Experimental and theoretical study of the infrared, Raman, and electronic spectra of two isomers of C-78 of C-2v symmetry

The two C-2 upsilon isomers of C-78 that satisfy the isolated-pentagon rule have been separated and studied by infrared, Raman (1064 nm excitation), and electronic spectroscopies backed up by semiempirical quantum chemical calculations, The structures have, respectively, 21 and 22 inequivalent atoms, The interplay between experiment and theory affords insight into the electronic and vibrational properties of the two molecules, In particular, through the comparison of the Raman and electronic spectra with their simulations, it is shown that the Raman spectra of the two isomers are different in nature. The spectrum of the isomer with 22 inequivalent atoms displays some preresonant character, while the spectrum of the other isomer does not. It is concluded that the properties of higher fullerenes must be treated on an individual basis, even when they share the same number of atoms and symmetry.