Variable-temperature high-resolution solid-state ¹³C N.M.R. spectra of chiral smectogenic 4-heptyloxyphenyl 4′-[(s)-2-methylbutyl]biphenyl-4-carboxylate

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.