Dispersion Corrections Essential for the Study of Chemical Reactivity in Fullerenes

In a previous paper (J. Phys. Chem. A2009, 113, 9721), we analyzed theoretically the Diels−Alder cycloaddition between cyclopentadiene and C60 for which experimental results on energy barriers and reaction energies are known. One of the main conclusions reached was that the two-layered ONIOM2(B3LYP/6-31G(d):SVWN/STO-3G) method provides results very close to the full B3LYP/6-31G(d) ones. Unfortunately, however, both the exothermicity of the reaction and the energy barrier were clearly overestimated by these two methods. In the present work, we analyze the effect of the inclusion of Grimme’s dispersion corrections in the energy profile of this reaction. Our results show that these corrections are essential to get results close to the experimental values. In addition, we have performed calculations both with and without dispersion corrections for the Diels−Alder reaction of C60 and several dienes and for the Diels−Alder cycloaddition of a (5,5) single-walled carbon nanotube and 1,3-cis-butadiene. The results obtained indicate that inclusion of dispersion corrections is compulsory for the study of the chemical reactivity of fullerenes and nanotubeThe following organizations are thanked for financial support: the Ministerio de Ciencia e Innovacion (MICINN, Project nos. CTQ2008-03077/BQU and CTQ2008-06532/BQU), the DIUE of the Generalitat de Catalunya (Project nos. 2009SGR637 and 2009SG R528), and the European Community (postdoctoral fellowship PIOF-GA-2009-252856). Excellent service by the Centre de Supercomputacio de Catalunya (CESCA) is gratefully acknowledged. The authors also are grateful for the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Center-Centro Nacional de Supercomputacion. Support for the research of M. Sola was received through the ICREA Academia 2009 prize for excellence in research funded by the DIUE of the Generalitat de Catalunya. We thank Dr. Caries Curutchet for locally adapting the Gaussian 09, revision A.02 program and Prof. Dr. Per E. M. Siegbahn for providing us with a copy of ref 2