Conformational analysis in solution of C-2-symmetric 1,1 '-binaphthyl derivatives by circular dichroism spectroscopy and cholesteric induction in nematic mesophases

The twisting ability of a series of 1,1'-binaphthalene compounds used as do pants in nematic solvents has been related to the dihedral angle theta betw een the two naphthalene moieties, While in the case of the more flexible co mpounds the sign and value of the helical twisting power is affected by sev eral structural features that prevent a simple assignment of the conformati on in the presence of a covalent bridge that restricts the rotation around the C(1)-C(1') bond a reliable estimate of the conformational helicity coul d be obtained. This technique is complementary to CD spectroscopy that, for the investigated molecules, presents the same exciton patterns irrespectiv e of the actual theta value.