Acta Chim. Slov. 2008, 55, 419–424 419 Scientific paper Theoretical Studies on Stabilities and Spectroscopy of C80CH2 Xuguang Wena, Xin Renb and Shi Wua,* Department of Chemistry, Zhejiang University, Hangzhou 310027, China Department of Pharmacy, Zhejiang University, Hangzhou 310027, China * Corresponding author: E-mail: wushi@zju.edu.cn tel: 8657188206529; fax: 8657188206529 Received: 29-02-2008 Abstract The electronic structures and stabilities of the nine possible isomers of C80CH2 based on C80(D5d) were studied using density function theory (DFT) at B3LYP/6-31G level. Based on the optimized geometries, the electronic spectra, IR and 13C NMR spectra of the isomers of C80CH2 were calculated using INDO/CIS, PM3 and B3LYP/6-31G methods, respectively. The most stable geometry of C80CH2 is predicted to be 27,28–C80CH2(A) with an annulene structure, where the additive bond is 6/6 bond near the equatorial belt of C80(D5d). Compared with those of C80(D5d), the first absorptions in the electronic spectra and main absorptions in the IR spectra of the stable C80CH2 isomers are red-shifted. The 13C chemical shifts of the bridged carbon atoms in the cyclopropane structures in comparison with those in the annulene structures are changed upfield. The aromaticities are better maintained in the annulene structures than cyclopropane structures according to the NICS values of C80CH2 at B3LYP/6-31G level. Keywords: C80CH2, B3LYP/6-31G, electronic spectra, 13C NMR, NICS. 1. Introduction The functionalization of fullerenes has been an interesting research topic for scientists. One of the C80 isomers with D5d symmetry has been successfully isolated and characterized with 13C NMR and UV spectra. The 13C NMR results suggested that there are five types of carbon atoms in C80(D5d).1 The energy gap of C80(D5d) calculated using AM1 method is 4.72 e V.2 C80(D5d) has been found to be the lowest-energy isomer with the wide energy gap at HF/4-31G level.3 The optical gap of C80 is reduced and the UV-vis-NIR absorption is red-shifted owing to the addition of the two CF3 groups.4 Many exohedral adducts of C80 like Sc3N@C80(CH2)2NR and n-Bu4N+[Sc3C2@C80 (Ad)]– have been synthesized with the help of the high stabilities improved by endohedral complexes containing metal or other groups.5,6 On one hand, the reactivity of C80 can be improved due to the dense negative charge on the surface caused by the electronic transfer from the inside metals to the fullerene cage.5 On the other hand, the X-ray determination can be easily performed because of the cycloaddition of the adamantylidene carbene (Ad) to the cage.6 The methylene adducts of C60 and C70 can be prepa- Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 red by direct carbene addition and dipolar cycloadditions of diazo compounds.7 Similar covalent derivatives of C78 have been obtained through the reaction between fullere-nes and diethyl 2-bromomalonate.8 These derivatives like Th–C60(C(COOH)2)6 can be used as electrolytes.9 Hitherto, the methylene adducts of C80(D5d) have not been synthesized. Although C80O has been studied theoretically,10,11 C80CH2 based on C80(D5d) has not been investigated yet. Herein the nine possible geometries of C80CH2 are explored to predict the properties of C80CH2 and simulate similar derivatives. First, we want to know which geometry of C80CH2 is the most stable one and whether the additive bond is opened. Then we want to study the electronic structures and spectroscopy of C80CH2. Finally, we want to study the aromaticity of C80CH2 through computing the NICS values. 