SEPARATION OF LOCAL MAGNETIC-FIELDS OF INDIVIDUAL PROTONS IN NEMATIC PHASE BY STATE-CORRELATED 2D NMR-SPECTROSCOPY

A nematic-isotropic phase-correlated 2D NMR spectrum was successfully obtained in 4′-ethoxybenzylidene-4-n-butylaniline (EBBA). The transition from nematic to isotropic phase was realized within 0.2 s using a microwave pulse of 2.45 GHz in the transition period. Local dipolar fields of 11 magnetically different protons in EBBA in the nematic phase were separately observed in the F1 dimension of a 2D experiment by means of well-resolved signals in the isotropic phase. The spectrum of the methyl protons of the ethoxy group clearly showed a triplet pattern, whereas those of the aromatic, methylene, and methine protons showed doublet patterns. Spin diffusion caused mixing of the spin states and gave mixed patterns in the 2D NMR spectrum in the F, dimension. Inspection of the amplitude of the mixing pattern gave information on spin diffusion pathways in EBBA in the nematic phase. © 1991.