Fullerene Cage Research Articles

Spherical trihedral metallo-borospherenes

The discovery of borospherenes unveiled the capacity of boron to form fullerene-like cage structures. While fullerenes are known to entrap metal atoms to form endohedral metallofullerenes, few metal atoms have been observed to be part of the fullerene cages. Here we report the observation of a class of remarkable metallo-borospherenes, where metal atoms are integral parts of the cage surface. We have produced La3B18– and Tb3B18– and probed their structures and bonding using photoelectron spectroscopy and theoretical calculations. Global minimum searches revealed that the most stable structures of Ln3B18– are hollow cages with D3h symmetry. The B18-framework in the Ln3B18– cages can be viewed as consisting of two triangular B6 motifs connected by three B2 units, forming three shared B10 rings which are coordinated to the three Ln atoms on the cage surface. These metallo-borospherenes represent a new class of unusual geometry that has not been observed in chemistry heretofore.

How to Stabilize a Heptagon-Containing C80 Cage by Endohedral Derivation.

Nonclassical fullerene is a new member of the fullerene family. In the present work, a systematic investigation on LaxSc3-xN@C80 (x = 0-3) covering both classical and nonclassical C80 cages was performed utilizing density functional theory combined with statistical mechanics. At absolute zero, LaSc2N@Hept(6)-Cs(2)-C80 with a heptagon-containing nonclassical carbon is the second most stable isomer, whereas at the temperature range of endohedral metallofullerene (EMF) formation, due to the large vibrational frequencies, LaSc2N@Hept(6)-Cs(2)-C80 is the third most abundant isomer, and its mole fraction is very low, accounting for the low experimental yield of LaSc2N@Hept(6)-Cs(2)-C80; La2ScN@Hept(6)-Cs(2)-C80, and La3N@Hept(6)-Cs(2)-C80 are the overwhelming isomers of the corresponding series, but compared with the cases of Sc3N@C80 and LaSc2N@C80, La2ScN and La3N clusters suffer much larger constraints from the C80 cages, perhaps preventing the synthesis of La2ScN@C80 and La3N@C80 species. Because of the large mole fractions and large electron donation and back-donation of La2ScN@Hept(6)-Cs(2)-C80 and La3N@Hept(6)-Cs(2)-C80, it can be inferred that La2ScN and La3N clusters may be used to stabilize some other larger nonclassical fullerene cages. This work will provide useful insights into the origins of stabilization of nonclassical fullerene cages by endohedral derivation and guidelines for synthesis EMF with nonclassical cages.

Non-Functionalized Fullerenes and Endofullerenes in Aqueous Dispersions as Superoxide Scavengers.

Endohedral metal fullerene are potential nanopharmaceuticals for MRI; thus, it is important to study their effect on reactive oxygen species (ROS) homeostasis. Superoxide anion radical is one of the key ROS. The reactivity of aqueous dispersions of pristine (non-functionalized) fullerenes and Gd@C82 endofullerene have been studied with respect to superoxide in the xanthine/xanthine oxidase chemiluminescence system. It was found that C60 and C70 in aqueous dispersions react with superoxide as scavengers by a similar mechanism; differences in activity are determined by cluster parameters, primarily the concentration of available, acting molecules at the surface. Gd endofullerene is characterized by a significantly (one-and-a-half to two orders of magnitude) higher reactivity with respect to C60 and C70 and is likely to exhibit nanozyme (SOD-mimic) properties, which can be accounted for by the nonuniform distribution of electron density of the fullerene cage due to the presence of the endohedral atom; however, in the cell model, Gd@C82 showed the lowest activity compared to C60 and C70, which can be accounted for by its higher affinity for the lipid phase.

Scandium Tetrahedron Supported by H Anion and CN Pentaanion inside Fullerene C80.