2. Research Approach An initial geometry of C80(D5d) was drawn in Chem3D, and the full geometry optimization without any 420 Acta Chim. Slov. 2008, 55, 419–424 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 symmetric restriction was performed using PM3 method and DFT at B3LYP/STO-3G, B3LYP/3-21G and B3LYP/6-31G levels progressively in Gaussian 03 program package.12 These methods have been used to study the electronic structures and stabilities of the supramole-cular complexes,13 conducting polymers,14 and other organic compounds.15 Then the equilibrium geometry of C80(D5d) was obtained. There are 5 unique carbon atoms and nine kinds of C–C bonds in C80(D5d). Based on the optimized geometry of C80(D5d) at B3LYP/6-31G level, CH2 was added to the nine different bonds above the equatorial belt of C80(D5d), respectively. In the isomer 27,28–C80CH2(A) (Figure 1), 27,28- stands for the bond added by CH2. This numbering system was according to the IUPAC rule for carbon clusters.16 These isomers of C80CH2 were optimized in the same way as the above, then the equilibrium geometries with the minimum energy of C80CH2 were accomplished. According to Koopmans’ theory, vertical ionization potential (IP) is approximately defined as the negative value of HOMO (the highest occupied molecular orbital) energy. Vertical electron affinity (EA) is defined as the negative value of LUMO (the lowest unoccupied molecular orbital) energy. Absolute hardness (?) is equal to the half of the difference between IP and EA. Absolute electron negativity (?) is defined as the half of the sum for IP and EA. All these variables were calculated at B3LYP/6-31G level. Based on the B3LYP/6-31G optimized geometries of C80CH2, the electronic spectra were computed using INDO/CIS method17 without any adjustment of the para-meters.18 One hundred and ninety-seven configurations including the ground state were generated by exciting electrons from 14 HOMOs to 14 LUMOs. The IR spectra were calculated using PM3 method. The 13C NMR spectra and NICS (nucleus independent chemical shifts) values of the isomers were calculated on GIAO (gauge-including atomic orbitals) method at B3LYP/6-31G level. The NICS values were used to measure the aromaticity, which was proposed by Schleyer et al.19 3. Results and Discussion Relative energies at B3LYP/6-31G level: The optimized results of C80(D5d) were compared with the experimental values and other calculation results to assure the reliability of the method. The bond lengths of C80(D5d) at B3LYP/6-31G level are within the range of 0.1395– 0.1473 nm, which is consistent with the ranges of 0.1391– 0.1462 and 0.140–0.146 nm calculated using ZINDO and SCF-MO methods.20,21 The length and width in the polar and equatorial directions of C80(D5d) are 0.9169 and 0.6773 nm, which are in agreement with the calculated results (0.946 and 0.716 nm).21 The ratio between the long and short axes of C80(D5d) is 1.35, which is compatible with the experimental value 1.3.1 According to the relative energies of C80CH2 isomers (Table 1), the most stable geometry of C80CH2 is found to be 27,28–C80CH2(A), where the CH2 group is added to the C(27)–C(28) bond near the equatorial belt of C80(D5d) (Figure 1). The length 0.1468 nm of the C(27)– C(28) bond is relatively larger than the others in C80(D5d) since the C(27)–C(28) bond is surrounded by four neighbored hexagons. Thus the C(27)–C(28) bond is weak and easy to undergo an addition. The second stable isomer is (a) 27,28–C80CH2 with an annulene structure (b) 1,9–C80CH2 with a cyclopropane structure Figure 1. The optimized geometries of 27,28–C80CH2 and 1,9–C80CH2 at B3LYP/6-31G level. Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 Acta Chim. Slov. 2008, 55, 419–424 421 1,9–C80CH2(B), where the C(1)–C(9) bond inserted by CH2 is between the two fused hexagons (6/6 bond) and near the pole of C80(D5d). In C80CH2(C), (D) and (E), the C–C bonds added by CH2 are formed by a hexagon and pentagon (6/5 bonds). In general, the 6/6 bonds in C80(D5d) are easier to be added than 6/5 bonds. The isomers with annulene structures of C80CH2 are more stable than those with cyclopropane structures since the cyclic tension can be reduced in the annulene structures. The lengths of the additive bonds in C80CH2(A), (C), (D), and (E) are 0.2312, 0.2225, 0.2208, and 0.2208 nm, respectively. These bonds are broken, thus the annulene structures are formed. The lengths of the additive bonds in C80CH2(B), (F), and (G) are 0.1633, 0.1658, and 0.1592 nm. These bonds are not opened, thus the cyclopropane structures are formed. The weak additive bonds 0.1468, 0.1473, 0.1462, 0.1457, 0.1435, and 0.1459 nm in C80CH2(A), (C), (D), (E), (H) and (I) lead to the formation of the annulene structures. The strong additive bonds 0.1395, 0.1399, and 0.1404 nm in C80CH2(B), (F), and (G) result in the generation of the cyclopropane structures. The angle of C(27)–C(81)–C(28) in the annulene structure of C80CH2(A) is 101.8°, basically consistent with 111.5° in C O.10 27,28-C80CH2(A) 0 -5.1193 –4.0363 1,9-C80CH2(B) 0.5007 -5.0355 -3.9484 25,26-C80CH2(C) 0.5551 -5.1220 -3.9811 1,2-C80CH2(D) 0.5714 -5.0524 -3.9998 9,10-C80CH2(E) 0.7021 -5.0671 –4.0246 10,11-C80CH2(F) 0.8680 –4.9582 –4.0167 26,27-C80CH2(G) 1.0585 -5.1582 -3.8842 10,26-C80CH2(H) 1.0803 -5.0516 -3.9887 27,46-C80CH2(I) 1.7252 -5.0660 –4.0390 Optimized parameters at B3LYP/6-31G level: The energies of HOMO and LUMO of C80CH2(A) are –5.1193 and –4.0363 eV. The energy gap of C80CH2(A) is 1.0830 e V, which is wider than 1.0523 eV of C80(D5d). This calculation result is similar to the experiment showing that the electrochemical band gap 1.78 eV of bisadduct of C78(C2v) is larger than 1.62 eV of C78(C2v).22 The energy gaps of C80CH2(B), (C) and (D) are 1.0871, 1.1410 and 1.0525, wider than that of C80(D5d). As a consequence the stability of C80CH2 to the excitation of electrons will increase. The IP, EA and ? values of C80(D5d) are 5.1667, 4.1144 and 4.6406 eV. The IP, EA and ? values of the C80CH2 isomers are lower than those of C80(D5d). Then the C80CH2 isomers readily loose electrons and only with difficulty catch the electrons. Since the ?values of C80CH2(A), (B), (C), (D), (G), and (H) are higher than 0.5262 eV of C80(D5d), these isomers are thermally more stable. by In C80CH2(A) with Cs symmetry, the Mulliken ato-and mic charges of the bridged carbon atoms C(27) and C(28) the are all 0.0202. The Mulliken charges of C(81), H(82) and and H(83) in CH2 are –0.3816, 0.1703 and 0.1721, respecti-in vely, so the bonds C(27)–C(81) and C(28)–C(81) are polar covalent bonds. The Mulliken charge on CH2 is are –0.0392, thus the electrons are attracted from C80(D5d) to nce the CH2 group. ctu- Electronic absorption spectra: The main absorption (C), peaks in the electronic spectrum of C80(D5d) are located at nm, 628.6, 490.6, 423.7, 360.3, 333.2, and 324.9 nm. These ene absorptions can be comparable to the experimental results s in of 880, 845, 606, 589, 484, and 446 nm after being multi-592 plied with a factor 1.4. The error is mainly caused by the ane less configurations used in the calculation and systematic 68, deviation of ZINDO method for higher fullerenes. The in strongest peak of