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Expanded Rosarin. A Versatile Fullerene (C60) Receptor Xian-Sheng Ke, Taeyeon Kim, James T. Brewster, Vincent M Lynch, Dongho Kim, and Jonathan L. Sessler J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b00735 • Publication Date (Web): 20 Mar 2017 Downloaded from http://pubs.acs.org on March 20, 2017
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Expanded Rosarin. A Versatile Fullerene (C60) Receptor Xian-Sheng Ke†, Taeyeon Kim‡, James T. Brewster II†, Vincent M. Lynch†, Dongho Kim*‡, and Jonathan L. Sessler*† † ‡
Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712-1224, United States. Department of Chemistry, Yonsei University, Seoul 120-749, Korea
Supporting Information Placeholder ABSTRACT: An expanded rosarian (P3P6) with a bowl-like conformation has been prepared and characterized. It is prepared in a one pot procedure that involves condensing a bispyrrole pyridine precursor (P1P2) with benzaldehyde, followed by oxidation. Single crystal X-ray diffraction analysis reveals a bowl-like conformation in the solid state with an upper rim diameter defined by the meso-phenyl substituents of ca. 13.5 Å and a depth of roughly 6.3 Å. P3P6 forms both 1:1 and 2:1 complexes with C60 in the solid state. DFT calculations reveal similar energies for the two binding modes. Nevertheless, a 1:1 binding stoichiometry dominates in 1,2-dichlorobenzene-d4 at the millimolar concentrations dictated by solubility consideration. The solution phase interactions between rosarian and C60 were studied using 1H NMR, UVvis, and femtosecond transient absorption (fs-TA) spectroscopies in 1,2-dichlorobenzene-d4 or toluene. To our knowledge, this is the first report of an unfunctionalized porphyrinoid that forms a well-defined complex with C60 in solution as well as in the solid state.
Supramolecular porphyrin-fullerene assembles are of particular interest due to their potential application in the area of light harvesting and artificial photosynthesis.1 Porphyrins have been used as components to create receptors for fullerenes since the 1990’s.2 However, porphyrins per se are not particularly effective fullerene receptors in solution. To increase the complexation capability, several elaborate jaw-3 or tweezers-4 like bridge systems and cavity-confined cyclic porphyrins5 have been developed. In addition, some ring-contracted porphyrinoids, such as subphthalocyanine6 and subporphyrins,7 bearing substituents (e.g., thiols and pyrenes) have been shown to display fullerene binding ability. Apart from porphyrins and their analogues (collectively “porphyrinoids”), a large number of fullerene receptors, including those based in calix[n]arenes,8γ-cyclodextrin (γ-CD),9 crown ethers,10 corannulenes,11 triquinacenes,12 phosphangulenes,13 and tetrathiafulvalene (TTF) modified calixpyrroles,14 are known. However, creating a simple, unfunctionalized porphyrinoid system that binds fullerenes effectively remains an unmet challenge. Here, we report an expanded rosarin that act as a stand-alone receptor for fullerene (C60) both in solution and in the solid state. Rosarin (formally a hexaphyrin (1.0.1.0.1.0)) was reported by our group in 1992.15 It contains three meso-aryl linked bipyrrole subunits and is one of the many hexapyrrolic expanded porphyrins now known.16 As true for many expanded porphyrins, the original rosarin adopts a highly twisted conformation, a feature that presumably militates against its ability to act as a receptor for guests other than some simple anions, such as chloride.15 Recently, Setsune and coworkers reported core-modified expanded rosarins
containing three 1,4-substituted benzene17 and 2,5-substituted thiophene18 subunits. These systems adopt near planar conformations in the solid state, making them unsuitable as receptors for substrates, such as C60, characterized by convex surfaces. We considered it likely that expanded rosarins based on the 2,6bis(3,4-diethyl-2-pyrryl)pyridine19 (P1P2) subunit and bearing meso-aryl substituents (Scheme 1) would display relatively greater curvature due to steric strain and thus adopt bowl-like conformations suitable for fullerene recognition. This led to the preparation of the expanded rosarin P3P6. Scheme 1 Synthesis of expanded rosarin P3P6.
