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[email protected]·NiII(OEP)·1.73C6H6·1.27CHCl3 crystal with thermal ellipsoids set at ... Crystal and structure data of [email protected](6)-C82 at 107 K. ... Empirical formula.

Supplementary Information for:

An Improbable Monometallic Cluster Entrapped in a Popular Fullerene Cage: [email protected](6)-C82 Shangfeng Yang1, Chuanbao Chen1, Fupin Liu1, Yunpeng Xie2, Fengyu Li3, Mingzhi Jiao1, Mitsuaki Suzuki4, Tao Wei1, Song Wang1, Zhongfang Chen3, Xing Lu2,4 & Takeshi Akasaka4 1

Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Materials for Energy Conversion & Department of Materials Science and Engineering, University of Science and Technology of China (USTC), Hefei 230026, China 2

State Key Laboratory of Materials Processing and Die & Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China 3

Department of Chemistry, Institute for Functional Nanomaterials, University of Puerto Rico, San Juan, Puerto Rico 00931, USA 4

Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki 305-8577, Japan

Contents S1. Isolation of [email protected] S2. Estimation of the relative yield of [email protected] to those of [email protected] and [email protected] (I) S3. X-ray crystallographic data of [email protected] S4. Complete 13C NMR spectrum of [email protected] and detailed analysis S5. UV-vis-NIR spectroscopic results of [email protected] S6. XPS spectroscopic analysis of [email protected] S7. Cyclic voltammogram of [email protected] S8. Computational study of [email protected]

S1

S1. Isolation of [email protected]: The typical chromatogram of fullerene mixture obtained from mixture of Y2O3 and TiO2 with addition of N2 is shown in Figure S1I (Y2O3/TiO2/N2, curve a), which includes also that obtained from pure Y2O3 with N2 addition (Y2O3/N2, curve b) for comparison. Fractions A are collected and measured by LD-TOF MS (Figure S1II), indicating that the mass peak of 1099 (YC83N) exists only in the Y2O3/TiO2/N2 extract and is absent in the Y2O3/N2 extract.

Fig. S1  (I) Chromatograms of the fullerene extract mixtures synthesized from Y2O3/TiO2 with N2 addition (Y2O3/TiO2/N2, a), Y2O3 with N2 addition (Y2O3/N2, b). 20 × 250 mm 5PYE column; flow rate 15.0 ml/min; injection volume 15 ml; toluene as eluent (mobile phase); 25°C. (II) Negative-ion laser desorption time-of-flight (LD-TOF) mass spectra of the fraction A collected from Y2O3/TiO2/N2 (a) and Y2O3/N2 (b).

[email protected] was successfully isolated from Fraction A by the following four-step HPLC. In the first-step recycling HPLC isolation running in a 20 × 250 mm 5PYE column (Figure S2I), three fractions are collected after four cycles. LD-TOF MS spectroscopic measurements indicate that fraction A-3 comprises of three major mass peaks at 1032 (C86), 1099 (YC83N) and 1200 (Y2TiNC80) and thus was collected for further isolation. The collected subfraction A-3 is then subjected for the second-step HPLC running in a 10 × 250 mm Buckyprep-M column and the chromatogram is shown in Figure S2II, resulting in the collection of three fractions (A-3-1, A-3-2, A-3-3). The subfraction A-3-2 is collected for the third-step recycling HPLC running in the same Buckyprep-M column. After six cycles, subfraction A-3-2-2 was collected which contains (YC83N, m/z=1099) according to LD-TOF MS spectroscopic measurements. In the fourth-step recycling

S2

HPLC isolation of subfraction A-3-2-2 running in the same Buckyprep-M column, the residual subfraction A-3-2-2-1 (corresponding to subfraction A-3-2-1 of the third-step HPLC) was successfully removed and a pure fraction A-3-2-2-2 was obtained after 7 cycles, which was then measured by LD-TOF MS spectroscopy, confirming its chemical composition and purity (see Fig. S3I). The isolated [email protected] is further checked by the recycling HPLC, indicating a single chromatographic peak even after 9 cycles (see Fig. S3II). Thus, the high isomeric purity of [email protected] (≥ 99.5 %) is assured.

Fig. S2  (I) Recycling HPLC chromatogram of the subfraction A of the Y2O3/TiO2/N2 extract. (20 × 250 mm 5PYE column; flow rate 15.0 ml/min; injection volume 15 ml; toluene as eluent; 25°C). (II) The second-step HPLC chromatogram of the subfraction A-3 collected from the last step. (10 × 250 mm Buckyprep-M column; flow rate 5.0 ml/min; injection volume 5 ml; toluene as eluent; 25°C). (III) The third-step HPLC chromatogram of the subfraction A-3-2 collected from the second step. (10 × 250 mm Buckyprep-M column; flow rate 5.0 ml/min; injection volume 5 ml; toluene as eluent; 25°C). (IV) The fourth-step HPLC chromatogram of the subfraction A-3-2-2 collected from the third-step. (10 × 250 mm Buckyprep-M column; flow rate 5.0 ml/min; injection volume 5 ml; toluene as eluent; 25°C).

