Theoretical Identification of the Six Stable C84 Isomers by IR, XPS

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Theoretical Identification of the Six Stable C Isomers by the IR, XPS and NEXAFS Spectra Yong Ma, Sheng-Yu Wang, Jing Hu, Yong Zhou, Xiuneng Song, and Chuan-Kui Wang J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b12018 • Publication Date (Web): 03 Jan 2018 Downloaded from http://pubs.acs.org on January 3, 2018

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The Journal of Physical Chemistry

Theoretical Identification of the Six Stable C84 Isomers by the IR, XPS and NEXAFS Spectra Yong Ma,†,‡ Sheng-Yu Wang,† Jing Hu,† Yong Zhou,† Xiu-Neng Song,∗,† and Chuan-Kui Wang† †Shandong Province Key Laboratory of Medical Physics and Image Processing Technology, School of Physics and Electronics, Shandong Normal University, 250014 Jinan, P. R. China ‡Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm, Sweden E-mail: [email protected] Phone: +86 13953138878. Fax: +86 (0)531 89611170

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ACS Paragon Plus Environment

The Journal of Physical Chemistry 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 57 58 59 60

Abstract Six stable C84 isomers satisfying isolated pentagon rule (IPR) have been theoretically identified by infrared (IR), X-ray photoelectron (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectra. The XPS and NEXAFS spectra at the K-edge for all non-equivalent carbon atoms were simulated by the density functional theory method. NEXAFS spectra show stronger dependence than IR and XPS spectra on the six C84 isomers, which can be properly used for isomer identification. Furthermore, spectral components of total spectra for carbon atoms in different local environment have been explored.

Introduction Since the first fullerene C60 was discovered 1 experimentally, the fullerene family have been widely investigated due to their unique spatial structures and peculiar physicochemical properties. At present, numerous new-type fullerenes regarded as new carbon materials have been successfully prepared, they show huge potential applications in the field of the solar cells, 2–4 superconducting materials, 5 nano-electronic devices 6 and biomedicine 7 because of their excellent specialities. However, the study of these important applications of fullerenes is not absolutely straightforward, because there are rapidly increasing isomeric forms of fullerenes with the growing size of carbon cages. Therefore, isomers identification is with considerable significance for the fullerene research. Fullerene C84 has attracted much attention since it was identified as the third most abundant isomer in arc-generated fullerene soot in 1991. 8 Biddulph et al. found that C84 is the most effective primary ion providing higher secondary ion yields and a high molecular to fragment ion ratio. 9 Dang et al. demonstrated that an indene-C84 bisadduct is a promising electron acceptor in organic solar cells and a C84 -bisanthracene copolymer can be utilized as a charge-transfer material. 10 There are 24 possible C84 isomers following the isolated pentagon rule (IPR). 11 Systematic theoretical studies using the density functional theory (DFT) method indicate that six isomers 11(C2 ), 16(Cs ), 2


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19(D3d ), 22(D2 ), 23(D2d ) and 24(D6h ) (the number is based on the spiral algorithm 11 ) are the most energetically stable among the 24 isomers, 12,13 shown in Figure 1a. Early

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C nu-

clear magnetic resonance (NMR) spectroscopy studies provided evidence that the extracted C84 samples consisted of approximately a 2:1 mixture of 22(D2 ) and 23(D2d ) isomers. 14–16 Additionally, 19(D3d ) and 24(D6h ) have been successfully separated and isolated from arc burned soot of Gd-doped composite rods of a mixture (in an abundance ratio of 3:2). 17 The other two configurations, 11(C2 ) and 16(Cs ) can also be stabilized though perfluoroalkylation method. 18 For the deeper investigation and further application of C84 , in this work, we paid attention to identifying the six abovementioned IPR-satisfying isomers of C84 fullerene by several useful spectroscopy technologies. As yet, familiar spectroscopy technologies including

