Supramolecular approaches to selective mercury cation binding and crystal engineering of covalent crystalline materials.

摘要

The first part of this dissertation focuses on the preparation, characterization and Hg2+ binding efficiency of a microparticulate sorbent based on a novel p-xylyl-peraza[2.2.2]cryptand-based polymer. The polymer was characterized in terms of surface morphology, size distribution and porosity. Sorption kinetics were measured and fitted to a homogeneous surface diffusion model whereby intraparticle diffusion parameters were determined. In order to gain insight into the mechanism(s) of binding, adsorption isotherms were constructed and sorbing capacity and specificity of a similar but non-macrocycle-containing polymer were investigated. Desorption studies were also carried out and the regenerability of the sorbent was demonstrated. The mercury capacity and selectivity of the sorbent in the presence of calcium ions was compared to the non-macrocycle-based polymer as well as a commercially available ion-exchange resin used for mercury removal.;The second part of this dissertation involves the use of non-covalent intermolecular interactions in the purposeful design of dihydrogen-bonded (hydridic-to-protonic hydrogen bonding) crystalline molecular solids in the pursuit of extended covalent crystalline materials. The field of crystal engineering seeks to understand and utilize the intermolecular interactions that organize molecular crystals. The properties of covalent solids depend strongly on their crystallinity. Topochemical transformation of dihydrogen bonds to covalent bonds (M--H...H--X → M--X + H2 ) in crystalline solids potentially merges these areas by converting molecular to covalent crystals. Retaining the long-range order through this type of transformation faces two challenges: (1) geometry change on M--X bond formation and (2) gas release within the lattice. In dihydrogen-bonded salts where either the cationic or anionic partner is much larger than the other, the packing of the large partners determines the lattice dimensions. These structures can tolerate bond reorganization and gas release, maintaining their crystalline order. In an effort to extend previous demonstrations of this approach based on large cations and simple borohydride anions, the present effort expands the range of large cations studied and explores the use of bulky 2-substituted benzimidazole boranes, zwitterionic structures that contain both the bulky cation and hydridic partner within the same molecule.