The proton NMR spectra of biphenyl dissolved in two nematic liquid-crystalline solvents have been analysed to yield 12 independent dipolar coupling constants, D(ij). The D(ij) have been used to obtain the probability distribution, P(nem)(phi), for the angle phi between the ring normals. Two methods of relating D(ij) to P(nem)(phi) have been used: the ME method, which invokes the maximum-entropy principle, and the AP method, which is based on the construction of a potential of mean torque from an addition of contributions from the rigid subunits in a molecule. The value of phi when P(nem)(phi) is a maximum is found to be essentially independent of the solvent, and is determined to be 34 +/- 1-degrees by the ME method, and 37.2 +/- 0.1-degrees by the AP method.
STRUCTURE OF BIPHENYL IN A NEMATIC LIQUID-CRYSTALLINE SOLVENT
CELEBRE, Giorgio;DE LUCA, Giuseppina;
1991-01-01
Abstract
The proton NMR spectra of biphenyl dissolved in two nematic liquid-crystalline solvents have been analysed to yield 12 independent dipolar coupling constants, D(ij). The D(ij) have been used to obtain the probability distribution, P(nem)(phi), for the angle phi between the ring normals. Two methods of relating D(ij) to P(nem)(phi) have been used: the ME method, which invokes the maximum-entropy principle, and the AP method, which is based on the construction of a potential of mean torque from an addition of contributions from the rigid subunits in a molecule. The value of phi when P(nem)(phi) is a maximum is found to be essentially independent of the solvent, and is determined to be 34 +/- 1-degrees by the ME method, and 37.2 +/- 0.1-degrees by the AP method.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