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C NMR spectra, infrared spec-

troscopy(IR), Raman spectra, and electronic spectra, as well as X-ray spectroscopies have been used to characterize fullerene isomers. 19–24 The IR spectrum is one of the most common techniques in absorption spectroscopies, which is produced by constant vibrations of atoms that make up the chemical bonds. IR spectroscopy is usually termed as the fingerprint region, since the bands are particularly dense and sensitive to the changes of molecular structures, even tiny variations often lead to distinct differences in the spectrum. The soft X-ray spectroscopies have been reviewed as convenient and valid tools to explore electronic structure of molecules, compounds and material surfaces through core-orbitals excitations or de-excitations. 25–28 Especially, X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy have been intensively investigated to identify fullerene isomers. XPS corresponds to the ionization process of core electron, presenting the information of core orbital, while NEXAFS spectroscopy represents that the core electron is excited to unoccupied orbitals, mostly depicting the features of virtual orbitals. So far, previous researches indicated that IR and XPS spectra, as well as NEXAFS spectroscopy which represent relatively strong dependence on geometry of systems have been efficiently applied to distinguish fullerene isomers and fullerene-based systems. 29–32 In present work, we

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calculated IR spectra, carbon K-shell (1s) XPS and NEXAFS spectra of six most energetically stable C84 fullerene isomers. Then, we discussed the sensitivity of IR, XPS and NEXAFS spectra to the different isomeric forms. Furthermore, the availability of recognising fullerene configurations and dependence of spectra on the local structural environment of fullerenes has been investigated. Theoretical identification of the six C84 isomers by the spectroscopic dependence presents an efficient technique for identification of fullerene isomers, which will be valuable and stimulative for the experimental researches in future.

Computational details The optimization of geometric structures of the six C84 isomers were accomplished by using gradient-corrected DFT method at B3LYP/6-31G(d,p) level in the Gaussian09 program. 33 During the optimization process, all the atoms were completely released. Frequencies of six C84 isomers were analyzed after the optimization. Frequency analysis cannot only obtain the relationship between frequencies and the vibration intensity, but also can ensure that the studied geometric structures are stable. Meanwhile, the calculated frequencies have been scaled uniformily by a factor 0.98, as already proposed by Stratmann et al. 34 The absolute IR absorption intensity A depends on the variation of the electric dipole moment, 35

A=(

4π 2 ) |µab |2 E20 t 2 h

(1)

where E0 expresses electric field vector of infrared electromagnetic wave, and µab denotes the transition dipole moment. The intensity were gained through Lorentz function broadening in order to get IR spectra with the full width at half maximum (FWHM) of 6 cm−1 . In this work, such a value by broadening was in good agreement with the results of the experiment. 36 The C 1s XPS and NEXAFS spectra of the six isomers were calculated by StoBe 37 program with the DFT method. In this DFT computation, we adopted the Becke88 38 (BE88) exchange functional and the Perdew86 39 (PD86) correlation functional. This choice of exchange4


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correlation functional has been proven to provide high-quality oscillator strengths matched with previous experimental researches very well. 25,28 In terms of basis set, the excited carbon atoms of core orbitals were described by localized orbitals with triple-ζ quality individual gauge (IGLO-III). 40 And for the other atoms, we applied the triple-ζ plus valence polarization (TZVP) basis set. 41 The non-excited carbon atoms were described by using model core potentials, and farraginous auxiliary basis sets were set for the whole atoms to expedite the self-consistent field (SCF) convergence. Furthermore, we added an augmented diffuse basis set (19s,19p,19d) 42 to produce the transition moment and the excitation energy. XPS spectra corresponds to the ionization of core electrons. The C 1s ionization potentials (IP’s) were taken as the energy differences between the ground state (GS) and core-excited state, IP = N −1 EFCH − N EGS .

