No description available.

As an additional study, effect of tyrosine nitration on the BCD of protonated and metalated peptides was investigated. Some fragment ions that were inhibited in the ECD of protonated peptides were liberated in the ECD of metalated peptides. By theoretical calculation of the cation-pi and cation-nitro group coordination using the metal ions nitrated phenol complex as a model, it is found that the metal ions might favor coordinating with the nitro group of the nitrated tyrosine residue in the peptides. / In order to improve the performance of the electron capture dissociation (BCD) mass spectrometry for structural analysis of peptides/proteins, BCD of peptides cationized with various transition metal ions was investigated. It was found that peptides adducted with different divalent transition metal ions generated different BCD tandem mass spectra. For Mn2+and Zn2+, the incoming low-energy electron would not favor being trapped by the metal ions and instead trigger the usual BCD dissociation channel(s) via "hot-hydrogen" or "superbase" intermediates to form a series of c-/z·- fragments. For other first row transition metal ions, including Fe2+, Co2+, Ni 2+and Cu2+, reduction of the metal ions occurs preferentially during the electron capture event and lead to the formation of usual "slow-heating" type of fragment ions, i.e. metalated a-/y-fragments & metalated b-/y- fragments. / To further compare the behavior of metal ions with the same electronic configuration, BCD of Group IIB metal ions adducted peptides were investigated. In contrast to the ECD behavior of Zn2+ adducted peptides, peptide radical cations (M+· ) and fragment ions corresponding to losses of neutral side chain from M+· were observed in the ECD spectra of Hg2+ and Cd2+ adducted peptides. The experimental observations appeared to depend on the balance of the ionization energy of peptide and the solvation modulated ionization energies of the metal atom. The reduction of divalent metal ions by the electron capture event could induce spontaneous electron transfer from the peptide moiety to the monovalent metal centre and generate hydrogen-deficient M +· species. / Chen, Xiangfeng. / Adviser: T.-W. Dominic Chan. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 131-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

A binary mixture of copper (II) chloride and gold (III) chloride solutions were introduced into a FT-ICR Mass Spectrometer through electrospray ionization techniques to produce ion clusters in the gaseous state. A series of families of ion clusters were detected across a range of different concentrations and they were identified as heterometallic mono-cationic clusters with possible hydrated and ligated species present as well. Ab initio calculations on the first member of the family of hetero-metallic monocationic species detected in the mass spectra were carried out using density function theory (DFT) methods and correlation consistent (cc) basis sets. Equilibrium bond lengths and vibrational frequencies were computed and resulting values compared with published literature values. / published_or_final_version / Applied Geosciences / Master / Master of Science

No description available.

No description available.

Thesis (Ph.D.)--University of Houston, 2003. / Adviser: Allan J. Jacobson. Includes bibliographical references.

Thesis (M.Sc.)--Memorial University of Newfoundland, 2004. / Restricted until October 2005. Bibliography: leaves 135-154.

