π-electron structure,reactivity, and absorption spectra of anthrapyridone

The π-electronic spectra, heats of atomization, and electronic indexes of the lactam and lactim forms of anthrapyridone were calculated by the Pariser-Parr-Pople method with allowance for 25 one-electron configurations. An examination of the π-bond orders and the charges on the atoms showed that a system with a π-electron distribution close to the distribution in anthraquinone and in α-pyridone for the lactam tautometer and in α-hydroxypyridine and anthraquinone for the lactim form is formed in the lactam and lactim of anthrapyridone. The electronic absorption bands were assigned. An analysis of the calculated values demonstrated that the long-wave band in the spectrum of the anthrapyridone is due to charge transfer from the amide group to the ketone group. The reactivity and localization energy indexes of aromatic substitution reactions calculated by the Hückel MO method are in satisfactory agreement with the experimental data.