Robin Harris | University of Durham (original) (raw)
Papers by Robin Harris
Journal of the Chemical Society, Dalton Transactions, 1987
Page 1. J. CHEM. SOC. DALTON TRANS. 1987 795 Menthyl-substituted Organophosphorus Compounds. Part... more Page 1. J. CHEM. SOC. DALTON TRANS. 1987 795 Menthyl-substituted Organophosphorus Compounds. Part 6.' Preparation of P(L-men)RCI and P(L-men)R(S)CI (R = Me, Et, Pr', But, or Ph; men = cyc/oC,H,- 2-Pr'-5-Me) and ...
The Journal of Organic Chemistry, 1965
Physical Chemistry Chemical Physics, 2002
ABSTRACT The thermodynamic theory of cross-polarization (CP) between one abundant and one rare sp... more ABSTRACT The thermodynamic theory of cross-polarization (CP) between one abundant and one rare spin is well understood and widely applied. CP dynamics between several abundant spin baths has some inherent complications that lead to misinterpretation of the CP rates and relaxation parameters if not properly accounted for. A general thermodynamic description of CP dynamics involving up to six spin baths is developed and implemented with MATLAB. The CP dynamics for a fluorinated polymer, (2-perfluorohexylethyl acrylate)–styrene co-polymer, was analysed as a system with five spin baths—four 19F and one 1H. The CP behaviour was successfully simulated above the glass-transition temperature. The CP rates and T1ρ's are discussed in terms of the structure and dynamic behaviour of the polymer.
European Journal of Inorganic Chemistry, 2001
The title compound has been synthesised, and characterised by multinuclear magnetic resonance spe... more The title compound has been synthesised, and characterised by multinuclear magnetic resonance spectroscopy, both in solution and in the solid state. The bandshapes of variable-temperature solution-state 19 F NMR spectra have been iteratively fitted to obtain information on the ...
Journal of Molecular Structure, 2002
Molecular modelling computation using the gaussian 94 package of programs was carried out to esti... more Molecular modelling computation using the gaussian 94 package of programs was carried out to estimate four different barriers to internal rotation about amine nitrogen to sp 2 carbon bonds for two compounds with triazine rings. Whereas two of the processes appear to retain a planar side-chain nitrogen environment throughout the internal rotation, the other two involve pyramidalisation. In the latter two cases, after the barrier is passed, the process may or may not include a transient inversion at nitrogen. The internal rotation for cyclotriazine systems is discussed in relation to those for aniline and formamide. The four barrier magnitudes calculated for the triazines are in the same order as (though somewhat larger than) those measured by variable-temperature NMR bandshape analysis for a relevant compound. q
The 1 H, 13 C and 19 F magic-angle spinning NMR spectra have been recorded for Form 1 of flurbipr... more The 1 H, 13 C and 19 F magic-angle spinning NMR spectra have been recorded for Form 1 of flurbiprofen. In the case of 19 F, spinning sideband analysis has produced data for the components of the shielding tensor. The chemical shift of the hydrogen-bonded proton was found to be 14.0 ppm. Shielding parameters for all three nuclei have been calculated using Density Functional Theory (DFT) together with the Gauge Including Projector Augmented Wave (GIPAW) method which takes full allowance for the repetition inherent in crystalline structures. Such computations were made for the reported geometry, for a structure with all the atomic positions relaxed using DFT, and with only the hydrogen positions relaxed. The relationships of the computed shifts to those observed are discussed. In general, the correlations are good.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1983
is shown that the techmque of magic-angle rotation suffices to narrow "B NMR hnes for solid tetra... more is shown that the techmque of magic-angle rotation suffices to narrow "B NMR hnes for solid tetrahaloborates so that peaks due to different ions can be resolved. The method is found to give detailed structural information for a sample containing a mixture of ions of the type [BCl,Br,_,]-.