A long standing problem in catalysis is the identification and characterization of the active sites, i.e. an atom or an ensemble of atoms spouse on the surface of a catalyst.[Taylor1925] One relevant case, that is treated in this thesis, is constituted by the Phillips catalyst.[Hogan1958] For several reasons, even though this catalyst has be applied at industrial scale for decades and is accounted for a majority of the high density polyethylene (HDPE) production, the identification and the mechanism of the active sites are still under debate. This work was initiated in the framework of the PARACAT project, which is dedicated to study the paramagnetic species in catalysis, and focuses on 'The role of Cr paramagnetic states in olefin polymerization over Phillips catalyst.' In the course of the study, I brought this research to a larger scale which included but was not limited to the Phillips catalyst itself. Considering the relevance of the interaction between transition metal ions (TMI) and the support to the catalytic activity, I worked on systems that cover a number of oxide-supported TMIs by means of electron paramagnetic resonance (EPR) spectroscopy. In this thesis I investigated the paramagnetic Cr(V) and Cr(III) species in the Phillips catalyst. The Cr(III) species were suggested with possible relevance to the catalytic reaction while Cr(V) species were suggested as just the spectators in the reaction.[McDaniel2010, Groppo2018] Nevertheless, Cr(V) species were used in this work as spin probes to provide more information on the overall system. Field-sweep methods including continuous wave (CW) EPR and echo detected field sweep (EDFS) showed that the there are two Cr(V) species with different local geometries. Quantitative analysis of the CW EPR showed that these two Cr(V) species have different reactivity with ethylene. The instantaneous diffusion analysis were performed on the Cr(V) species to provide information on the dispersion of the Cr on the silica surface and the results suggested clusters were formed locally. Besides studying the Phillips catalyst itself, I studied also the silica supported organometallic-Cr catalyst, Cr[CH(SiMe3)2]3/SiO2, which served as a model system to investigate the catalytic active Cr species with well-defined oxidation states and geometry. Two categories of the Cr(III) species were assigned to the active sites for olefin oligomerization and polymerization. The assignment were done by comparing their distortion of the local geometries with that of the different precursors. On the other hand, microporous materials including zeolites and zeotype materials such as aluminophosphate (AlPO) can be engineered with different physical and chemical properties in terms of chemical composition and provide a relevant example of structure sensitivity of a heterogeneous catalyst.[Hartmann2002, Hartmann1999] Such structure sensitivity is highly relevant in catalysis and can be very well studies with EPR spectroscopy. In this regard, I investigated a series of SAPO-5 materials doped with different TMI. In the first place, the incorporation of Cr in SAPO-5 was studied focuses on the discrimination of isomorphous substitution at framework sites and extra-framework sites. In the hyperfine sublevel correlation (HYSCORE) spectrum, large hyperfine interaction (hfi) of 27Al with the matrix 31P signal provide solid evidence for the isomorphous substitution of Cr(V) at framework sites. In addition to the Cr-incorporated SAPO-5, a method to prepare a bi-metallic Mo/V-SAPO-5 system was developed and the metal-metal synergy was validated with a single electron transfer reaction and the short range hyperfine interaction. HYSOCRE spectra showed large \textit{hfi} of both 27Al and 31P and suggested the V species grafted at extra-framework sites. Moreover, the HYSCORE spectrum showed signals at low frequency region which were attributed to the 95,97Mo species with large hfi, confirming the short range interaction. Finally, the surface properties of SAPO-5 were studied by adsorbing NO radicals in the pores and investigating their interaction with the surface. Different adsorption sites of NO molecules according to different activation conditions were first discriminated by the g-factors obtained from the CW EPR. From the 27Al HYSCORE spectra, it is observed that when the activation temperature is higher the NO molecules are situated in vicinity of some defect Al sites. However, the dominant Al species were observed either in samples activated at lower temperature or by increasing the NO dosage. This is postulated as that the defect sites were blocked by residual water molecules or saturated by excessive NO molecules. The presence of water molecules were validated by 1H HYSCORE experiments and the coordination of NO-water was estimated from the hfi structure. [Taylor1925] Taylor, H. S. Proc. R. Soc. London. Ser. A, Contain. Pap. a Math. Phys. Character 1925, 108, 105-111 [Hogan1958] Hogan, J. P.; Banks, R. L. Polymers and production thereof US Patent 2,825,721, 1958. [McDaniel2010] McDaniel M. P. Advances in Catalysis, 1st Ed. 2010; Vol. 52, pp 123-606 [Groppo2018] Groppo, E.; Martino, G. A.; Piovano, A.; Barzan, C. ACS Catal. 2018, 8, 10846-10863 [Hartmann2002] Hartmann, M.; Kevan, L. Res. Chem. Intermed. 2002, 28, 625-695 [Hartmann1999] Hartmann, M.; Kevan, L. Chem. Rev. 1999, 99, 635-663

Hybrid inorganic-organic networks have been studied in both chemistry and materials science due to properties, (e.g. porosity, magnetic and electronic behaviors) that may lead to applications in catalysis, gas absorption and storage. It is important to understand the different structural topologies shown by hybrid networks to help develop practical applications for these materials. The research is focused on the design and synthesis of well-defined hybrid network structures that have potential to contain molecular size cavities that can be used for catalysis and gas storage. In the field of organic-inorganic hybrid networks, the goals are to design and synthesize 1D, 2D and 3D networks with cavities, and to characterize them by X-ray, TGA and surface area measurements. Twenty-six networks have been successfully made with interesting structure topologies. These hybrid network structures are classified into three series based on their ligands. Series I contains ten hybrid networks constructed from the flexible ligand, 4, 4′-trimethylenedipyridine (TMDP), Zn2+ ions, and H3PO3, and with aromatic alcohols as templates to direct the formation of various hybrid network structures. Series II consists of five structures constructed from the relatively rigid ligand, 4, ′-bisimidazolelybipyridine (BIB) with metal ions (Cu2+, Ni2+) and the conjugated bases of H3PO3 and H3PO4. The BIB ligand is not commercially available so is produced and characterized by NMR, mass spectrometry and TGA. Rigid network structures were expected to construct with pores of molecular dimensions with the BIB ligand. To date, the BIB ligand has not yield the desired porous network, however, these 3D hybrid networks have interesting topologies, one of which is an interdigitated network that is the precursor for 3D interpenetrated networks. Series III contains five hybrid structures constructed from various organic ligands, such as tartaric acid, picolinic acid and 1, 2, 4-triazole. In addition to the hybrid networks, six hydrogen bonded networks were prepared. Graph-Analysis is applied to study these hydrogen bonded network structures. The Ï â ¦.Ï interaction is also discussed within the hydrogen bonded networks. / Ph. D.

