ИСТИНА

Insertion of bridge moieties into C–C bond of fullerene cage activates bridgehead carbon atoms making possible to perform regioselective derivatization of fulleroids. For example, it was shown that treatment of [6,6]-open С60(СF2) dianions with alkyl halides resulted in regioselective alkylation at bridgehead carbon atoms yielding [6,6]-open С60(СF2)R2 which demonstrated photovoltaic activity [1]. Early it was demonstrated that treatment of [6,6]-closed aziridinofullerene C60(NCO2R) with metallic Zn and acetic acid in toluene solution resulted in the regioselective hydrogenation at bridgehead carbon atoms yielding [6,6]-open С60(NCO2R)H2 [2]. Nevertheless the reasons of the observed regioselectivity and details of the [6,6]-closed/open transformation in case of aziridinofullerenes were not discussed. Here we report a novel approach of azahomofullerenes dihydride C60(NCO2R)H2 synthesis based on protonation of in situ generated anion C60(NCO2Bn)2– (Fig. 1, Cbz=CO2Bn). [6,6]-Closed aziridinofullerene, C60(NCbz), and [6,6]-open C60(NCbz)H2 were identified using NMR spectroscopy and structurally characterized by means of X-ray single crystal diffraction. The electrochemical behavior of [6,6]-closed C60(NCbz) and [6,6]-open C60(NCbz)H2 were studied by means of cyclic voltammetry (CVA). These studies along with quantum chemical calculation at DFT level reveal reasons of high regioselectivity of the reaction. The reduction of C60(NCbz) to dianionic state results in its transformation to [6,6]-open configuration with extra negative charge at the bridgehead carbon atoms (Fig. 1b). The addition of the small electrophilic particles regioselectively occurs at these position whereas addition of bulky ones is restricted by Cbz group. This work was supported by the Ministry of Education and Science of Russia (project № MD-1775.2017.3). References [1] V.A. Brotsman, V.A. Ioutsi, A.V. Rybalchenko, V.P. Bogdanov, S.A. Sokolov, N.M. Belov, N.S. Lukonina, V.Y. Markov, I.N. Ioffe, S.I. Troyanov, T.V. Magdesieva, V.A. Trukhanov, D.Y. Paraschuk, A.A. Goryunkov, Electrochim Acta. (2016) 130–142. [2] M.R. Banks, J.I.G. Cadogan, I. Gosney, A.J. Henderson, P.K.G. Hodgson, W.G. Kerr, A. Kerth, P.R.R. Langridge-Smith, J.R.A. Millar, A.R. Mount, J.A. Parkinson, A.T. Taylor, P. Thornburn, Chem Commun. (1996) 507–408.