No description available.

The photoracemization of Ru(bipy)₃⁺⁺ in aqueous solution was studied. Quenching studies show the involvement of the (CT)³ Ru(bipy)₃⁺⁺ in the mechanism of racemization and the low quantum yield (2.9 x 10⁻⁴) shows that this state is asymmetric. Quenching studies show no increase of racemization rate for Ru(I) or (III) species. The temperature dependence gives evidence for a dissociative racemization mechanism. Quenching with Co(acac)₃ shows chiroselective electron transfer as measured by the resulting photochemistry. / Science, Faculty of / Chemistry, Department of / Graduate

International Telemetering Conference Proceedings / October 29-November 02, 1990 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Global Positioning System (GPS) translator signals have been used to track U.S Navy Trident missile test launches for the past 15 years. Absolute position accuracies of better than 20 meters in real-time and 8 meters in post mission have been consistently demonstrated. Flight qualified GPS translators 40 cubic inches in size have been developed for the U.S. Army Exoatmospheric Re-entry Vehicle Interceptor Subsystem (ERIS) program and are currently available for use by U.S. and allied government test ranges. More widespread use of GPS translators is constrained, however, by the great expense and size of the custom ground equipment currently used to acquire GPS translator signals and compute the position and velocity of the vehicle. To address this problem, the U.S. Air Force Western Space and Missile Center (WSMC) placed 3S under contract to design a lower-cost GPS translator processor based mainly on using commercial telemetry equipment. This paper describes how a working prototype was constructed to demonstrate the feasibility of the Translator Record and Interface System (TRIS). This prototype shows that TRIS can be built from a combination of commercially-available telemetry equipment, GPS equipment developed for the U.S. Air Force Range Applications Joint Program Office (RAJPO), and a few elements of custom equipment.

