Mendeleev Communications Electronic Version, Issue 2, 2002 1 Synthesis and electrochemical properties of 2-(azahomo[60]fullereno)- 5-nitropyrimidine Irina P. Romanova,*a Vladislav V. Kalinin,a Dmitry G. Yakhvarov,a Adilya A. Nafikova,a Valery I. Kovalenko,a Pavel V. Plekhanov,b Gennady L. Rusinovb and Oleg G. Sinyashina a A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, 420088 Kazan, Russian Federation. Fax: + 7 8432 75 2253; e-mail: romanova@iopc.knc.ru b Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, 620219 Ekaterinburg, Russian Federation.Fax: + 7 3432 74 1189; e-mail: rusinov@ios.uran.ru 10.1070/MC2002v012n02ABEH001567 2-(Azahomo[60]fullereno)-5-nitropyrimidine was synthesised by the cycloaddition reaction of C60 and 2-azido-5-nitropyrimidine. The practical applications of fullerenes are determined by their solubility and electron affinity.These properties can be modified by the addition of electron-withdrawing organic fragments to fullerenes. However, the number of fullerene derivatives with electron affinities higher than that of parent fullerenes is limited.1–4 In most cases, the opening of fullerene �-bonds leads to a decrease in the electron affinity.For [60]fullerene, the lowest decrease in the electron affinity was observed in homofullerenes; however, the synthesis and identification of such C60 derivatives are difficult to perform. Earlier, we prepared isocyanurato-substituted azahomo[ 60]fullerene.5 Its electrochemical reduction was 80 mV easier than that of C60.Two N-aryl-substituted azahomofullerenes, 3 which are reduced easier than C60, are known. However, the structure of N-aryl-substituted azahomofullerenes was not reliably determined by UV spectroscopy. We described here the synthesis and electrochemical properties of nitropyrimidino-substituted azahomo[60]fullerene.Pyrimidinofullerenes were earlier obtained in a reaction of [60]fullerene with pyrimidine o-chinodimethanes and presented 6,6-closed adducts of C60.6 To introduce an electron-withdrawing nitropyrimidinic fragment to a fullerene molecule, we used the cycloaddition of organic azides to the fullerene, which led to the formation of azahomofullerenes.7 We were the first to use a pyrimidino-substituted azide in this reaction.Azide 2† (0.14 mmol) reacted with [60]fullerene (0.08 mmol) in boiling o-dichlorobenzene. The reaction was monitored by mass spectrometry. After heating for 4.5 h, two peaks (720 and 858) were detected in the mass spectrum of the reaction mixture. The former peak corresponded to C60, and the latter peak corresponded to monoadduct 1. The unreacted fullerene (30%) and monoadduct 1 (18%) were separated by column chromatography (toluene as an eluent).After drying in a vacuum, monoadduct 1 was obtained as brown powder readily soluble in toluene, chloroform and methylene chloride. Its structure was studied by 13C NMR, 1H NMR, UV and IR spectroscopy. In the 13C NMR spectrum‡ of monoadduct 1, signals due to the carbons of a fulleroid sphere and nitropyrimidinic fragment were observed.The positions of signals of fulleroid sphere carbons (d 133–147 ppm), their number (32 signals) and relative intensities (24 signals had intensity 2C, 2 signals had intensity 4C, due to the signals overlapping, and 4 signals had intensity 1C) pointed at azahomo[60]fullerene structure of the molecule with Cs symmetry.This conclusion was proved by the UV spectrum.