C80(D5d) appears at 237.3 nm. tion Since the absorption at 657.2 nm of C80(D5d) arising nds from HOMO to LUMO is electronically forbidden transi-(G) tion, the first peak at 633.1 nm, the main absorptions at res. 598.8, 497.6, 371.1, 361.3, 352.0, and the strongest peak ctu- at 244.0 nm of C80CH2(A) are red-shifted relative to those ith of C80(D5d) (Figure 2). The first and main absorptions of C80CH2(B) compared with those of C80CH2(A) are blue- 1.0830 5.1193 4.0363 0.5415 4.5778 1.0871 5.0355 3.9484 0.5436 4.4920 1.1410 5.1220 3.9811 0.5705 4.5515 1.0525 5.0524 3.9998 0.5263 4.5261 1.0425 5.0671 4.0246 0.5212 4.5458 0.9415 4.9582 4.0167 0.4708 4.4875 1.2740 5.1582 3.8842 0.6370 4.5212 1.0629 5.0516 3.9887 0.5314 4.5201 1.0270 5.0660 4.0390 0.5135 4.5525 The shifted owing to the wide energy gap. The first and main 193 absorptions of C80CH2(C) and (D) in contrast to those of 830 C80(D5d) are red-shifted. When CH2 is added to C80(D5d), cu- the symmetry is reduced, and the peaks split with the de-the crease in oscillator strength. The more obvious red-shift C2v) for the first absorption of C80CH2(I) relative to that of of C80(D5d) takes place because of the narrow energy gap. 25, IR spectra: There exist some narrow bands within lity 500–1000 cm–1, flat region within 1000–1300 cm–1 and some strong sharp peaks within 1300–1700 cm–1 in the IR 67, spectrum of C80(D5d). The main absorptions at 933.4, the 1551.2, and 1685.0 cm–1 of C80(D5d) are ascribed to the the puckering vibration of the aryl rings and stretching vibra-iffi- tions of the C–C and C=C bonds. These absorptions split A), with the decreased intensity in the isomers of C80CH2, of which is caused by the addition of the CH2 group and the decrease in the symmetry. Table 1. Relative energies (Er) and some parameters (eV) of C80CH2 isomers at B3LYP/6-31G level. Compounds Er EHOMO ELUMO Energy gap IP EA ?? Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 422 Acta Chim. Slov. 2008, 55, 419–424 o jg 2 v. O i o- 2 14.0 C80CH2(A) Llk__JuJMiZl^_ 633.] 300 400 500 600 7O0 Wavelength (nm) zli S 3 I 2 C80CH2(B) 243.6 356.8 615.1 200 300 400 500 600 Wavelength (nm) 7CKI Figure 2. The electronic spectra of C80CH2(A) and (B) using INDO/CIS method. The strongest peak at 1675.3 cm–1 of C80CH2(A) (Figure 3) compared with 1685.0 cm–1 of C80(D5d) is red-shifted, thus the C=C bonds in C80CH2(A) are weakened. A new absorption at 3153.7 cm–1 of C80CH2(A) is produced, which is attributed to the C–H stretching vibration. The main peaks at 1675.3, 1682.4, and 1675.6 cm–1 of C80CH2(A), (C), and (I) compared with 1685.0 cm–1 of C80(D5d) are red-shifted, whereas the absorptions at 1686.6 and 1688.7 cm–1 of C80CH2(B) and (F) are blue-shifted. The Mulliken charges of the CH2 groups in C80CH2(A), (C) and (I) are negative –0.0392, –0.0195, and –0.0068, whereas 0.1918 and 0.1938 of C80CH2(B) and (F) are positive. Since the electrons are attracted from C80(D5d) to the CH2 groups in C80CH2(A), (C), and (I), the electron density on C80(D5d) is reduced and the C=C bonds are weakened. On the contrary, the electron density on the cage is increased owing to the positive charges of CH2 in C80CH2(B) and (F). A similar calculation has shown that the four characteristic bands of C80O compared with those of C80 are red-shifted, supporting our conc-lusion.10 Since the electronegativities of the CH2 groups in the order of C80CH2(A), (C), (I), (B), and (F) are decreasing, the polarities of the C–H bonds are weakened and the covalence characters increased. Thus the strong C–H stretching vibrations at 3153.7, 3163.8, 3168.8, 3174.3, and 3174.6 