Endohedral metallofullerenes have greatly expanded the range of the fullerene family due to their nesting structure and unusual encapsulated clusters protected by a fullerene cage. Herein, we report a metallofullerene Sc4CNH@Ih-C80, which has a scandium tetrahedron supported by H and CN anions inside fullerene C80. Sc4CNH@Ih-C80 has a rare multilayer nesting structure, and the internal Sc4CNH is the most complex endohedral cluster disclosed to date. Sc4CNH@Ih-C80 has so many bonding types (metal-carbide, metal-nitride, and metal-hydride), which weave a polyhedron of Sc4CNH clusters. This work shows that the endohedral metallofullerenes have the potential to build inorganic nesting polyhedra that have distinctive architectures and unique electronic properties. Sc4CNH@Ih-C80 was synthesized by means of the arc-discharge method using scandium and graphite under the mixed atmosphere of hydrogen, nitrogen, and helium. It is the first time to disclose an unprecedented metal-hydride bond in a fullerene cage. This result shows that the endohedral fullerenes bearing hydrogen species can be synthesized by the arc-discharge technique under an atmosphere of hydrogen. This work demonstrates that a fullerene cage can be an ample carrier to encapsulate unusual cluster moieties.

Endohedral metallofullerene single molecule magnets

Nanoscale magnetic materials have been attracting enormous interests during the past few decades due to the rapid development of high-density magnetic storage devices. A breakthrough in nanomagnetism is the discovery of single molecule magnets (SMMs), which exhibit slow relaxation and quantum tunneling of the magnetization resulted from a molecular-based blocking anisotropy, and thus have potential applications in high-density data storage, molecular spintronics and quantum computing. Since the report of Mn12-complex as the first SMM by Sessoli et al. in 1993, a large number of SMMs based on organometallic coordination compounds have been synthesized. Compared to the traditional bulk magnets, the magnetic properties of SMMs are determined by their instrinsic spin structures resulting in slow magnetic relaxation. SMM is characterized by a bi-stable magnetic ground state and a certain spin-reversal barrier ( U eff). Additionally, hysteresis loops can be observed below the blocking temperature ( T B). Therefore, SMMs with excellent magnetic properties always have high T B and U eff. U eff depends strongly on spin ground state ( S ) and magneto-crystalline anisotropy ( D ), and can be expressed with the formula U eff =| D|S 2. For transition metal-based SMMs, their low magneto-crystalline anisotropies ( D ) result in relative low U eff. In recent years, lanthanide based SMMs have been studied intensively and become the most promising high-performance SMMs, owning to their strong single ion anisotropy. Encapsulating metal atoms or metallic clusters into fullerene cages generate a special class of fullerenes, the so-called endohedral metallofullerenes (EMFs), for which the encapsulation of metal atoms endow EMFs more fascinating properties compared to empty fullerenes. For instance, EMFs are paramagnetic when the entrapped metal ions have unpaired electrons. Furthermore, EMFs were able to show excellent SMM properties when the encapsulated clusters induce appropriate ligand-fields. EMFs with lanthanide open up a new avenue in the field of SMMs in 2012 when single molecule magnetism was proved for the metal nitride clusterfullerene (NCF) DySc2N@ I h-C80. Fullerene cages are stable in air and thus they can protect the magnetic ions from ambient conditions, and the negatively charged nonmetallic atom(s) within the cluster and the negatively charged carbon atoms of fullerene cages provide magnetic anisotropy which is necessary for single molecule magnetism. Moreover, the molecular structures of EMFs can be modulated by varying the encapsulated metal ions, metal cluster and cage isomer; hence the research on EMF-SMMs has been developed rapidly since 2012. Up to now, metal nitride clusterfullerenes (NCFs), metal carbide clusterfullerenes (CCFs), metal oxide clusterfullerenes (OCFs), metal sulfide clusterfullerenes (SCFs), metal cyanide clusterfullerenes (CYCFs) and dimetallofullerenes (di-EMFs) have been confirmed as SMMs. In this paper, we present an exhaustive review on all kinds of EMF-SMMs reported to date including their 1D, 2D and 3D assemblies. We mainly discuss the influences of the types and the numbers of the encapsulated metal ions and non-metal atoms on the magnetic properties of EMF-SMMs. Finally, the prospects and challenges of EMF-SMMs are also discussed.

New Isolated‐Pentagon‐Rule Isomers of Fullerene C96 Captured as Chloro Derivatives

Fullerene C96 possesses 187 isomers obeying the isolated pentagon rule (IPR), from which five, nos. 144, 145, 175, 176 and 183, have been confirmed earlier as chloro derivatives, whereas two isomers in pristine form, nos. 3 and 181, have been detected in fullerene soot as adducts with Ni porphyrinates. High‐temperature chlorination of C96‐containing mixtures afforded crystals of several chloro derivatives C96Cl22/24/26 and the structure elucidation by X‐ray crystallography with the use of synchrotron radiation revealed the presence of new isomers nos. 127, 129, 143, and 146 in the fullerene soot. The structural data on new chloro derivatives C96(144)Cl18/24 have been also obtained. The chlorination patterns of the chlorides are discussed in terms of the formation of isolated C=C bonds and aromatic substructures on the fullerene cages. An overview of all structurally confirmed isomers of C96 fullerene is presented.