‡ The bands of a pyrimidine ring, nitro group and a band characteristic of a monoadduct [60]fullerene were observed in the IR spectrum‡ of monoadduct 1. The structure of the nitropirimidine fragment was also confirmed by the 1H NMR spectrum of monoadduct 1.‡ We studied the thermal stability of azahomo[60]fullerene 1 and found that, contrarily to isocyanurate-substituted azahomo- [60]fullerenes, which thermally isomerised to [60]fullereno- [1,2-b]aziridines,5,8 nitropyrimidine-substituted azahomo[60]- fullerene 1 was unusually stable on boiling in a solution of o-dichlorobenzene for 10 h.Only after 20 h heating azahomo- [60]fullerene 1 decomposed to the parent fullerene. The redox-properties of azahomofullerene 1 were studied by cyclic voltammetry.The cyclic voltammogram of C60 exhibited four classically reversible waves of reduction with peak potentials, summarised in Table 1 (Figure 1). At these potentials the reduction of azide 2 also occured (Table 1). Thus, the cyclic voltammogram of azide 2 exhibited four waves of reduction, two of them having the greatest currents were irreversible. All the reduction waves of azide 2 correspond to the reduction of the nitropyrimidine fragment since the azide group was not reduced in the studied range of potentials.5 The relative irreversibility of the reduction waves of the nitro group is explained by carrying out the reduction process at the potential development from –0.7 to –2.5 V, accompanied by the transfer of four electrons to the molecule and its decomposition.The cyclic voltammogram of azahomo[60]fullerene 1 is presented in Figure 1. At the development of potential up to –0.9 V, the first one-electron wave (I) is reversible. Note that the potential of the peak of this reduction wave is 80 mV less negative than the potential of the first peak of reduction of parent C60. Based on the values of potential and reversibility of the wave of reduction, we consider that the first peak in the cyclic volt- † IR spectra were obtained on a Bruker IFS-113V instrument. The 1H and 13C NMR spectra were recorded on a Bruker MSL-400 spectrometer at 250 and 100 MHz, respectively.Chemical shifts were measured with reference to the signals of CDCl3, which was used as a solvent. The mass spectra were measured on a MALDI TOF MS instrument (Dynamo).Compound 2 was obtained by the published method.9 1H NMR (250MHz, CDCl3) d: 9.35 [s, 2H, CH(4,6)]. 13C{1H} NMR (100 MHz, CDCl3) d: 139.06 [C(5)], 155.30 [CH(4,6)], 166.15 [C(2)]. UV-VIS (CH2Cl2, lmax/nm): 290. IR (KBr, n/cm–1): 1571, 1331, 873, 833 (NO2), 1417, 639 (pyrimidine cycle), 2138 (N3). ‡ Compound 1: Rf 0.76 (Silufol; eluent, toluene). 1H NMR (250 MHz, CDCl3) d: 9.38 [s, 2H, CH(4,6)]. 13C NMR (100 MHz, CDCl3) d: 140.17 [d, C(5), 2JCH 1.2 Hz], 155.30 [d, CH(4,6), 1JCH 188.6 Hz], 141.77 [d, C(2), 3JCH 6.7 Hz], 138.06, 138.90, 139.02, 143.71 (C60N, 1C), 134.35, 135.30, 135.87, 137.45, 138.06, 138.75, 140.10, 141.76, 141.82, 142.87, 143.03, 143.10, 143.21, 143.41, 143.66, 143.83, 144.17, 144.35, 144.37, 144.41, 144.52, 145.04, 146.30, 147.34 (C60N, 2C), 144.15, 144.59 (C60N, 4C).UV-VIS (CH2Cl2, lmax/nm): 259, 325, 431 (br.), 539 (br.). IR (KBr, n/cm–1): 526 (C60), 1575, 1332, 849 (NO2), 1456, 645 (pyrimidine cycle). N N N NO2 1 2 3 4 5 6 C60 N3 N N NO2 o-DCB 180 °C, 4.5 h 1 2Mendeleev Communications Electronic Version, Issue 2, 2002 2 ammogram of azahomofullerene 1 corresponds to