cm–1 in these isomers are gradually intensified. NMR spectra: The 13C signals of the five unique carbon atoms in C80(D5d) are within 124.4–165.4 ppm, which are in agreement with 128.9–163.9 ppm.1 The lines with the chemical shifts at 152.7 and 165.4 ppm are ascribed to the first and second unique carbon atoms near the pole of C80(D5d), which correspond to the experimental values 156.3 and 163.9 ppm.1 The lines with the chemical shifts at 164.4, 124.4, and 156.5 ppm are assigned as the third, forth, and fifth types of the carbon atoms in C80(D5d), and twenty carbon atoms are included in each type. In C80CH2(A), the signals are distributed within 116.9–174.6 ppm, which arises from the sp2–C atoms on the cage (Figure 4). This range is wider than that of C80(D5d), which is caused by the decrease in symmetry upon the addition of CH2. The peak at 19.2 ppm of C80CH2(A) arises from the sp3–C atom in the CH2 group. The experiment shows that the chemical shifts of the methylene carbon atoms in the isomers of C70CH2 are within 13.8–34.0 ppm.23 The signals at 179.3 ppm are generated by the bridged carbon atoms C(27) and C(28), which 60-50-^40-'S S 30-20-10-0- 1675.3 C80CH2(A) 933.4 1553.5 3153.7) 1,772.6 J ) 500 1000 1500 2000 2500 3000 3 Frequency (cm" ) 500 60 50 ž"40 g 30 "S 20 10 0 1 553.6 932.7 CsnCH?(B) 3174.3 1776.4 500 1000 1500 2000 2500 3000 3500 Frequency (cm" ) Figure 3. The IR spectra of C80CH2(A) and (B) using PM3 method. Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 Acta Chim. Slov. 2008, 55, 419–424 423 are shifted downfield compared with the value of 156.5 ppm for C80(D5d). The electron densities on C(27) and C(28) are lowered owing to the electronegativity of CH2. In C80CH2(B), the signal at 16.5 ppm is assigned as the sp3–C atom and the signals of the bridged carbon atoms appear at 78.2 and 92.2 ppm. It has been indicated that the chemical shifts of the bridged carbon atoms in the cyclopropane structure of C60CH2 are 71.0 ppm.23 At the same time, the region of the chemical shifts for the signals of sp2–C atoms in C80CH2(B) is changed upfield because of the increased electron density on the cage. The signals at 19.2, 24.9, and 30.1 ppm of the sp3–C atoms in the order of C80CH2(A), (C), and (I) are changed downfield because of the decreased electron density. At the same time, the regions of the chemical shifts produced by the sp2–C atoms in these isomers are changed upfield to 116.9–174.6, 116.0–174.0, and 107.2–172.2 ppm, respectively, because of the increased electron density on the cage. In C80CH2(I), the signals at 107.8 and 107.7 ppm result from the bridged carbon atoms in the annulene structure, which are shifted upfield relative to those of C80(D5d) owing to the positive charge on CH2. These values are similar to 118.0 ppm of the bridged carbon atoms in the an-nulene isomer of C70CH2.23 conclusion that 3He experimental chemical shift at –8.11 ppm for the cyclopropane isomer of C60CH2 is lower than –6.36 ppm of C60(Ih).7 The magnetic ring current related to ? electrons is reduced in C80CH2(B) and (F) because of the transfer of the bridged carbon atoms in the cyclopropane structures from sp2–C to sp3–C atoms. Thus the aro-maticities of the C80CH2 isomers with the cyclopropane structures relative to that of C80(D5d) are predicted to be decreased. The isomers of C80CH2 with the high NICS values and wide energy gaps such as C80CH2(A) and (C) are more stable than the others, whereas those with the low NICS values and narrow energy gaps like C80CH2(F) are less stable. 