Here

N −1

(2)

EFCH denoted the energy of the core-ionized state represented by a full core hole

(FCH) 25 state, and

N

EGS denoted the ground-state energy. The FCH approximation was

employed to calculate energies in excited state, the results computed by this method were regarded as a highest accurate way in the aspect of core-excited calculation, which was the best consistent with the experimental values. For the NEXAFS spectra calculations, we adopted FCH approximation combining with final-state rule. 43–46 Given the random orientations of space molecular distributions, the absorption oscillator strength was calculated finally by averaging over x, y, z directions,

ff i =

2mεf i (|⟨ψf |x|ψi ⟩|2 + |⟨ψf |y|ψi ⟩|2 + |⟨ψf |z|ψi ⟩|2 ), 3¯ h2

(3)

where ψi,f expresses two molecular orbitals (MOs) (i denotes intial state, and f denotes final state) in the process of X-ray absorption, and εf i denotes the transition energy from i to f . We used ∆KS scheme 47,48 to standardize the absorption spectra in order to gain absolute energy positions of features, i.e., we calculated the transition energy from C 1s to the lowest 5



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unoccupied molecular orbital (LUMO),

ε∆KS = N E1s→LUMO − N EGS ,

(4)

Where the transition energy from 1s to LUMO by ∆KS scheme was taken as the energy difference between the GS and comprehensive optimized core-excited state, where an electron of core-orbital is excited to LUMO. This method fully considered the relaxation to obtain first excited energy. In addition, considering the relativistic effect, a unified correction of 0.2 eV was added to calculate IP’s or transition energies. Then, the range of below ionization energy in the spectral line was broadened by Gaussian function with FWHM of 0.3 eV, as for the area of higher than ionization energy, we employed Stieltjes imaging approach 49 to broaden the continuous spectral line. According to the present investigations, 50–54 the FWHM value of 0.3 eV for NEXAFS was appropriate for this study of C84 molecules, and the calculated spectra well showed distinct transitions and spectral profiles. The XPS spectra was broadened by a Gaussian function with FWHM of 0.15 eV. Such a broadening was relatively small referred to available experiments currently in the past researches 55,56 and we adopted the small FWHM to obtain high-resolution theoretical spectra and well assign ionizations of carbon atoms of different local environment. According to different symmetry of molecules, the spectrum of each nonequivalent carbon atom was calculated, and then the total spectra were obtained by summing up the contributions weighed by the relative abundance of every type of carbon atom.

Results and discussion Structures The point group symmetries of six aforementioned IPR-satisfying isomers of C84 fullerene are C2 , Cs , D3d , D2 , D2d and D6h , respectively. As displayed in Figure 1a. C84 fullerene

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possesses 44 carbon rings including 12 pentagon rings and 32 hexagon rings. The assignments of pentagons and hexagons are diverse for different configurations. In this work, the six IPR-satisfying C84 isomers are denoted as 11(C2 )(with 42 non-equivalent carbon atoms), 16(Cs )(with 43 non-equivalent carbon atoms), 19(D3d )(with 8 non-equivalent carbon atoms), 22(D2 )(with 21 non-equivalent carbon atoms), 23(D2d )(with 11 non-equivalent carbon atoms), 24(D6h )(with 5 non-equivalent carbon atoms), respectively. The number of symmetry-independence carbon atoms, the relative energies of the six C84 isomers and the energy gaps between the highest occupied molecular orbital (HOMO) and LUMO are shown in table 1. Obviously, 22(D2 ) and 23(D2d ) have similar energies, and the energy of 22(D2 ) is only 0.03 kcal/mol higher than 23(D2d ) isomer. Compared with other configurations, 11(C2 ), 16(Cs ) and 19(D3d ) have relative closer energies, about 7-10 kcal/mol higher than the 23(D2d ), 24(D6h ) is only 3.90 kcal/mol higher than the 23(D2d ) isomer. The marshalling sequence of the six C84 fullerene isomers from high to low on stabilities is 23(D2d ), 22(D2 ), 24(D6h ), 16(Cs ), 11(C2 ), 19(D3d ), the current calculated results agree with previous studies. 13 For the further study, the HOMO-LUMO gaps of the six C84 IPR-satisfying isomers were investigated. The 23(D2d ) isomer which holds the lowest energy exhibits relative big HOMO-LUMO gap, while the HOMO-LUMO gap of 19(D3d ) with the highest energy is the smallest by comparing with the other five C84 isomers. The marshalling sequence of the size of HOMO-LUMO gaps for the six C84 fullerene isomers in descending order is 24(D6h ), 23(D2d ), 22(D2 ), 16(Cs ), 11(C2 ), 19(D3d ), which shows generally consistent with the above mentioned sequence about stability. It thus may indicate that the HOMO-LUMO gap reflect isomer stability. For the fullerene studies, particularly paying attention to molecular spectra, carbon atoms are generally categorized according to different local environment. 19,20,23,24 In this work, the carbon atoms of C84 fullerene are sorted into three types, as shown in Figure 1b, (1)the pyrene site, where the carbon atom is surrounded by three hexagons, (2)the corrannulene site, where the carbon atom is shared by one pentagon and two hexagons connecting to

