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Title: Advanced coordination networks for electronic and absorptive properties : between serendipity and rational design
Other Titles: Ju you dian zi xue he xi fu xing zhi de xian jin pei wei wang luo de mo suo he she ji
Authors: He, Jun (何軍)
Department: Department of Biology and Chemistry
Degree: Doctor of Philosophy
Issue Date: 2010
Publisher: City University of Hong Kong
Subjects: Organometallic compounds.
Notes: CityU Call Number: QD411 .H4 2010
xix, 167 leaves : ill. (some col.) 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references.
Type: thesis
Abstract: In spite of the rapid growth of the field of coordination networks in the past decade, two major directions remain highly worthwhile to be further explored: 1) to achieve more efficient and more intense photophysical and electronic properties in the solid-state network, such as photoluminescence, conductivity and magnetic properties; 2) design functionalized molecular and network systems to achieve advanced solid-state absorption properties - not just for small gas molecules (e.g., N2, CO2, H2), but for guest species (e.g., organic molecules and metal salts) with more significant functions. In this connection, we present particular interests in bifunctional organic molecules based on thiol or thioether-carboxylate as the building blocks [e.g., 2,5-dimercapto- benzenedicarboxylic acid (H4DMBD), 2,5-bis(2-(methylthio)ethylthio)terephthalic acid (L1)], which can offer richer functional diversity that provides for advanced material properties in the prospective solids. The crux here is to select the two sets of functions judiciously - with one set being the chemically hard carboxylic group, and the other being the chemically soft thiol or thioether group. Consequently, on one hand, the thiol groups (e.g., in H4DMBD) will bind with distinct preference to soft metal ions (such as Cu+) to integrate metal-thiolate functions into the resultant network, which will generate significant electronic communications throughout the whole nets; on the other hand, the carboxylate groups (e.g., in H4DMBD, L1) will firstly bind to chemically hard metal ions (such as Eu3+, Zn2+) to form a robust metal-carboxylate coordination network, while leaving the soft thiol or thioether groups as secondary groups free standing inside the established networks. And thus various soft metal species (such as HgCl2) can then be attracted into the porous network by interacting with the thioether groups. Moreover, an idea of involving the secondary groups in the coordination spheres of the metal centers, as a means to fine-tune the coordination spheres of the metal centers and the associated material properties has been demonstrated. L1 and L2 (2,5-bis-(2-hydroxy-propylsulfanyl)-terephthalic acid), respectively reacted with Pb(NO3)2 to afford two coordination networks featuring similar network topology but much different photophysical properties. Especially, the complex based on L2 is single component white light-emitting, which makes it have good potential application in lighting and displays. We also have explored a class of branchy molecules with back-folded, centripetal geometry as mulitfunctional building blocks for coordination networks. Two centripetal molecules respectively reacted with AgSbF6 to afford two coordination networks featuring novel coordination modes, network connectivity and chiral/helical structures. In comparison to the methodical molecular modification for functionalizing the frameworks, a 3D open framework based on a copper iodide cluster and bipyrozole molecule (with a relatively simple functionality) has shown interesting electronic properties stemming from serendipitous copper iodide clusters. Specifically, this mixed-valent CuIICuI15I17 cluster, gives rise to distinct fluorescent emission and thermochromism, and the mixed-valent feature generates paramagnetic behavior in the solid-state network.
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