Large Carbon Clusters with Entrapped Gadolinium Atoms

Gadolinium metallofullerenes have long shown promise as potential MRI contrast agents. The ability to entrap up to three gadolinium atoms permits a high concentration of metal content per fullerene cage. The protective carbon cage prevents the escape of otherwise toxic free Gd ion. In this presentation, we will discuss purification strategies to isolate gadolinium clusters entrapped within larger carbon cages (C96-C120). We have recently isolated a series of fullertubes, which consist of a nanotube belt of carbons with fullerene endcaps. It is unknown if the entrapped Gd atoms are inside fullerene or fullertube cages.

(Invited) Visualizing the Dynamics of Metallofullerenes with Variable Temperature Single Crystal X-Ray Diffraction

The empty interior space of fullerenes is ready to hold atoms/clusters to become endohedral fullerenes. Metal ions can be encapsulated in various fullerene cages, known as metallofullerenes. The interplay between the encapsulated metal ions and the fullerene cage carbon atoms is fundamental to understanding these molecules. Recently, we succeeded on the visualization of the dynamics of Dy2@Ih (7)-C80-CH2Ph in the crystal lattice1 as well as M3N@Ih (7)-C80 (M3N = Ho2LuN or Lu3N) in the crystal lattice of co-crystals with nickel octaethylporphyrin2 by variable temperature X-ray diffraction, see the following figure for the comparison of the equivalent atomic displacement parameters of heavy atoms. In this contribution, the details of the observed temperature dependent dynamics of the metallofullerenes will be discussed. 1. Liu, F.; Velkos, G.; Krylov, D. S.; Spree, L.; Zalibera, M.; Ray, R.; Samoylova, N. A.; Chen, C.-H.; Rosenkranz, M.; Schiemenz, S.; Ziegs, F.; Nenkov, K.; Kostanyan, A.; Greber, T.; Wolter, A. U. B.; Richter, M.; Büchner, B.; Avdoshenko, S. M.; Popov, A. A., Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal–metal bond. Nat. Commun. 2019, 10, 571.2. Liu, F.; Spree, L., Molecular Spinning Top: Visualizing the Dynamics of M3N@C80 with Variable Temperature Single Crystal X-ray Diffraction. Chem. Commun. 2019, 55, 13000-13003. Figure 1

(Invited) Actinide-Based Buckyball Maracas: Fullerene Cages As Nanocontainers That Stabilize Monometallic and Actinide Clusters inside

Monometallic uranium endohedral fullerene compounds with formula U@C2n where 2n = 72, 74, 76, 78, 80, 82, 84 86, 88 and 90 have been prepared in an arc-discharge reactor using U3O8 as the starting material. Many of these have been purified using HPLC techniques and have been fully characterized using many techniques, including MALDI MS, UV-Vis, electrochemistry, etc, but more importantly, with single crystal X-Ray diffractometry. Interestingly, the majority of these compounds obey the isolated pentagon rule (IPR) so all five-membered rings are adjacent to five six-membered rings, but there are some exceptions, namely U@C76 and U@C80, which possess non-IPR carbon cage structures. The reason for these exceptions is due to strong interactions of U with the cage via the metal 5f orbitals. More interestingly we have observed never-reported U-based clusters with formula U2X (X = C, N, O, and S) encapsulated inside C2n with 2n = 72, 78 and 80. More recently we have isolated UGd@C72 and UGd@C78 and also fully characterized these. The most recent structural and properties on some of these compounds will be presented and discussed.

