A Deuteron NMR Study on the Rotational Dynamics and the Orientation of Benzene Molecules Adsorbed on Graphite and Boron Nitride

The 52.7 MHz deuteron (2H) solid state NMR spectra of benzene-d6 adsorbed on microcrystalline boron nitride and on two graphitized carbon blacks (G raphon and Sterling MT) were measured at temperatures between 75 and 120 K. Both on boron nitride and on the graphitized carbons the benzene molecules exhibit hexad axis rotation which is fast on the NMR time scale. From the spectra of benzene on the graphitized carbon blacks it is deduced that the molecules are oriented with their planes parallel to the graphite basal planes exposed. At the deuteron sites the shielding tensor which is set up by the action of the static field on the susceptibility tensor of the graphite microcrystallites possesses a shielding anisotropy of + 150 ppm and + 200 ppm for the Graphon and Sterling MT blacks, respectively.