S3

It should be noted that, by comparing the MS spectra of Y2O3/TiO2/N2 and Y2O3/N2 extracts, clearly the mass peak of 1099 correlated to [email protected] exists only in the Y2O3/TiO2/N2 extract and is absent in the Y2O3/N2 extract (see Fig. S1II), and our attempt to isolate [email protected] from Y2O3/N2 extract was also not successful. These results indicate that the introduction of TiO2 in the raw mixture is essential for the formation of [email protected]

Fig. S3  (I) Negative-ion laser desorption time-of-flight (LD-TOF) mass spectrum of isolated [email protected] The insets show the measured and calculated isotope distributions of YC83N. (II) Chromatogram of isolated [email protected] (10 × 250 mm Buckyprep-M column; flow rate 5.0 ml/min; injection volume 5 ml; toluene as eluent; 25 °C).

S4

S2. Estimation of the relative yield of [email protected] to those of [email protected] and [email protected] (I): The relative yield of each fraction shown in Figs. S1I and S2 is estimated based on the integrated area of the corresponding peak in the chromatogram, the results are summarized in Table S1. Table S1. Assignments of each (sub)fraction and their relative yield and abundance fraction

subfraction

product

relative yield

relative abundance

A

A-1

[email protected]

1:3.5:1.75

16%

A-2

C86

(A-1:A-2:A-3)

56%

A-3

YC83N (I-III)a + C86 +

28%

[email protected] A-3

A-3-2

A-3-2-2

B a

A-3-1

C86

1:0.52:0.89

41.6%

A-3-2

YC83N (I-III)a + C86

(A-3-1: A-3-2: A-3-3)

21.5%

A-3-3

[email protected]

A-3-2-1

YC83N (I)

1:1.65:1

27.4%

A-3-2-2

YC83N(I) + [email protected]

(A-3-2-1: A-3-2-2:

45.2%

A-3-2-3

YC83N (III) + C90

A-3-2-3)

27.4%

A-3-2-2-1

YC83N (I)

1:5.17

16.2%

A-3-2-2-2

[email protected]

(A-3-2-2-1: A-3-2-2-2)

83.8%

-

-

36.8%

b

[email protected] (I)

36.9%

YC83N (I-III) represent three isomers of YC83N, among which the second isomer was identified as [email protected] in the present work;

b

The composition of fraction B was analyzed by recycling HPLC (not shown) and the

[email protected] (I, C2v) was found to be the major component with the abundance of ~ 36.8%.

(1) The relative abundance of [email protected] (fraction A-3-2-2-2) in the entire fraction A is: 83.8% × 45.2% × 21.5% × 28% ≈ 2.3 % (2) The relative abundance of [email protected] in the entire fraction A had been already reported in our previous paper (ref. [S1]): 16% × 78.1% ≈ 12.5 % Therefore, the relative yield of [email protected]:[email protected] is 2.3%: 12.5% ≈ 1:5.4 (3) To calculate the relative yield of [email protected]:[email protected] (I), the relative abundance of fraction A:B should be calculated (~ 1.33:1). Since the relative abundance of [email protected] (I) in the entire fraction B is ~ 36.8%, the relative yield of [email protected]:[email protected] (I) is (2.3% × 1.33): 36.8% ≈ 1:12

S5

S3. X-ray crystallographic data of [email protected]

Fig. S4  (a) A perspective view of the relative orientations of [email protected] and Ni(OEP) within the [email protected]·NiII(OEP)·1.73C6H6·1.27CHCl3 crystal with thermal ellipsoids set at 30 % probability level. Two disorders of the C82 cage with 0.55 and 0.45 occupancies were found and shown in (b) and (c), respectively. (d) Relative orientations of Y, C, N atoms within [email protected] with 0.55 occupancy of the C82 cage. Five yttrium atom sites (Y1 – Y5) with occupancies of 0.50, 0.25, 0.19, 0.03, and 0.03 are shown respectively.

