Structure and energy spectra of a class of polybenzenoid Clar's hydrocarbons and 1-D polymers

The energy spectra of a class of 2-D polybenzenoid Clar's hydrocarbons with a large number N(N similar to 10(4)) of carbon atoms is studied theoretica lly. It is shown that at the asymptotic case N --> infinity the energy gap (EG) DeltaE (N --> infinity) is different from zero, i.e.. the pi -systems should possess semiconductor properties. The results for the EG DeltaE (N - -> infinity) not equal 0 of the hydrocarbons are in qualitative agreement w ith the results for the EG calculated for a class of 1-D ladder polymers ha ving the same edge structure as the hydrocarbons. With increasing the numbe r (M) of the pi -centers of the elementary unit of the polymers, the band g ap DeltaE(M --> infinity) approaches also to a value different from zero. T he quantitative results on the equilibria geometries of the hydrocarbons an d the polymers correspond to Clar's qualitative characterization of benzeno ids composed of disjoint "pi -sextets". The energetics of the hydrocarbons with different types of defects and the corresponding Tamm and Frenkel stat es were also investigated.