Syntheses, structures, and luminescence of four lanthanide metal–organic frameworks based on lanthanide-oxide chains with C2- or C3-symmetric trigonal-planar polycarboxylate ligands

Abstract

Solvothermal reactions of two trigonal-planar ligands and lanthanide metal cations of Ln^III afford four new coordination polymers (CPs), {[LnNa_0.33H_0.67(PBPP)₂]·2H₂O}_n (Ln = Pr for 1, Gd for 2, Ce for 3) and {[Sm(TATB)(H₂O)]}_n (4) (H₂PBPP = 4-phenyl-2,6-bis(4′-carboxyphenyl)pyridine, H₃TATB = 4,4′,4′′-s-triazine-2,4,6-tribenzoic acid). Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric (TG) analyses. Complexes 1–3 are isomorphous and exhibit an unprecedented (4,6,6)-connected 3D architecture, which is built up from lanthanide-oxide chains. Complex 4 shows a 3D (6,6)-connected net with (4⁴.6⁷.8⁴)₆(4⁸.6⁷) topology, in which TATB³⁻ is extremely unsymmetrical due to three metal-oxide chains in the directions of [101], [101] and [110]. Moreover, their luminescent properties have been investigated.