the transposition of one electron on the fullerene sphere.At a further development of the potential up to .2.5 V, five waves of reduction were observed in the cyclic voltammogram of azahomofullerene 1. In the potential range from .1.00 to .1.50 V, the reduction of both fullerene and pyrimidine fragments takes place, as can be seen in two overlapped reduction waves II and III.Wave II is irreversible, and its potential is in the range of potentials of reduction of azide 2. In this connection, we consider that wave II corresponds to the reduction of the nitropyrimidine fragment in the molecule of azahomofullerene 1. The reversibility of waves III points at the reduction of a fullerene sphere of azahomofullerene 1, and this process occurs easier (.Ep = 20 mV) than the addition of the second electron to initial C60.A comparison of the peak potentials of reduction waves IV, V and VI with the potentials of the reduction waves of C60 and azide 2 allowed us to conclude that reversible waves IV and VI correspond to the reduction of the fullerene sphere and irreversible wave V, to the reduction of the nitropyrimidinic fragment.Thus, we found that 2-(azahomo[60]fullereno)-5-nitropimidine 1 is reduced easier than parent C60. The reduction of fullerene and nitropyrimidine fragments occurs in the same interval of potentials, but the first electron is transfered to the homofullerene fragment of the molecule. The compounds of this type are interesting for the synthesis of complexes with organic donors, which can exhibit ferromagnetic properties.References 1 B. M. Illesca and N. Martin, J. Org. Chem., 2000, 65, 5986. 2 P. Zeng, Y. Liu, D. Zhang, C. Yang, Y. Li and D. Zhu, J. Phys. Chem. Solids, 2000, 61, 1111. 3 J. Zhou, A. Rieker, T. Grosser, A. Skiebe and A. Hirsch, J. Chem. Soc., Perkin Trans. 2, 1997, 1. 4 H. Irngartinger and T. Escher, Tetrahedron, 1999, 55, 10753. 5 O.G. Sinyashin, I. P. Romanova, G. G. Yusupova, A. A. Nafikova, N. M. Azancheev, V. V. Yanilkin, V. I. Kovalenko and Y. G. Budnikova, Mendeleev Commun., 2000, 61. 6 A. C. Tome, R. F. Enes, J. A. S. Cavalero and J. Elguero, Tetrahedron Lett., 1997, 38, 2557. 7 M. Casses, M. Duran, J. Mestres, N. Martin and M. Sola, J. Org. Chem., 2001, 66, 433. 8 O. G. Sinyashin, I. P. Romanova, G.G. Yusupova, A. A. Nafikova, V. I. Kovalenko, N. M. Azancheev, S. G. Fattakhov and V. S. Reznik, Izv. Akad. Nauk, Ser. Khim., 2001, 2064 (Russ. Chem. Bull., Int. Ed., 2001, 50, 2162). 9 V. L. Rusinov and O. G. Chupakhin, Nitroazines, Nauka, Novosibirsk, 1991, p. 133 (in Russian). 3 ¥ìA I II III IV V VI .1.0 .2.0 .E/V 1 2 I Figure 1 Cyclic voltammograms of (1) C60 and (2) azahomo[60]fullerene 1. Table 1 Peak potentials and currents of waves in the cyclic voltammograms of C60, adduct 1 and azide 2 [in a mixture of o-dichlorobenzene and MeCN (3:1) at 25 ¡ÆC].a Compound Ered p / V (Ip /¥ìa) K1 b K2 K3 K4 K5 K6 C60 .0.83 (4.2) .1.24 (3.8) .1.70 (3.9) .2.16 (4.6) 2 .1.11 (24.5)c .1.51 (2.5) .2.02 (25)c .2.20 (4.0) 1 .0.75 (3.5) .1.11 (2.3)c .1.22 (1.3) .1.68 (3.3) .1.88 (3.5)c .2.18 (3.6) I II III IV V VI aSolution concentrations, 1¡¿10.3 mol dm.3; supporting electrolyte, 0.1 M Bu4NBF4; cathode, carbon glass (CG) (Swork = 3.14 mm2; reference electrode, 0.01 M Ag/AgNO3 in MeCN; Vpot = 50mV s.1). bThe reduction waves of substrates observed in cyclic voltammograms. cThe irreversible wave. Received: 25th February 2002; Com. 02/1893