Photoelectron spectra and electronic structures of highly substituted polyenes

The electronic structures of the alpha,alpha,omega,omega -tetra-t-butyl substituted conjugated polyenes 1-6 have been investigated by UV photoelectron spectroscopy and quantum chemical calculations. The all-trans-hexatriene (1), octatetraene (2), decapentaene (3), and the tetradecaheptaene (4) have essentially planar polyene chromophores and accordingly their pi MOs are spread by about 3-5 eV. On the other hand, interaction of the double bonds is Limited in the moderately twisted cis-hexatriene (5) and the highly distorted cis-3,4-dimethylhexatriene (6). The first U-Vis absorption of alpha,alpha,omega,omega -tetra-t-butyl-polyenes with three to thirteen conjugated C=C double bonds is linearly correlated with the PM3 calculated HOMO-LUMO energy gap. (C) 2001 Elsevier Science B.V. All rights reserved.