The synthesis of P3P6 is shown in Scheme 1. Briefly, P1P2 was treated with excess benzaldehyde (3.5 equiv) and heated in propionic acid under N2, followed by oxidation with 2,3-dichloro-5,6dicyano-1,4-benzoquinone (DDQ); this produced the target macrocycle P3P6 directly in 15% yield. Macrocycle P3P6 was characterized by 1H, 13C, 2D-correlation spectroscopy (COSY) NMR and UV-vis spectroscopies, high-resolution ESI mass spectrometry, as well as single crystal X-ray diffraction analysis (Figure S14). Diffraction grade single-crystals of P3P6 were grown from CH2Cl2/n-hexane. The resulting X-ray structure is shown in Figure 1. The core structure without peripheral alkyls adopts an approximate C3v symmetry in the solid state and is composed of three apparently conjugated dipyrromethenes separated by three pyridine subunits. The dihedral angles between the pyridine and the two flanking pyrrole moieties are 35.5o and 53.6o, respectively. The distances between the three pyridine nitrogen atoms are identical at 7.623 Å (Figure 1b). The top of the bowl structure can be defined by the lid-like, triangle pocket formed by the three metacarbon atoms of the meso-phenyl substituents, which are separated from one another by 15.649 Å. The diameter (D) of the bowl defined by the meso-phenyl groups is 13.533 Å (Figure 1b). The bottom of the bowl structure may be considered as defined by the three γ-‐carbons of the pyridine subunits. The measured distances between the γ-‐carbons are all equal to 5.504 Å. Thus, the estimated depth of the bowl structure is approximately 6.30 Å (Figure 1b). The deep and large bowl-like structure revealed by the single
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Figure 1. X-ray structure of P3P6; a) top view, b) side view and cartoon sectional view (right) of the bowl-like structure giving some key metric parameters. Hydrogen atoms and alkyl groups have been omitted for clarity in the side view. Proton NMR analysis of the expanded rosarin P3P6 exhibits a relative simple well resolved spectrum in CDCl3 with signals at ca.13.00, 7.64-7.73, 7.33-7.45 and 0.74-2.77 ppm ascribable to the inner NH, pyridine, meso-phenyl, and peripheral alkyl protons, respectively (Figure S1). Upon adding C60 to P3P6 in 1,2dichlorobenzene-d4, significant chemical shift changes are observed for the inner NH (Δδ = 0.70 ppm) and pyridine β-H (Δδ = 0.14 ppm) proton signals (Figure 3 and S5-6). This was taken as initial evidence that a host-guest complex was being formed. The host-guest interactions between P3P6 and C60 were further probed by various optical measurements. Steady-state absorption spectroscopic titration of P3P6 with C60 revealed red-shifts in the absorption features in toluene (Figure S11). Femtosecond transient absorption spectroscopy (fs-TA) revealed an obvious C60 anion peak at 1075 nm20 immediately after photoexcitation at 500 nm (Figure 2). The decay of the P3P6 excited state could be fit to a double exponential with time constants of 22 and 2 ps, respectively (Figure S9). The former decay feature was assigned to electronic relaxation and the latter was assigned to vibrational relaxation in light of its relatively small contribution to the observed ground state bleaching. The putative P3P6•C60 complex showed additional 200 fs and long-lived components that were assigned to charge-separation (CS) and charge recombination processes, respectively (Figure S12). These quantitative features are consistent with the formation of a complex between P3P6 and C60. 0.02
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Figure 2. Femtosecond transient absorption spectra of a) P3P6 and b) P3P6 in the presence of 1 equiv. of C60 in toluene recorded following photoexcitation at 500 nm.