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an additional hexagon, (3)the pyracylene site, where the carbon atom is embraced by one pentagon and two hexagons connecting to an additional pentagon. The contributions of the carbon atoms of different chemical environment to the total systematic spectra are discussed in the next section.

IR spectra The calculated IR spectra of the six IPR C84 isomers, as well as the experimental IR spectra of 23(D2d ) isomer 36 are shown in Figure 2. Comparing the theoretically calculated spectra and experimental spectra for 23(D2d ), their spectral profiles and energy position of each absorption peak are basically identical. Thereinto, there are two comparative strong spectral bonds existing in two ranges of 450 cm−1 - 800 cm−1 and 1050 cm−1 - 1700 cm−1 . In the range of 450 cm−1 - 1700 cm−1 , the positions of four relative strong peaks in the theoretically calculated IR spectra of 23(D2d ) exist in 648 cm−1 , 692 cm−1 , 1385 cm−1 and 1430 cm−1 , respectively. While the four relative strong peak of experiment are located in 650 cm−1 , 790 cm−1 , 1385 cm−1 and 1425 cm−1 ,respectively. Obviously, the theoretical spectra agreed well with experimental spectra on energy positions and intensities. In view of high similarity between theoretical spectrum and experimental spectrum for basic and significant characteristics, we can hold a powerful evidence to prove validity of our theoretical method. So we also calculated IR spectra theoretically for the other five C84 isomers. Based on the number of spectral peaks, the six configurations can approximately be classified into two categories. The first one contains 19(D3d ) and 24(D6h ), and the second one contains 11(C2 ), 16(Cs ), 22(D2 ) and 23(D2d ). The spectral peaks of the former class are much less than the latter class in quantity, especially in the range of 1120 cm−1 - 1670 cm−1 . In the former class, the intensities of spectral peaks of 24(D6h ) at 1385 cm−1 and 1430 cm−1 are much stronger than peaks of 19(D3d ). In the latter class, the 23(D2d ) isomer shows relative strong spectral peaks at 1385 cm−1 and 1430 cm−1 , while 11(C2 ), 16(Cs ) and 22(D2 ) exhibit similar IR spectra. According to the relationships between these distinct isomers and 8


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their corresponding IR spectra, one can see that IR spectroscopy is inadequate to distinguish all the six C84 isomers.

XPS spectra The calculated C 1s XPS spectra of the six C84 fullerene isomers was shown in Figure 3. In the six configurations, only the C 1s XPS spectra of 19(D3d ) exist four spectral peaks , the other five isomers merely have two peaks, hence 19(D3d ) can be distinguished from the other five isomers. In the following description, we mainly discussed 11(C2 ), 16(Cs ), 22(D2 ), 23(D2d ) and 24(D6h ). The XPS spectra of the five C84 have the same spectral profile, a relative strong spectral peak a and a relative weak peak b, however, the energy positions and the widths of the spectral peaks of the five isomers exist discrepancy. The strongest peak a of the five structures have the same energy position at about 289.65 eV, while the energy positions and widths of spectra for the other spectral peak b are different. The feature b of 11(C2 ) and 16(Cs ) are distinctly broader than the other three isomers. 24(D6h ) isomer shows the peak b at around 290.10 eV, 22(D2 ) and 23(D2d ) exhibit the feature b at about 0.05 eV higher than 24(D6h ). All in all, the C 1s XPS spectra can not distinguish well these four configurations. The previous investigations 32,57 indicated that the XPS might be employed to identify fullerene isomers with different symmetry. However, these six configurations of C84 cannot be completely identified by the XPS spectra, even though they have different symmetry. As displayed in Figure 1b, carbon atoms were sorted into different types based on similar local environment, and the contributions of each carbon type to total spectra were shown in Figure 4. Carbon atoms of pyracylene site and corrannulene site generate the feature a in the lowest energy position. At the highest energy position the spectral peak b is mainly generated by carbon atoms at the pyrene type. The spectra components corresponding to the carbons at pyrene site have some shifts toward higher energy regions comparing with the pyracylene and corrannulene carbon atoms, and the fused pentagons may be responsible 9



