Variable-temperature high-resolution solid-state13C N.M.R. spectra of chiral smectogenic 4-heptyloxyphenyl 4′-[(s)-2-methylbutyl]biphenyl-4-carboxylate

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Abstract
High-resolution solid-state 13C N.M.R. spectra are studied for a chiral smectogenic compound 5*BBCOOBO7 at various temperatures. Below the ambient temperatures two spectral lines of protonated carbons show the existence of a 180[ddot] flip of the phenylene ring surrounded by the carboxyl and the alkoxy groups and the activation energy was obtained to be about 17kJ/mol (4 kcal/mol). The cooperative librational motions are present, which include the exchange between two conformers in the unit cell. The 13C chemical shifts induced in the solid state are also discussed with relation to the crystal structure.