The absorption and CD spectra of a series of Fréchet (compounds 7-10) and backfolding (compounds 11-12) dendrimers derived from enantiopure (S)-2,2-dihydroxy-1,1-binaphthalene have been recorded (THF) in the range 200-350 nm. All the compounds examined show a positive couplet between 200 and 240 nm (1B transition of the 2-naphthol chromophore), the intensity of which (max of the low-energy branch) ranges between 100 and 40. By means of the DeVoe polarizability model the intensity of the 1B couplet has been calculated vs. the dihedral angle . This analysis provides angles of 95-110° for the Fréchet dendrimers and 100-110° for the backfolding compounds. These values clearly indicate that the torsional angle , defined by the two naphthalene planes, never exceeds the critical value of 110°. This investigation confirms the wide utility of CD spectroscopy to provide geometrical information that cannot be obtained by other types of structural analysis.
|Number of pages||10|
|Journal||European Journal of Organic Chemistry|
|Publication status||Published - 2000|