Solid State Nuclear Magnetic Resonance, 2006
Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with... more Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1 Â 10 6 and 2 Â 10 3 Da by GPC, respectively, have been analysed by 19 F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T 1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately À115 and approximately À117 ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters. r
Solid-state 19 F NMR has been applied to poly(vinylidenefluoride) to investigate, inter alia, the... more Solid-state 19 F NMR has been applied to poly(vinylidenefluoride) to investigate, inter alia, the location of the reverse units. The application of relaxation filters in pulse sequences revealed fundamental differences relating to the domain structure of PVDF. A T 1r ðFÞ spin-lock experiment gave a spectrum of the crystalline phase along with some intensity from signals associated with reverse units. The proximity of reverse units to the amorphous and crystalline domains was further investigated by T 1r ðFÞ-filtered radio frequency driven recoupling (RFDR) and spin-diffusion experiments. The results showed the majority of reverse units to be relatively mobile (i.e. amorphous). However, weak RFDR cross-peaks were detected which suggest the presence of some reverse units in relatively rigid domains. A signal arising from a highly mobile site was detected at d F ¼ 2115 ppm by a delayed acquisition experiment and is tentatively assigned to -CH 2 CF 2 H end-groups. q
Macromolecular Rapid Communications, 2005
Fluorine-19 NMR spectra of solids have some special features, which are discussed in this article.
Solid State Nucl Magn Reson, 1997
In order to check the efficiency of high-power decoupling when used with the two-dimensional mult... more In order to check the efficiency of high-power decoupling when used with the two-dimensional multiple-quantum MAS method recently proposed to obtain isotropic spectra from quadrupolar nuclei, we applied this new technique to NMR for a hydrous layered silicate compound, makatite, with and without decoupling. A remarkable improvement of the spectral resolution in the isotropic dimension was observed by the decoupling, showing that it is effective in the 2D MQ-MAS method and suggesting that proton decoupling should be generally applied in experiments concerning these kinds of compound.
J Mater Chem, 1998
ABSTRACT
Solid State Nuclear Magnetic Resonance, 1997
In order to check the efficiency of high-power 1 H decoupling when used with the two-dimensional ... more In order to check the efficiency of high-power 1 H decoupling when used with the two-dimensional multiple-quantum MAS method recently proposed to obtain isotropic spectra from quadrupolar nuclei, we applied this new technique to 23 Na NMR for a hydrous layered silicate compound, makatite, with and without 1 H decoupling. A remarkable improvement of the spectral resolution in the isotropic dimension was observed by the decoupling, showing that it is effective in the 2D MQ-MAS method and suggesting that proton decoupling should be generally applied in 23 Na experiments concerning these kinds of compound. q 1997 Elsevier Science B.V.
Journal of Materials Chemistry, 1998
ABSTRACT
J Phys Chem a, 1997
ABSTRACT
The Journal of Physical Chemistry A, 1997
ABSTRACT
Journal of Magnetic Resonance, 2003
Simulations have been carried out on z-magnetizations produced by (and hence of the resulting spe... more Simulations have been carried out on z-magnetizations produced by (and hence of the resulting spectra from) the dipolar filter (DF) and the recently suggested "Discrimination Induced by Variable-Amplitude Minipulses" (DIVAM) pulse sequences [S. Ando et al., Polymer 42 (2001) 8137; Magn. Reson. Chem. 40 (2002) 97]. The strengths of dipolar interactions have been modelled by introducing different values for transverse relaxation times. The DF case has been extended by allowing the pulse angles to be smaller than 90 degrees. The pulse intervals have also been used as variables. For the DIVAM case, the variables are similarly the minipulse nutation angles and minipulse intervals. The computations show that DIVAM is superior to DF in terms of selectivity for spectra of heterogeneous materials such as semi-crystalline polymers. The effects of the pulse sequences on 19F spectra of poly(vinylidene fluoride) (PVDF) and of a copolymer of vinylidene fluoride and trifluoroethylene (p(VDF/TrFE)) are presented, together with fits of the experimental results by the simulations.
Journal of the Chemical Society, Dalton Transactions, 1987
Page 1. J. CHEM. SOC. DALTON TRANS. 1987 795 Menthyl-substituted Organophosphorus Compounds. Part... more Page 1. J. CHEM. SOC. DALTON TRANS. 1987 795 Menthyl-substituted Organophosphorus Compounds. Part 6.' Preparation of P(L-men)RCI and P(L-men)R(S)CI (R = Me, Et, Pr', But, or Ph; men = cyc/oC,H,- 2-Pr'-5-Me) and ...