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In pioneering work carried out by Boyd et al.,2a involving studies of tetraarylporphyrins and C60 in organic media, neither the binding stoichiometry nor the association constants could be accurately defined. In our case, a continuous variation plot could be constructed using the changes in the signal for the inner NH proton observed during the course of the 1H NMR spectroscopic titration (Figure 3a). The resulting plot, with a maximum at ca.0.5, provides support for the conclusion that a 1:1 binding stoichiometry dominates in solution (Figure 3b). A slight deviation from perfect symmetry, as well as better fits to the data, led to a 2:1 binding model being used. This gave first and second Ka values of 2210 ± 30 and 262 ± 11, respectively (Figure S7).21 Since no Ka values have been reported for the interaction of C60 with unsubstituted (and relatively flat) porphyrins,2a,2b comparison are not possible. However, the Ka value recorded for P3P6 and C60 compares well with that seen for corannulenes, a well-known class of standalone fullerene receptors (e.g., for a pentakis-(4methoxyphenylthio)corannulene the Ka is 474 ± 28 M-1 as measured by 1H NMR spectroscopic methods in toluene-d8),11a,11c as well as thiol modified subporphyrins (for which the measured Ka is 857 ± 58 M-1 as determined by 1H NMR spectroscopy in toluene-d8).7a
Figure 3. a) Changes in the chemical shift of the inner NH proton resonance seen in a 1H NMR spectral titration of P3P6 with C60 in 1,2-dichlorobenzene-d4 where the starting concentration of the receptor was 5.00 mM; b) Job plot constructed from the chemical shift changes during a 1H NMR spectral titration of P3P6 with C60 in 1,2-dichlorobenzene-d4 where the starting concentration of P3P6 was 5.00 mM. Single-crystals of the 1:1 complex of P3P6 and C60 were grown by allowing n-heptane to diffuse into a toluene solution containing the host (P3P6) and guest (C60) in a 1:1 mole ratio. The X-ray structure confirmed the expected concave-convex binding interaction between the two species (Figure 4). The C60 molecule is located above the P3P6 macrocycle while the lower six-membered carbon rings of the fullerene guest are nearly parallel to the plane defined by the pyridine N atoms (dihedral angle ≤1.8o). The distances between the bottom and the center of the C60 guest and the pyridine nitrogen atom plane were 1.614 and 4.853 Å (Figure 4c), respectively. These values provide quantitative support for what would be obtained from simple visual inspection of the structure, namely that the C60 is bound to the concave side of cavity and nearly half of the fullerene moiety is encapsulated by the P3P6 receptor. Relative to the free host, the binding of C60 results in modest changes in the P3P6 structure. The dihedral angles between the pyridine subunit and the corresponding flanking pyrrole moieties are decreased to 27.9-29.5o and 32.6-41.9o, respectively, with small differences respect to the three different pyridine moieties due to the alternate five-six membered ring surface of C60. Compared to the free P3P6 macrocycle (in which the distance between the γ-carbons of the pyridine subunits are identical at 5.045 Å), the distance between the γ-carbons of the pyridine subunits is decreased (to 4.248-4.665 Å; cf. Figure 4a). On this basis we infer
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that binding of C60 leads to a rotation about the bridging pyridine subunits allowing the pyridine planes to move closer to the bound C60 guest.
= 3.555 Å; Figure S16). This results in what is presumably a greater π-surface overlap in the case of the 2:1 species relative to the 1:1 complex. In the 2:1 complex, on P3P6 host molecule is rotated ca. 60o relative to the other P3P6 macrocycle; presumably, this avoids steric clashes and maximizes the extent of encapsulation (Figure 5a and b).
Figure 4. Single crystal X-ray structure of the 1:1 complex between P3P6 and C60 seen in crystals grown by allowing n-hexane to diffuse into a toluene solution containing one stoichiometric equiv of each species. a) Top view and b) side view, c) stick view showing the interactions between C60 and the P3P6 host, and crystal packing pattern of the 1:1 complex in d) top and e) side view. The small red spheres (from bottom to top) indicate, respectively, the centroids of the plane defined by the pyridine nitrogen atoms, the midpoint of the six-membered ring of C60, closest to the receptor, and the geometric center of the fullerene as a whole.
Figure 5. Single crystal X-ray structure of P3P6•C60 2:1 complex. (a) Top view and (b) side view, and crystal packing pattern of the 2:1 complex in c) top and d) side views. Toluene molecules have been omitted for clarity.
