ИСТИНА

Fullerenes and their derivatives have been proposed to be employed in the design of materials for a considerable variety of applications including nano- and molecular electronics (photovoltaic cells, optical limiters, organic light-emission diodes and field-effect transistors) [1] and medicine (antioxidants, neuroprotective agents, antimicrobial agents, agents for photodynamic therapy and magnetic resonance imaging) [2]. Their value in electronics stems from their spherically conjugated π-electron system that gives rise to n-type conductivity, low reduction potential and low reorganization energy in electron-transfer reactions. In addition, there is a broad selection of fullerene derivatives suitable for solution-based technology. However, there is still a need for improvement and fine tuning of their electronic properties, which requires development of the regioselective techniques of exohedral functionalization as well as skeletal transformation. Enhancement the electron withdrawing properties of the fullerene cage is readily and efficiently achievable via derivatization with fluorinated moieties. To date, three rather broad and extensively explored classes of the fluorine-containing fullerene derivatives are available. These are fluorofullerenes (e.g. C60Fn, n=2–48), trifluoromethylfullerenes (C60(CF3)2n and C70(CF3)2m, n=1–9 and m=1–10), and difluoromethylenofullerenes (C60(CF2)n, C70(CF2)n, n=1–3). Contrary to the anticipated enormous compositional and isomeric complexity to arise from concurrence of a multitude of reaction sites, these fullerene derivatives can be prepared as relatively simple mixtures of products or even as individual isomers. According to our extensive quantum chemical DFT surveys, the observed selectivity can be explained by both thermodynamic and kinetics factors. Further regioselective functionalization of the fluorine-containing fullerenes with various organic functions can be achieved via nucleophilic addition or cycloaddiction. We found that the addition motifs of the initially attached groups controls the regioselectivity of further derivatization. Efficient and reliable methods to predict the structure of the diversely functionalized fullerene compounds will be presented. In fullerene derivatives, such key electronic properties as electron affinity and ionization energy are largely determined by the number of addends and their attachment pattern. Therefore, both compositional and isomeric purity of the complex fullerene derivatives are crucial for their applicability in organoelectronics. Yet another requirement is chemical stability under the electron-transfer conditions. We will discuss the effect of the attachment motifs in the fluorine containing fullerene compounds on their electron affinity and on the exohedral rearrangements and bond opening processes. [1] Medicinal Chemistry and Pharmacological Potential of Fullerenes and Carbon Nanotubes (Eds.: F. Cataldo, T.Da Ros), Springer 2008. [2] a) J. L. Delgado, P. Bouit, S. Filippone, M. A. Herranz, N. Martin, Chem. Commun. 2010, 46, 4853 –4865; b) A. J. Ferguson, J. L. Blackburn, N. Kopidakis, Mater. Lett. 2013, 90, 115 –125; c) Y. Liang, Z.Xu, J. Xia, S. Tsai, Y. Wu, G. Li, C. Ray, L. Yu, Adv. Mater. 2010, 22, E135– E138.d) R. Meerheim, S. Olthof, M. Hermenau, S. Scholz, A. Petrich, N. Tessler, O. Solomeshch, B. Lüssem, M. Riede, K. Leo, J. Appl. Phys., 2011, 109, 103102