Theoretical absorption spectra of charged oligodiacetylenes

We perform quantum chemical calculations on the singly and doubly charged s pecies of the lowest unsubstituted oligodiacetylenes, in order to achieve i nformation on the charged states originated in the photoexcitation of polyd iacetylenes. On the basis of the optimized AMI geometries of the radical io ns and dications we obtain their low-energy vertical transitions in an INDO -SCI framework to ensure a proper treatment of electron correlation effects . We get the simulated absorption spectra of the charged oligomers by a con volution of the transition energies, and compare the linearly extrapolated polymer values with the photoinduced absorption results.