%0 Journal Article %J Journal of Physical Chemistry B %D 2003 %T Inclusion complexes oriented in thermotropic liquid-crystalline solvents studied with carbon-13 NMR %A Marjanska, M. %A Goodson, B. M. %A Castiglione, F. %A Pines, A. %K xe-129 %X

The inclusion complex of cryptophane-A and chloroform dissolved in two nonchiral liquid-crystalline environments was investigated via C-13 NMR. Stable solutions of oriented complexes were prepared using aromatic (ZLI 1132) and aliphatic (ZLI 1695) thermotropic nematic liquid crystals as solvents; ordering of the complexes was manifested by the H-1-C-13 dipolar splitting of the C-13 resonance of labeled chloroform. In both solutions, the dipolar splitting for the bound ligands was substantially larger than that obtained for the free ligands, indicating a significant increase in ligand ordering upon complexation despite the absence of direct contact with the oriented solvent molecules. A similar enhancement in ordering was observed for complexed ligands compared to that for free ligands in both liquid-crystalline solvents. Also, the application of heteronuclear decoupling to the ZLI 1695 solution resulted in a reduced line width for the bound C-13 chloroform resonance, suggesting that a significant component of the observed line broadening may originate from intermolecular couplings between host and guest molecules. These results demonstrate the potential for using restored dipolar couplings to investigate structural and dynamical aspects of inclusion complexes in solution.

%B Journal of Physical Chemistry B %V 107 %P 12558-12561 %8 Nov 20 %@ 1520-6106 %G English %U ://WOS:000186574500003 %N 46 %M WOS:000186574500003 %! Inclusion complexes oriented in thermotropic liquid-crystalline solvents studied with carbon-13 NMR %R Doi 10.1021/Jp030431e %0 Journal Article %J Journal of Magnetic Resonance %D 2002 %T Measurement of dipolar couplings in partially oriented molecules by local field NMR spectroscopy with low-power decoupling %A Marjanska, M. %A Castiglione, F. %A Walls, J. D. %A Pines, A. %K resolution %X

Low-power phase-modulated Lee-Goldburg homonuclear decoupling was used to record PDLF spectra of fluorine-substituted benzene derivatives dissolved in nematic thermotropic liquid crystalline solvents. The low-power decoupling minimizes sample heating during RE irradiation while still achieving highly resolved PDLF spectra. The method is illustrated by recording spectra for 1,3-dichloro-4-fluoro-5-nitrobenzene, 1,3-dichloro-4-fluorobenzene, and 1, 2-difluoro benzene dissolved in different nematic solvents. (C) 2002 Elsevier Science (USA). All rights reserved.

%B Journal of Magnetic Resonance %V 158 %P 52-59 %8 Sep-Oct %@ 1090-7807 %G English %U ://WOS:000179497500006 %N 1-2 %M WOS:000179497500006 %! Measurement of dipolar couplings in partially oriented molecules by local field NMR spectroscopy with low-power decoupling %R Doi 10.1016/S1090-7807(02)00059-9 %0 Journal Article %J Chemical Physics Letters %D 2002 %T Selective excitation in dipole coupled systems %A Walls, J. D. %A Marjanska, M. %A Sakellariou, D. %A Castiglione, F. %A Pines, A. %K spin-diffusion %X

In this Letter the possibility of selective excitation in coupled multispin systems is studied theoretically. A general method of transforming any selective pulse developed for uncoupled systems into a form that is selective in coupled systems is presented. This is accomplished by adding a small perturbation to a decoupling radiofrequency (RF) field. When viewed in an interaction frame given by the decoupling RF field, this method generates, in an averaged sense, a propagator similar to the propagator of uncoupled spins under a shaped RF pulse. Preliminary experimental results are presented for the case of selective excitation in proton nuclear magnetic resonance in liquid crystals. (C) 2002 Elsevier Science B.V. All rights reserved.

%B Chemical Physics Letters %V 357 %P 241-248 %8 May 10 %@ 0009-2614 %G English %U ://WOS:000175958700012 %N 3-4 %M WOS:000175958700012 %! Selective excitation in dipole coupled systems %R Doi 10.1016/S0009-2614(02)00493-1