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  • 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.

The role of free radicals in hair bleaching and damage

Clarke, Kristy January 2006 (has links)
No description available.

Studies on polynuclear copper (II) complexes

Hopkins, Terence Gerrard January 1973 (has links)
A study has been made of the copper catalyst employed in the oxidative coupling of phenols and also of some polynuclear copper (II) complexes which are closely related to the catalyst system. The preparation of pyridine complexes of copper (I) halides and their characterisation by infrared spectra is described and the nature of these complexes in the solid state and in solution discussed. The preparation and properties of several new tetranuclear copper (II) complexes of the type cu4ox64L, where X is Cl or Br and L is a monodentate ligand, are described and, in addition, several of these tetranuclear complexes containing mixed halide bridges have been prepared for the first time and characterised. In theory, several of these mixed halide complexes should exhibit structural isomerism, and the two isomers of the complex cu40Cl2Br44py have been positively identified .from physical measurements. Tetranuclear copper (II) complexes have been shown to undergo halide, exchange reactions in solutions and from conductivity studies it is postulated that these complexes may well be considerably dissociated in solvents such as nitromethane. In addition, tetranuclear complexes with pyridine ligands have been shown to undergo redox decomposition reactions at temperatures above l50°C to yield copper {I) halide and a halopyridine.

Some aspects of the chemistry of cationic intermediates

Kemp, Graham January 1976 (has links)
A review of the chemistry of the reactions between trivalent phosphorous derivatives and sources of positive halogen is presented. The alkylation of various nucleophilic substrates has been achieved using alkoxy-tris(dimethylamino)phosphonium hexafluorophosphates. In particular a new method for the preparation of alkyl aryl ethers and alkyl aryl sulphides has been developed which is both stereospecific and proceeds without rearrangement. The alkoxy-tris(dimethylamino)phosphonium hexafluorophosphates are stable, highly crystalline solids,which can be stored for long periods of time with no sign of decomposition.

Spectroscopy of cesium isotopes beyond the proton dripline

Wady, Paul Thomas January 2011 (has links)
This thesis reports on gamma-ray spectroscopy experiments performed to observe transitions between excited states in 112Cs and 113Cs. Five (tentatively six) transitions are assigned to 112Cs using the very selective technique of recoil-decay tagging. Four of these transitions are assigned on the basis of systematics to a band based on the ¼(h11/2) ­ º(h11/2) configuration. These are the first gamma rays assigned to this proton-unstable nucleus. The first, tentative observation of fine structure in the proton-decay of 112Cs is reported. Recoil-decay tagged gamma-ray spectroscopy of 113Cs results in the identification of 22 (tentatively 24) gamma-ray transitions, a slight improvement in the level scheme proposed previously in Ref. [1]. In addition, the order of the transitions within the bands are assigned based on coincidence arguments and gamma-gated intensity measurements. The underlying configurations of the bands are assigned based on blocking arguments, cranked shell model calculations and with reference to the excitation-energy systematics of neighbouring neutron-deficient cesium isotopes. Finally, the differing decay energies reported for the proton decay of 113Cs in previous works are discussed and a possible cause is identified in the form of pile-up of implant and decay events.

Estimation of chemical information in scattering media using radiative transfer theory to remove multiple scattering effects

Steponavicius, Raimundas January 2011 (has links)
Two approaches for removing multiple light scattering effects using the radiative transfer theory in order to improve the performance of multivariate calibration models have been proposed namely: partial correction of multiple scattering effects and full correction of multiple scattering effects. The first approach is applicable for predicting the concentration of a scattering-absorbing (particulate) component as well as the concentration of an absorbing only species. The second approach is applicable only for estimation of the concentration of an absorbing only species. Application of the first approach to a simulated four component system showed that it will lead to calibration models which perform appreciably better than when empirically scatter corrected measurements of total transmittance or total reflectance are used. The validity of the method was tested experimentally using a two-component (polystyrene-water) and a fourcomponent (polystyrene - ethanol - water - deuterated water) system. The proposed methodology of partial correction showed significantly better performance than the empirically pre-processed direct measurements (total transmittance, total reflectance and collimated transmittance) in all experiments. The results of applying the full correction approach showed that despite all errors the performance of PLS calibration model built on the corrected bulk absorption coefficient was marginally better than the performance of PLS model built on uncorrected bulk absorption coefficient. Finally, the benchmarking analysis revealed that there is still a significant potential for an improvement in the prediction performance in the quantitative analysis of turbid samples.

