Self-assembly of zinc polymers based on a flexible linear ligand at different pH values: Syntheses, structures and fluorescent properties

Five novel coordination polymers, [Zn(imbz)2]n (1), {[Zn(imbz)2]·H2O}n (2), [Zn(imbz)(μ2-OH)]n (3), [Zn3(imbt)2(p-bdc)3]n (4), [Zn4(μ3-OH)2(imbt)2(p-bdc)3]n (5), (imbt = 4′-(imidazol-1-ylmethyl)benzonitrile, imbz− = 4′-(imidazol-1-ylmethyl)benzoate and p-bdc = terephthalic acid) have been hydrothermally prepared through systematically changing the pH values of reaction mixture, and structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray crystallography. Compounds 1 and 2 exhibit similar 2D (4,4) grid structures, whereas compound 2 contains a right-handed helix along b-axis. Compound 3 has a distorted diamond framework which was constructed via imbz− ligands and μ2-OH groups linking metal atoms. Compound 4 shows a 2D 6-connected network with trinuclear zinc clusters as secondary building units (SBUs), whereas 5 shows a distorted α-Po with tetranuclear zinc clusters as SBUs, in which p-bdc ligands act as bridges. Moreover, compounds 1-5 all exhibit strong blue photoluminescence in the solid state at room temperature.