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Relative populations of three energy-lowest IPR (isolated-pentagon-rule) isomers of Eu@C88 are computed using the Gibbs energy based on characteristics from density functional theory and MP2 calculations (M06-2X/3-21G∼SDD entropy term, and the MP2=FU/6-31G*∼SDD or B2PLYPD=FU/6-31 + G*∼SDD energetics). The calculations predict coexistence of three isomers, in agreement with extraction using a polar solvent, and offer a possible explanation why the Eu@C 2(27)-C88 species should prevail with a non-polar solvent. Role of extraction solvents and catalysis is thus pointed out.

Relative equilibrium populations of the IPR (isolated-pentagon-rule) isomers of Gd@C82 under the high-temperature synthetic conditions are calculated. The calculations are based on the Gibbs energy derived using characteristics from the density functional theory calculations (B3LYP/3-21G ∼ SDD entropy term, B2PLYPD/6-31+G* ∼ SDD energetics). In agreement with observations, Gd@C 2v (9)-C82 is the prevailing isomer while Gd@C s (c; 6)-C82 is predicted as a minor species.

Computations can help understanding of various forms of isomerism in endohedral fullerenes. They can confirm the observed isomers, predict their abundancies and properties, deduce approximate temperature during synthesis (or other parameters difficult to measure) from observed isomeric ratios. These features will be illustrated on topical isomeric systems like Ce@C82, Eu@C86, C86, (H2O)3@C84, nanoelectronic devices based on fullerenes and others. Factors influencing comparison of experiments and calculations will be also discussed like kinetics, catalysis, solubility, metal sources, effects of the crystal environment.

Stability and spectra of rotamers of a previously via Prato reaction prepared conjugate of dimetallofullerene La2@C80 and dodecafluoro-subphthalocyanine with summary formula C113H10BF12La2N7O and bridging over the cage C–C bond between five- and six-membered rings are calculated. The inter-rotameric energetics is evaluated at the M06-2X/6-311G* ∼ SDD level while the entropy term with the M06-2X/3-21G ∼ SDD approach. The rotamer most-populated at room and higher temperatures has a structure in which both the nitrogen atom of the pyrrolidine ring and the dodecafluoro-subphthalocyanine moiety are inclined toward the five-membered ring belonging to the bridged-over C–C bond. The vibrational and electronic spectra are simulated and the latter spectrum agrees with the observed features. The calculated nanocarbon system is about the largest of its type computationally treated so far.

Position and motion of the internal metals in endohedral metallofullerenes show significant influences, via strong metal-cage interactions, on the structures and properties, especially the chemical reactivity, on the whole molecules. First, the cages structures of the resulting endohedrals are evidently dictated by the encapsulated metallic species, even when only one metal is inside (e.g. Yb@C2n). Then, the motional behavior of the internal cluster is sometimes highly temperature sensitive, and it is effective enough to alter the whole molecular symmetry (e.g. Sc2C2@C80). Moreover, the encapsulated metals can also differentiate the chemical reactivity of cage carbons (e.g. Y@C82), while the paramagnetic species always tend to pursue a close-shell electronic configuration whenever possible (e.g. La@C2n). Finally, the [5,5]-carbons in non-IPR metallofullerenes are effectively stabilized by the internal metals via strong coordination which can be probed by exohedral modification (e.g. La2@C72).

There are several stability problems important for fullerenic species, namely relative populations of (i) isomeric endohedrals, (ii) non-isomeric metallofullerenes differing in the number of the encapsulated metal atoms placed in still isomeric carbon cages, and (iii) monometallofullerenes with different metals encapsulated in one selected carbon cage. The related computational approaches are illustrated on endohedrals with encapsulated La and its congeners, evaluated using various density-functional theory (DFT) treatments or the second order Moller-Plesset perturbation theory (MP2). One of the illustrative examples treats encapsulations in the T_d IPR C76 cage using the metal series Al, Sc, Y, La, and Ac. Three formal reaction steps can be considered with the encapsulations: (i) double- (or triple-) ionization of the free metal, (ii) double (or triple-) charging of the empty cage, and (iii) placing the metal di- (or tri-) cation into the di- or (tri-) anionic cage. The (ii) energy change is identical for all members of the series, and the (iii) terms should be similar as they are controlled by electrostatics. Hence, only the (i) energy term comes as a differentiating factor. In other words, the free-metal ionization potentials should actually represent the critical yield-controlling parameter.The computed relative potential-energy changes upon encapsulation δE and the relative observed ionization potentials of the free atoms δIP should (according to the above three-step analysis) be correlated. Interestingly, Ac has the second best encapsulation energy after La in the series.