Solvothermal synthesis of novel inorganic materials

Lees, Rachel Jane Elizabeth January 2007 (has links)
Solvothennal and hydrothennal synthesis is widely applied in the generation of . metastable crystalline phases, and is used in this work to prepare a range of novel antimony-sulphide and rare-earth oxy-anion compounds in' the presence of linear, branched and macrocycle amines. The new crystalline phases were characterised using single-crystal X-ray diffraction, elemental analysis, diffuse reflectance spectroscopy and SQUID magnetometry. Transition-metals included in the reactions resulted in the fonnation of both binary antimony-sulphide and ternary transition-metal-antimony-sulphide structures. Binary phases include [Fe(en)3]Sb2Ss.0.55H20, [Fe(en)3hSb4Sg, [T(dien)2]Sb6SIO.xH20 (T= Ni, Co), [Co(en)3]SbgS13 and tNi(en)3]Sb12S19, where discrete [Sb2Sst units, SbS2chains, Sb6SI0 6- and SbgS13 2- layers and a three-dimensional Sbl2Slt framework are charge balanced by transition-I.l1etal-amine complexes. The ternary phases synthesised using tris(2-aminoethyl)amine (tren) and diethylenetriamine (dien) include [Cr(tren)]Sb4S7 chains with [Cr(tren)f+ pendent complexes, and [T(dien)hSblgS30[ T(dien)2] (T= Mn, Fe, Co), in which complex antimony-sulphide chains are bridged via dimeric [T2S2] units to fonn novel layers. The transition-metal ions all exhibit paramagnet~c behaviour and the band gaps of the phases were found to increase from 1.79(4) to 2.46(1) eV with increasing framework density. The first examples of hydrothennal antimony-sulphide reactions using a macrocycle, cyclam, as the structure directing agent resulted in the synthesis of novel , layered and three-dimensional phases of[cyclarnH2]Sb6SIO and [cyclamH2]Sb4S7. By including transition-metal salts in the reaction mixture, it was possible to incorporate transition-metal ions within the macrocyclic rings in [Ni(cyclam)]Sb4S7 and [Co(cyclam)]x[cyclarnH2]J_xSb4S7, where the C02+ occupancy varies between O.08<x<O.74. This unexpected result reveals that metalated and nonrnetalated cyclam rings are present within this crystal structure. The first examples of lanthanide-carbonate frameworks were prepared from aqueous ethylenediamin~ (en) solutions. During the synthesis of [Lll4(C03)6(H20)2].en.H20 (Ln= Dy-Lu, Y), the oxalic acid starting reagent decomposes completely in the presence of sulphur to form carbonate ions which link the lanthanide ions into new three-dimensional structures. Free ethylenediamine and water molecules were located in the one-dimensional channels that run through the structure. Magnetic analysis of the lanthanide-carbonate series revealed paramagnetic behaviour, with the exception of [Er4(C03)6(H20)2].en.HiO, which exhibited a competing ferrimagnetic interaction, which results in ordering below 9.85 K and a saturated magnetic moment achieved at 10,000 G.

