanide complexes were synthesized using 5,5' -dimethyl-2,2' bipyridine(5,5’-DM-2,2’-bipy) and 3-Dimethylaminobenzoic acid(3-N,N-DMHBA) as ligands, and all five lanthanide complexes were found to be dimeric by single crystal X-ray diffraction. The general chemical formula is [Ln(3-N,N-DMBA)3(5,5’-DM-2,2’-bipy)]2·2(3-N,N-DMHBA), Ln=(La(1), Pr(2), Dy(3), Eu(4)), [Ln(3-N,N-DMBA)3(5,5’-DM-2,2’-bipy)]2, Ln=(Sm(5)). 3-N,N-DMBA=3-Dimethylaminobenzoate. DTG-DSC/FTIR coupling technique was used to examine the thermal decomposition mechanism of the five lanthanide complexes, and the fluorescence properties of complexes 3, 4 and 5 were also measured. The fluorescence lifetime of complex 4 was 0.6941(3) ms. The mono- and trimorphic states of the ligand were calculated by DFT. The mechanism of luminescence of the complexes was explained from the point of view of energy transfer.