From Overcrowded Polycyclic Aromatic Enes to Semifullerenes

Abstract

Bi-9H-fluoren-9-ylidene (2) and bi-4H-cyclopenta[def]phenanthren-4-ylidene (5) are potential starting materials for the preparation of bowl-shaped fragments of fullerenes. Semiempirical MNDO-PM3 calculations of C₂₆H_n and C₃₀H_n (n = 12, 14, 16) species 2-12 are used to analyze energetic effects on the dehydrocyclization and isomerization reactions of these species. Oxidative photocyclizations on Z-2,2′-bridged derivatives of 2 and 5 are briefly outlined.

Key words::

• non-planar PAHs
• strain
• overcrowding
• semiempirical calculations
• photocyclization