• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 115
  • 15
  • 12
  • 4
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 284
  • 284
  • 71
  • 60
  • 57
  • 56
  • 50
  • 44
  • 41
  • 32
  • 32
  • 30
  • 27
  • 26
  • 19
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Substitution Kinetics Of The Pentacarbonylbis(trimethylsilyl)ethynetungsten(0) With Triphenylbismuthine

Ercan, Bayram 01 June 2003 (has links) (PDF)
The reaction between pentacarbonylbis(trimethylsilyl)ethynetungsten(0), W(CO)5(&amp / #951 / 2-btmse), and triphenylbismuthine, Bi&Oslash / 3, yields pentacarbonyltriphenylbismuthinetungsten(0), W(CO)5(Bi&Oslash / 3), as the sole product. The kinetics of the substitution of btmse by Bi&Oslash / 3 was studied by means of quantitative FT-IR Spectroscopy. The starting complex was prepared photochemically from hexacarbonyltungsten, W(CO)6, in the presence of excess btmse in n-hexane and identified by FT-IR and NMR Spectroscopies. The substitution reactions were performed in cyclohexane solutions at different concentrations of both leaving and entering ligand to observe the dependence of observed rate constant, kobs, on the concentration of entering and leaving ligands and also, at different temperatures to evaluate the activation enthalpy (&amp / #8710 / H&amp / #8800 / ) and the activation entropy (&amp / #8710 / S&amp / #8800 / ). The IR extinction coefficients for CO stretching were determined for both the starting complex W(CO)5(&amp / #951 / 2-btmse), and the product W(CO)5(Bi&Oslash / 3). Quantitative IR Spectroscopy does not show any significant reduction in the total amount of substance (material balance). Formation of W(CO)6 (in small amount) was attributed to the decomposition of the product, W(CO)5Bi&Oslash / 3. From the evaluation of kinetic data, a mechanism was proposed in which the rate determining step is the cleavage of btmse ligand from the starting complex, W(CO)5(&amp / #951 / 2-btmse) and the formation of solvated complex, W(CO)5(solvent). Thus, the reaction is essentially dissociative. The large positive value of activation entropy (&amp / #8710 / S&amp / #8800 / ) and large value of activation enthalpy (&amp / #8710 / H&amp / #8800 / ) are indicative of a dissociative mechanism.
162

Tetracarbonyl[n,n

Akyol, Ceyhun 01 March 2005 (has links) (PDF)
N,N&rsquo / -bis(ferrocenylmethylene)ethylenediamine was prepared from the reaction of ferrocenecarboxaldehyde and ethylenediamine and characterized by IR, Raman, 1H and 13C-NMR spectroscopy. The electrochemical behaviour of this ligand was also studied for the first time by cyclic voltammetry. Diferrocenyl diimine ligand was used in the thermal substitution of 1,5-cyclooctadiene in Cr(CO)4(2:2-1,5-cyclooctadiene) at 38&deg / C in toluene for two hours to form the tetracarbonyl[N,N&rsquo / -bis(ferrocenylmethylene)ethylenediamine]chromium(0), [Cr(CO)4(BFEDA)]. This complex was succesfully isolated and crystallized from its 1:1 toluene/dichloromethane solution and characterized by elemental analysis, MS, IR, 1H, 13C-NMR spectroscopy. Electrochemical behaviour of the complex was also studied by cyclic voltammetry and the mechanism of electrode reaction was investigated by in-situ UV-VIS and IR spectroscopy measurements. This new complex has the iron atom of ferrocene unit in conjugation with the chromium metal center and, therefore, shows an electronic communication between two metal atoms.
163

Synthesis And Characterization Of Tetracarbonyl[n,n&#039 / -bis(ferrocenylmethylene) Ethylenediamine]molybdenum(0) Complex

