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The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent

The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent
The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent
The deuterium decoupled, proton nuclear magnetic resonance spectrum of a sample of diphenylmethane-d(3) dissolved in a nematic liquid crystalline solvent has been analyzed to yield a set of dipolar couplings, D-ij. These have been used to test models for the conformational distribution generated by rotation about the two ring-CH2 bonds through angles tau(1) and tau(2). Conformational distributions, particularly when obtained from a quantum chemistry calculation, are usually described in terms of the potential energy surface, V(tau(1),tau(2)), which is then used to define a probability density distribution, P(tau(1),tau(2)). It is shown here that when attempting to obtain P(tau(1),tau(2)) from experimental data it can be an advantage to do this directly without going through the intermediate step of trying to characterize V(tau(1,)tau(2)). When applied to diphenylmethane this method shows that the dipolar couplings are consistent with a conformational distribution centered on tau(1)=tau(2)=56.5+/-0.5degrees, which is close to the values calculated for an isolated molecule of 57.0degrees, and significantly different from the asymmetric structure found in the crystalline state.
dipolar couplings, alkyl chains, nmr-spectra, parameters, phases
0021-9606
6417-6426
Celebre, G.
75851a36-1291-4c3c-bea7-b1442d0016b0
De Luca, G.
b190a7b3-3729-4118-b4c7-3a04da54f2b8
Emsley, J.W.
9d219d5e-28c0-4a8c-bf3d-1f78cd707c17
Foord, E.K.
1dd94799-4c16-4ae7-a50a-24f2db36143a
Longeri, M.
39ff086e-7606-4a08-9296-1528644fdef5
Lucchesini, F.
6913725a-a256-4069-a449-8e97d25274cb
Pileio, G.
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8
Celebre, G.
75851a36-1291-4c3c-bea7-b1442d0016b0
De Luca, G.
b190a7b3-3729-4118-b4c7-3a04da54f2b8
Emsley, J.W.
9d219d5e-28c0-4a8c-bf3d-1f78cd707c17
Foord, E.K.
1dd94799-4c16-4ae7-a50a-24f2db36143a
Longeri, M.
39ff086e-7606-4a08-9296-1528644fdef5
Lucchesini, F.
6913725a-a256-4069-a449-8e97d25274cb
Pileio, G.
13f78e66-0707-4438-b9c9-6dbd3eb7d4e8

Celebre, G., De Luca, G., Emsley, J.W., Foord, E.K., Longeri, M., Lucchesini, F. and Pileio, G. (2003) The conformational distribution in diphenylmethane determined by nuclear magnetic resonance spectroscopy of a sample dissolved in a nematic liquid crystalline solvent. The Journal of Chemical Physics, 118 (14), 6417-6426. (doi:10.1063/1.1555631).

Record type: Article

Abstract

The deuterium decoupled, proton nuclear magnetic resonance spectrum of a sample of diphenylmethane-d(3) dissolved in a nematic liquid crystalline solvent has been analyzed to yield a set of dipolar couplings, D-ij. These have been used to test models for the conformational distribution generated by rotation about the two ring-CH2 bonds through angles tau(1) and tau(2). Conformational distributions, particularly when obtained from a quantum chemistry calculation, are usually described in terms of the potential energy surface, V(tau(1),tau(2)), which is then used to define a probability density distribution, P(tau(1),tau(2)). It is shown here that when attempting to obtain P(tau(1),tau(2)) from experimental data it can be an advantage to do this directly without going through the intermediate step of trying to characterize V(tau(1,)tau(2)). When applied to diphenylmethane this method shows that the dipolar couplings are consistent with a conformational distribution centered on tau(1)=tau(2)=56.5+/-0.5degrees, which is close to the values calculated for an isolated molecule of 57.0degrees, and significantly different from the asymmetric structure found in the crystalline state.

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Published date: 8 April 2003
Keywords: dipolar couplings, alkyl chains, nmr-spectra, parameters, phases
Organisations: Chemistry

Identifiers

Local EPrints ID: 19926
URI: https://eprints.soton.ac.uk/id/eprint/19926
ISSN: 0021-9606
PURE UUID: 9e3e5a45-ae4f-4bc6-8d39-1ec4acd248df
ORCID for G. Pileio: ORCID iD orcid.org/0000-0001-9223-3896

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Date deposited: 23 Feb 2006
Last modified: 06 Jun 2018 12:41

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