Thesis (Ph.D.) - University of St Andrews, October 2009.

This dissertation focuses on the challenge of developing porous metal arylphosphonates with both high crystallinity and functional porosity by using different synthetic approaches. Metal phosphonates are an extensive class of materials based upon extended inorganic-organic architectures such as chains, layers and three-dimensional networks. Metal phosphonates generally favor extended inorganic architectures leading to pillared materials with no porosity. We found that the use of template molecules, type of ligand and choice of metal ions could be used to deviate from the pillared structure. Many of these structures had interesting properties that were explored. The results can be divided into three areas: We developed non-pillared monovalent metal phosphonates by investigating both the role of water and template molecules in the solvothermal synthesis. The role of water in solvothermal reactions was found to have a profound influence on the structure of monovalent metal phosphonates and the structures could be tailored from zero/one-dimensional to two-dimensional. Non-pillared structures could be synthesized by using template molecules. For a zinc phosphonate, we converted a layered structure into a three-dimensional framework by using small template molecules in the solvothermal reaction. The compound exhibited reversible dehydration behavior. The change in the framework structure and guest positions was monitored during this process. Two different ligands were used in the development of porous aluminum phosphonates. One series exhibited reversible dehydration behavior, which had a dramatic influence on permanent porosity of the material. The stability of the dehydrated phase is a result of the geometry of the aluminum atom, which in some cases has coordinatively unsaturated metal sites. The second series was developed with ion exchange applications in mind therefore the pore environment was tailored to favor ion exchange processes. The most important aspect is that these compounds exhibit high selectivity for Th^(4+) ions. In total 28 new compounds were prepared, and their utility and structures clarified.

Ph.D. (Chemistry) / This thesis was devoted to the synthesis of new bisphosphonates molecules, the study of their reactivity and the evaluation of their biological activities. The synthesis of epoxyalkylgembisphosphonates was carried out in three steps. The first step was the synthesis of arynyl and alkynylphosphonates by metallation of alkyl and aryl acetylenes followed by condensation with diethylchlorophosphate at low temperature. The second step was the synthesis of vinylgembisphosphonates by a tributylphosphine catalyzed phosphorylation of arynylphosphonates. The last step to epoxyalkylgembisphosphonates was achieved by oxidation of vinylgembisphosphonates using ethylmethyldioxirane generated in situ from potassium monopersulfate (caroate) and butanone in a phase transfer system. The synthesized epoxyalkylgembisphosphonates were studied in order to assess their reactivity with different nucleophiles and their chemical usefulness. All the synthesized compounds were characterized by nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy and mass spectrometry (GCxGC-TOF-MS). In term of reactivity, epoxyalkylgembisphosphonates were found to be less reactive than epoxyphosphonates. As far as their biological activities are concerned, epoxyalkylgembisphosphonates were found to be more potent than some commercially available antibiotics.

The primary goal of the work described in this dissertation was the incorporation of functionality into metal phosphonates. This was done in one of several ways. The first involved using phosphonate ligands that had covalently attached organic functional groups. In some cases, these ligands undergo reactions during the solvothermal syntheses which can impart new chemical reactivity. Another method used to introduce functionality was to partially or completely substitute metal atoms within phosphonate clusters to create materials which may have interesting magnetic properties. By controlling the way these clusters pack in the solids, their magnetic properties may be able to be augmented. The final method used to impart functionality to metal phosphonates was the incorporation of N-donor and bulky aryl groups into the phosphonate ligands. These influences caused structural variations which exposed potentially active sites within the materials, including both Lewis acidic and basic sites, as well as Bronsted acid sites. The first strategy was employed in the design of tetravalent metal phosphonates which have covalently incorporated bipyridine moieties. The materials are porous so that the bipyridine sites can chelate Pd atoms from solution, which can then be reduced to stable nanoparticles trapped within the phosphonate matrix. This approach was also used in the synthesis of surface-functionalized divalent metal phosphonates which exhibit interesting amine uptake properties. Solvent and cation substitution effects were used to control the packing and connectivity of phosphonate-based clusters. The selective substitution of metal atoms within the clusters may lead to interesting magnetic materials. In other work, N-donor and bulky phosphonates were used to influence the structure of several SnII phosphonates, which resulted in the discovery of a new layered structure type. The effect of the Sn-N interaction on the structures is investigated, and found to have significant effects on the structural units formed and how they pack in the solid state. The work presented herein represents only a small fraction of the rich chemistry of metal phosphonates. Creative researchers will continue to push boundaries and find new and interesting applications for phosphonate-based materials.

