Studies On Structures And Properties Of Metal Complexes With Flexible Ligands Containing N Or O Heteroatoms

One of the major goals of supramolecular chemistry is to understand theself-assembly of organic and inorganic molecules, which could help us summarize therules of coordination chemistry and extend the range of new materials having potentialapplications in various field, such as electrics, magnetism, electrochemistry, optics andcatalysis. Generally speaking, the generation of self-assembling coordinationarchitectures depends on the combination of several factors—the coordinationgeometry of the metal ions, the performance of the ligands, the coordinated and/ornon-coordinated counter ions, the solvent systems, the reaction conditions, and so on.Among them, the ligand is no doubt the key factor of manipulating the structure of thesupramolecular complexes. Therefore, the application of well-designed ligands tocontrol the assembly of molecular architectures has become a popular and rapidlygrowing discipline.Many coordination architectures have been constructed with rigid bridgingheterocyclic ligands and the various properties of the materials were reviewed. Morerecently, increasing attention has been paid to employ flexible ligands in order todevelop novel supramolecular frameworks and research useful functions. We havedesign and prepared some different flexible ligands with N or O heteroatoms: based on1,3,4-oxadiazole consisting of five-membered heterocyclic as link; based on alkyl linearchain with oxygen atoms in the backbone linking benzotriazoles; based on chiralreduced Schiff Bases of amino acids. The crystal structures and properties of theircomplexes have also been investigated. The thesis is included six parts.1. A brief review of the background and application on supramolecularcoordination compounds was concisely given. The nature of supramolecular chemistryand the class of ligands were summarized. The regulation of basal supramolecularframeworks, the building of helical structure, the forming of coordination polymers, thedesign of sensors and the application of luminescent materials based on lanthanide wereintroduced emphatically.2. A series of amide-based 2,5-diaryl-1,3,4-oxadiazole derivative ligands weredesigned and synthesized. The relationship between the conjugated structure of theseligands and the fluorescence of their lanthanide complexes was studied. The terminalgroup effect of ligands on the fluorescence was explored by comparing the complexesprepared by different amide-based ligands.3. Four salicylamide ligands with different terminal group based on1,3,4-oxadiazole derivative were designed and synthesized. Their lanthanide complexeswere tried to prepare under the same condition. The crystal structure and luminescent properties of the complexes have been investigated. The results suggested that the fineregulation of the terminal group influence the structure and the fluorescence of thecomplexes.4. A new flexible ligand 2,5-bis[(quinolin-8-yloxy)methyl]-1,3,4-oxadiazole basedon 1,3,4-oxadiazole and 8-hydroxyquinoline was designed and synthesized. The organiccompound possess specific space which could selectively accommodate Cd²⁺ accordingto ionic radius and a prominent fluorescence enhancement only for Cd²⁺ was found inaqueous methanol solution. The properties and mechanism of the sensor were studiedand explored.5. A series of structurally related flexible ligands by using benzotriazole as terminalgroup and alkyl linear chain as link were synthesized. On the backbone chain, somebackbone carbon atoms are replaced by oxygen atoms. The disturbance of increasingthe length of the backbone chain and the influence of changing the species of metal ionson the effective regulation of supramolecular complex structures were investigated.6. On the base of the previous research on lanthanide-based clusters, a pair ofenantiomorphous chiral reduced Schiff bases of amino acids was synthesized. Theself-assembly coordination chemistry and unique triple-helical structures oflanthanide-based supramolecular clusters were investigated further, and thecomprehension of small molecule encapsulated into the cluster was rectified. Theexperiment exhibited that CO₂ molecules from the atmosphere were efficiently capturedand fixed into these clusters through chemical conversion. Chiral signal analysis of theligands could be successfully applied to anion-selective recognition for CO₃^2- insolution.