Molecular gyroscopes and compasses: Engineering motion into organic crystalline materials

ORGN 100

Zachary J. O'Brien, zobrien@chem.ucla.edu and Miguel A. Garcia-Garibay. Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive east, Los Angeles, CA 90095
Samples of 4,4'-bis(3,3,3-tri-d5-phenylpropynyl)biphenyl, 9,10-bis(3,3,3-tri-d5-phenylpropynyl)anthracene, 1,4-bis(3,3,3-tri-d5-phenylpropynyl)naphthalene, and 4,4'-bis(3,3,3-tri-d5-phenylpropynyl)-1,1'-binaphthyl were prepared via a Sonogashira coupling of d15-3,3,3-triphenylpropyne and the appropriate aryl dibromide. The compounds were then characterized by 13C CPMAS NMR experiments with varying contact times in order to determine whether the carbon signals of the central rotator group could be isolated and studied without any interference or overlap of signals from the stator group, which was deuterated and, therefore, insensitive to the cross polarization technique. It was found that the cross polarization experiment is sensitive enough such that the 13C signals of the rotator group can be observed even at very short contact times (ca. 50 μs) without interference from other 13C signals in the molecule. This technique could prove useful in studying the rotational dynamics of these compounds as well as many others at varying temperatures.