The Journal of Organic Chemistry, 1965
Physical Chemistry Chemical Physics, 2002
ABSTRACT The thermodynamic theory of cross-polarization (CP) between one abundant and one rare sp... more ABSTRACT The thermodynamic theory of cross-polarization (CP) between one abundant and one rare spin is well understood and widely applied. CP dynamics between several abundant spin baths has some inherent complications that lead to misinterpretation of the CP rates and relaxation parameters if not properly accounted for. A general thermodynamic description of CP dynamics involving up to six spin baths is developed and implemented with MATLAB. The CP dynamics for a fluorinated polymer, (2-perfluorohexylethyl acrylate)–styrene co-polymer, was analysed as a system with five spin baths—four 19F and one 1H. The CP behaviour was successfully simulated above the glass-transition temperature. The CP rates and T1ρ's are discussed in terms of the structure and dynamic behaviour of the polymer.
European Journal of Inorganic Chemistry, 2001
The title compound has been synthesised, and characterised by multinuclear magnetic resonance spe... more The title compound has been synthesised, and characterised by multinuclear magnetic resonance spectroscopy, both in solution and in the solid state. The bandshapes of variable-temperature solution-state 19 F NMR spectra have been iteratively fitted to obtain information on the ...
Journal of Molecular Structure, 2002
Molecular modelling computation using the gaussian 94 package of programs was carried out to esti... more Molecular modelling computation using the gaussian 94 package of programs was carried out to estimate four different barriers to internal rotation about amine nitrogen to sp 2 carbon bonds for two compounds with triazine rings. Whereas two of the processes appear to retain a planar side-chain nitrogen environment throughout the internal rotation, the other two involve pyramidalisation. In the latter two cases, after the barrier is passed, the process may or may not include a transient inversion at nitrogen. The internal rotation for cyclotriazine systems is discussed in relation to those for aniline and formamide. The four barrier magnitudes calculated for the triazines are in the same order as (though somewhat larger than) those measured by variable-temperature NMR bandshape analysis for a relevant compound. q
The 1 H, 13 C and 19 F magic-angle spinning NMR spectra have been recorded for Form 1 of flurbipr... more The 1 H, 13 C and 19 F magic-angle spinning NMR spectra have been recorded for Form 1 of flurbiprofen. In the case of 19 F, spinning sideband analysis has produced data for the components of the shielding tensor. The chemical shift of the hydrogen-bonded proton was found to be 14.0 ppm. Shielding parameters for all three nuclei have been calculated using Density Functional Theory (DFT) together with the Gauge Including Projector Augmented Wave (GIPAW) method which takes full allowance for the repetition inherent in crystalline structures. Such computations were made for the reported geometry, for a structure with all the atomic positions relaxed using DFT, and with only the hydrogen positions relaxed. The relationships of the computed shifts to those observed are discussed. In general, the correlations are good.
Spectrochimica Acta Part A: Molecular Spectroscopy, 1983
is shown that the techmque of magic-angle rotation suffices to narrow "B NMR hnes for solid tetra... more is shown that the techmque of magic-angle rotation suffices to narrow "B NMR hnes for solid tetrahaloborates so that peaks due to different ions can be resolved. The method is found to give detailed structural information for a sample containing a mixture of ions of the type [BCl,Br,_,]-.