4. Conclusions The most stable isomer at the ground state of C80CH2 was calculated to be 27,28–C80CH2(A) with an annulene-like structure. The first and main absorption peaks in the electronic spectra for the stable C80CH2 isomers relative to those of C80(D5d) are red-shifted. The main IR bands of the C80CH2(B) 92.2 108.9 169.5 16.5 78.2 0 20 40 60 80 100 120 140 160 180 Chemical shift (ppm) Figure 4. The 13C NMR spectra of C80CH2(A) and (B) at B3LYP/6-31G level. Aromaticity: The NICS value of C80(D5d) at B3LYP/6-31G level was calculated to appear at –8.83 ppm. This method has been successfully used to study the NICS value of C84(D2).24 The NICS values of C80CH2(A), (C), (D), (H), and (I) with the annulene structures are located at –7.30, –4.34, –8.73, –7.44, and –6.65 ppm. These values are higher than that of C80(D5d) and are similar to the 3He experimental chemical shifts at –27.46 and –27.82 ppm for the two annulene isomers of C70CH2; higher than –28.81 ppm corresponding to C70(D5h).7 The large magnetic cyclic current is maintained in these C80CH2 isomers owing to the formation of the annulene structures. The NICS values of C80CH2(B) and (F) with the cyclopropane structures are situated at –9.85 and –14.63 ppm. These values are lower than that of C80(D5d), which is similar to the C80CH2 isomers compared with those of C80(D5d) are also red-shifted owing to the negative charges on the CH2 groups. The 13C chemical shifts of the bridged carbon atoms in C80CH2 with cyclopropane structures are moved upfield upon the formation of the sp3–C atoms. The bonds near the CH2 group are activated, becoming the most possible addition sites of the next CH2 group. 5. References 1. C. R. Wang, T. Sugai, T. Kai, T. Tomiyama, H. Shinohara, Chem. Commun. 2000, 557–558. 2. S.-L. Lee, M.-L. Sun, Z. Slanina, Int. J. Quantum Chem.: Quantum chemistry Symposium 1996, 30, 1567–1576. Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 424 Acta Chim. Slov. 2008, 55, 419–424 3. Z. Slanina, S.-L. Lee, L. Adamowicz, Int. J. Quantum Chem. 1997, 63, 529–535. 4. N. B. Shustova, A. A. Popov, M. A. Mackey, C. E. Coumbe, J. P. Phillips, S. Stevenson, S. H. Strauss, O. V. Boltalina, J. Am. Chem. Soc. 2007, 129, 11676–11677. 5. C. M. Cardona, A. Kitaygorodskiy, A. Ortiz, M. A. Herranz, L. Echegoyen, J. Org. Chem. 2005, 70, 5092–5097. 6. Y. Iiduka, T. Wakahara, T. Nakahodo, T. Tsuchiya, A. Saku-raba, Y. Maeda, T. Akasaka, K. Yoza, E. Horn, T. Kato, M. T. H. Liu, N. Mizorogi, K. Kobayashi, S. Nagase, J. Am. Chem. Soc. 2005, 127, 12500–12501. 7. A. B. Smith III, R. M. Strongin, L. Brard, W. J. Romanow, J. Am. Chem. Soc. 1994, 116, 10831–10832. 8. A. Herrmann, F. Diederich, J. Chem. Soc. Perkin Trans. 2 1997, 1679–1684. 9. J. [kerjanc, Acta Chim. Slov. 2006, 53, 331–337. 10. M. Ibrahim, Acta Chim. Slov. 2005, 52, 153–158. 11. H. Sun, Q. Teng, S. Wu, Z. Wang, Indian J. Chem. 2006, 45A, 1345–1350. 12. M. J. Frisch, G. W. Trucks, H. B. Schlegel, et al., Gaussian 03, Revision B. 01, Gaussian Inc., Pittsburgh, PA, 2003. 13. (a) J. Dolenc, J. Koller, Acta Chim. Slov. 2006, 53, 229–237. (b) C. Yan, S. Wu, Acta Chim. Slov. 2007, 54, 755–760. 14. L. Yang, A. M. Ren, J. K. Feng, J. F. Wang, J. Org. Chem. 2005, 70, 3009–3020. 15. (a) H. Arslan, A. Demircan, Acta Chim. Slov. 2007, 54, 341–353. (b) A. F. Jalbout, B. Trzaskowski, Y. Xia, Y. Li, Ac- ta Chim. Slov. 2007, 54, 769–777. (c) R. Abbasoglu, A. Ma-gerramov, Acta Chim. Slov. 2007, 54, 882–887. (d) W. Zhang, S. Wu, X. Wen, Indian J. Chem. 2007, 46A, 1911–1916. 16. E. W. Godly, R. Taylor, Pure Appl. Chem. 1997, 69, 1411– 1434. 17. R. D. Bendale, M. C. Zerner, J. Phys. Chem. 1995, 99, 13830–13833. 