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

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.