Table S1. Crystal and structure data of [email protected](6)-C82 at 107 K. Temperature Empirical formula

T=107 K C127.65 H52.65 Cl3.81 N5 1938.88 1.54180 P 21/c (no. 14) Monoclinic a= 17.672(4) Å a= 16.929(3) Å a= 27.338(6) Å α= 90º β= 107.82(3) º

Crystal size Theta range for data collection Index ranges

Volume Z

γ= 90º 7787(3) 4

Data/restrains/parameters Goodness-of-fit on F2 Final R indices [I>2sigma(I)]

Density

1.654 g/cm3

R indices (all data)

Absorption coefficient F(0000)

3.042 3941.0

Largest diff. peak hole

Formula weight Wavelength Crystal system Space group Unit cell dimensions

Reflections collected Independent reflections Completeness to θ Absorption correction Max. and min. transmission Refinement method

S6

0.37×0.30×0.30mm3 3.11 to 67.60º -20≤h≤20 -19≤k≤20 -31≤l≤32 10964 [R(int) =0.0279] 95.6 % (θ = 67.60º) Numerical 0.3991 and 0.4622 Full-matrix least-squares on F2 13450 / 1922 / 1765 1.036 R1 = 0.0806, wR2 = 0.2246 R1 = 0.0938, wR2 = 0.2403 1.267 and -1.536 e/Å-3

S4. Complete 13C NMR spectrum of [email protected] and detailed analysis

Fig. S5  Expanded

13

C NMR (125 MHz) spectrum of [email protected] in a proton-decoupled mode. The asterisk

represents the instrument quadrature spike.

Table S2. Summary of the chemical shift values (δ, ppm) signal 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

intensity 2C 2C 1C 2C 2C 2C 2C 2C 1C 1C 2C 2C 2C 1C 2C 2C 2C 2C 2C 2C 2C 2C

δ 123.96 128.87 129.57 129.64 130.61 132.57 132.87 133.41 133.57 134.42 135.30 135.68 135.77 135.82 135.96 136.17 136.33 136.74 136.90 137.80 137.87 137.90

signal 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

intensity 2C 1C 2C 2C 2C 2C 2C 2C 2C 2C 1C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 2C 1C S7

δ 138.32 138.75 139.21 139.24 139.91 140.04 140.14 140.89 141.60 141.88 142.52 142.68 142.87 144.08 144.16 144.76 145.67 146.42 147.43 147.58 150.00 151.22 292.37

S5. UV-vis-NIR spectroscopic results of [email protected] The UV-vis-NIR spectrum of [email protected] dissolved in toluene solution is shown in Fig. S6I. Based on the absorption spectral onset of ca. 1620 nm, the optical band-gap of [email protected] is estimated to be ca. 0.77 eV. The electronic absorption spectrum of [email protected] exhibits three broad shoulder peaks at about 389, 491 and 741 nm in the visible region and is more rich in features in the NIR region, where a broad absorption peak with two absorption maxima at 1064 and 1123 nm along with a distinct absorption peak at 1318 nm are observed. As a result the colour of [email protected] in toluene is brown-yellow (see inset of Fig. S6I). With the same Cs(6)-C82 cage, several endohedral fullerene isomers including [email protected], [email protected] and [email protected] have been reported.[S2-S4] Although their absorption feature differs to that of [email protected], they demonstrate the common feature of the obvious NIR absorptions, suggesting that the electronic absorption properties of these endohedral fullerenes based on Cs(6)-C82 isomer are essentially determined by the cage whereas the obvious perturbation by the entrapped species occurs.

Fig. S6  (I) UV-vis-NIR spectrum of [email protected] dissolved in toluene. The insets show the enlarged spectral range (600-1640 nm) and the photograph of [email protected] solution in toluene. (II) Comparison of the experimental UV-vis-NIR spectrum of [email protected] (a, copied from Fig. S6I) with the simulated one (b). The insets show the enlarged spectral range (550-1300 nm) of the simulated UV-vis-NIR spectrum.

The TD-DFT (time-dependent density functional theory) computations on 200 excited states was carried out at the PBE/3-21G~LanL2DZ//PBE/ECP level of theory so as to simulate the UVvis-NIR spectra of [email protected] (Cs) conformer determined by X-ray crystallography, which show reasonable agreements to the experimental one (Fig. S6II). The excited states (381.66, 516.50, 355.89, and 356.30 nm) (out of 200 excited states) have the largest oscillator strengths of 0.0295, S8

0.0236, 0.0282, and 0.0281 respectively for the two [email protected] conformers. The first allowed electronic transition with nonzero oscillator strength (1478.29 nm, HOMO→LUMO) corresponds to the optical band-gap of [email protected] (~ 0.84 eV), which are comparable to the experimentally measured optical band-gap (0. 77 eV). S6. XPS spectroscopic analysis of [email protected]: Figure S7 shows the XPS spectrum of the 3d level of Y within [email protected], which may give a tentative direct determination of the valency of Y. The observed Y 3d5/2 and 3d3/2 binding energies in [email protected] are 158.4, 160.5 eV, respectively. Comparing to the Y 3d5/2 binding energies of other Y-containing compounds in which Y has a valence state of 3, i.e., 156.0 eV in Y2O3, 159.6 eV in YF3, the observed Y 3d5/2 binding energy in [email protected] (158.4 eV) is between those in Y2O3 and YF3, in which Y takes a valence state of 3 for both cases,[S5] suggesting that the valence state of Y in [email protected] is 3. The XPS spectra of N1s and C1s are also illustrated in Figure S7. The observed N1s binding energy is 399.0 eV, coinciding with the binding energy of N3- within NH3 and cyanides.[S5] Likewise, the observed C1s binding energy of 284.6 eV is the typical value for the carbon atoms of endohedral fullerenes.

