A DIFFERENCE BETWEEN THE π-ELECTRON PROPERTIES OF CATAFUSENES AND PERIFUSENES

It is shown that there is a remarkable difference between the Kekulé- and Clar-structure-dependence of the total π-electron energy (E) of catafusenes and perifusenes (catacondensed and pericondensed benzenoid molecules). Within classes of isomeric catafusenes the main parameter determining E is the Kekulé structure count whereas the influence of Clar-structure-based features is negligible. Within classes of isomeric perifusenes, Clar-structure-based features, in addition to the Kekulé structures, exhibit a significant effect on E. The present analysis is performed by using the mathematical formalism of the Zhang-Zhang polynomial [whose details are found in the recent paper: Gutman, Furtula, Balaban, Polycyclic Aromatic Compounds 26 (2006) 17–35].

Keywords:

• benzenoid hydrocarbons
• catafusenes
• Kekulé
• structure
• perifusenes
• total π-electron energy
• Zhang-Zhang polynomial