for such chemical shifts. We find that the features of corannulene components are generally stronger than the features of pyracylene and pyrene components in the intensities of spectral peaks owing to the number of carbon atoms at corannulene site is more than pyracylene and pyrene sites.

NEXAFS spectra The NEXAFS spectroscopy reflects the electron excitation from core orbitals to unoccupied orbitals, which provides more plentiful information of molecular electronic structures, herein the NEXAFS spectroscopy shows well the distinctions of structures of fullerene isomers. The C 1s NEXAFS spectra of the six C84 isomers have been explored theoretically, as shown in Figure 5. The spectral profiles of six C84 configurations exhibit significant differences. In order to compare the absorption spectra of the six isomers more detailed, we first discuss the spectra between 283 eV and 286 eV and show the energy positions of the corresponding spectral features in table 2. The six C84 isomers can be divided into two categories according to whether or not a spectral peak d exist at about 285.2 eV: 1. 11(C2 ), 16(Cs ), 19(D3d ), 2. 22(D2 ), 23(D2d ), 24(D6h ). For the former class, in the lowest energy region the feature a of 19(D3d ) arises at about 0.2 eV-0.3 eV lower than the other two configurations 11(C2 ) and 16(Cs ) observed obviously in the Table 2. Additionally, in the NEXAFS spectrum of 19(D3d ) the relative intensities of feature b and feature c are inverse in the spectra of 11(C2 ) and 16(Cs ), so 19(D3d ) can be distinguished from 11(C2 ) and 16(Cs ) through these deviations. In the absorption spectrum of 11(C2 ), the intensities of features a, b, c have a gradually incremental trend, while the feature b is the weakest of the three spectral features a, b, c in the spectrum of 16(Cs ), which may be employed to identify 11(C2 ) and 16(Cs ). In the latter class, compared with 22(D2 ) and 24(D6h ), 23(D2d ) only has three spectral features a, d, e at around 283.89 eV, 285.24 eV, 285.76 eV, respectively. The NEXAFS spectrum of 22(D2 ) shows a main peak 10


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a at about 283.89 eV, however, the peak a in the spectrum of 24(D6h ) was about 0.13 eV higher than that in 22(D2 ). Moreover, a weak shoulder b appears at around 284.48 eV on the right of peak a in the spectrum of 22(D2 ), which does not exist in the spectra of 23(D2d ) and 24(D6h ), thus the feature b of 22(D2 ) can be known as a fingerprint to discriminate 22(D2 ) from 23(D2d ) and 24(D6h ). The six isomers of C84 fullerene can be identified absolutely according to these spectral features. In conclusion, the abilities of IR and C 1s XPS spectra to distinguish the six isomers of C84 fullerene exist obstacles, but the NEXAFS spectra are efficient enough for the discrimination of the six isomers of C84 fullerene. The calculated C 1s NEXAFS spectra of the six C84 isomers and the components of total spectra originated by the different types of carbon atoms are exhibited in Figure 6. The decompositions of total spectra generated by different types of carbon atoms are explored in order to understand the contribution of carbon atoms of different local chemical environment to main spectral features of total spectra and the dependence of NEXAFS spectra on the local structures of C84 fullerene. In the lowest energy region, the feature a of the NEXAFS spectra of the six C84 fullerene isomers is primarily originated by the carbon types containing pyracylene and corannulene sites, which agrees with the XPS spectra. The most remarkable feature e arises mainly from carbon type of corannulene, because of the superiority in number of carbon atom at corannulene site in each C84 cage. Obviously, the spectral profiles and the energy positions of features generated by different carbon types are diverse, which reflects the sensitivity of C 1s NEXAFS spectra on local structures of carbon atoms. Then, in order to explain the precise dependence of the NEXAFS spectra on the local construction of fullerenes, we investigate the spectra of the six isomers in a more delicate way. The K -edge NEXAFS spectra of carbon atoms have been fully explored at the same site classified above. The independent atoms of symmetry will provide more information for the NEXAFS by thorough scanning. We can see that the characteristics of identical atoms do not appear in the spectra at the same place. Although most of the carbon atoms in the same location show similar spectra, some other atoms even show significantly different spectra. The configurations of