Water and water-dimer encapsulations into D5h-C70 and D2(22)-C84 & D2d(23)-C84 fullerenes are evaluated. The water-dimer equilibrium populations are computed using the potential-energy change from the ab initio G3 theory and anharmonic partition functions from the MP2/AUG-cc-pVQZ approach. The encapsulation energetics is treated at the M06-2X/6-31++G** level and it is found, for example, that the water-dimer storage in C84 is attractive, yielding an energy gain of more than 10kcal/mol. This substantial encapsulation energy together with the computed temperature increase of the water-dimer population in the saturated steam suggest that the (H2O)2@Cn endohedrals could also be produced in a high-temperature/high-pressure approach similarly to encapsulation of rare gases in fullerenes.

Location recognition in molecular-scale provides valuable information on positional relationship, absolute conformation and dynamics of molecules. They can be used for deep understanding of nature of functional molecular materials or for elucidating biological processes. Therefore, a number of molecular probes have been developed and reported to date for molecular recognition and location determination. Recently, our group has reported anisotropic magnetism of an endohedral metallofullerene (EMF) Ce@C82 both in a pristine form and chemically functionalized form.1,2 Remarkably, the anisotropy of the magnetism which is led by the encapsulated Ce atom was slightly influenced by the carbene addition reaction. In addition, absolute position of the hydrogen atoms of the addend were assigned by the difference in the effective distance of the anisotropic magnetism, which is decreased with the cube of distance between the Ce and hydrogen atoms. In this study, we have developed Ce@C82 derivatives that demonstrate a potential of EMFs for location recognition in molecular-scale. Five derivatives of Ce@C82 were successfully synthesized and isolated by a similar radical reaction that we reported recently.3 Addition position of the two isomers of them were unambiguously determined by a single crystal structure and/or characteristic absorption spectra. DFT calculations provide reasonable criteria to predict the addition position by the radical coupling reaction. The carbon atoms that have high SOMO density and positive charge are preferable for the addition position. Temperature-dependent 1H-NMR measurements demonstrated unique paramagnetic shifts that are derived by the anisotropic magnetism of the Ce atom. And further analysis of the shifts revealed the dependency of the shift based on the distance and relative position from the Ce atom. This result indicates that the paramagnetic shifts provide location information of the addend. Therefore, Ce@C82 is capable to act as an molecular probe for location recognition of atoms by utilizing anisotropic magnetism of an EMF. Reference: 1. T. Wakahara et al. J. Am. Chem. Soc. 2004, 126, 4883-4887. 2. Y. Takano et al. J. Am. Chem. Soc. 2009, 131, 9340-9346. 3. Y. Takano et al. J. Am. Chem. Soc. 2008, 130, 16224-16230.

The isolated pentagon rule (IPR) states that stable fullerenes have each of their 12 pentagons surrounded by five hexagons. On the contrary, in 2000, that idea was altered by the discovery of the first non-IPR fullerenes, Sc2@C66 and Sc3N@C68. Themolecular structure of Sc2@C66 was assigned to possess a C2v(4348)-C66 cage that contained two sets of double fused pentagons by using 13C NMR spectroscopy and powder X-ray diffraction data analysis. However, that structure has remained a long-standing controversy, since it is thermodynamically unfavorable. Here, we demonstrate definitively that Sc2@C66 does not have the structure that was long believed to be but a brand new type. 2D-NMR spectroscopic and single-crystal X-ray analysis disclose that Sc2@C66 has a C2v(4059)-C66 cage containing two sets of unsaturated linear triquinanes (ULTs), in which three pentagons abut one another and two scandium ions are located within the folds of each of the ULT units. Our identication of Sc2@C66 as Sc2@C2v(4059)-C66 shows that new motifs in carbon cage geometry continue to be discovered and calls attention to the ULT unit, whose aromaticity and coordination chemistry deserve further study.