The studies described herein relate to the co-ordination chemistry of l,3,5-tris(trifluoromethyl)benzene, Ar(^F)H. The unique combination of steric bulk and a highly electron-withdrawing nature found in the a- bound Ar(^F) ligand has already been exploited to stabilise a variety of unusual main group compounds including the surprisingly air- and moisture-stable diphosphene Ar(^F)P=Par(^F). Other examples are discussed in the introductory chapter, as is the increasingly active area of diphosphene research. Chapter 2 describes the synthesis and structural characterisation of six early σ-Ar(^F) transition metal complexes, Mo(N(^t)Bu)(_2)(Ar(^F))2, Cr(NAd)(_2)(Ar(^F))(_2), [Mo(NAr)(_2)(Ar(^F))Cl-LiCl(dme)](_2), V(Ar(^F))(_2)Cl(thf), V(Ar(^F))(_3)-O -Li(thf)(_3) and Cr(Ar(^F))(_2)(PMe(_3))(_2). The first five of these compounds exhibit the rare phenomenon of weak metal-fluorine interactions, which is discussed in terms of several structural factors such as tilting of the aryl ring towards the direction of the M-F interaction The co-ordination chemistry of the diphosphenes Ar(^F)p=PArF, Ar*P=PAr* and Ar*P=PArF (Ar* = 2,4,6-(^t)BuC6H3) is reported in chapter 3. Ar(^F)p=Par(^F) is shown to displace olefins from a bis(imido)molybdenum centre to generate complexes such as Mo(NR)(_2)(PMe)(_3)(Ti2-ArFp=PArF) (R = tBu, 2,6-iPr2C6H3). The crystal structure of Mo(NtBu)2(PMe)3(Ti2- ArFp=PArF) has been elucidated. Related investigations have focused on the co-ordination mode of the diphosphenes Ar*P=PAr* and Ar*P=PArFwith [Pt(PEt3)Cl2]2/ and a variety of Til-complexes has been spectroscopically observed. The development of phosphorus based analogue of the industrially important olefin metathesis reaction is detailed in chapter 4. The reaction of ArPCl2, [Ar = Ar(^F), Ar* and 2,6-(CF3)2-C6H3 (Ar(^f1)] with the halide abstractor W(PMe3)6 leads to the generation of ArP=PAr via a postulated [W]=PAr phosphinidene intermediate. The unsymmetrical diphosphene ArFp=PAr* has been synthesised analogously from a mixture of ArFPCl2 and Ar*PCl2 with W(PMe3)6- When Ar is small (2,4,6-iPr3C6H2, 2,4,6- Me3C6H2), ArPCl2 reacts with W(PMe3)6 to give three-membered tricyclophosphanes, [ArP](_3) π-bound complexes of the Ar(^F)H ligand have been synthesised via metal vapour synthesis experiments, carried out in collaboration with Prof. F.G.N. Cloke at Sussex University. Chapter 5 describes the preparation of the bis-arene complexes M(T|6-ArFH)2 (M=Cr, V, Nb) and Ru(Ti6-ArFH)(Ti4-ArFH).Full experimental details and characterising data for chapters 2-5 are collected in chapter 6.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Ressonância Paramagnética Eletrônica (RPE) e Absorção Ótica Eletrônica foram utilizadas para estudar-se os complexos de Cobre (II) com tris-hidroximetil aminometano em solução. A análise dos parâmetros de RPE e óticos medidos na solução a diversos pHs foi feita tendo-se à mão as curvas de formação dos complexos. Estas curvas foram construídas em função do pH da solução, usando os dados de equilíbrio químico publicado por K. S. Bai e Martell (J. Inorg. Nucl. Chem. 31 (1969) 1697-1707), numa faixa de concentração de tris na qual este reagente é usando como tampão em estudos biológicos e químicos. Determinou-se cinco conjunto de parâmetros de RPE (go, ao, a11 e A11, correspondentes a diferentes complexos de íon metálico. Cada um desses espectros é encontrado em determinados intervalos de pH, sendo possível associá-los aos complexos previstos nas curvas de formação. A maior estabilidade dos complexos que se formam a pHs mais altos segundo as constantes de equilíbrio é evidenciada pelos valores e go isotrópico (RPE) menores pelos desdobramentos hiperfino isotrópico ao (RPE) e de campo cristalino (ótica) maiores do que os encontrados nas soluções menos alcalinas. A formação do complexo quelato neutro a pH alcalino foi observada, e obteve-se seu tensor g, das medidas do cristal simples. Este tensor encontra-se em bom acordo com o valor de g isotrópico determinado em solução (go=1/3(gxx+gyy+gzz)). Existe evidência de que este complexo seja pentacoordenado). Observou-se similaridade entre os parâmetros para os complexos coordenados por: 2N e 1N+1 0‾ 3N e 2N+1 0&#8254 ; 4N e 2N+2 0&#8254. Isto leva à conclusão de que do ponto de vista energético a coordenação de nitrogênio Cu2+ e a coordenação do oxigênio negativo ao Cu2+ nestes complexos são equivalentes, pelo menos dentro de nossa resolução experimental. / Electron Paramagnetic Ressonance (EPR) and optical visible spectroscopies were used to study the complexes of Cu (II) íon with tris-hydroxymethylamino methane (tris) in solution. Analyses of EPR and optical parameters measured in solution were made using the calculated formation curvesof the complexes. These formation curves were calculated as function of the solution pH, on the basis of the equilibrium constants published by K.S. Bai and Martell (J. Inorg.Nucl. Chem. 31 (1969)-1967-1707), for a concentration of this normally employed in a buffer in biochemical studies. Five sets of EPR parameters ((go, ao, a11 e A11) were determined corresponding to different metal complexes. Each det is found in a characteristic pH range and it was possible to make a correlation of these complexes with the appear in the formation curve plot. The greater stability of the complexes in the high pH range is indicated by the values of go, wich are smaller and the values of the hyperfine splittings ao and the crystal field splittings (from optical measurements) which are greater tahn at the less alcaline solutions. The formation of the neural chelate complexa t alcaline pH was observed, and its g-factors were obtained from measurements with the single crystal. These g-factors agree very well with the solution value (go=1/3(gxx+gyy+gzz)) and the orthorombic symmetriy is obtained. Evidence is present that this complex is penta-coordinated. It was observed a similarity between the EPR parameters for the complexes coordinated by: : 2N e 1N+1 0‾ 3N e 2N+1 0&#8254 ; 4N e 2N+2 0&#8254. This lead us the conclusion that from the energetical point of view the coordination of Cu2+ to nitrogen or to negative oxigen in these cases are equivalent, at or our resolution is not sufficent to differentiate between them.

