Syntheses, structures, and properties of lanthanide–organic frameworks with flexible disulfide derivative of carboxylate

Reaction of disulfide-containing ligand 6,6′-dithiodinicotinic acid (H2cpds) with lanthanide metal salts led to three compounds {[Ln2(cpds)3(H2O)5]·7H2O}n (Ln = Gd, 1; Tb, 2; Er, 3) under hydrothermal conditions. The single-crystal X-ray diffraction analysis revealed that complexes 1–3 are isostructural. Two eight-coordinated metal centers are connected with carboxylate groups of H2cpds to give a binuclear [Ln2(CO2)4] unit. H2cpds discloses two independent binding modes resulting in the two types of 1-D chains by the connection of [Ln2(CO2)4] unit. Finally, the 1-D chains are linked by H2cpds to construct a 3-D network with an uncommon twofold interpenetrating 4-connected CdSO4 structure type (65,8 topology). It is worth noting that polyrotaxane-like motif is also exhibited in the 3-D network. The Tb(III) compound exhibits strong green photoluminescence in the visible region. Furthermore, the magnetic property of the Gd(III) compound has been investigated in the temperature range of 2–300 K. The thermal behaviors and XPRD patterns of three compounds have also been discussed.