No description available.

The influence of the chemical phosphite on Phytophthora species was investigated by studying the morphological and molecular changes induced by phosphite. In vitro experiments were conducted to study the effects of phosphite on five isolates of each of five species of Phytophthora grown in low phosphate defined medium. Sensitivity to phosphite varied greatly among the five isolates of each species and resulted in a significant interaction between isolate and phosphite effect. The EC50 values ranged from less than 5 to 10 ìg/ml for P. cinnamomi, to 13 ìg/ml for P. nicotianae, to 27 ìg/ml for P. citricola, to 24 ìg/ml for P. palmivora and to 49 ìg/ml for P. capsici. Phosphite concentrations from 5 to 100 ìg/ml caused different degrees of morphological changes. Mycelial growth of all species was significantly suppressed by phosphite at 5 ìg/ml while at 100 ìg/ml there was hyphal lysis. Swelling of hyphae with stunted sidebranches and shrinking of cytoplasm from hyphal tips and hyphal walls were characteristic changes observed. Phosphite also retarded the development and caused distortion and lysis of chlamydospores, sporangia and zoospores. Zoosporogenesis was also adversely affected. Differential display reverse transcription-PCR was used to study changes in gene expression in P. cinnamomi induced in response to phosphite stress. The differential conditions were simulated by growth on a defined medium with and without phosphite amendment. This technique resulted in the isolation of 34 putative differentially expressed cDNA fragments which were cloned and sequenced. Nucleotide sequences of 26 of these cDNA clones were generated. BLASTX analysis of these nucleotide sequences against the NCBI database revealed that 18 exhibited homology to gene sequences encoding known proteins involved in various biological processes. The remaining eight showed homology to either hypothetical or unknown or unnamed proteins. The expression level of four of these cDNA clones were further analysed by real-time quantitative RT-PCR using SYBR Green 1 assay. Three candidate endogenous reference genes namely, tubulin, cyclophilin and actin were evaluated to determine their expression level under the influence of phosphite. None of these genes were significantly regulated by phosphite. As tubulin had the highest expression among the three, it was chosen as the endogenous reference gene. Amplification efficiencies between the reference gene and each of the target genes were validated and found to be approximately equal or within 5% of each other. The relative gene expression between the phosphite-treated and untreated samples can thus be determined using the comparative CT (ÄÄCT) method. One of the cDNA clones, CP6 which showed differential expression of three-fold was up-regulated. The remaining three were constitutively expressed. CP6 which encodes 1564 nucleotides showed sequence homology, at the amino acid level with proteophosphoglycans from Leishmania major. This study demonstrated the growth inhibition and morphological deformities caused by phosphite in Phytophthora species. It also illustrated the use of a modified DDRT-PCR method to study genes expressed in phosphite stress regulation. The application of real-time quantitative RT-PCR with SYBR Green I assay facilitated the quantification of the expression level of some of these genes.

Thesis (M.S.)--Youngstown State University, 2008. / Also available online via OhioLINK's ETD Center.

Thesis (M.Phil.)--Murdoch University, 2006. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 103-116.

Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 57-58). Also available via the World Wide Web in PDF format.

Thèses (M.Sc.)--Université de Sherbrooke (Canada), 1997. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.