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

Abstract

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.