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OLIDS AND LIQUIDS

Stepwise Computational Synthesis of Fullerene C60 Derivatives. Fluorinated Fullerenes C60F2k1 E. F. Sheka General Physics Department, Peoples’ Friendship University of Russia, Moscow, 117198 Russia email: [email protected] Received January 8, 2010

Abstract—Reactions of fullerene C60 with atomic fluorine are studied by the unrestricted broken spin sym metry Hartree–Fock (UBS HF) approach implemented in semiempirical codes based on the AMI tech nique. The calculations are focused on a successive addition of a fluorine atom to the fullerene cage following the indication of the highest chemical susceptibility of the cage atom, which is calculated at each step. The proposed computational synthesis is based on the effectively unpairedelectron concept of the chemical sus ceptibility of fullerene atoms. The obtained results are analyzed from the standpoints of energy, symmetry, and the composition abundance. A good fitting of the data to experimental findings proves a creative role of the suggested synthetic methodology. DOI: 10.1134/S1063776110090098 1

1. INTRODUCTION

The fluorinated fullerene C60 decade, started with the first synthesis in 1991 (see reviews [1–4]) and ended by a generalizing theoretical approach to the characterization of fluorinated fullerenes in 2003 [5], without a doubt is one of the best examples of the power and ability of modern chemistry to produce, characterize, and describe a new family of fascinating chemicals at a microscopic level. This is especially impressive because the number of species hidden under the general formula C60F2k (with k = 1, …, 30), is definitely countless if all possible isomers at each particular k are taken into account. The first break through in the problem was achieved by experimental ists who showed that 1) only species with an even num ber of fluorine atoms can be observed, 2) not all k = 1, …, 30 fluorinated products but only a restricted set of them can be produced and identified in practice, and 3) a very limited number of isomers, from one to three, are revealed. Products with chemical formulas C60F18, C60F36, and C60F48 dominate in the production list, while minor products from C60F2 to C60F20 have also been identified [6]. Mass spectrometry, IR, 19F, and 3He NMR spectroscopy manifested themselves as reliable constituents of a convincing analytical plat form for identification of the species. At the same time, quantum chemical simulations have faced the manyfold isomerism problem in the full measure. Thus, to suggest a convincing atomistic structure of the products produced experimentally, one to three isomers [6] must be chosen among 600873146368170 isomers of C60F36 [7] and 1 The article is published in the original.

23322797475 isomers of C60F48 [7]. To make compu tations feasible the isomer number must be restricted to unity. Obviously, this might be possible if some glo bal regularities, which govern the fluorination process, can be exhibited. To proceed along this way, it was nec essary to answer the following questions. 1. T