To estimate the torsion sensitivity of dipolar coupling
biphenylic molecules have been chosen as probes due to their relatively
simple structure and the surprisingly high ambiguity of the only flexible
parameter – interring torsion angle. Solution structures of 4,4’-dibromobiphenyl
and 4,4’-diiodobiphenyl are reported for the first time in two liquid crystals
I52 and ZLI 1695. The comparison of NMR structures of various para-substituted
biphenyls, calculated by APME (Additive Potential Maximum Entropy) approach
shows that the small spread of torsion angle values in case of different
solvents and para-substituents is in good agreement with theoretical expectations
from hybrid DFT methods. Furthermore, the real structural changes of interring
torsion and the prevalence of solvent effects over para-halosubstitution
can be correctly revealed from these small fluctuations.
Aleksandr B. Sahakyan /go to my home page/