Syntheses, Structures, and Photoluminescent Properties of Coordination Polymers Based on 1,4-Bis(imidazol-l-yl-methyl)benzene and Various Aromatic Dicarboxylic Acids

Nine coordination polymers, formulated as {[Zn­(p-bdc)­(bix)]­(DMF)2}n (1), {[Co­(p-bdc)­(bix)]­(DMF)2}n (2), {[Cd­(p-bdc)­(bix)]­(DMF)2}n (3), {[Zn­(bpdc)­(bix)]­(DMF)3}n (4), {[Co­(bpdc)­(bix)]­(DMF)3}n (5), {[Cd­(m-bdc)­(bix)­(H2O)]­(DMF)}n (6), {[Zn­(m-bdc)­(bix)]­(solv)x}n (7), {[Zn2(m-bdc)2(bix)2]­(solv)x}n (8), and {[Zn­(m-bdc)­(bix)]­(solv)x}n (9) (p-H2bdc = 1,4-benzenedicarboxylic
acid, H2bpdc = biphenyl-4,4′-dicarboxylic acid,
m-H2bdc = 1,3-benzenedicarboxylic acid), have been prepared
by solvothermal reactions of the semirigid neutral ligand 1,4-bis­(imidazol-l-yl-methyl)­benzene
(bix) with metal ions in the presence of various aromatic dicarboxylic
acids. These complexes were characterized by Fourier transform infrared
(FT-IR) spectroscopy, elemental analysis, thermogravimetric analysis
(TGA), and single-crystal X-ray diffraction analysis. Isostructural
complexes 1 and 2 reveal a 3-fold interpenetrating
three-dimensional (3D) framework with dia topological
type. Compound 3 exhibits a non-interpenetrating, highly
undulating two-dimensional (2D) network with (4,4) topology. Compounds 4 and 5 exhibit (6,3) layer structures consisting
of hexagonal meshes and loops. Compound 6, from the topological
point of view, shows the same (4,4) topology as compound 3; however interestingly all the layers can be divided into pairs
in the overall network. Complex 7 also possesses a 3-fold
interpenetrated 3D dia framework similar to 1 and 2. Compound 8 comprises two independent
2D (4,82) nets that interpenetrate in a parallel manner.
Non-interpenetrating 2D (4,4) layers are also observed in compound 9 that are further packed into a 3D framework featuring one-dimensional
(1D) channels. The structural diversity of nine coordination polymers
indicates that the structures can be tuned by metal ions, various
ditopic carboxylate anions, and changeable conformations of neutral
ligand. In addition, photoluminescent properties of four coordination
polymers were also investigated in this paper.