Kocak, Fatma Sanem 01 May 2005 (has links) (PDF)
In this study a bidentate ligand containing two ferrocenyl moieties, N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine, was prepared by condensation reaction of ferrocenecarboxyaldehyde and ethylenediamine on refluxing in benzene. The molecule was identified by IR, Raman, UV-Vis, 1H-, 13C-NMR spectroscopies. Then, this bidentate molecule was reacted with tetracarbonyl(bicyclo[2.1.1] hepta-2,5-diene)molybdenum(0). The ligand substitution reaction in toluene yielded the new complex, tetracarbonyl[N,N&acute / -bis(ferrocenylmethylene)ethylenediamine] molybdenum(0). This new complex could be isolated from the reaction solution in the form of orange crystals and fully characterized by elemental analysis, IR, UV-Vis, MS, 1H- and 13C-NMR spectroscopies. As a bidentate ligand, N,N&acute / -bis(ferrocenylmethylene)ethylenediamine binds the metal atom in the two cis positions in the pseudooctahedral geometry of the molybdenum-complex. Electrochemistry of the tetracarbonyl[N,N&acute / -bis(ferrocenylmethylene) ethylenediamine]molybdenum(0) was studied by cyclic voltammetry, chronoamperometry and controlled potential electrolysis combined with the UV-Vis or infrared spectroscopy. One irreversible oxidation and three reversible oxidations were observed in the cyclic voltammogram. Irreversible and a reversible oxidations are attributed to molybdenum and the other two reversible oxidation to iron centers. It is found that the two ferrocene groups started communication with each other after formation of molybdenum-complex.
164

Synthesis And Characterization Of Carbonyl - Tungsten(0) Complexes Of [n,n&#039 / -bis(ferrocenylmethylene)ethylenediamine]

Kavakli, Cuneyt 01 June 2005 (has links) (PDF)
In this study a bidentate ligand containing two ferrocenyl moieties, N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine, was prepared by condensation reaction of ferrocenecarboxyaldehyde and ethylenediamine on refluxing in benzene. The molecule was identified by IR, Raman, UV-VIS, 1H-, 13C-NMR spectroscopies. Then, this bidentate ligand was reacted with pentacarbonylbis-(trimethyl)silylethyne)tungsten(0). The ligand substitution reaction in dichloromethane yielded the new complex, tetracarbonyl [N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine]tungsten(0) (W(CO)4(BFEDA)). This new complex was isolated from the reaction solution in the form of orange crystals and fully characterized by elemental analysis, IR, UV-VIS, MS, 1H- and 13C-NMR spectroscopies. As a bidentate ligand, [N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine] binds the metal atom in the two cis positions in the pseudooctahedral geometry of the tungsten-complex. Electrochemistry of the tetracarbonyl [N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine]tungsten(0) was studied by cyclic voltammetry, and controlled potential electrolysis combined with the UV-VIS spectroscopy. One irreversible oxidation and three reversible oxidations were observed in the cyclic voltammogram. One of these reversible and the irreversible oxidations are attributed to tungsten and the other two reversible oxidations to iron centers. It is found that the two ferrocene groups started communication with each other after formation of tungsten-complex. N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine was also reacted with photogenerated pentacarbonyl(tetrahydrofuran)tungsten(0) complex and the pentacarbonyl [N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine]tungsten(0) (W(CO)5(BFEDA)) as an intermediate on the route to the tetracarbonyl[N,N&#039 / -bis(ferrocenylmethylene)ethylenediamine]tungsten(0) was isolated from the reaction medium in the form of red crystals and fully characterized by, IR, 1H- and 13C-NMR spectroscopies. The conversion of W(CO)5(BFEDA) to the W(CO)4(BFEDA) in dichloromethane by a ring closure mechanism was observed by IR spectroscopy.
165

Synthesis And Characterization Of Tetracarbonyl[6-ferrocenyl-2,2&#039 / -bipyridine]tungsten(0) Complex

