Coordination complexes based on V-shaped ligand and rare earth(III) ions: lanthanide contraction effect induced structural changes

Abstract

A series of metal-organic frameworks, {Ln2(SDB)3(H2O)5}n [Ln = Eu(1), Gd(2), Tb(3), Dy(4)], {[Ln2(SDB)3(H2O)4]·H2O}n [Ln = Ho(5), Er(6), Tm(7), Y(8)] and {[Lu2(SDB)3·(H2O)3]·4H2O}n (9) (H2SDB = 4,4’-sulfonyldibenzoic acid), have been synthesized under hydrothermal conditions by using the V-shaped ligand H2SDB. The structures of the complexes have been determined by single-crystal X-ray diffraction and further characterized using IR spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. The single crystal X-ray structures show that 1–4 are isostructural featuring a 2-D weaving structure based on two chain structures containing binuclear units and organic linkers. The structures of 5–8 are analogous to those of 1–4 except that they contain coordinated solvent. Complex 9 forms a 1-D structure containing binuclear units connected by organic linkers. This series affords an opportunity to study the effect of lanthanide contraction, demonstrating that the average C–S–C bond angle in coordinated H2SDB decreases as the atomic number increases. The luminescence of 1 and 3 are also reported.