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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 per...

The thermodynamic and dynamic stabilities of Sc3 X@C80 (X = C, N, and O) are explored via density functional theory combined with statistical thermodynamic analysis and ab initio molecular dynamics. It is the first time to comprehensively consider the effect of nonmetal atoms on trimetallic endohedral clusterfullerenes. Relative to Sc3 X@Ih (31924)-C80 (X = N and O) with general six-electron transfer, an intriguing electronic structure of unexplored Sc3 C@D5h (31923)-C80 with thermodynamic and dynamic stabilities is clearly disclosed. Natural bond orbitals and charge decomposition analysis simultaneously suggest that one unpaired electron appears on the cage for neutral Sc3 C@D5h (31923)-C80 , which could be prospectively stabilized by effective exohedral derivatization and ionization in the future. Moreover, isoelectronic endohedral clusterfullerenes, (Sc3 C@C80 )- , Sc3 N@C80 , and (Sc3 O@C80 )+ , are also uniquely taken into account. The geometries, electronic structures, reactivities, and reactive sites of isoelectronic species are examined, and it turns out that all the three isoelectronic species would rather electrophilic than nucleophilic reactions. © 2019 Wiley Periodicals, Inc.

The geometric, electronic structure and thermodynamic stability of Sc2O@C92 has been characterized by using hybrid density functional theory calculations combined with statistical thermodynamic analyses. Results indicate that the isolated pentagon rule (IPR) isomers Sc2O@Cs(126339)-C92, Sc2O@C1(126367)-C92 and Sc2O@C1(126390)-C92 are favorable. Noteworthy, it is the first time to declare that fullerene isomer Cs(126339)-C92 could be considered as the suitable cage to encapsulate metallic cluster. The electronic properties of these three isomers were performed with frontier molecular orbital (HOMO and LUMO) analyses and bond order calculations. Finally, 13C NMR and UV-vis-NIR spectra were simulated to provide valuable information for future experiments.

A family of dilanthanum-containing endohedral metallofullerene La2C2n (n = 46–51) was synthesized recently. In the present work, a systematical investigation on La2C96 series including the carbide clusterfullerene form La2C2@C94 and the conventional dimetallofullerene form La2@C96 was implemented by density functional theory, combined with statistical mechanics. Three isomers, i.e., La2@D2(191838)-C96, La2C2@Cs(153479)-C94, and La2C2@C1(153491)-C94 were disclosed to be thermodynamically stable at the temperature region of endohedral metallofullerene formation. La2@D2(191838)-C96 is the prevailing isomer at low temperature, while La2C2@Cs(153479)-C94 and La2C2@C1(153491)-C94 are the most and second-most abundant isomers at high temperature. Interestingly, the highest occupied molecular orbital (HOMO) of La2C2@C1(153491)-C94 is distributed on one pole of the cage, and the lowest unoccupied molecular orbital (LUMO) of this isomer is mainly located on the equator of the cage, which can facilitate synthesis of...

Structure elucidation is a vital step to study endohedral metallofullerene (EMF), and theoretical investigation is a useful complementary way to elucidate structures of EMFs. However, our recent work exposed that density functional theory (DFT) methods without long-range corrections are prone to overestimate energies of Sc2C2@C72 isomers. In this work, the role of long-range interaction in energy estimation of EMFs was rigorously investigated by comparing energies and interaction energies of Sc2C70 and La2C96 series with wB97XD, M06-2X, B3LYP, and PBE0 methods, and it was disclosed that long-range interaction is ubiquitously imperative for metal cluster fullerenes and conventional metallofullerenes whose cages are absent of adjacent pentagon pair(s). Meanwhile, thermodynamic stabilities of the controversial Sc2C70 series were thoroughly investigated, and Sc2C2@C2v(6073)-C68 with the highest abundance on the temperature range of EMF formation instead of Sc2@C2v(7854)-C70 was confirmed to be the experimenta...

Among the very recently reported dimetallic oxide fullerenes Sc2O@C2n (n = 35-47), a representative Sc2O@C78 still lacks of further characterizations. Herein, a systematical investigation on Sc2O@C78 has been performed by density functional theory combined with statistical thermodynamic studies. Two isolated pentagon rule (IPR) satisfying isomers, Sc2O@D3h(24109)-C78 and Sc2O@C2v(24107)-C78, are disclosed to possess prominent thermodynamic stabilities at the temperature region of fullerene formation. Significantly, these two structures are related by a single Stone-Wales transformation. Moreover, bonding critical points, bond orders, and delocalization indices have been analyzed to uncover covalent interactions in both isomers. In addition, (13)C NMR spectra and UV-vis-NIR adsorptions of the two stable structures are introduced to assist experimental identification and characterization in the future.