Fig. S7  XPS spectra of the 3d level of Y, 1s levels of N and C in [email protected]

S9

S7. Cyclic voltammogram of [email protected]:

Fig. S8  Cyclic voltammograms of [email protected] in different scanning regions showing the correlation of each reduction step with the corresponding re-oxidation step. The asterisk labels the oxidation peak of ferrocene. The small peak at around -1.50 V is due to an unknown impurity. Scan rate: 100 mV/s.

S8. Computational study of [email protected] The generalized gradient approximation of PBE functional[S6] and DNP basis set with core effective potentials (PBE/ECP) were employed to study the geometry structures, electrochemical redox and oxidation potentials, infrared spectrum of [email protected] by using DMol3 code.[S7] The structures were fully optimized with no symmetry or spin constrains. The single-point energy computations were carried out at the PBE/6-31G*~LanL2DZ level as implemented in Gaussian 09 program for electronic property analysis,[S8] here 6-31G*~LanL2DZ denotes 6-31G* basis set for C and N atoms, and the effective core potential plus valence double-ζ basis set (LanL2DZ) for Y atom. TD-DFT (time-dependent density functional theory)[S9] computations on 200 excited states was carried out at the PBE/3-21G~LanL2DZ//PBE/ECP level of theory. Figure S9 shows the DFT-computed Kohn-Sham molecular orbital levels in C82, C822- and [email protected], and several frontier molecular orbitals of [email protected] are illustrated in Figure S10. For [email protected] a dramatic increase of the HOMO-LUMO gap (Eg) compared to those of C82 and C822S10

is clearly revealed, indicating a significant stabilization of C822- by the endohedal [Y3+(CN)-]2+ moiety. Interestingly, all the considered eight frontier orbitals are mainly localized on the C82 cage. As a result, both the oxidation and reduction steps of [email protected] should correspond predominantly to the change of the charge state of the C82 cage whereas the encapsulated YCN cluster maintains its initial charge state as [(Y3+)(CN)−]2+.

Fig. S9  Kohn-Sham (B3LYP/6-311G*) molecular orbital levels in [email protected], C82 and C822-. For clarity, the HOMO energy is set as zero for each molecule.

Fig. S10  Frontier molecular orbitals of [email protected]

S11

Figure S11 compares the plots of the electrostatic potential surfaces (EPS) of C822- (a) and [email protected] (b) in terms of total electron density. Clearly the negative potential region of C822located at the top (the red region) is energetically favorable to attach a positively charged Y atom, and such a charge neutralization is evidenced in the EPS of [email protected]

Fig. S11  The plots of electrostatic potential surfaces (EPS) of C822- (a) and [email protected] (b). The isovalues were set as ±0.02 a.u.

References [S1].

Chen, C. B.; Liu, F. P.; Li, S. J.; Wang, N.; Popov, A. A.; Jiao, M. Z.; Wei, T.; Li, Q. X.; Dunsch, L.; Yang, S. F. Inorg. Chem. 51, 3039-3045 (2012).

[S2].

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[S3].

Lu, X.; Nakajima, K.; Iiduka, Y.; Nikawa, H.; Mizorogi, N.; Slanina, Z.; Tsuchiya, T.; Nagase, S.; Akasaka. T. Am. Chem. Soc. 133, 19553-19558 (2011).

[S4].

Akasaka, T.; Kono, T.; Matsunaga, Y.; Wakahara, T.; Nakahodo, T.; Ishitsuka, M. O.; Maeda, Y.; Tsuchiya, T.; Kato, T.; Liu, M. T. H.; Mizorogi, N.; Slanina, Z.; Nagase, S. J. Phys. Chem. A 112, 1294-1297 (2008).

[S5].

J. F. Moulder, W. F. Stickle, P. E. Sobol, K. D. Bomben, Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corp., Eden Prairie, MN, USA, 1992.

S12

[S6].

Perdew, J. P.; Burke, K.; Ernzerhof, M. Phys. Rev. Lett. 77, 3865–3868 (1996).

[S7].

(a) Delley, B. J. Chem. Phys. 92, 508-517 (1990). (b) Delley, B. J. Chem. Phys. 113, 77567764 (2000).

[S8].

Gaussian 09, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 2009.

[S9].

Casida, M. E.; Jamorski, C.; Casida K. C.; Salahub, D. R. J. Chem. Phys. 108, 4439-4449 (1998).

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