Study of the coordination chemistry of phosphinines and phosphabarrelenes

Wallis, Christopher J. January 2007 (has links)
The syntheses of a series of 2,6-(2'-haloaryl)-4-tolylphosphinines, ranging from the fluoro, chloro, bromo and iodo derivatives, as well as the 2,6-dixylyl-4- phenylphosphinine ligand are reported. The coordination chemistry of these ligands has been evaluated by coordinating them to pentacarbonyltungsten(O), to form the complex W(CO)s(L), where L = fluoro, choloro, bromo, iodo or dixylyl derivatives of the phosphinine secondly to Rh(COD)Cl 2, to form the complex Rh(COD)Cl(L), where COD = 1,5-cyclooctadiene, and L= fluoro, chloro, bromo or dixylyl derivatives of the phosphinine and thirdly to Rh(CO)2Cl 2 to form Rh(CO)Cl(L) 2, where L = 2,6,-dixylyl-4-phenylphosphinine only. These complexes were fully characterised by spectroscopic means, their coordination chemistry studied and the metal-phosphorus bond in these complexes is elucidated by comparison to analogous complexes of phosphines, and phosphites. Finally the 2,6-dixylyl-4-phenylphosphabarrelene is synthesised from its parent phosphinine, and applied in a survey of transition metal complexes to evaluate its properties as a ligand. The complexes made were W(CO)s(L), Re(CO)4Cl(L), Ru(cymene)(L)Cl2, Fe(r 5-C5H4SiMe3)(CO)2L + PF6", Rh(CO)Cl(L)2, Rh(COD)Cl(L), Ir(COD)Cl(L), PtCl2(L)2, Ag(L)2 + Tf Cu(L)Cl, and Pd(L). Where L = 2,6-dixylyl-4-phenylphosphabarrelene, cymene = 4-isopropyltoluene, Cp = cyclopentadienyl and COD = 1,5-cyclooctadiene are described. The coordination chemistry of the phosphabarrelene was established and the nature of the phosphorus- metal bond in each complex was elucidated by comparison to analogous complexes of triarylphosphines and triarylphosphites. In addition the phosphabarrelene was tested in the rhodium catalysed hydroformylation of 4-octene, in comparison with the commonly used (2,4-di-t-butylphenyl)phosphite.

Studies into the synthesis of primary phosphines for the preparation of macrocycles by template methods

Reixach, Elisenda January 2006 (has links)
This thesis is focused in the synthesis of phosphine-based macrocycles by template methods. Furthermore, it explores some alternative methods for the synthesis of known and unknown polydentate primary phosphine compounds necessary for the preparation of new macrocycles. Following this new procedure the novel tripodal primary phosphine cis, cis-1,3,5-triphosphinomethylcyclohexane (2.15) has been prepared in good yields as well as the reported bis(2-phosphinoethyl)amine (PNP, 3.4). Mono-alkylation of 3.4 allowed the preparation of the asymmetric 2-(allylphosphino)-N-(2-phosphinoethyl)ethanamine ligand (3.16) in low yields. Whilst ligands 2.15 and 3.16 failed to form well-defined facially coordinated molybdenum(O) and chromium(O) complexes respectively, 3.4 formed octahedral complexes with Cr(0) and Fe(II) metals, {/ac-Cr(CO)<sub>3</sub>(PNP)}, 3.8 and {n5-C<sub>5</sub>H<sub>4</sub>(SiMe<sub>3</sub>)}Fe(PNP) PF6, 3.10. Different attempts have been made to cyclise the facially coordinated chromium complex 3.8, however all of them have failed. The synthesis of 3.8 and 3.10 has been confirmed by X-ray diffraction. The synthesis of a new Mn(I) 9-membered tribenzanulated I1 triphosphamacrocycle complex Mn(CO)<sub>3</sub>{(C<sub>6</sub>H<sub>4</sub>F)PC<sub> 6</sub>H<sub>4</sub>PHC<sub>6</sub>H<sub>4</sub>PHC<sub>6</sub>H<sub>4</sub>} OTf, 4.10 has been successfully synthesised by sequential introduction of 1,2-diphosphinobenzene and tris(2-fluorophenyl)phosphine on a manganese(I) complex and subsequent addition of /-BuOK. Alkylation of the two secondary phosphorus of 4.10 with Mel allowed the isolation of the more stable manganese complex II Mn(CO)<sub>3</sub>{(C<sub>6</sub>H<sub>4</sub>F)PC<sub>6</sub>H<sub> 4</sub>P(CH<sub>3</sub>)C<sub>6</sub>H<sub>4</sub>P(CH<sub>3</sub>)C<sub> 6</sub>H<sub>4</sub>} OTf/I 4.12. The liberation of the phosphine trioxide macrocycle, {(C<sub>6</sub>H<sub>4</sub>F)J>(0)C<sub>6</sub>H<sub>4</sub>P(0)(CH<sub> 3</sub>)C<sub>6</sub>H<sub>4</sub>(0)(CH<sub>3</sub>)C<sub>6</sub>H<sub>4 </sub>} 4.14 from the metal has been achieved using 4-methylmorpholine N-oxide in excess. In addition, the X-ray crystal structures of the non-cyclised precursor intermediate Mn(CO)<sub>3</sub>{(C<sub>6</sub>H<sub>4</sub>F)<sub>3</sub>P}{C<sub> 6</sub>H<sub>4</sub>(PH<sub>2</sub>)<sub>2</sub>-o} OTf 4.9 and the half cyclised intermediate (I Mn(CO)<sub>3</sub>{(C<sub>6</sub>H<sub>4</sub>F)<sub>2</sub>PC<sub> 6</sub>H<sub>4</sub>PHC<sub>6</sub>H<sub>4</sub>PH<sub>2</sub>} OTf 4.11 as well as the final macrocycle 4.12 have also been established.

