The geometry and harmonic frequencies of naphthalene,
azulene, phenanthrene, and anthracene have been
computed using the Becke three-parameter Lee−Yang−Parr functional
(B3LYP) and basis sets of spd and
spdf quality. A simple scaling procedure for the
harmonic frequencies is proposed that brings computed
harmonics to within 10−20 cm-1 or better of
experimental fundamentals without resorting to internal
coordinate
transformations. A complete reassignment of the vibrational
spectrum of phenanthrene is proposed, and
several reassignments are due for anthracene as well. The
assignments of Sellers, Pulay, and Boggs (J. Am.
Chem. Soc.
1985, 107, 6487) for
naphthalene, and of Kozlowski, Rauhut, and Pulay (J. Chem.
Phys.
1995,
103, 5650) for azulene, are largely confirmed.
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