Volume of the Fullerene Cages of Endofullerenes and Hydrogenated Endofullerenes with Encapsulated Atoms of Noble Gases and Nonadditivity of Their Polarizability

The polarizability of endohedral complexes of fullerenes and fullerene hydrides with atoms of noble gases Ng@СN (N = 20, 24, 28, 30, 36, 50, 60, 70; X = He, Ne, Ar), Kr@СN (N = 28, 30, 36, 50, 60, 70), Xe@Сn (n = 50, 60, 70), C60Hn (n = 2, 6, 18, 36), and C20Hn (n = 2, 6, 12, 20) is studied by the PBE/3ζ level of density functional theory. It is established that the deviation of the calculated average polarizability of endohedral complexes from the additive scheme correlates with the change in the volumes of the СN and C20/60Hn fullerene cages upon encapsulation. The change in volume governs the absolute deviation of the average polarizability from additivity, while its sign depends on the direction of charge transfer in an endohedral complex.

(Invited) Trapping Metallic Oxide Cluster inside Fullerene Cage

The sub-nanometer sized void inside fullerene cage permits the accommodation of a single atom, atomic cluster or even small molecule, resulting in the formations of endohedral fullerenes. Particularly, clusterfullerenes can be formed by encapsulating multiple metallic ions in most cases along with non-metal ions (i.e., N3-, C2 2-, S2-, O2-) inside the fullerene cage. Such an association makes clusterfullerene more functional than empty fullerenes and conventional mono-metallofullerenes. Up to date, a variety of clusterfullerenes have been reported, including metal nitrides, carbides, oxides, sulfides, cyanides and so on. Among them, oxide clusterfullerenes (OCFs) can contain variable oxide clusters (i.e., M4O2, M4O3, M3O and M2O; M=Sc or other metal), yielding one of the most versatile families. Thus, OCFs may provide a more convenient platform for developing new functional molecules and for studying the previously less-explored topics such as formation mechanism of clusterfullerenes.In this Account, we review recent progress in the field of OCFs, including their synthesis, isolation, structural and electrochemical studies as well as the preliminary exploration in their potential functions and applications. Thanks for the concrete crystallographic results of an OCF series, we can track the transition of endohedral cluster and fullerene cage. It is suggested that the configuration and internal dynamics of oxide cluster are highly dependent on not only the cage size but also cage structure. On the other hand, based on the experimental observations, two competitive transformation pathways are established for the majority of OCFs, verifying the bottom-up or top-down formation mechanism. It is also found that the redox behaviors of OCFs are more or less comparable to their isoelectronic species with common cage structure and similar cluster geometry, but varied greatly with the cluster variety (i.e., Sc2O vs Sc4O2-3). The mechanism behind such phenomena has been discussed. In addition, the potential of Dy-based OCFs as single molecular magnets (SMMs) is presented theoretically. Nevertheless, experimental advance remains to be achieved. Figure 1

Encapsulated Yttrium Atoms in Carbon Cages: Spheres or Tubes?

Yttrium clusters entrapped within smaller C60-C90 fullerene cages are well known. However, there is minimal literature for yttrium atoms entrapped in the larger carbon cages. To avoid the separation nightmare that is soot extract, we simplify the mixture by chemically removing co-eluting contaminants. Herein, we describe a selective chemical reaction that effectively serves as a pre-cleanup step prior to introducing HPLC fraction collection. In Stage 2, the enriched Y-based carbon species are readily isolated chromatographically. In this presentation, we describe our two-step purification of yttrium atoms entrapped in the larger carbon cages, (e.g., C92-C102). Subsequent characterization, such as UV-Vis, of these yttrium metallofullerenes are underway.

