DUGi

The Frozen Cage Model: A Computationally Low-Cost Tool for Predicting the Exohedral Regioselectivity of Cycloaddition Reactions Involving Endohedral Metallofullerenes

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@2072@@300374

Functionalization of endohedral metallofullerenes (EMFs) is an active line of research that is important for obtaining nanomaterials with unique properties that might be used in a variety of fields, ranging from molecular electronics to biomedical applications. Such functionalization is commonly achieved by means of cycloaddition reactions. The scarcity of both experimental and theoretical studies analyzing the exohedral regioselectivity of cycloaddition reactions involving EMFs translates into a poor understanding of the EMF reactivity. From a theoretical point of view, the main obstacle is the high computational cost associated with this kind of studies. To alleviate the situation, we propose an approach named the frozen cage model (FCM) based on single point energy calculations at the optimized geometries of the empty cage products. The FCM represents a fast and computationally inexpensive way to perform accurate qualitative predictions of the exohedral regioselectivity of cycloaddition reactions in EMFs. Analysis of the Dimroth approximation, the activation strain or distortion/interaction model, and the noncluster energies in the Diels–Alder cycloaddition of s-cis-1,3-butadiene to X@D3h-C78 (X = Ti2C2, Sc3N, and Y3N) EMFs provides a justification of the method

The following organizations are thanked for financial support: the Ministerio de Ciencia e Innovacion (MICINN, Project Nos. CTQ2011-25086/BQU and CTQ2011-23156), and the DIUE of the Generalitat de Catalunya (Project Nos. 2009SGR637 and 2009SGR528). MG.-B. thanks the Spanish MEC for doctoral fellowship AP2010-2517. S.O. is grateful to the European Community for postdoctoral fellowship PIOF-GA-2009-252856. Excellent service by the Centre de Serveis Cientific i Academics de Catalunya (CESCA) is gratefully acknowledged. The authors also are grateful to the computer resources, technical expertise, and assistance provided by the Barcelona Supercomputing Center-Centro Nacional de Supercomputation. Support for the research of M.S. was received through the ICREA Academia 2009 prize for excellence in research funded by the DIUE of the Generalitat de Catalunya