Endohedral scandium fullerenes have attracted substantial interest since they were synthesized and isolated in 1992. The Sc2C74 series including both Sc2@C74 and Sc2C2@C72 forms were thoroughly investigated with density functional theory (DFT) methods including B3LYP, CAM-B3LYP, M06-2X, wB97XD, and some other DFT methods combined with statistical mechanics in the present work. Among all the Sc2C74 isomers, Sc2C2@Cs(10528)-C72 is the most thermodynamically stable one, and it is overwhelming at the temperature region of fullerene formation, which is very consistent with experiments. A deviation that the B3LYP method as well as other DFT methods without long-range corrections tends to overestimate energies of Sc2C2@C72 series was exposed for the first time to our best knowledge, and this deviation may not only be restricted to the Sc2C2@C72 series but also apply to other scandium carbide fullerenes Sc2C2@C2n (2n ≠ 72) and even other metal carbide fullerenes. Misleading conclusions will be drawn on the basis ...

Single-walled carbon nanotubes (SWNTs) were subjected to alkylation using alkyl bromide and alkyl dibromide, and the photoluminescence (PL) properties of the resulting alkylated SWNTs were characterized. Two new PL peaks were observed along with the intrinsic PL peak at 976 nm when alkyl bromide was used (SWNT-Bu: ∼1095 and 1230 nm, SWNT-Bn: 1104 and 1197 nm). In contrast, the use of α,α'-dibromo-o-xylene as an alkyl dibromide primarily resulted in only one new PL peak, which was observed at 1231 nm. The results revealed that the Stokes shift of the new peaks was strongly influenced by the addition patterns of the substituents. In addition, the time-resolved PL decay profiles of the alkylated SWNTs revealed that the PL peaks possessing a larger Stokes shift had longer exciton lifetimes. The up-conversion PL (UCPL) intensity of the alkylated SWNTs at excitation wavelengths of 1100 and 1250 nm was estimated to be ∼2.38 and ∼2.35 times higher than that of the as-dispersed SWNTs, respectively.

The Sm-containing endohedral metallofullerene (EMF) Sm@C 94 has been investigated by quantum chemical and statistical thermodynamic methods. Sm@ C 1 (153491)-C 94 and Sm@ C 3 v (153493)-C 94 which both satisfy the isolated-pentagon rule (IPR) are exposed to possess considerable thermodynamic stabilities within the fullerene-formation temperature region (500⿿3000 K). Sm@ C 3 v (153493)-C 94 has been indeed determined experimentally, and a novel structure, Sm@ C 1 (153491)-C 94 , is reported for the first time. These two isomers are related by a single Stone⿿Wales transformation. Meanwhile, frontier molecular orbital, natural electron configuration, and Mayer bond order analyses were employed to uncover their electronic properties. In addition, their optical spectra were simulated to support experimental identification and characterization.

Noncovalent interactions involving aromatic rings, such as π···π stacking, CH···π are very essential for supramolecular carbon nanostructures. Graphite is a typical homogenous carbon matter based on π···π stacking of graphene sheets. Even in systems not involving aromatic groups, the stability of diamondoid dimer and layer-layer graphane dimer originates from C - H···H - C noncovalent interaction. In this article, the structures and properties of novel heterogeneous layer-layer carbon-nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on [n]-graphane and [n]-graphene and their derivatives are theoretically investigated for n = 16-54 using dispersion corrected density functional theory B3LYP-D3 method. Energy decomposition analysis shows that dispersion interaction is the most important for the stabilization of both double- and multi-layer-layer [n]-graphane@graphene. Binding energy between graphane and graphene sheets shows that there is a distinct additive nature of CH···π interaction. For comparison and simplicity, the concept of H-H bond energy equivalent number of carbon atoms (noted as NHEQ), is used to describe the strength of these noncovalent interactions. The NHEQ of the graphene dimers, graphane dimers, and double-layered graphane@graphene are 103, 143, and 110, indicating that the strength of C-H···π interaction is close to that of π···π and much stronger than that of C-H···H-C in large size systems. Additionally, frontier molecular orbital, electron density difference and visualized noncovalent interaction regions are discussed for deeply understanding the nature of the C-H···π stacking interaction in construction of heterogeneous layer-layer graphane@graphene structures. We hope that the present study would be helpful for creations of new functional supramolecular materials based on graphane and graphene carbon nano-structures. © 2017 Wiley Periodicals, Inc.