Conformational analysis of the alkyl spacer of a dimer liquid crystal in the solid and liquid crystalline states by 13C-13C dipolar coupling

The conformation around the C-epsilon-C-epsilon 1 bond of the alkyl spacer of alpha,beta-bis[(4,4'-cyanobiphenylyl)oxy] decane (CBA-10) was evaluated in the solid and liquid crystalline states through the detection of the dipolar interaction between C-delta and C-delta'. CBA-10 C-13-labelled in the delta position of the alkyl spacer was prepared and for the measurement in the solid state a variation of the Carr-Purcell-Meiboom-Gill sequence was used. The spectra in the nematic state were measured with the pulse saturation method. It was concluded that in the solid state the trans conformation is assumed whereas in the liquid crystalline state the fraction of the trans conformers is around 0.6. (C) 1998 John Wiley & Sons, Ltd.