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11.
Martina Schwager Emil Roduner Ivan D. Reid Paul W. Percival Jean-Claude Brodovitch Stanislaw Wlodek Robert F. Marzke 《Hyperfine Interactions》1994,87(1):859-864
SR spectra of the ethyl radical adsorbed on porous silica were observed in transverse and in longitudinal magnetic fields in the temperature range 190–298 K. The line widths reflect the dynamic partial averaging of the hyperfine anisotropy due to reorientation and surface diffusion. 相似文献
12.
13.
O'Hair RA Androutsopoulos NK Reid GE 《Rapid communications in mass spectrometry : RCM》2000,14(18):1707-1716
The proposal that protonated peptides react with NH(3) in the gas phase via transacylation reactions (Tabet et al., Spectros. Int. J. 5: 253 1987) has been investigated by studying the reactions of the fixed charge derivatives [RC(O)NMe(2)CH(2)CO(2)H](+) (R=Me and Ph) with pyridine and triethylamine and the reactions of protonated glycine oligomers and leucine enkenphalin with butylamine. Under the near thermal conditions of the quadrupole ion trap, both the fixed charge derivatives as well as the protonated peptides react with the amines via either proton transfer or proton bound dimer formation. Collision induced dissociation of protonated peptides in the presence of butylamine yields b(n) and y(n) sequence ions as well as [b(n) + BuNH(2)](+) and [y(n) + BuNH(2)](+) ions. MS(3) experiments reveal that a major route to these [b(n) + BuNH(2)](+) and [y(n) + BuNH(2)](+) ions involves ion-molecule reactions between the b(n) and y(n) sequence ions and butylamine. MS(4) experiments, carried out to determine the nature of the [b(n) + BuNH(2)](+) ions, reveal that they correspond to a mixture of hydrogen bonded (i.e. proton bound dimer) and covalent amide bond structures. 相似文献
14.
Milanesi L Reid GD Beddard GS Hunter CA Waltho JP 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(7):1705-1710
A new series of photocleavable protein cross-linking reagents based on bis(maleimide) derivatives of diaryl disulfides have been synthesised. They have been functionalised with cysteine and transient absorption spectra for the photolysis reaction have been recorded by using the pump-probe technique with a time resolution of 100 femtoseconds. Photolysis of the disulfide bond yields the corresponding thiyl radicals in less than a picosecond. There is a significant amount of geminate recombination, but some of the radicals escape the solvent cage and the quantum yield for photocleavage is 30 % in water. 相似文献
15.
Levason W Matthews ML Reid G Webster M 《Dalton transactions (Cambridge, England : 2003)》2004,(1):51-58
High yield syntheses for 1,2-, 1,3-, and 1,4-xylyl distibines (1,2-C6H4(CH2SbMe2)2, 1,3-C6H4(CH2SbMe2)2, 1,4-C6H4(CH2SbMe2)2, respectively) from Me2SbCl (conveniently made in situ from Me2PhSb and HClgas) and the appropriate di-Grignard are reported. The 1,3- and 1,4-phenylene distibines, 1,3-C6H4(SbMe2)2 and 1,4-C6H4(SbMe2)2, were made similarly. The new ligands have been characterised by mass spectrometry, 1H and 13C[1H] NMR spectroscopy, and by the preparation of methiodide derivatives. The crystal structures of 1,4-C6H4(CH2SbMe2)2 and [1,3-C6H4(CH2SbMe3)2]I2 have been determined. The synthesis of 1,2-C6H4(CH2SbPh2)2 has been achieved similarly in modest yield and the distibine converted into the tetra-iodo-derivative 1,2-C6H4(CH2SbPh2I2)2. The coordination modes available to these ligands have been probed by the synthesis and characterisation of complexes with nickel, iron and tungsten carbonyls. The crystal structure of [[Fe(CO)4]2[micro-1,3-C6H4(CH2SbMe2)2]] has been determined. The spectroscopic properties of these carbonyl derivatives have been compared with those of complexes of other antimony ligands, and in some cases with diphosphine and diarsine complexes, to probe the electronic properties of the new ligands. 相似文献
16.
Charles E. Reid 《International journal of quantum chemistry》1972,6(2):383-386
It is a standard theorem of group representation theory that the dimension of an irreducible representation is a divisor of the order of the group. This paper gives a new, relatively simple proof, intended to make the theorem understandable to readers unfamiliar with algebraic integers. 相似文献
17.
Intramolecular energy migration and trapping by acceptor species which are an integral part of a macromolecule have been studied in three polymer systems using the techniques of fluorescence depolarization. The effect of energy migration produces depolarization of both donor and acceptor emissions. Copolymers of styrene with 1-vinylaphthalene or 2-phenyl-5-(p-vinyl)phenyloxazole have been studied. In addition, energy transfer to a terminal anthracene species has been studied in a polyvinyltoluene sample. When energy transfer occurs with unit efficiency, the depolarization of acceptor emission reflects the path length available to the migrating exciton. In cases of lesser transfer efficiency, the acceptor emission exhibits depolarization characteristics which reflect the distribution of migration lengths from the site of energy absorption. 相似文献
18.
