Figure 6. PELF-mix spectra of MBBA reveal long-range correlations.
2D PELF-mix spectra correlating 13C chemical shift and 1H-13C dipolar coupling provide long-range correlations in aligned N-(4-methoxybenzylidene)-4-butylaniline (MBBA). (A) The molecular structure of MBBA with carbon atoms labeled. (B) 2D PELF spectrum with no proton mixing time display a single dipolar coupling frequency for each carbon chemical shift. The short distance dipolar couplings are labeled in blue; note that some 13C-1H dipolar couplings are equivalent because of rapid ring-flip motions. (C) A 2D PELF-mix spectrum acquired with tmix=150 µs. The long distance dipolar couplings are labeled in blue. Dipolar couplings labeled by an asterisk are not between directly bonded 13C-1H pairs, but rather between 13C-1H nuclear pairs on opposite sides of the phenyl ring (as C6 and H2 would be in Figure 2).