New aspects of low co-ordination phosphorus chemistry

Brym, Markus January 2005 (has links)
Chapter six describes miscellaneous results obtained during these investigations; some revolve around several iridium compounds, e.g. ortho-metallated Vaska's compound, [IrHC1(CO)(PPh3){eta2-PPh 2(C6H4)}], others around group 15 formamidinate and phenolate compounds, and others around ruthenium phosphaalkenyl chemistry.

Cyclic triphosphenium ions and related species

Monks, Phillipa Kay January 2008 (has links)
A series of cyclic triphosphenium ions containing three adjacent phosphorus atoms linked by a hydrocarbon backbone has been synthesised. They vary in ring size (four- to seven- membered rings), substituents on the four-coordinate phosphorus atoms, and organic backbone, and have been characterised by (^31)P NMR spectroscopy. Variable temperature studies probing the mechanism of formation of cyclic triphosphenium ions from a reaction of PX(_3) with a diphosphane have shown a three-step mechanism: (i) the addition of PX(_3) to the diphosphane to form an acyclic intermediate, (ii) cyclisation to afford a heterocycle with a halogen still bonded to the central P atom, and (iii) removal of the halogen to afford the cyclic triphosphenium ion. The syntheses of P(_c)-alkyl and aryl derivatives of cyclic triphosphenium ions using two different methods are described. Direct ethylation of a cyclic triphosphenium ion using ethyl triflate is only possible when the substituents on the four-coordinate phosphorus atoms are small e.g. Et. Synthesis of Pc-alkyl and aryl derivatives with larger substituents on the four-coordinate P atoms, and/or Pc, have been achieved via reaction of a diphosphane with a dichlorophosphane in the presence of AICI(_3_ or SnCI(_2). A series of tetraphosphonium ions containing four adjacent P atoms linked by an organic backbone has also been synthesised. These derivatives have been characterised using (^31)P NMR spectroscopy and where possible X-ray diffractions studies and elemental analyses. The P-P bonds in these derivatives are typical values for single bonds. The synthesis of Pt(II) complexes containing cyclic triphosphenium ions has been achieved to afford cis and/or trans isomers via reaction of a cyclic triphosphenium ion with trans-[Pt(PR(_3))CI(µCl)](_2). However, if the cyclic triphosphenium ion contains phenyl groups on both of the four-coordinate phosphorus atoms, ring scission followed by complexation of the diphosphane to Pt is observed. In the Pt(II) complexes containing cyclic triphosphenium ions, an unusually small 'J(_pt-p) value to the phosphenium central P (981-1267 Hz) suggests that the bond between the phosphenium central P atom and the Pt centre is long. Hydrolysis reactions of several Pt(II) complexes containing chlorophosphane ligands have been monitored by (^31)P NMR spectroscopy.

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