(Invited) Synthesis and Properties of Endohedral Open-Cage Fullerenes

Open-cage fullerene derivatives are fascinating molecules because a small molecule can be introduced inside the fullerene cage through the opening. When the NMR active molecules are introduced inside the open-cage fullerene derivatives, the resulting endohedral species are used for the study with the encapsulated molecule as a magnetic probe. First, the regioselectivity in the Diels.Alder reaction of an unsymmetrical open-cage C60 derivative with anthracene was studied. By using an encapsulated H2 molecule as a magnetic probe, the product population was successfully evaluated in detail, indicating the formation of approximately ten compounds as major components. The NICS calculations showed a close resemblance to the observed 1H NMR spectrum, which allowed for a facile characterization of the products. Theoretical studies on the formation of all 29 possible anthracene adducts were also performed. The results indicated that the regioselectivity is strongly governed by steric factors, values of the frontier orbital coefficients, and thermodynamic stabilities. Single-crystal X-ray analysis of the dominant compound revealed the supramolecular architecture between the anthracene moiety and the Π-sphere of a neighboring molecule.[1] Second, The H2O/CH2=CH2-type hydrogen-bonding model was experimentally constructed using a water complex of an open-cage C60 derivative, in which an olefinic double bond and a single molecule of H2O are geometrically confined. To investigate OH/Π-type H-bonding, we performed 1H NMR spectroscopic studies that demonstrated the monotonic downfield shift of the proton signal corresponding to H2O with remarkable rotational perturbation by lowering the temperature. From the temperature dependence of the angular momentum correlation time, the interaction energy was quantitatively estimated to be ca. 0.3 kcal/mol. The computational studies were thoroughly conducted to clarify its inherent nature. As a consequence, the orientation of H2O was found to play a prominent role in varying the bonding strength as well as contribution from the electrostatic attraction and orbital-orbital interaction significantly driven by the favorable orbital overlap.[2][1] Probing the Regioselectivity by Encapsulated H2: Diels-Alder Reaction of a Cage-Opened C60 Derivative with Anthracene, Hashikawa, Y.; Murata, Y. Chem. Eur. J. 2019, 25, 2482-2485.[2] H2O/Olefinic-Π Interaction inside a Carbon Nanocage, Hashikawa, Y.; Murata, Y. J. Am. Chem. Soc. 2019, 141, 12928-12938.

(Invited) Excited States of Atoms Encapsulated in the C60 Cage: A Spin-Polarized Time-Dependent Density-Functional Study

Among various endohedral fullerenes, "X@C60", the icosahedral-symmetry C60 cage and an atom trapped inside the cage, has been studied for more than thirty years ever since the proposal of the C60 fullerene cage based on the carbon-cluster mass spectra because of its importance from the viewpoint of an artificial atom and also as the realization of an isolated singel atom trapped inside the chemically inert cage. The system is now also attracting interests in the field of neutrino mass spectroscopy for using the coherent isolated atoms to detect the radiative emission of neutrino pair. In the present work, we study the excited state properties of atoms trapped inside the C60 cage using the spin-ploarized time-dependent density-functional theory. In the Figure, the photoabsorption spectra of the empty C60 cage, the N atom, and the N@C60 system are shown. From the spin-polarization analysis, the peak at 8.5 eV of the N@C60 spectrum is found to correspond to the excitation of the N atom trapped inside the C60 cage. The presence of the outer C60 cage therefore slightly modifies the excitation energy of the N atom by +0.2 eV. We will also discuss the excitations of various atoms including Cu, Ag, and Au atoms which are trapped inside the C60 cage. Figure 1

Selective Chemical Reaction of Empty Cage Fullertubes with Variable-Chain Aminoalcohols

Little is published on larger size empty cage fullerenes due to their low yield in soot extracts and inefficient isolation techniques. Even less is known about the newer Fullertubes – molecular carbon structures comprised of fullerene endcaps with a nanotube belt. We have developed a novel method to purify these rarely studied fullertubes and have now opened the door for research into these unique nanoparticles. In this poster presentation, I will discuss the chemical selectivity of various combinations of straight-chain aminoalcohols and solvents to enrich the abundance of Fullertubes in preparation for facile HPLC isolation.

Chloro‐ and Trifluoromethyl Derivatives of Fullerene C82, C82Cl14 and C82(CF3)14

AbstractHigh‐temperature chlorination of a HPLC fraction containing fullerene C82 resulted in the isolation and X‐ray structure elucidation of the first chloro derivative of IPR C82, C82(3)Cl14. High‐temperature trifluoromethylatiion of a higher fullerene mixture followed by HPLC separation allowed the isolation and structural characterization of a new CF3 derivative, C82(3)(CF3)14. The addition patterns of C82(3)Cl14 and C82(3)(CF3)12–18 are discussed in terms of the formation of stabilizing substructures on a fullerene cage such as isolated C=C bonds and benzenoid rings.

Investigation of detection and adsorption properties of β-propiolactone with silicon and aluminum doped fullerene C60 using density functional theory

β-propiolactone (BPL) appears as an important element of many medicinal applications particularly in the production of vaccines. Since it also shows some carcinogenic properties, the controlled usage of BPL in every step of the production of new substances extra attention must be paid. In this work, based on the density functional theory (DFT), the adsorption properties of BPL between silicon/aluminum doped fullerenes were examined. The results of the investigations showed that aluminum doped fullerenes more strongly interacts with BPL and the water media as solvent strongly effects the charge mobility of the examined system leading different level of sensitivity to the presence of BPL of the examined fullerene cages.

