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

Solvothermal reactions of two trigonal-planar ligands and lanthanide metal cations of Ln(III) afford four new coordination polymers (CPs), {[LnNa(0.33)H(0.67)(PBPP)(2)]center dot 2H(2)O}(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, H(3)TATB = 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 (4(4).6(7).8(4))(6)(4(8).6(7)) topology, in which TATB(3-) is extremely unsymmetrical due to three metal-oxide chains in the directions of [101], [101] and [110]. Moreover, their luminescent properties have been investigated.