Vibrational Spectrum and Structure of the Tropylium Ion

The infrared and Raman spectra of tropylium ion, C7H7+, are presented and discussed in terms of possible structures. An assignment of the fundamental frequencies has been made for a D7h structure and used to carry out a normal coordinate analysis. The Wilson FG technique was used to calculate valence force symmetry constants and valence force constants. A comparison of the vibrational spectrum and force constants with those for benzene indicates a striking similarity between the two structures. The structure of tropylium ion was concluded to be a planar aromatic D7h molecule ion.