U2O@C76: Non-Isolated-Pentagon-Rule Cages Prevail with the U2O Configuration Determined by Cage Shape and Dominated by Multicenter Bonds.

Endohedral clusterfullerenes (ECFs) are fullerene cages with various metallic clusters trapped inside. So far, the actinide-based ECFs are rather scarce with their possible structures and chemistry remaining largely unexplored. Herein, density functional theory calculations characterized that the recently synthesized U2O@C76 could be U2O@Cs(17 490)-C76 or U2O@C2v(19 138)-C76, whose cages have two or one pentagon adjacencies (PAs) and thus both violate the isolated pentagon rule (IPR). It is noteworthy that they are the first actinide-based ECFs bearing non-IPR outer cages. They are also the first Cs(17 490)- and C2v(19 138)-C76-based oxide ECFs. Moreover, U2O@C2v(19 138)-C76 is the first example of a hexavalent metal cluster within the C2v(19 138)-C76 cage. Interestingly, although trapped by the two same-sized cages, the U2O unit exhibits a bent and a perfect linear configuration, respectively, indicative of the crucial role of cage shape in steering the internal cluster configuration. Their electronic structures can be formally described as (U2O)6+@C766- with primary electrostatic attractions and secondary covalent interactions between cluster and cage. Significantly, bonding analyses reveal that the encaged U2O moiety may only features two three-center, two-electron (3c-2e) U-O-U bonds with completely absent common two-center bonds.

Star-like hexakis[di(ethoxycarbonyl)methano]-C60 with higher electron mobility: An unexpected electron extractor interfaced in photovoltaic perovskites

Abstract Fullerene has been demonstrated to be one of the most efficient electron extractors in perovskite solar cells (PSCs). For feasibly preparing photovoltaic device by solution process, fullerene is normally functionalized in multiple for efficient increase of its solubility in polar solvents. However, multifunctionalization typically results in neighboring fullerene cages alienating to each other and, in principle, reduces electron mobility. Herein, we show a star-like multiadducted fullerene electron extractor, hexakis[di(ethoxycarbonyl)methano]-C60 (HEMC), which possesses a proper solubility in polar solvents as well as a close packing as revealed by crystallography. Likely due to its Th-symmetric structure with twelve ester ‘tentacles’ that can interact with neighboring fullerene derivatives or unsaturated Pb2+ of perovskites, the HEMC displays efficient photovoltaic performance with a power conversion efficiency of 20%, a storage stability of 3840 h, a thermal stability of 300 h and a light-soaking stability of 240 h in the HEMC-interfaced PSCs. The present work exemplifies an unusual application of fullerene multiadducts, in addition to increasing solubility, for solving charge accumulation and recombination problems in high-efficiency PSCs.

Undiscovered Effect of C↔N Interchange Inside the Metal Carbonitride Clusterfullerenes: A Density Functional Theory Investigation.

Putting different metal clusters into the fullerene cages form the so-called "endohedral clusterfullerenes" (ECFs), among which all the carbonitride ECFs feature a common NC unit coordinating with either one or three metal atoms. Unfortunately, their internal N and C atoms are difficult to be distinguished experimentally, resulting in the fact that the exact structure and bonding nature of the encased metal cluster still remain unclear thus far. In this work, density functional theory calculations were performed for several representative carbonitride ECFs: MNC@C2n (M = Y, Tb; 2n = 76, 82) and Sc3CN@C2n (2n = 78, 80). For the first time, we focused on the C ↔ N interchange inside the cages and its effect on the chemical bonding of the trapped clusters. Computational results reveal that the two types of ECFs energetically favor the N and C atoms at the cluster center, respectively. The preference can be interpreted by the difference in several aspects, such as the energy of isolated clusters, charge states of (CN)-/3-, and cluster-cage interactions, as well as hyperconjugation of the internal clusters. The detailed wave function analyses indicate that MNC@C2n and Sc3CN@C2n bear a C≡N triple bond and a C═N double bond, respectively, regardless of the NC orientation. Compared with its slightly influence on the bonding patterns of the encaged MNC clusters, the C ↔ N interchange dramatically affects that of the Sc3CN units involving two-center two-electron (2c-2e) bonds, undiscovered three-center two-electron (3c-2e), and four-center two-electron (4c-2e) bonds.