Theoretical calculations of the geometries and of the lowest optical transitions of singly and doubly charged oligodiacetylenes

We have performed theoretical calculations on the singly and doubly charged species of the lowest unsubstituted oligodiacetylenes, with the scope of achieving information on the charged photoexcitations of polydiacetylenes. On the basis of the AM1-optimized geometries of the radical ions and of the dications we have computed their low-energy vertical transitions, using the INDO-SCI method in order to take into account the electron correlation. Extrapolated polymer results are compared with the photoinduced absorption spectra.