A few other interactions between P3P6 and C60 are noteworthy. Firstly, the average distance between the geometric center of the three pyridine rings to the nearest carbon atoms of C60 is 3.402 Å, whereas the corresponding average distance is 3.622 Å in the case of the six pyrrole subunits (Figure S13). These distances are shorter than the sum of van der Waals radii, leading us to suggest that π-π interactions help stabilize the 1:1 P3P6•C60 complex in the solid state. Second, several of the pyrrole alkyl substituents, which along with the meso-phenyls groups, define the rim of the overall bowl-like structure, reside close to the bound C60 guest (average carbon-carbon distance = 3.723 Å; Figure S13). This is consistent with the presence of stabilizing C–H-π interactions between the host and the guest. Finally, the average distance between the pyridine and pyrrole nitrogen atoms and the nearest carbon atoms of the bound C60 is ca. 3.22 Å (Figure 4e and S13), which may reflect a stabilizing interaction between these heterocyclic nitrogen atoms and the C60 guest. As shown in Figure 4d, the 1:1 P3P6•C60 complex packs in a zigzag pattern which is defined by repeating units consisting of two P3P6•C60 moieties oriented in opposite directions. The distance between the two centroids of the C60 guests in ensuing repeat units is 13.210 Å (Figure S14). Within the zigzag array, each C60 molecule is surrounded by three P3P6 macrocycles in addition to the one that defines the monomeric 1:1 host-guest complex. The distances between the nearest carbons of fullerene and peripheral alkyls are 3.470, 3.512, and 3.584 Å, respectively (Figure S15). These short distances provide support for the contention that intermolecular CH-π interactions between adjacent P3P6•C60 complexes play a central role in stabilizing the observed packing. Crystals of the 2:1 complex between P3P6 and C60 suitable for X-ray diffraction analysis were obtained via the slow diffusion of n-heptane into a toluene solution containing the host and guest in a 2:1 molar ratio. In this case, a well-encapsulated sandwich structure was observed in the solid state. While the overall arrangement clearly differs from that of the corresponding 1:1 complex discussed above, the key distances between the bound C60 and the two P3P6 hosts, as well as their conformations, are similar in the two complexes (Figure 5a). In the 2:1 complex, the pyridine plane is oriented in a face-to-face fashion relative to the fivemembered ring of the C60 guest (average center-to-center distance
Much more substantial differences between the 1:1 and 2:1 complexes are seen in the packing diagram. In contrast to the zigzag arrangement found for the 1:1 complex, the 2:1 complex packs in a linear fashion with the repeating units containing only one 2:1 host guest complex (Figure 5c and d). In this latter structure, the distance (16.692 Å) between the centroids of the adjacent C60 guests is larger than that in the 1:1 complex (Figure S17), which could reflect a relatively looser level of packing. Based on the observed arrangements of host and guest, the driving force for the inter-complex aggregation seen in the solid state is thought to involve van der Waals dispersion forces coupled with weak π-π interactions between parallel pyrrole units in adjacent complexes (pyrrole-pyrrole distance = 3.556 Å; Figure S18). The disparity in structures (2:1 vs. 1:1) seen in the solid state, coupled with the difficulties associated with defining the solution phase stoichiometry encountered in the early studies of porphyrinfullerene recognition by Boyd et al.,2a prompted us to explore the energetics of complex formation at the B3LYP/6-31G(d) level. Optimized structures of both the 1:1 and 2:1 P3P6•C60 complexes were calculated based on their crystal structures and found to be in good agreement with the experimental data (Figure S19). The 1:1 and 2:1 complexes were found to be energetically similar, with binding energies of 130 and 126 meV, respectively. Both complexes were found to be rather insensitive to slight distortions in the binding arrangement, including the C60 – host distance and the relative orientation of the two P3P6 subunits in the case of the 2:1 complex (Figure S20-21). This insensitivity to geometric deviations and the similarity in binding energies for the 1:1 and 2:1 complexes provides theoretical support for the fact that both limiting forms could be observed in the solid state upon varying the crystallization conditions. On the other hand, no cooperative benefit for formation of a 2:1 complex was predicted. Thus, in dilute condition where the concentration of P3P6 is low, 1:1 complexes with C60 were expected to dominate, as found by experiment. In conclusion, a simple, one-pot synthesis of an expanded rosarin from the known precursor P1P2 has been developed. The resulting bowl-like system (P3P6) acts as a stand-alone receptor for C60. In contrast to the corresponding free meso-substituted porphyrins, P3P6 stabilizes well-characterized complexes with this quintessential fullerene both in organic solution and in the3
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solid state. The fact that complexation of C60 can be achieved without the need to create elaborated constructs augurs well for the use of this and related systems to create new porphyrinoidfullerene materials that could see use in a range of application areas where controlled self-assembly is useful. Studies along these lines are currently in progress.
ASSOCIATED CONTENT Supporting Information Experimental details and characterization data. This material is available free of charge via the Internet at http://pubs.acs.org.” AUTHOR INFORMATION
Corresponding Author
[email protected];
[email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENT The work in Austin was supported by the National Science Foundation (CHE-1402004 to J.L.S.) and the Robert A. Welch Foundation. This research at Yonsei University was supported by the Global Research Laboratory Program (2013K1A1A2A02050183) funded by the Ministry of Science, ICT & Future, Korea (D.K.). The quantum mechanical calculations were supported by the National Institute of Supercomputing and Network (NISN)/Korea Institute of Science and Technology Information (KISTI) with supercomputing resources including technical support (KSC2015-C3-024).
