Measurements of the absorption, polarized fluorescence, and MCD of 1,6-methano[10]annulene, 1,6:8,13-bismethano[14]annulene, and 1,6:8,17:10,15-trismethano[18]annulene along with the semiempirical p-electron and AVE calcns. on these and related annulenes are reported. The transannular interaction in the methano-bridged annulenes is strong, and these homoarom. mols. can be viewed as examples of arrested transition states along electrocyclic reaction paths. In addn. to the anticipated Lb, La, Bb, and Ba transitions originating in the conjugated (4N + 2)-electron annulene perimeter, at least one further low-energy transition is present, but its nature is not well understood. The MCD of the bridged annulenes agrees with the expectation based on the general theory for cyclic (4N + 2)-electron systems and the abs. signs agree with the relative size of orbital energy differences obtained from CNDO/S calcns.
No takes yet. Share an insight, caveat, or question.
Dewey et al. (1980) studied this question.