99277-30-2Relevant articles and documents
Investigation of Spin Density Transfer into Cyclopropyl and Cyclohexyl Groups by ENDOR and TRIPLE Resonance, INDO and MINDO/3 Calculations
Kirste, Burkhard,Broser, Waldemar,Grain, Kornelia,Kurreck, Harry,Schloemp, Gerhard
, p. 3464 - 3480 (2007/10/02)
By performing EPR, ENDOR, and TRIPLE experiments on the 1-cyclopropyl- and 1-cyclohexylphenalenyl radicals as well as the radical anions of 9-cyclopropyl- and 9-cyclohexylanthracene the hyperfine coupling constants, including their signs, were determined.An attempt was made to determine the optimum geometries of these radicals or of model systems by MINDO/3 caclculations.The dependence of the potential functions as well as the hyperfine coupling constants of the radicals on the dihedral angle between the cycloalkyl group and the ?-system were calculated by the INDO method.Conclusions with respect to the preferred conformations and the mechanism of spin density transfer into the cycloalkyl groups were drawn from a comparison with the experimental data.The hindrance of free rotation of the cycloalkyl groups is mainly caused by steric interactions with hydrogen atoms in peri-positions.Whereas the two ring systems are oriented almost perpendicular to each other in the radical anion of 9-cyclohexylanthracene, the eclipsed conformation is preferred in the corresponding cyclopropyl compound.