Phthalocyanines (Pcs) are planar, two-dimensional aromatic pophyrinoids which possess outstanding structural, optical and electrical properties as well as stability that render them perfect building blocks for the incorporation into multifunctional materials. Similarly, Ih -Sc3N@C80 fullerene – the most abundant member of the fullerenes family after C60 and C70 – in addition to have excellent electron-accepting properties, provides conditions for an extra stabilization of charge-separated states due to the presence of the internal Sc3N species. This makes Ih -Sc3N@C80 an ideal molecular partner for photo- and electroactive molecular systems such as Pcs. Although several reports have appeared on the preparation of covalent Sc3N@Ih-C80 ensembles, there is no use of Ih -Sc3N@C80 for the preparation of non-covalent assemblies. In this context, plenty of supramolecular systems arranged via coordination interactions have been successfully demonstrated for Pc-C60 supramolecular dimers and trimers. Low accessability of non-covalent supramolecular systems with Ih -Sc3N@C80 is mainly caused by the more sophisticated synthesis and purification of the corresponding fullerene derivatives. Herein, we report a novel example of donor-acceptor Pc/Ih -Sc3N@C80 supramolecular dimers assembled via metal-ligand coordination interactions between Zn(II)Pcs and pyridil-substituted Ih -Sc3N@C80 or C60 fullerene. Photophysical (ground- and excited state) and electrochemical studies on these ensembles showed that depending on the electron-donor or electron-acceptor character of the ZnPcs, a switchable electron transfer reactivity occurs in the case of the Ih -Sc3N@C80 supramolecular systems, revealing the ability for this endohedral metallofullerene to behave either as electron donor or electron acceptor unit.

The water-dimer formation and its encapsulation into D2(22)-C84 and D2d(23)-C84 fullerenes is computed, following similar evaluations [1] with C60. The water-dimer equilibrium populations are calculated using the potential-energy change from the ab initio G3 theory and anharmonic partition functions from the MP2/AUG-cc-pVQZ approach. The encapsulation energetics is treated at the M06-2X/6-31++G** level and it is found that the water-dimer storage in C84 is attractive, yielding an energy gain of more than 10kcal/mol. This substantial encapsulation energy together with the computed temperature increase of the water-dimer population in the saturated steam suggest that the (H2O)2@C84 endohedrals could be produced in a high-temperature/high-pressure approach similarly to encapsulation of rare gases in fullerenes. [1] F. Uhlik, Z. Slanina, S.-L. Lee, B.-C. Wang, L. Adamowicz, S. Nagase, J. Comput. Theor. Nanosci. 12, 959 (2015); 12, 2622 (2015).

The inside metals of endohedral metallofullerenes (EMFs) lead remarkable features, such as unique molecular structures, and magnetic and electronic properties.[1] Among EMFs, paramagnetic EMFs are of particular interest because interplay between π-electron spins on the fullerene cage and inside metal atoms is expected to produce unconventional magnetic features. Unique properties of paramagnetic EMFs may lead to unique chemical reactivities. In this regard, despite the former efforts, much work is still needed for a better control on the chemical reactivity of the increasing variety of EMFs. For an easier accessibility to EMFs based materials, a wider availability of chemical functionalization methods on EMFs is required. Meanwhile, La@C82 has extensively been investigated as a prototype paramagnetic fullerene because it is the first EMF which was reported the successful isolation for the first time.[2] Moreover, it was demonstrated that a family of lanthanum containing fullerenes were produced and that extraction with toluene yielded abundantly La@C82. La@C82 has an electronic structure which is best described as [La]3+[C82]3- with an open-shell electronic character that is a consequence of transferring three electrons from lanthanum to C82(Scheme). The resulting electron spin imposes unique chemical reactivity, radical character, and magnetic properties. In this talk, I will present remarkable chemical reactivities and molecular properties of paramagnetic EMFs; La@C 2v -C82,[3] La@Cs -C82 [4] and Ce@C 2v -C82.[5] Their unique characteristics cannot be expected in ordinary chemical compounds and empty fullerenes, and are promising for creating novel electronic and magnetic materials with utilizing their unprecedented electronic properties. References: [1] (For reviews of EMFs) (a) Chemistry of Nanocarbons; Akasaka, T., Wudl, F., Nagase, S., Eds.; Wiley: Chichester, 2010. (b) Popov, A. A. et al. Chem. Rev. 2013, 113, 5989. [2] Chai, Y. et al. J. Phys. Chem. 1991, 95, 75648. [3] (a) Takano, Y. et al. J. Am. Chem. Soc. 2008, 130, 16224. (b) Takano, Y. et al. Chem. Commun. 2010, 46, 8035. [4] Takano, Y. et al. J. Am. Chem. Soc. in press. DOI: 10.1021/ja509407j [5] Takano, Y.et al. J. Am. Chem. Soc. 2009, 131, 9340. Figure 1

