Is 2-D Graphite an Ultimate Large Hydrocarbon? II. Structure and Energy Spectra of Polycyclic Aromatic Hydrocarbons with Defects

The structure and energy spectra of four classes of polybenzenoid hydrocarbons with different edge structures, a large number N ( N ∼ 10 4 ) of carbon atoms, and different types of defect states (Tamm, Schottky and chemisorption states) have been studied theoretically. Several types of (probably) stable monoradicals and triplet biradicals with singly occupied MOs in the energy gap (molecular analogues of semiconductors with defect states) are characterized which could be used in the molecular electronics. A new concept for viewing high-spin π systems with ferromagnetically coupled electrons within the half-filled band of NBMOs in term of point defects (vacancies) was developed. The NBMOs can be considered as surface states (Tamm or Schottky).