Rigidity versus Flexibility of Ligands in the Assembly of Entangled Coordination Polymers Based on Bi- and Tetra Carboxylates and N-Donor Ligands

Abstract

Seven Zn(II) coordination polymers including [Zn(pbda)(p-bimb)]·H2O (1), [Zn(pbda)(bpa)0.5] (2), [Zn(pbda)(bpp)] (3), [Zn(Hpbda)2(bibm)2] (4), [Zn(pbta)0.5(m-bimb)]·H2O (5), [Zn(pbta)0.5(bpp)(H2O)] (6), and [Zn(H2pbta)(bibm)]·H2O (7) (H2pbda = 4,4′-{[1,4-phenylenebis(methylene)]bis(oxy)}dibenzoic acid; p-bimb = 1,4-bis(1H-imidazol-l-yl)methyl)benzene; bpa = 1,2-bis(4-pyridyl)ethane; bpp = 1,3-bis(4-pyridyl)-propane; bibm = 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl; m-bimb = 1,3-bis(1H-imidazol-l-yl)methyl)-benzene; H4pbta = 5,5′-phenylenebis(methylene)-1,1′-3,3′-(benzene-tetracarboxylic acid) were prepared under solvothermal conditions and structurally characterized. Compound 1 shows a three-dimensional (3D) channel-like architecture constructed by helical chain subunits. Compound 2 shows a rare 2D + 2D + 2D → 2D network with both polyrotaxane and polycatenane features. 3 holds a 2D layer structure constituted of metal-sharing right- and left-handed helical chains. Compound 4 presents a one-dimensional (1D) chain which is decorated by long side arms around the chain. Compound 5 possesses a 2D wave-like layer formed by [Zn2(m-bimb)]n chains by linear pbta ligands. Compound 6 displays a 3D framework that is stabilized by hydrogen bonding interactions between the coordinated H2O molecules and the neighboring carboxylate oxygen atoms. Compound 7 possesses a 1D + 1D → 2D polycatenation motif. The results demonstrated that the rigidity versus flexibility of the ligands along with the number of carboxyl groups make an impact on the structural diversities of the entangled coordination polymers. Moreover, compounds 3 and 6 as representative examples possessed high catalytic efficiency for the photodecomposition of methyl blue in water using natural sunlight irradiation.