Conformational studies on helicenes VI. A comparison between experimental and calculated conformations

The force-field method of Warshel has been used for the calculation of the conformations of hexahelicene, two methyl substituted hexahelicenes and heptahelicene. The calculated models have been compared with the known X-ray structure and the generally small differences have been discussed. The method has also been used for the calculation of the structure of 5,6-dihydrohexahelicene. The dihedral angles in the aliphatic moiety of the model agree reasonably well with those calculated from NMR data.