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C84 molecules, irregular sphere, may result in distinct spectra of the carbon atoms at the same location type because of the discrepant tortuosities at different site. Additionally, the previous research work of Zhao 58 pointed that the permutations of the polygons in the second layer can make influences on the generation of the NEXAFS spectrum of the corresponding atom in fullerens, excepting that the first layer of polygons (pentagons and hexagons) surrounding the carbon atom have the same effect. At present, the XPS and NEXAFS spectra of C84 molecules are not available in experiments. We refer to the experimental result 59 and the corresponding theoretical calculation 25 of C60 as references for this theoretical study of C84 . The theoretical calculated C 1s IP of C60 was near to the preceding experimental results and the calculated NEXAFS spectra are in good agreement with the experimental spectra. We used the same approach applied for C60 to calculate the C84 molecules, so our calculated results are reliable.

Conclusion In summary, we have theoretically calculated the IR, C 1s XPS and NEXAFS spectra of the six IPR-satisfying C84 fullerene isomers. The spectral components of XPS and NEXAFS spectra according to carbon atoms of different chemical environment have also been investigated in order to illuminate the origins of the spectral features. The IR and XPS spectra could not fully discriminate the six configurations with different symmetry of C84 fullerene, while the prediction of the IR and XPS of the fullerene isomers could have a big promotion for the experimental study in future. In contrast with the IR and XPS spectra, the NEXAFS spectra showed stronger isomer dependence, so the NEXAFS spectra could be applied to completely distinguish all the six stable C84 isomers.

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Acknowledgement This work is supported by National Natural Science Foundation of China (Grant NO. 11404193, 21303096, 11374195) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry. Thanks to the support of the Taishan scholar project of Shandong Province.

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Page 20 of 27

Table 1: Number of nonequivalent carbon atoms (Cnon ) and relative energies (kcal/mol) of the six C84 fullerene isomers, as well as HOMO-LUMO gaps (eV) for all the studied objects at B3LYP/6-31G(d,p) level. C84 isomers Cnon 11(C2 ) 42 16(Cs ) 43 19(D3d ) 8 22(D2 ) 21 23(D2d ) 11 24(D6h ) 5

Relative energy HOMO-LUMO gap 8.30 1.64 7.98 1.76 10.06 1.39 0.03 1.97 0.00 2.05 3.90 2.34

Table 2: Energies (eV) of dominated spectral features between 283 eV and 286 eV for the six C84 isomers. C84 isomers 11(C2 ) 16(Cs ) 19(D3d ) 22(D2 ) 23(D2d ) 24(D6h )

a 283.77 283.89 283.59 283.89 283.89 284.02

b 284.27 284.31 284.49 284.48 -

20

c d 284.72 284.81 284.69 284.92 285.32 285.24 284.87 285.11


e 285.67 285.68 285.59 285.68 285.76 285.74

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Figure 1: (a) Optimized geometric structures of the six C84 fullerene isomers following IPR. (b) Schematic diagram of the three chemical environments according to different carbon site, and the excited carbon atoms are colored by green, blue and red.