Tris(hydroxymethyl)phosphine (THP) was prepared by the addition of a stoichiometric amount of base to tetrakis(hydroxymethyl)phosphonium chloride (THPC). Freshly prepared THP was successfully immobilised onto wool through a Mannich-type condensation reaction between a hydroxymethyl group and an amine on the wool surface, forming stable gt;P-CH2-Nlt; coupling links. The immobilisation of THP to wool stabilised the THP, which resulted in the decreased oxidation of THP to tris(hydroxymethyl)phosphine oxide (THPO). The presence of immobilised phosphine groups was determined colorimetrically by reaction with Ni2+ ions, which produced a bright orange nickel-phosphine complex, as well as quantitatively, by measuring nickel uptake using ICP-MS. Immobilised THP-wool showed proportional binding for varying concentrations of metal solution. Decreasing or increasing the concentration of the metal solution resulted in a corresponding proportional response of metal binding. Following immobilisation onto wool, oxidation of the system by 6% H2O2 resulted in a reduced binding of 24% for Cu, 25% for Co, 27% for Ni, and 93% for Cd relative to unoxidised THP immobilised onto wool. Additional modification of the THP-wool systems via reaction with amino acids and other related compounds overall did not appear to enhance the metal binding capacity relative to the unmodified THP-wool system. The only modified THP-wool system that showed either retention or an increase in metal binding capacity for all metals analysed was that of 2-aminopyridine, followed by oxidation with H₂O₂.

Ressonância Paramagnética Eletrônica (RPE) e Absorção Ótica Eletrônica foram utilizadas para estudar-se os complexos de Cobre (II) com tris-hidroximetil aminometano em solução. A análise dos parâmetros de RPE e óticos medidos na solução a diversos pHs foi feita tendo-se à mão as curvas de formação dos complexos. Estas curvas foram construídas em função do pH da solução, usando os dados de equilíbrio químico publicado por K. S. Bai e Martell (J. Inorg. Nucl. Chem. 31 (1969) 1697-1707), numa faixa de concentração de tris na qual este reagente é usando como tampão em estudos biológicos e químicos. Determinou-se cinco conjunto de parâmetros de RPE (go, ao, a11 e A11, correspondentes a diferentes complexos de íon metálico. Cada um desses espectros é encontrado em determinados intervalos de pH, sendo possível associá-los aos complexos previstos nas curvas de formação. A maior estabilidade dos complexos que se formam a pHs mais altos segundo as constantes de equilíbrio é evidenciada pelos valores e go isotrópico (RPE) menores pelos desdobramentos hiperfino isotrópico ao (RPE) e de campo cristalino (ótica) maiores do que os encontrados nas soluções menos alcalinas. A formação do complexo quelato neutro a pH alcalino foi observada, e obteve-se seu tensor g, das medidas do cristal simples. Este tensor encontra-se em bom acordo com o valor de g isotrópico determinado em solução (go=1/3(gxx+gyy+gzz)). Existe evidência de que este complexo seja pentacoordenado). Observou-se similaridade entre os parâmetros para os complexos coordenados por: 2N e 1N+1 0‾ 3N e 2N+1 0&#8254 ; 4N e 2N+2 0&#8254. Isto leva à conclusão de que do ponto de vista energético a coordenação de nitrogênio Cu2+ e a coordenação do oxigênio negativo ao Cu2+ nestes complexos são equivalentes, pelo menos dentro de nossa resolução experimental. / Electron Paramagnetic Ressonance (EPR) and optical visible spectroscopies were used to study the complexes of Cu (II) íon with tris-hydroxymethylamino methane (tris) in solution. Analyses of EPR and optical parameters measured in solution were made using the calculated formation curvesof the complexes. These formation curves were calculated as function of the solution pH, on the basis of the equilibrium constants published by K.S. Bai and Martell (J. Inorg.Nucl. Chem. 31 (1969)-1967-1707), for a concentration of this normally employed in a buffer in biochemical studies. Five sets of EPR parameters ((go, ao, a11 e A11) were determined corresponding to different metal complexes. Each det is found in a characteristic pH range and it was possible to make a correlation of these complexes with the appear in the formation curve plot. The greater stability of the complexes in the high pH range is indicated by the values of go, wich are smaller and the values of the hyperfine splittings ao and the crystal field splittings (from optical measurements) which are greater tahn at the less alcaline solutions. The formation of the neural chelate complexa t alcaline pH was observed, and its g-factors were obtained from measurements with the single crystal. These g-factors agree very well with the solution value (go=1/3(gxx+gyy+gzz)) and the orthorombic symmetriy is obtained. Evidence is present that this complex is penta-coordinated. It was observed a similarity between the EPR parameters for the complexes coordinated by: : 2N e 1N+1 0‾ 3N e 2N+1 0&#8254 ; 4N e 2N+2 0&#8254. This lead us the conclusion that from the energetical point of view the coordination of Cu2+ to nitrogen or to negative oxigen in these cases are equivalent, at or our resolution is not sufficent to differentiate between them.

