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

摘要

Five novel coordination polymers, [Zn(imbz)_2]_n (1), {[Zn(imbz)_2] centre dot H_2O}_n (2), [Zn(imbz)(mu_2-OH)]_n (3), [Zn_3(imbt)_2(p-bdc)_3]_n (4), [Zn_4(mu_3-OH)_2(imbt)_2(p-bdc)_3]_n (5), (imbt=4'-(imidazol-l-ylmethyl)benzonitrile, imbz~-=4'-(imidazol-l-ylrnethyl)benzoate and p-bdc= terephthalic acid) have been hydrother-mally 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 mu_2-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 alpha-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.