18. (a) Q. Teng, S. Wu, Int. J. Quantum Chem. 2005, 104, 279–285. (b) Q. Teng, S. Wu, J. Mol. Struct.: Theochem 2005, 719, 47–51. (c) Q. Teng, S. Wu, J. Mol. Struct.: Theoc-hem 2005, 756, 103–107. (d) S. Wu, Q. Teng, Int. J. Quantum Chem. 2006, 106, 526–532. (e) Q. Teng, S. Wu, Z. Zhu, Int. J. Quantum Chem. 2003, 91, 39–45. 19. P. v. R. Schleyer, C. Maerker, A. Dransfeld, H. Jiao, N. J. R. v. E. Hommes, J. Am. Chem. Soc. 1996, 118, 6317–6318. 20. S. Wu, Q. Teng, Chinese J. Struct. Chem. 2005, 24, 21–24. 21. K. Nakao, N. Kurita, M. Fujita, Phys. Rev. B 1994, 49, 11415–11420. 22. C. Boudon, J. P. Gisselbrecht, M. Gross, A. Herrmann, M. Ruttimann, J. Crassous, F. Cardullo, L. Echegoyen, F. Diede-rich, J. Am. Chem. Soc. 1998, 120, 7860–7868. 23. A. B. Smith III, R. M. Strongin, L. Brard, G. T. Furst, W. J. Romanow, K. G. Owens, R. J. Goldschmidt, R. C. King, J. Am. Chem. Soc. 1995, 117, 5492–5502. 24. H. Sun, S. Wu, X. Ren, J. Mol. Struct.: Theochem 2008, 855, 6–12. Povzetek S pomo~jo teorije gostotnih funkcionalov (DFT) na nivoju B3LYP/6-31G smo preu~ili elektronsko strukturo in stabilnost devetih mo`nih izomerov C80CH2, ki temeljijo na strukturi C80(D5d). Glede na optimizirane geometrije smo z metodami INDO/CIS, PM3 in B3LYP/6-31G izra~unali elektronske, IR in 13C NMR spektre izomerov C80CH2. Kot najbolj stabilno geometrijsko obliko C80CH2 smo napovedali 27,28–C80CH2(A) z anulensko strukturo, kjer je adicija potekla na vez 6/6 blizu ekvatorialnega pasu molekule C80(D5d). Polo`aj prve absorpcijske ~rte v elektronskih spektrih in obmo~je glavnih absorpcij v IR spektrih so za C80CH2 v primerjavi z C80(D5d) pomaknjeni bolj v rde~e obmo~je. Kemijski premiki v 13C NMR spektrih so za mostne atome v ciklopropanski strukturi glede na premike v anulenski strukturi premaknjeni v vi{je polje. Aromati~nost je ve~ja v anulenski kot v ciklopropanski strukturi, kar je skladno z NICS vrednostmi za C80CH2 napovedanimi na nivoju B3LYP/6-31G. Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 Acta Chim. Slov. 2008, 55, 419–424 S425 Supporting materials: C(D,β) 628.6 200 300 400 500 600 700 Wavelength (um) "3) IL 3 n. 1 240.4 LL_ 366.6 CsnCH?(D) 200 300 400 500 600 700 Wavelength (nm) 5n h S 2 O 1 CS0CH2(I) (>?K.2 200 300 400 500 600 Wavelength (nm) 7110 Figure 1. The electronic spectra of C80(D5d), C80CH2(D) and (I) using INDO/CIS method. Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 S426 Acta Chim. Slov. 2008, 55, 419–424 i JU- ICIO- 1685.0 C80(D5d) vi g 60- 40- 1551.2 20-0- 933.4 |jl761. ) 500 1000 1500 2000 2500 3000 3500 Frequency (cm" ) 60 50 40 & S 30. u "S M 20-10 0 C80CH2(C) 1558.2 932.1 ^jUlwJAixiir 1682.4 1778.1 3163.8. 0 500 1000 1500 2000 2500 3000 3500 Frequency (cm" ) 60 50 | 30 a 20. 10 C80CH2(F) 3174.6 1775.W 1 500 1000 1500 2000 2500 3000 3500 1 60 50 40 30 21) II) 0 Frequency (cm" ) Figure 2. The IR spectra of C80(D5 d), C80CH2(C), (F), and (I) using PM3 method. 1675.6 1550.2 CS0CH2(I) 3168.8 1777.6 500 1000 1500 2000 2500 3000 3500 Frequency (cm" ) Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2 Acta Chim. Slov. 2008, 55, 419–424 S427 O Csn(D ) 156.5 165.4 124.4 152.7 164.4 C80CH2(C) 24.9 16.0 174.0 120 130 140 150 160 170 Chemical shift (ppm) 40 60 SO 100 120 Chemical shift (ppm) 2n 0 C80CH2(D) 22.2 111.8 173.6 \ ' E ' i \ i I..... I J 1 0 20 40 60 80 100 120 140 160 180 Chemical shift (ppm) (i C80CH2(I) 30.1 107.2 172.2 ,i ¦ r^ 0 20 40 60 80 100 120 140 160 180 Chemical shift (ppm) Figure 3. The 13C NMR spectra of C80(D5d), C80CH2(C), (D), and (I) at B3LYP/6-31G level. Wen et al.: Theoretical Studies on Stabilities and Spectroscopy of C80CH2