The Mössbauer spectra of 57Fe3+ substituted in 0.2 to 0.4 atom % of the octahedral sites in the host lattices Na0.9Mg0.45Ti1.55O4, TiO2, Sc2O3, LiScO2 and MgAl2O4 have been examined. Hyperfine splittings of the spectra were observed for all cases except Sc2O3. In all cases the electron spin resonance spectrum was found, or has been shown to be highly anisotropic as a result of the presence of strong axial or rhombic fields and consequent splitting of the 3d5 ground state energy levels. In several cases resolution of the and Mössbauer spectra was observed. Mössbauer spectra of the solid solutions Na0.9Mg0.45Ti1.55O4Na0.9Fe0.9Ti1.1O4, LiScO2LiFeO2 and TiO2FeNbO4 have also been examined. 相似文献
19.
Rebecca J. Hopkins Rachel Symes Robert M. Sayer Jonathan P. Reid 《Chemical physics letters》2003,380(5-6):665-672
Cavity-enhanced Raman scattering is used to determine the size and composition of multicomponent ethanol/water droplets in the concentration range 7.5–19% ethanol by volume. Under the experimental conditions presented here, the integrated CERS signal from ethanol shows an exponential increase with increase in ethanol concentration when compared with the integrated intensity of the water band. The calibration is shown to be invariant with particle size over the droplet radius range 20–35 μm. In addition to providing a method for determining particle size and composition, initial studies show that the evaporation dynamics of these multicomponent droplets can be probed by CERS. 相似文献
20.
The preparations of the new complexes [AsBr(3)[MeS(CH(2))(2)SMe]], [AsX(3)([9]aneS(3))] (X = Cl, Br or I; [9]aneS(3) = 1,4,7-trithiacyclononane), [AsCl(3)([14]aneS(4))] ([14]aneS(4) = 1,4,8,11-tetrathiacyclotetradecane), [AsX(3)([8]aneSe(2))] ([8]aneSe(2) = 1,5-diselenacyclooctane), [(AsX(3))(2)([16]aneSe(4))] ([16]aneSe(4) = 1,5,9,13-tetraselenacyclohexadecane), and [(AsBr(3))(2)([24]aneSe(6))] ([24]aneSe(6) = 1,5,9,13,17,21-hexaselenacyclotetracosane) are described. These are obtained from direct reaction of the appropriate AsX(3) and 1 mol equiv of the thio- or selenoether ligand in anhydrous CH(2)Cl(2) (or thf for X = I) solution. The products have been characterized by microanalysis and IR and (1)H NMR spectroscopy. In solution they are extensively dissociated, reflecting the weak Lewis acidity of AsX(3). Reaction of AsX(3) with MeSe(CH(2))(2)SeMe or MeC(CH(2)EMe)(3) (E = S or Se) gave only oils. Treatment of PCl(3) or PBr(3) with Me(2)S, MeE(CH(2))(2)EMe, or [9]aneS(3) failed to give solid complexes, and there was no evidence from NMR spectroscopy for any adduct formation in solution. The crystal structures of the first series of thioether and selenoether complexes of As(III) are described: [AsBr(3)[MeS(CH(2))(2)SMe]], C(4)H(10)AsBr(3)S(2), a = 10.2818(6) A, b = 7.8014(5) A, c = 14.503(1) A, beta = 102.9330(2) degrees, monoclinic, P2(1)/c, Z = 4; [AsI(3)[MeS(CH(2))(2)SMe]], C(4)H(10)AsI(3)S(2), a = 9.1528(1) A, b = 11.5622(2) A, c = 12.0939(2) A, beta = 93.863(1) degrees, monoclinic, P2(1)()/n, Z = 4; [AsCl(3)([9]aneS(3))], C(6)H(12)AsCl(3)S(3), a = 17.520(4) A, b = 17.520(4) A, c = 16.790(7) A, tetragonal, I4(1)cd, Z = 16; [AsCl(3)([14]aneS(4))], C(10)H(20)AsCl(3)S(4), a = 13.5942(2) A, b = 7.7007(1) A, c = 18.1270(3) A, beta = 111.1662(5) degrees, monoclinic, P2(1)()/n, Z = 4; [(AsCl(3))(2)([16]aneSe(4))], C(12)H(24)As(2)Cl(6)Se(4), a = 9.764(3) A, b = 13.164(1) A, c = 10.627(2) A, beta = 114.90(1) degrees, monoclinic, P2(1)()/n, Z = 2; [(AsBr(3))(2)([16]aneSe(4))], C(12)H(24)As(2)Br(6)Se(4), a = 10.1220(1) A, b = 13.4494(2) A, c = 10.5125(2) A, beta = 113.49(2) degrees, monoclinic, P2(1)()/n, Z = 2. [AsBr(3)[MeS(CH(2))(2)SMe]] and [AsI(3)[MeS(CH(2))(2)SMe]] reveal discrete mu(2)-halo As(2)X(6) dimeric structures involving distorted octahedral As(III), with the dithioether ligand chelating. [AsCl(3)([9]aneS(3))] adopts a discrete molecular distorted octahedral geometry with the thioether behaving as a weakly coordinated fac-capping ligand. [AsCl(3)([14]aneS(4))] forms an infinite sheet involving two mu(2)-chloro ligands on each As but bridging to two distinct As centers. Each macrocycle coordinates to two adjacent As centers via one S atom, giving a cis-octahedral Cl(4)S(2) donor set at As(III). The structures of [(AsCl(3))(2)([16]aneSe(4))] and [(AsBr(3))(2)([16]aneSe(4))] adopt 2-dimensional sheet structures with mu(2)-dihalo As(2)X(6) dimers cross-linked by mu(4)-tetraselenoether macrocycles, giving a disorted cis-X(4)Se(2) donor set at each As center. These species are compared with their antimony(III) and bismuth(III) analogues where appropriate. 相似文献