24 IPR isomers of fullerene C84: Cage deformation as geometrical characteristic of local strains

The structures of 24 IPR-isomers of C84 fullerene with distributed single, double and delocalized bonds are presented. Obtained results are fully supported by DFT quantum-chemical calculations of electronic and geometrical structures of these isomers. Two reasons of instability of fullerene molecules are their radical origin and/or high local strain. Distortion of pentagons as well as hexagons with alternating single and double bonds is the most significant geometrical parameter reflecting local strain of a molecule. These distortions are measured as maximal dihedral angles of those cycles and reach 20 degrees in mostly deformed hexagons and pentagons. In contrast high values of dihedral angles in hexagons with delocalized p-bonds are typical for stable isomers. Other geometric parameters such as valence angles, sums of valence angles and dihedral angles between approximate planes of fused rings have no marked influence on stability. The development of strain-related criteria for fullerene stability will be helpful in the prediction which isomers might potentially be observable in experiment. V C 2011 Wiley Periodicals, Inc. Int J Quantum Chem 112: 1055-1065, 2012