Yes / One-pot reaction between 8-hydroxyquinoline-2-carboxaldehyde (HQC) and tris(hydroxymethyl)aminomethane (TRIS) followed by in situ cyclization yielded an oxazolidine based ligand which produced four mononuclear complexes of MnII(1), CoII(2), NiII(3), ZnII(4), a tetranuclear iron (FeIII4) complex (5) and a trinuclear cobalt (CoIICoIII2) complex (6). Magnetic studies show dominant antiferromagnetic interaction in tetranuclear iron (FeIII4) complex 5 and presence of the slow relaxation of magnetisation in 6. The compounds were also studied for their antibacterial properties. The oxazolidine ligand (H3L2) of this study showed good antimicrobial activity not only against Gram-positive bacteria but against Gram-negative bacteria too. The antimicrobial efficacy of the metal complexes (1–6) is also reported. / The full-text of this article will be released for public view at the end of the publisher's embargo period on 11 Apr 2019.

The enzymatic degradation of polyethylene terephthalate (PET) occurs at mild reaction conditions and may find applications in environmentally friendly plastic waste recycling processes. The hydrolytic activity of the homologous polyester hydrolases LC cutinase (LCC) from a compost metagenome and TfCut2 from Thermobifida fusca KW3 against PET films was strongly influenced by the reaction medium buffers tris(hydroxymethyl)aminomethane (Tris), 3-(N-morpholino)propanesulfonic acid (MOPS), and sodium phosphate. LCC showed the highest initial hydrolysis rate of PET films in 0.2 M Tris, while the rate of TfCut2 was 2.1-fold lower at this buffer concentration. At a Tris concentration of 1 M, the hydrolysis rate of LCC decreased by more than 90% and of TfCut2 by about 80%. In 0.2 M MOPS or sodium phosphate buffer, no significant differences in the maximum initial hydrolysis rates of PET films by both enzymes were detected. When the concentration of MOPS was increased to 1 M, the hydrolysis rate of LCC decreased by about 90%. The activity of TfCut2 remained low compared to the increasing hydrolysis rates observed at higher concentrations of sodium phosphate buffer. In contrast, the activity of LCC did not change at different concentrations of this buffer. An inhibition study suggested a competitive inhibition of TfCut2 and LCC by Tris and MOPS. Molecular docking showed that Tris and MOPS interfered with the binding of the polymeric substrate in a groove located at the protein surface. A comparison of the Ki values and the average binding energies indicated MOPS as the stronger inhibitor of the both enzymes.