The effect of the conformation of flexible carboxylate ligands on the structures of metal–organic supramolecules

Three flexible bent dicarboxylate ligands, 2,2′-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(sulfanediyl)dibenzoic acid (H2L1), 2,2′-(1,4-phenylenebis(methylene))bis(sulfanediyl)dibenzoic acid (H2L9) and 2,2′-(2,3,5,6-tetramethyl-1,4-phenylene)bis(methylene)bis(oxy)dibenzoic acid (H2L10), have been designed and synthesized. The positions of the functional substituents are in 1,4-positions of the central benzene ring, and all the ligands can adopt syn and anti conformations. By applying these flexible ligands to assemble with thulium ions or zinc ions, three metal–organic supramolecules with metallamacrocycles or 1D chains have been isolated. L1 adopts a syn conformation in complex 1, leading to a 0D metallamacrocycle, L9 in complex 2 adopts an anti conformation to form a 1D "rainbow-like" chain while L10 in complex 3 adopts both syn and anti conformations. L10 in a syn conformation connects Zn4(OH)2(CO2)4 SBU to form a 0D metallamacrocycle, which is further connected by the ligand in an anti conformation to generate a 1D coordination polymer.