T. Tachikawa et al., PPP molecular orbital calculations of polyenyl cations and their analogs using new-gamma and pseudo atom modeling, MOLEC CRYST, 345, 2000, pp. 387-392
Thr first absorption bands of the tetramethyl polyenyl cations were calcula
ted by the Pariser-Parr-Pople molecular orbital method. By considering the
extraordinary hyperconjugation effect of methyl substituents and using the
new-y, the calculated absorption wavelengths reproduce well the observed on
es.