REFERENCES (1) (a) Guldi, D. M. Chem. Soc. Rev. 2002, 31, 22. (b) Fukuzumi, S.; Ohkubo, K.; D'Souza, F.; Sessler, J. L. Chem. Commun. 2012, 48, 9801. (c) Umeyama, T.; Imahori, H. Photosynth.Res. 2006, 87, 63. (d) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res. 2009, 42, 1890. (2) (a) Boyd, P. D. W.; Hodgson, M. C.; Rickard, C. E. F.; Oliver, A. G.; Chaker, L.; Brothers, P. J.; Bolskar, R. D.; Tham, F. S.; Reed, C. A. J. Am. Chem. Soc. 1999, 121, 10487. (b) Olmstead, M. M.; Costa, D. A.; Maitra, K.; Noll, B. C.; Phillips, S. L.; Van Calcar, P. M.; Balch, A. L. J. Am. Chem. Soc. 1999, 121, 7090. (c) Boyd, P. D. W.; Reed, C. A. Acc. Chem. Res. 2005, 38, 235. (3) (a) Sun, D.; Tham, F. S.; Reed, C. A.; Chaker, L.; Burgess, M.; Boyd, P. D. W. J. Am. Chem. Soc. 2000, 122, 10704. (b) Hosseini, A.; Taylor, S.; Accorsi, G.; Armaroli, N.; Reed, C. A.; Boyd, P. D. W. J. Am. Chem. Soc. 2006, 128, 15903. (4) Wu, Z.-Q.; Shao, X.-B.; Li, C.; Hou, J.-L.; Wang, K.; Jiang, X.-K.; Li, Z.-T. J. Am. Chem. Soc. 2005, 127, 17460. (5) (a) Tashiro, K.; Aida, T.; Zheng, J.-Y.; Kinbara, K.; Saigo, K.; Sakamoto, S.; Yamaguchi, K. J. Am. Chem. Soc. 1999, 121, 9477. (b) Zheng, J. Y.; Tashiro, K.; Hirabayashi, Y.; Kinbara, K.; Saigo, K.; Aida, T.; Sakamoto, S.; Yamaguchi, K. Angew. Chem., Int. Ed. 2001, 40, 1858. (c) Shoji, Y.; Tashiro, K.; Aida, T. J. Am. Chem. Soc. 2010, 132, 5928. (d) Zhang, C.; Wang, Q.; Long, H.; Zhang, W. J. Am. Chem. Soc. 2011, 133, 20995. (6) (a) Sánchez-Molina, I.; Grimm, B.; Krick Calderon, R. M.; Claessens, C. G.; Guldi, D. M.; Torres, T. J. Am. Chem. Soc. 2013, 135, 10503. (b) Sanchez-Molina, I.; Claessens, C. G.; Grimm, B.; Guldi, D. M.; Torres, T. Chem.Sci. 2013, 4, 1338. (c) Shimizu, S.; Nakano, S.; Hosoya, T.; Kobayashi, N. Chem. Commun. 2011, 47, 316. (d) Nakano, S.; Kage, Y.; Furuta, H.; Kobayashi, N.; Shimizu, S. Chem. Eur. J. 2016, 22, 7706. (7) (a) Yoshida, K.; Osuka, A. Chem. Asian J. 2015, 10, 1526. (b) Yoshida, K.; Osuka, A. Chem. Eur. J. 2016, 22, 9396. (8) (a) Atwood, J. L.; Koutsantonis, G. A.; Raston, C. L. Nature 1994, 368, 229. (b) Suzuki, T.; Nakashima, K.; Shinkai, S. Chem. Lett. 1994, 699. (c) Haino, T.; Yanase, M.; Fukazawa, Y. Angew.
