Coordination Polymers Based On Bis-imidazolyl Ligands And Their Photocatalytic Properties

Over the last two decades, coordination polymers have emerged as promising materials for adsorption, separation, magnetism, catalysis and luminescence owing to their intriguing structures and properties. Photocatalytic degradation of organic dyes and photoluminescence sensing using coordination polymers are two unique features of coordination polymers that attract less attention compared to other properties. In this thesis,we chose two bis-imidazolyl ligands, namely 4,4′-bis(4-methyl-1-imidazolyl)biphenyl(bmimb) and 2-amino-4,4′-bis(1-imidazolyl) biphenyl(abimb) to react with transition metal ions in the presence of various polycarboxylates to produce an array of seven different coordination polymers. We investigated their crystal structures, their use as photocatalysts in the degradation of organic dyes, and their photoluminescence sensing towards nitroaromatics. These results were briefly summarized as follows:1. Reactions of Zn(NO3)2?6H2O and Cd(NO3)2?4H2O with bmimb in the presence of 1,3-benzenedicarboxylic acid(H2-1,3-BDC) or 1,4-benzenedicarboxylic acid(H2-1,4-BDC)afforded four coordination polymers, namely, [Zn(1,3-BDC)(bmimb)]n(1), [Zn(1,4-BDC)(bmimb)]n(2), [Cd(1,3-BDC)(bmimb)]n(3) and [Cd(1,4-BDC)(bmimb)]n(4).Compounds 1, 2 and 4 are interpenetrated 3D frameworks while compound 3 has a 2D network. Compounds 2 and 3 are promising heterogeneous catalysts for the photodegradation of Rhodamine B(Rh B) in water and retain their structural integrity upon at least five reaction cycles.2. Since ligand bmimb and four coordination polymers [Zn(1,3-BDC)(bmimb)]n(1), [Zn(1,4-BDC)(bmimb)]n(2), [Cd(1,3-BDC)(bmimb)]n(3) and [Cd(1,4-BDC)(bmimb)]n(4)demonstrated reasonably strong luminescence, we further used bmimb and 2 as examples to investigated their photoluminescence sensing property. Compared to bmimb, the photoluminescence of 2 could be more effectively quenched by nitroaromatics such as nitrobenzene, 4-dinitrophenol, nitrophenol, paranitroaniline. The results suggest that coordination polymers based on bmimb can be a good platform for explosives sensing.3. Reactions of Zn(NO3)2?6H2O, Cd(NO3)2?4H2O and Pb(NO3)2with bmimb and abimb in the presence of 1,4-naphthalenedicarboxylic acid(H2-1,4-NDC) afforded three coordination polymers, namely, {[Zn(1,4-NDC)(abimb)]·0.25CH3OH}n(5), {[Cd(1,4-NDC)(abimb)]·H2O}n(6) and [Pb(1,4-NDC)(bmimb)]n(7). Compounds 5 and 6are 2-fold interpenetrated 2D networks, while compound 7 features a 3D framework with 4-fold interpenetration.