Theoretical description of benzene–fullerene and its organometallic derivative Anabel Ruiz-Espinoza, Estrella Ramos, Roberto Salcedo ⇑ Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacán 04510, Mexico City, Mexico article info Article history: Received 15 November 2012 Received in revised form 10 April 2013 Accepted 11 April 2013 Available online 21 April 2013 Keywords: Benzene–fullerene Aromaticity Organic derivatives Organometallic derivative abstract The ubiquitous benzene derivative of fullerene has been analyzed from a theoretical point of view. The pronounced difficulties involved in its preparation relate to the structure of the frontier orbitals of the primitive fragments (i.e. benzene and fullerene C 60 ) and their corresponding interactions. The nature of the inductive effect is studied on the basis of the nitro and amino derivatives (functional groups substi- tuted on benzene ring). The electrophilic activation/deactivation patterns induced by substituent groups added to phenyl-fullerene molecule are studied applying the criteria of reactivity indexes in conjunction with the molecular electrostatic potential and the dipole moment of the molecules. The capacity of the resultant molecule to generate organometallic derivatives similar to the dibenzene-chromium is also studied. All structures were calculated using DFT methods. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction The organo-fullerene compounds comprise a rare classification of substances because the direct reactions between fullerene and organic fragments are not common [1]. There are several methods which can be used to synthesize the so-called organohydrofulle- renes where a double bond on the fullerene surface is broken to yield the substitution of a functional group and a hydrogen atom [2]. Among these, it is important to mention those compounds where the substitution makes it possible for an aromatic ring to take a substituent on one end of a double bond, and a hydrogen atom on the other [3,4], causing an elecrophilic aromatic substitu- tion to occur. This type of compound constitutes the subject of our interest. The phenyl-fullerene (PF) is presented in Fig. 1; the molecule is the only product resulting from the substitution of a benzene mol- ecule on a (6,6) fullerene bond and its corresponding proton. The first attempt to prepare this compound was undertaken by Olah and his co-workers [5], but the problem encountered in a direct reaction lies in the possibility that a multiple substitution will take place at the surface of the C 60 , it is thus convenient that the prod- ucts should consist of a mix of several substances. The titration method [3,4] has been shown to represent a better option and the phenyl-fullerene can be synthesized in this way, however little information exists concerning its structure and reactivity. The goal of this study is to analyze the nature of the electronic structure of this molecule from a theoretical point of view, ana- lyzing the intrinsic properties involved in possible reactive behav- ior, the changes precluded by new substituents on the benzene fragment and the possibility of preparing organometallic derivatives. 2. Methods All calculations were carried out by applying a pure DFT method for energy evaluations. In the case of structures of all derivatives of benzene, Becke’s gradient corrections [6] for exchange and Per- dew–Wang’s for correlation [7] were applied. This is the scheme for the BPW91 method which forms part of the Gaussian 09 [8] Package. The calculations were performed using the 6-31G  basis set. The structure of complex di-benzenechromium-fullerene (BCF) was optimized using DFT in the generalized gradient approxima- tion (GGA) with the Materials Studio DMol3 program [9,10] from Accelrys Inc. We employed the Perdew–Wang 1991 (PW91) ex- change–correlation functional [11] with a double numerical, plus a polarization function basis set (DNP) to describe the valence elec- trons, in combination with Hartree–Fock effective core potentials [12,13] for the treatment of the ionic cores. The structure was re- laxed until the total remaining force was below 0.002 Ha/Å, a ther- mal smearing of 0.05 Ha was used to optimize geometry. Finally, the structure was optimized with Gaussian 09. Frequency calculations were carried out at the same level of theory in order to confirm that the optimized structures were at a minimum on the potential surfaces. Work strategy was selected according to that proposed in the previous fullerenocene study [11]. The bond lengths of the optimized structures were used for 2210-271X/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.comptc.2013.04.011 ⇑ Corresponding author. Tel.: +52 5556224600. E-mail address: salcedo@unam.mx (R. Salcedo). Computational and Theoretical Chemistry 1016 (2013) 36–41 Contents lists available at SciVerse ScienceDirect Computational and Theoretical Chemistry journal homepage: www.elsevier.com/locate/comptc