INFLUENCE OF NITROGEN SUBSTITUTION ON THE ELECTRONIC BAND-STRUCTURE OF POLY(PERI-NAPHTHALENE)

The electronic valence band structure of PPDAN, a chemical modificatio n of poly(peri-naphthalene) where the central two carbon atoms of each naphthalene unit cell are substituted by nitrogen atoms, is theoretic ally investigated using the nonempirical VEH method. VEH calculations predict that PPDAN is a semiconductor with a small bandgap of 0.64 eV when a planar D-2h structure is assumed for the unit cell. The bandgap increases to 1.3 - 1.6 eV when the more stable C-2v and C-2h structur es are used.