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The competitive transport, extraction, and coordination chemistry for a series of N- (thio)phosphorylated (thio)amide and N-(thio)phosphorylated (thio)urea ligands were investigated with the seven transition and post-transition metal ions Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Cd(II) and Pb(II). Three N-benzylated derivatives of 1,4,7,10- tetraazacyclododecane (cyclen) were synthesized and a similar study carried out with the same metal ions and the deprotonated precursors. The ligands were all potential specific carriers (ionophores) in the organic phase. The seven metal ions had equal concentrations in the source phase. The experimental arrangement for the transport studies employed a set-up involving three phases: a source phase and a receiving phase (both aqueous), separated by a chloroform membrane (organic phase). Competitive metal ion solvent extraction involved two phases: an aqueous phase and an organic phase. Similar conditions were used in transport and extraction studies. The metal ion concentrations in the aqueous phases were analyzed by atomic absorption spectroscopy (AAS). The transport results of deprotonated N-(thio)phosphorylated (thio)amides and N- (thio)phosphoryated (thio)ureas showed that PhC(S)NPO(OPri)2 (L1), BrPhC(S)NPO-(OPri)2 (L11) and PriNHC(S)NPO(OPri)2 (L16) transported Ag(I) into the receiving phase. Under these experimental conditions, L1 had the highest Ag(I) transport efficiency, at 36.3%, while L11 only transported one metal ion, viz. Ag(I). With NH2C(S)NP(S)(OPri)2 (L4), 94.6% of Ag(I) remained in the membrane phase. Thus L4 appeared to have the highest formation constant with Ag(I). A small amount of Cu(II) was also transported by L1, NH2C(S)NP(O)(OPri)2 (L9), L16 and ButNHC(S)-NPO(OPri)2 (L20). L20 had the highest selectivity for Cu(II). Results of competitive metal ion extraction studies revealed that most ligands extracted up to 100% Ag(I), except L1 and morpholine substituted ligands (L7, L17) . The formation constant of L1 effects a subtle balance between metal uptake and metal loss into and out of the respective membrane phase. HL7 and HL17 had low solubility in chloroform. L4 extracted the highest percentage of Cu(II) (49%). Two neutral ligands, PhCONHPO(OPri)2 (1) and BrPhCONHPO(OPri)2 (2) were isolated and their molecular structure determined. They had monoclinic unit cells in the space groups C2/c and P21/n, respectively. An unprecedented octanuclear [Ag(I)(L4-S,N)]8 (3) complex was also crystallized. The extended structure showed three different cavities alternating with two unique 16-membered rings, creating a novel AgS2N2 cage. Two polynuclear Cu(I) chelates with deprotonated L4 and L6 (tBuNHC(S)NP(S)(OPri)2) were isolated by the same crystallization method. The complex [Cu(I)(L4–S,S)]9 (4) consisted of a hexagonal-prismatic hexamer, which exhibited an unusual and unprecedented supramolecular “honeycomb” packing. The trinuclear [Cu(I)(L6–S,S)]3 (5) consisted of a 6-membered Cu3S3 ring attached to a hydroxy tetrahydrofuran molecule. Di-, tri- and tetra-benzyl-1,4,7,10-tetraazacyclododecane (cyclen) was synthesized, and characterized. None of these compounds was effective in metal transport under these experimental conditions. Nevertheless, Tetra-benzyl cyclen showed the highest extraction efficiency for Ag(I), at 100%, and the highest selectivity for Ag(I) extraction, compared to Cu(II). An intermediate of dibenzyl cyclen compound dibenzylated dioxocyclen (6) was crystallized and found a host THF molecule in the lattice. The crystal and molecular structure confirmed the cis-configuration. The X-ray structure of the Cu(II) complex with dibenzylated cyclen (7) was determined for the first time. It was found to have an ideal square pyramidal coordination geometry around the central metal ion. A serendipitous organic compound of isopropylammonium(isopropylamino)- oxoacetate mono-hydrate (8) was crystallized. The crystal was held together by inter-molecular hydrogen bonds, which lead to two-dimensional layers with hydrophobic interactions.