Very recently, a new member of the lanthanum-containing metallofullerene family has been isolated and its structure determined from X-ray crystallographic analysis, namely [1] La2@C76(Cs,17490), even with two pairs of connected pentagons, hence violating the isolated-pentagon rule (IPR). In order to explain the interesting observation, a computational treatment is suggested for evaluations of the relative populations of non-isomeric metallofullerenes. As a comparative reference structure, the most stable La@C76 isomer is selected - the IPR-C76(Td)-cage based endohedral La@C76(Td). It is found that in the relevant temperature region the La2@C76(Cs,17490) species should be considerably more populated compared to La@C76(Td). The new computational stability treatment is applicable to a wider spectrum of non-isomeric metallofullerenes. [1] M. Suzuki, N. Mizorogi, T. Yang, F. Uhlik, Z. Slanina, X. Zhao, M. Yamada, Y. Maeda, T. Hasegawa, S. Nagase, X. Lu, T. Akasaka, Chem. Eur. J. 19, doi:10.1002/chem.201302821 (2013).

Endohedral metallofullerenes (EMFs) have attracted special interest as new spherical molecules because they have unusual physical and chemical properties that are imparted by the encapsulated metal atoms.[1] Among the fullerenes in general, paramagnetic EMFs have garnered much attention because of their unique electronic and magnetic properties, quite different from the closely related non-paramagnetic endofullerenes. La@C82 has extensively been investigated as a prototype paramagnetic fullerene because it is the first endohedral metallofullerene which was reported the successful isolation for the first time. [2] Moreover, it was demonstrated that a family of lanthanum containing fullerenes were produced and that extraction with toluene yielded abundantly La@C82. La@C82 has an electronic structure which is best described as [La]3+[C82]3- with an open-shell electronic character that is a consequence of transferring three electrons from lanthanum to C82 (Scheme).[3] The resulting electron spin imposes a unique chemical reactivity comparable to that of a radical character.[4] The latter is believed to induce magnetism[5] and enhance electron conductivity.[6] In this regard, our group has investigated and revealed unprecedented molecular properties of La@C82. In this talk, I will present its unique radical reactivity,[4] photo-induced intramolecular electron transfer,[7] and the SAM demonstrating electrochemical switching[5] based on La@C82. References: [1] (For reviews of EMFs) (a) Chemistry of Nanocarbons; Akasaka, T., Wudl, F., Nagase, S., Eds.; Wiley: Chichester, 2010. (b) Chaur, M. N. et al. Angew. Chem. Int. Ed. 2009, 48, 7514. (c) Popov, A. A. et al. Chem. Rev. 2013, 113, 5989. [2] Chai, Y. et al. J. Phys. Chem. 1991, 95, 75648. [3] Nagase, S. et al. J. Chem. Soc., Chem. Commun. 1994, 1837. [4] (a) Takano, Y. et al. J. Am. Chem. Soc. 2008, 130, 16224. (b) Takano, Y. et al. Chem. Commun. 2010, 46, 8035. [5] Takano, Y. et al. Chem. Commun. 2013, 49, 8145. (Selected for front cover) [6] Sato, S. et al. J. Am. Chem. Soc. 2011, 133, 2766. [7] Takano, Y. et al. J. Am. Chem. Soc. 2012, 134, 16103.

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