Hydrothermal syntheses, crystal structures and properties of lanthanide complexes with 4-Hydroxy-6-methylnicotinic acid

Four isomorphous lanthanide complexes, [Ln2(L)6(H2O)2]·2H2O [Ln = Ce (1), Ln = Nd (2), Ln = Sm (3), Ln = Pr (4)] (HL = 4-Hydroxy-6-methylnicotinic acid) were synthesized by the reaction of nitrate salts of LnIII and HL by hydrothermal method, which were characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectra, UV–vis spectra, TG analyses and X-ray powder diffraction (XRPD). The crystal structures of 1–4 consist of homodinuclear species, which bridged by two oxygen atoms from two L ligands. The photoluminescence properties of compounds 3 and 4 in the solid state at room temperature were investigated. The complex 3 is demonstrated orange–red luminescence, while the luminescence spectrum of complex 4 is typical for the praseodymium complexes.

► Four lanthanide complexes based on 4-Hydroxy-6-methylnicotinic acid were reported. ► The binuclear units are linked via four types of hydrogen bonding to form 3D network. ► Nitrogen atoms of the L ligands were protonated while oxygen atoms were deprotonated. ► Complex 3 exhibits orange–red luminescence.