Edinc, Pelin 01 September 2005 (has links) (PDF)
In this study, a bidentate ligand, 6-ferrocenyl-2,2&#039 / -bipyridine, was prepared by the reaction of lithiated ferrocene with bipyridine. The ligand was identified by 1H, 13C- NMR and HMQC and UV-Vis spectroscopies. Then, bidentate molecule was reacted with pentacarbonylbis-(trimethylsilylethyne)tungsten(0). The ligand substitution reaction in CH2Cl2 yielded the new complex, tetracarbonyl(6-ferrocenyl-2,2&#039 / bipyridine)tungsten(0). The isolated and purified complex was fully characterized by elemental analysis, IR, UV-Vis, MS, 1H and 13C- NMR spectroscopies. Tetracarbonyl(6-ferrocenyl-2,2&#039 / bipyridine)chromium(0) was also formed by ligand substitution reaction of 6-ferrocenyl-2,2&#039 / -bipyridine with pentacarbonyl(THF)chromium(0) which was prepared by photolytic substitution of CO from hexacarbonyl chromium(0) in THF. However, tetracarbonyl(6-ferrocenyl-2,2&#039 / bipyridine)chromium(0) could not be isolated by column chromatography. Electrochemistry of 6-ferrocenyl-2,2&#039 / -bipyridine and tetracarbonyl(6-ferrocenyl-2,2&#039 / bipyridine)tungsten(0) was studied by cyclic voltammetry and controlled potential electrolysis combined with UV-Vis. The ligand exhibits a reversible reduction and a reversible oxidation belonging to bipyridine and ferrocene moieties, respectively. One reversible reduction, two irreversible oxidation and a reversible oxidation were observed for tetracarbonyl(6-ferrocenyl-2,2&#039 / bipyridine)tungsten(0). The reversible reduction was attributed to bipyridine whereas two irreversible oxidations were assigned to tungsten centers and reversible oxidation to iron center.
166

