A series of lanthanide complexes with 2,4-dimethylbenzoic acid and 2,2:6′,2″-terpyridine: Supramolecular structures, thermal decomposition mechanism and photoluminescence

Six new binuclear lanthanide complexes [Ln(2,4-DMBA)3(terpy)(H2O)]2 (Ln = Eu (1), La (2), Pr (3), Nd (4), Sm (5), Gd (6)) (2,4-DMBA = 2,4-dimethylbenzoate; terpy = 2,2:6′,2″-terpyridine) and four mononuclear complexes [Ln(2,4-DMBA)3(terpy)(H2O)] (Ln = Dy (7), Ho (8), Er (9), Tb (10)) have been synthesized. Complexes 1–6 and 7–10 are isomorphous, adopting interesting structures. In the structures of complexes 1–6, two nine-coordinated Ln(III) centers are linked by two 2,4-DMBA ligands in bridging mode. The other two 2,4-DMBA ligands coordinate with one Ln(III) cation in monodentate and chelating modes. In the structures of complexes 7–10, the Ln(III) center is eight-coordinated. Complexes 1–6 and 7–10 can each aggregate to form one-dimensional and two-dimensional supramolecular structures. Thermal decomposition of complexes 1–10 has been investigated by TG-DSC/FTIR. Interestingly, all of the complexes exhibit a similar three-step decomposition process. The Eu(III) and Tb(III) complexes show strong red and green visible light luminescence. Finally, fluorescence lifetimes and intrinsic quantum yields have been calculated for complexes 1 and 10. © 2020 Elsevier B.V.