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Chem., Int. Ed. Engl. 1997, 36, 259. (d) Atwood, J. L.; Barbour, L. J.; Raston, C. L.; Sudria, I. B. N. Angew. Chem., Int. Ed. 1998, 37, 981. (9) Yoshida, Z.-i.; Takekuma, H.; Takekuma, S.-i.; Matsubara, Y. Angew. Chem., Int. Ed. Engl. 1994, 33, 1597. (10) (a) Moreira, L.; Calbo, J.; Krick Calderon, R. M.; Santos, J.; Illescas, B. M.; Arago, J.; Nierengarten, J.-F.; Guldi, D. M.; Orti, E.; Martin, N. Chem.Sci. 2015, 6, 4426. (b) Bhattacharya, S.; Sharma, A.; Nayak, S. K.; Chattopadhyay, S.; Mukherjee, A. K. J. Phys. Chem.B 2003, 107, 4213. (11) (a) Mizyed, S.; Georghiou, P. E.; Bancu, M.; Cuadra, B.; Rai, A. K.; Cheng, P.; Scott, L. T. J. Am. Chem. Soc. 2001, 123, 12770. (b) Sygula, A.; Fronczek, F. R.; Sygula, R.; Rabideau, P. W.; Olmstead, M. M. J. Am. Chem. Soc. 2007, 129, 3842. (c) Dawe, L. N.; AlHujran, T. A.; Tran, H.-A.; Mercer, J. I.; Jackson, E. A.; Scott, L. T.; Georghiou, P. E. Chem. Commun. 2012, 48, 5563. (d) Yokoi, H.; Hiraoka, Y.; Hiroto, S.; Sakamaki, D.; Seki, S.; Shinokubo, H. Nat. Commun. 2015, 6, 8215. (e) Yanney, M.; Fronczek, F. R.; Sygula, A. Angew. Chem., Int. Ed. 2015, 54, 11153. (12) (a) Pham, D.; Cerón Bertran, J.; Olmstead, M. M.; Mascal, M.; Balch, A. L. Org. Lett. 2005, 7, 2805. (b) Bredenkötter, B.; Henne, S.; Volkmer, D. Chem. Eur. J. 2007, 13, 9931. (13) (a) Yamamura, M.; Saito, T.; Nabeshima, T. J. Am. Chem. Soc. 2014, 136, 14299. (b) Yamamura, M.; Hongo, D.; Nabeshima, T. Chem.Sci. 2015, 6, 6373. (14) (a) Fukuzumi, S.; Ohkubo, K.; Kawashima, Y.; Kim, D. S.; Park, J. S.; Jana, A.; Lynch, V. M.; Kim, D.; Sessler, J. L. J. Am. Chem. Soc. 2011, 133, 15938. (b) Davis, C. M.; Lim, J. M.; Larsen, K. R.; Kim, D. S.; Sung, Y. M.; Lyons, D. M.; Lynch, V. M.; Nielsen, K. A.; Jeppesen, J. O.; Kim, D.; Park, J. S.; Sessler, J. L. J. Am. Chem. Soc. 2014, 136, 10410. (c) Kim, D. S.; Chang, J.; Leem, S.; Park, J. S.; Thordarson, P.; Sessler, J. L. J. Am. Chem. Soc. 2015, 137, 16038. (15) Sessler, J. L.; Weghorn, S. J.; Morishima, T.; Rosingana, M.; Lynch, V.; Lee, V. J. Am. Chem. Soc. 1992, 114, 8306. (16) (a) Sessler, J. L.; Seidel, D. Angew. Chem., Int. Ed. 2003, 42, 5134. (b) Saito, S.; Osuka, A. Angew. Chem., Int. Ed. 2011, 50, 4342. (17) Setsune, J.-i.; Toda, M.; Yoshida, T.; Imamura, K.; Watanabe, K. Chem. Eur. J. 2015, 21, 12715. (18) Ishimaru, Y.; Shimoyama, N.; Fujihara, T.; Watanabe, K.; Setsune, J.-i. Chem. Asian J. 2015, 10, 329. (19) (a) Setsune, J.-i.; Toda, M.; Watanabe, K.; Panda, P. K.; Yoshida, T. Tetrahedron Lett. 2006, 47, 7541. (b) Setsune, J.-I.; Watanabe, K. J. Am. Chem. Soc. 2008, 130, 2404. (20) (a) Cliffel, D. E.; Bard, A. J. J. Phys. Chem. 1994, 98, 8140. (b) Nakanishi, I.; Ohkubo, K.; Fujita, S.; Fukuzumi, S.; Konishi, T.; Fujitsuka, M.; Ito, O.; Miyata, N. J. Chem. Soc., Perkin Trans. 2 2002, 1829. (21) When lower concentrations, closer to ca. 1.00 mM were used for the Job plot and titrations, a maximum at a mole ratio of ca. 0.4 was seen (Figures S8-10). This is consistent with an ancillary interaction between a second fullerene and the 1:1 P3P6•C60 complex that it is presumed to dominate in solution. This deviation to a lower mole fraction stands in contrast to the skewing of the Job plot to higher mole fractions that would be expected were small quantities of the 2:1 receptor-fullerene complex being formed.
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