Supramolecular transition metal architectures

Cordes, David B., n/a January 2005 (has links)
This thesis describes the investigation of the coordination and supramolecular chemistry of three different types of pyridine-containing ligand with a selection of Ag(I), Cu(I), Cu(II) and Cd(II) salts. The ligand types are flexible and four-armed, rigid and four-armed and bent with two rigid arms. All the ligands also display the ability to form additional supramolecular interactions. Chapter one introduces supramolecular chemistry and crystal engineering and covers background on several areas of current interest in these fields. Network structures, both coordination polymers and hydrogen-bonded systems, are discussed and topological analysis as a method of describing and comparing network structures is introduced. An outline of the ligand design, choice of transition metals and anions is given. Chapter two provides a review of flexible four-armed pyridine-containing ligands and their use in coordination chemistry. The synthesis and characterisation of three flexible four-armed ligands 1,2,4,5-tetrakis(2-pyridylmethyl-sulfanylmethyl)benzene (2tet), 1,2,4,5-tetrakis(3-pyridylmethyl-sulfanylmethyl)benzene (3tet) and 1,2,4,5-tetrakis(4-pyridylmethyl-sulfanylmethyl)benzene (4tet) are given. The synthesis and characterisation of the Ag(I), Cu(II) and Cd(II) complexes formed with these three ligands are also given. The complex of [Cd(2tet)(NO₃)₄] was structurally characterised by X-ray diffraction and was found to be a discrete species. The complexes {[Ag₂(3tet)](ClO₄)₂}n̲, {[Ag₂(3tet)](PF₆)₂}n̲, {[Ag₂(3tet)](CF₃CO₂)₂}n̲, {[Ag₂(4tet)]-(ClO₄)₂�2MeCN�2CHCl₃}n̲, {[Ag₂(4tet)](PF₆)₂�6MeCN}n̲ and {[Ag₂(4tet)](ClO₄)₂-�3H₂O}n̲ were likewise structurally characterised by X-ray diffraction. All these complexes were three-dimensional coordination polymers. A comparison of the seven structures is given at the end of the chapter. Chapter three reviews rigid four-armed pyridine-containing ligands and their use in coordination chemistry. The preparation of the rigid four-armed ligand 2,3,4,5-tetrakis(4-pyridyl)thiophene (pyth) is given. The synthesis and characterisation of the Ag(I), Cu(I) and Cd(II) complexes formed with this ligand are also given. The complexes [Ag(pyth)](BF₄)�3MeCN�CH₂Cl₂}n̲, [Ag(pyth)](PF₆)�MeCN�CH₂Cl₂}n̲, [Ag(pyth)]-(CF₃SO₃)�2MeCN�CH₂Cl₂}n̲, [Cu(pyth)](PF₆)�MeCN�CH₂Cl₂}n̲ and [(Cu₂I₂)(pyth)]-(BF₄)�1/2CH₂Cl₂�H₂O}n̲ were structurally characterised by X-ray diffraction. The complex with CuI was a two-dimensional coordination polymer, and the other four complexes were three-dimensional coordination polymers. A comparison of the five structures is given at the end of the chapter. Chapter four begins with a review of rigid angular bridging ligands and their use in coordination and supramolecular chemistry. The preparation of the ligand bis(4-pyridyl)amine (bpa) is given. The structural arrangement of bpa in the solid state was determined by X-ray diffraction. Complexes of Ag(I), Cu(I), Cu(II) and Cd(II) formed with this ligand were synthesised and characterised. The complexes {[Ag(bpa)(MeCN)](CF₃SO₃)}n̲, {[Ag(bpa)](PF₆)�MeCN}n̲, {[Ag(bpa)](ClO₄)-�2MeCN}n̲, {[Ag(bpa)](ClO₄)}n̲, {[Ag(bpa)](NO₃)}n̲, [(Cu₂I₂)(bpa)₂]n̲, {[Cu(bpa)₂Cl₂]-�3DMF�3/2H₂O}n̲, {[Cd(bpa)₂(NO₃)(H₂O)](NO₃)}n̲, {[Cd(bpa)₂(SO₄)(H₂O)]�3H₂O}n̲, [Cd(bpaH)₂(SO₄)₂(H₂O)₂]�2MeCN and {[Cd(bpa)(SCN)₂]�1/5iPrOH}n̲ were structurally characterised by X-ray diffraction. All complexes with Ag(I) were one-dimensional coordination polymers, with two of them helical, the other three zigzag. Both complexes with Cu(I) and (II) were two-dimensional coordination polymers. One complex with CdSO₄ was discrete, with the bpa ligands mono-protonated, but all other three other Cd(II) complexes were three-dimensional coordination polymers. Seven of these complexes showed hydrogen-bonding interactions linking them together to form supramolecular structures of higher dimensionalities. A comparison of the twelve structures is given at the end of the chapter. Chapter five is a brief summary of the outcomes of this thesis.
167

Synthesis, radiosynthesis and biological evaluation of novel Re(I) and Tc(I)-metallocarboranes /

Sogbein, Oyebola Olusegun. Valliant, John Fitzmaurice. January 2005 (has links)
Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: John Fitzmaurice Valliant. Includes bibliographical references. Also available online.
168

Synthesis, radiosynthesis and biological evaluation of novel Re(I) and Tc(I)-metallocarboranes /

Sogbein, Oyebola Olusegun. Valliant, John Fitzmaurice. January 2005 (has links)
Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: John Fitzmaurice Valliant. Includes bibliographical references. Also available online.
169

Organometallics in the stabilization of dyed fibres : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at the University of Canterbury /

Ayling, Neroli. January 1900 (has links)
Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). "March 2008." Includes bibliographical references (leaves 217-225). Also available via the World Wide Web.
170

Structure/function studies on metallo-B-lactamase ImiS from Aeromonas bv. sobria

Sharma, Narayan Prasad. January 2007 (has links)
Thesis (Ph. D.)--Miami University, Dept. of Chemistry and Biochemistry, 2007. / Title from second page of PDF document. Includes bibliographical references.

Page generated in 0.1104 seconds