title: Relative Stability of Empty Exohedral Fullerenes: π Delocalization versus Strain and Steric Hindrance.
abstract: Predicting and understanding the relative stability of exohedral fullerenes is an important aspect of fullerene chemistry, since the experimentally formed structures do not generally follow the rules that govern addition reactions or the making of pristine fullerenes. First-principles theoretical calculations are of limited applicability due to the large number of possible isomeric forms, for example, more than 50 billion for C60X8. Here we propose a simple model, exclusively based on topological arguments, that allows one to predict the relative stability of exohedral fullerenes without the need for electronic structure calculations or geometry optimizations. The model incorporates the effects of π delocalization, cage strain, and steric hindrance. We show that the subtle interplay between these three factors is responsible for (i) the formation of non-IPR (isolated pentagon rule) exohedral fullerenes in contrast with their pristine fullerene counterparts, (ii) the appearance of more pentagon-pentagon adjacencies than predicted by the PAPR (pentagon-adjacency penalty rule), (iii) the changes in regioisomer stability due to the chemical nature of the addends, and (iv) the variations in fullerene cage stability with the progressive addition of chemical species.
authors.affiliation: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid , 28049 Madrid, Spain.
authors.forename: Yang
authors.identifier: 0000-0003-2540-2199
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , 28049 Madrid, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Díaz-Tendero
authors.affiliation: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , 28049 Madrid, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Alcamí
authors.affiliation: Departamento de Química, Módulo 13, Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid , 28049 Madrid, Spain.|Instituto Madrileño de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia) , 28049 Madrid, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Martín