SEMIEMPIRICAL SCF-MO STUDY OF BOWL-TO-BOWL INVERSION IN CORANNULENE AND SMALLER CIRCULENES

The results of MINDO/3, MNDO, AM1, and PM3 semi-empirical SCF MO calcu lations for angle deformation and resonance stabilization effects in c orannulene (1) indicate that for molecules in which the strain arises primarily from angle bendings, MNDO provides more reliable results. Bo th MINDO/3 and MNDO underestimate bowl-to-bowl inversion barrier in 1 by 2.7 and 2.3 kcal mol(-1), respectively; PM3 and AM1 exaggerate this barrier by 5.5 and 6.6 kcal mol(-1), respectively. Structural feature s and dynamic behaviour of smaller circulenes, compounds with a circul ar arrangement of four and three benzene rings, are also reported. (C) 1997 Elsevier Science B.V.