21



Figure 2: Calculated IR spectra of the six IPR C84 isomers, and the experimental IR spectrum of 23(D2d ) isomer. 36 The line of exp.23(D3d ) is reprinted (adapted) with permission from (Dennis, T. J. S.; Hulman, M.; Kuzmany, H.; Shinohara, H. Vibrational Infrared Spectra of the Two Major Isomers of [84]Fullerene:C84 {D2 (IV)} and C84 {D2d (II)}. J. Phys. Chem. B 2000, 104, 5411-5413.) Copyright (2000) American Chemical Society.

22


Page 22 of 27

Page 23 of 27

C

84

XPS a b

11(C2)

a b

Intensity(arb. unit)

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 57 58 59 60


a

16(Cs)

a’ b

b’

19(D3d)

a b

22(D2) a b

23(D2d) a b

24(D6h) 289

290 Energy(eV)

291

Figure 3: Calculated C 1s XPS spectra of the six C84 fullerene isomers following IPR. The main features of XPS spectra are labeled.

23



11(C ) 2

16(C ) a s

a

19(D

b b'

total


) a a'

3d

b

b

total

total b b'

b

b pyrene(24)

pyrene(24)

pyrene(24)

a

a

a a'

corannulene(36)

corannulene(36)

pyracylene(24)

23(D

2

2d

a'

a

pyracylene(24)

a

22(D ) a

pyracylene(24)

a

)

24(D

6h

)

b

b

b

total

total

total

b

b pyrene(24)

b pyrene(24)

a

a corannulene(40)

pyracylene(20) 290

pyracylene(20)

291 289

corannulene(36) a

a

Energy(eV)

pyrene(24) a

corannulene(40)

a

289

corannulene(36)

a

a


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 57 58 59 60

Page 24 of 27

290

291 289

Energy(eV)

pyracylene(24) 290

291

Energy(eV)

Figure 4: Calculated XPS with the individual components for the three different sorts of carbon atoms in six C84 isomers. These components are obtained by summing up the individual spectra of the independent carbon atoms scaled by their relative abundance for each sort of carbon atoms. The number of carbon atoms of each sort in every isomer is included in parentheses behind the labels of the carbon atom sites.

24


Page 25 of 27

C84 NEXAFS e

11(C2)

e

16(Cs)

c a

b

c ab e


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 57 58 59 60


19(D3d)

bc a e

22(D2)

de

23(D2d)

e

24(D6h)

cd

a b a

a cd

282

284

286 288 290 Energy(eV)

292

294

Figure 5: Calculated C 1s NEXAFS spectra of the six IPR C84 fullerene isomers. The major features are labeled.

25



11(C 2 )

16(C s)

e

19(D 3d )

e


total

e

total

total

a

a

a

e

e

22(D )

e

total

a

pyracylene(24)

e

2d

)

e

total

a

pyrene(24)

e corannulene(40)

a

a

pyracylene(20)

a

286

288

Energy(eV)

290

e

292 284

e

corannulene(40)

pyracylene(20)

e

286

288

290

24(D ) e 6h a

total

e

a

pyrene(24)

e corannulene(36)

a

292 284

Energy(eV)

pyracylene(24)

a

pyrene(24)

a

284

corannulene(36)

a

a

23(D e

pyrene(24)

corannulene(36)

a

pyracylene(24)

e

pyrene(24)

e

corannulene(36)

a

2

e

pyrene(24)

e

a


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 57 58 59 60

Page 26 of 27

pyracylene(24)

e

286

288

290

292

Energy(eV)

Figure 6: Calculated NEXAFS spectra with the individual components for the three different sorts of carbon atoms in six C84 isomers. These components are obtained by summing up the individual spectra of the independent carbon atoms scaled by their relative abundance for each sort of carbon atoms. The number of carbon atoms of each sort in every isomer is included in parentheses behind the labels of the carbon atom sites.

26


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TOC Graphic

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Theoretical Identification of the Six Stable C84 Isomers by IR, XPS

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