JAHN-TELLER EFFECT IN CYCLOPENTADIENYL RADICAL - DELOCALIZED VIBRONIC VALENCE ISOMERIZATION

Apparent D5h symmetry from experiments for C5H5 may be due to delocalization of vibronic wavefunctions. Ab initio (STO-3G) results for skeletal distortions yielded the largest stabilizationfor E′2 CC stretching with minima 14.5 kal mol-1 below the D5h point, separated by barriers of 3.5 kcal mol-1. Wavefunctions calculated for this two-dimensional finite nuclear motion interacting with two electronic states indicate considerable delocalization for both vibronic ground (E″1) and first excited (E″2) states. © 1979.