Date on Master's Thesis/Doctoral Dissertation

12-2004

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemistry

Committee Chair

Buchanan, Robert Martin

Author's Keywords

Second coordination sphere; Amide; Imidazole; Ligands; Hydrogen bonding

Subject

Imidazole

Abstract

This dissertation deals with various imidazole compounds with emphasis on hydrogen bond interactions and weaker intermolecular forces. New amide functionalized polyimidazole metal binding pockets are able to form intramolecular six-membered hydrogen bonded rings with apical ligands bonded to the metal. The design of such ligands has been successful in the stabilization and characterization of mononuclear Cu-OH and Cu-OOH species. The end-on Cu-OOH species was characterized by UV-visible(band at 365 nm with e = 1500 M-1cm-1), EPR, ESI-MS and Raman spectroscopy (vO-O = 854 cm-1 which shifts by 46 cm-1 upon 18O substitution). Simple imidazole ligands were synthesized by general Mannich-type reactions. The ligand LEt, Me (LEt,Me = 4,4'-methylene-bis(2-ethyl-5-methylimidazole)) stabilizes late divalent first row transition metal complexes in 1:1 and 2:1 ligand-to-metal ratios. N-H---Cl hydrogen bonds stabilize supramolecular assemblies with interesting chloride vii arrangements. The [Co(LEt,Me)2]Cl2 crystallizes in the monoclinic space group C2/c, Z =12, with lattice dimensions of a = 28.684(5) ?, b = 25.247 (5) ?, c = 13.393 (2) ? and ß = 110.743(4)°. Its crystal structure displays tubular channels with internal dimensions of 8.43 x 3.75 ?2 with Co(II) atoms facing each other within the channel. The study also includes crystal structures of nitroimidazole synthons used in amide ligand synthesis, which demonstrate the importance of weak C-H---O(nitro) hydrogen bonding in stabilizing supramolecular assemblies. The compound, (bis(1-methyl-imidazol-2-yl)methyl)((1-methyl-4-nitroimidazol-2-yl)methyl)amine, and boric acid co-crystallize in the monoclinic space group P21/n, Z = 4, lattice dimensions a =15.7997(18) ?, b = 8.2540(9) ?, c = 27.530(3) ? and ß = 92.861(2)°. The resulting supramolecular structure contains bundled antiparallel imidazole-boric acid coils and boric acid filled one-dimensional channels. A variety of imidazole hydrates has been characterized that illustrates many of the fundamental properties of water. Important forms of water have been isolated within imidazole hosts: one-dimensional water chains and also water clusters with four-, five and six-membered hydrogen bonded water rings. These forms of water are thought to play crucial roles in biological systems by participating in protein structure, function, hydration and recognition and in the transport of protons or water molecules.

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