INFRARED-SPECTRA OF POLYCYCLIC AROMATIC-HYDROCARBONS - NITROGEN SUBSTITUTION

The B3LYP/4-31G approach is used to compute the harmonic frequencies o f substituted naphthalene, anthracene, and their cations. The substitu tions include cyano (CN), aminio (NH2), imino (NH), and replacement of a CH group by a nitrogen atom. All unique sites are considered, namel y 1 and 2 for naphthalene and 1, 2, and 9 for anthracene, except for t he imino, where only 2-iminonaphthalene is studied. The IR spectra of these substituted species are compared with those of the unsubstituted molecules. The addition of a CN group does not significantly affect t he spectra except to add the C-N stretching frequency. Replacing a CH group by N has only a small effect on the IR spectra. The addition of the NH2 group dramatically affects the neutral spectra, giving it much of the character of the cation spectra. However, the neutral 2-iminon aphthalene spectra looks more like that of naphthalene than like the 2 -aminonaphthalene spectra. (C) 1998 Elsevier Science B.V. All rights r eserved.