Solid State Nuclear Magnetic Resonance, 2006
Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with... more Two fluoropolymers, poly(vinylidenefluoride) (PVDF) and a vinylidenefluoride telomer (VDFT), with molecular weights of 1 Â 10 6 and 2 Â 10 3 Da by GPC, respectively, have been analysed by 19 F solid-state nuclear magnetic resonance (NMR) spectroscopy. Relaxation-filtered proton-decoupled magic-angle spinning (MAS) experiments, namely T 1r filter, dipolar filter (DF), direct-polarisation delayed acquisition (DPDA) and discrimination induced by variable-amplitude minipulses (DIVAM), allowed signals in the direct polarisation (DP) spectra of PVDF and the VDFT to be discussed in terms of rigid and mobile domains. Both samples showed signals, which were multi-componential, but they differ in the nature of the crystalline form present. Thus, the Vinylidenefluoride (VDF) telomer exhibited a crystalline component corresponding to b PVDF, whereas the PVDF contained crystallites of the a form. Signals relating to end groups and reverse units, plus an anomalous signal displaying long-time transverse relaxation in the DPDA spectrum, were found for both polymers, though they showed diversity in chemical shift and content. Signals related to reverse units and/or end groups were seen between approximately À115 and approximately À117 ppm for both samples. High-speed MAS at higher magnetic field resulted in an increase in resolution so that signals previously attributed to single-phase characteristics are shown to indicate the possibility of several different mobilities. The results are debated with respect to molecular weight and relaxation parameters. r
Solid-state 19 F NMR has been applied to poly(vinylidenefluoride) to investigate, inter alia, the... more Solid-state 19 F NMR has been applied to poly(vinylidenefluoride) to investigate, inter alia, the location of the reverse units. The application of relaxation filters in pulse sequences revealed fundamental differences relating to the domain structure of PVDF. A T 1r ðFÞ spin-lock experiment gave a spectrum of the crystalline phase along with some intensity from signals associated with reverse units. The proximity of reverse units to the amorphous and crystalline domains was further investigated by T 1r ðFÞ-filtered radio frequency driven recoupling (RFDR) and spin-diffusion experiments. The results showed the majority of reverse units to be relatively mobile (i.e. amorphous). However, weak RFDR cross-peaks were detected which suggest the presence of some reverse units in relatively rigid domains. A signal arising from a highly mobile site was detected at d F ¼ 2115 ppm by a delayed acquisition experiment and is tentatively assigned to -CH 2 CF 2 H end-groups. q
Macromolecular Rapid Communications, 2005
Fluorine-19 NMR spectra of solids have some special features, which are discussed in this article.
Solid State Nucl Magn Reson, 1997
In order to check the efficiency of high-power decoupling when used with the two-dimensional mult... more In order to check the efficiency of high-power decoupling when used with the two-dimensional multiple-quantum MAS method recently proposed to obtain isotropic spectra from quadrupolar nuclei, we applied this new technique to NMR for a hydrous layered silicate compound, makatite, with and without decoupling. A remarkable improvement of the spectral resolution in the isotropic dimension was observed by the decoupling, showing that it is effective in the 2D MQ-MAS method and suggesting that proton decoupling should be generally applied in experiments concerning these kinds of compound.
J Mater Chem, 1998
ABSTRACT
Solid State Nuclear Magnetic Resonance, 1997
In order to check the efficiency of high-power 1 H decoupling when used with the two-dimensional ... more In order to check the efficiency of high-power 1 H decoupling when used with the two-dimensional multiple-quantum MAS method recently proposed to obtain isotropic spectra from quadrupolar nuclei, we applied this new technique to 23 Na NMR for a hydrous layered silicate compound, makatite, with and without 1 H decoupling. A remarkable improvement of the spectral resolution in the isotropic dimension was observed by the decoupling, showing that it is effective in the 2D MQ-MAS method and suggesting that proton decoupling should be generally applied in 23 Na experiments concerning these kinds of compound. q 1997 Elsevier Science B.V.
Journal of Materials Chemistry, 1998
ABSTRACT
J Phys Chem a, 1997
ABSTRACT
The Journal of Physical Chemistry A, 1997
ABSTRACT
Journal of Magnetic Resonance, 2003
Simulations have been carried out on z-magnetizations produced by (and hence of the resulting spe... more Simulations have been carried out on z-magnetizations produced by (and hence of the resulting spectra from) the dipolar filter (DF) and the recently suggested "Discrimination Induced by Variable-Amplitude Minipulses" (DIVAM) pulse sequences [S. Ando et al., Polymer 42 (2001) 8137; Magn. Reson. Chem. 40 (2002) 97]. The strengths of dipolar interactions have been modelled by introducing different values for transverse relaxation times. The DF case has been extended by allowing the pulse angles to be smaller than 90 degrees. The pulse intervals have also been used as variables. For the DIVAM case, the variables are similarly the minipulse nutation angles and minipulse intervals. The computations show that DIVAM is superior to DF in terms of selectivity for spectra of heterogeneous materials such as semi-crystalline polymers. The effects of the pulse sequences on 19F spectra of poly(vinylidene fluoride) (PVDF) and of a copolymer of vinylidene fluoride and trifluoroethylene (p(VDF/TrFE)) are presented, together with fits of the experimental results by the simulations.