The anharmonic force field of 1,3-cyclopentadienes

The cubic and quartic semi-diagonal anharmonic force fields of 1,3-cyclopentadienes, C5H6 and C5D6, of the 1,3-cyclopentadiene-5-d and 1,3-cyclopentadiene-1,2,3,4,5-d(5) have been obtained using density functional theory, DFT, with the B97-1 functional and a triple-zeta plus double polarization (TZ2P) basis set. The 108 fundamental frequencies computed by second order vibrational perturbation theory are in very good agreement with the experimental data, with a root mean square deviation (RMSD) equal to 7 cm(-1). Some fundamental frequencies have been reassigned and two have been assigned for the first time on the basis of the present results. The RMSD value, identical to that obtained for naphthalene (E. Cane, A. Miani and A. Trombetti, J. Phys. Chem. A, 2007, 111, 8218), indicates that computations based on this method can be confidently extended to larger polycyclic aromatic hydrocarbons.