Abstract
The geometries for the planar T1 states of linear polyenes CnHn+2 (n=8, 10, 12, 14, 16, 18, 20, and 22) were optimized by ab initio SCI calculations. It was found that the bond alternation which existed in the S0 state disappears only in the central region of the polyene chain. This is quite similar to the ‘triplet-excited region’ which was observed in PPP SDCI calculations for decapentaene (n=10), tetradecaheptaene (n=14), octadecanonaene (n=18), and docosaundecaene (n=22) (M. Kuki, Y. Koyama, N. Nagae, J. Phys. Chem. 95 (1991) 7171). However, CASSCF calculations performed for octatetraene (n=8) gave considerably different geometries from the SCI geometries. The reason for this is discussed and we conclude that the appearance of the ‘triplet-excited region’ in SCI and SDCI calculations is artifactual.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
