All-boron Fullerene Research Articles

First theoretical framework of superalkali metals [M3X(M = Li, Na, k; X = O, S, F, N)] doped all-boron B38 nanocluster: A promising class of nonlinear optical materials for optoelectronic applications

Developing highly efficient nonlinear optical (NLO) materials is an area of frontier research. For the first time, all-boron fullerene analogue B38nanocluster is utilized for creating highly efficient NLO materials. An effective computational design strategy of superalkali metals (Li3O, Na3O, K3O, Li3S, Na3S, K3S, Li3F, Li3N) doping is utilized on B38nanocluster, and sixteen stable isomers (A-P) of M3X@B38 (M = Li, Na, K; X = O, S, F, N) are amplified for NLO properties. Potential utilization of superalkali metals doped B38nanocluster for NLO response applications is confirmed through DFT and TD-DFT calculations executed for estimating NLO properties, photophysical features, interaction energies (Eint), vertical ionization energies (VIE), non-covalent interaction (NCI), natural bond orbitals (NBO), frontier molecular orbital (FMO), density of state (DOS) and molecular electrostatic potential (MEP) analysis. The VIE and Eint results indicate that superalkalis@B38 complexes are thermodynamically stable enough and show a strong interaction between B38 and doped superalkalis. Doping of superalkalis on B38 successfully lowers the energy gap from 1.99 (pristine B38) to 0.99 eV (doped B38). A triggering in dipole moment from 0.001924 D to 22.61 D is observed upon doping. NCI and NBO analysis confirmed the successful intermolecular charge transfer among superalkalis and B38. UV–Vis analysis showed that all superalkalis@B38 complexes are sufficiently transparent in the near-infrared (NIR) region. The NLO responses of developed complexes are evaluated by their polarizability and first hyperpolarizability (βo). Amplification in polarizability value from 413.69 a.u. to 865.60 a.u and in first hyperpolarizability from 0.71 a.u to 4.0 × 105 a.u. is achieved upon superalkalis@B38 doping. An eye-catching and highest NLO response (βo = 4.0 × 105 a.u) is exhibited by isomer E(K3O@B38). The NLO response of all studied complexes is also found more significant than the standard prototype molecule. This report provides an efficient superalkali doping technique for creating highly effective future NLO systems and recommends superalkali-doped all-boron fullerene analogue B38nanoclusters as ideal entrants for future NLO applications.

Coating all-boron B38 fullerene with Ca and Al atoms for enhancing CO2 capture: a DFT study

It is widely recognised that capturing and storing CO2 on porous materials is an efficient approach for lowering the concentration of this greenhouse gas in the atmosphere. The current work investigates the ability of Ca and Al decorated all-boron B38 fullerene to capture and store CO2 using dispersion-corrected density functional theory calculations. The results showed that Ca and Al atoms can both firmly attach to the boron atoms in the hexagon cavity of B38. This eliminates the clustering issue and may ensure the stability of the decorated B38 fullerenes. According to the findings, the B38 fullerene decorated with four Ca or Al atoms may retain up to 16 CO2 molecules, corresponding to a maximum gravimetric density of about 55 wt%. The adsorption energy per CO2 in the Ca and Al decorated systems is about −0.70 eV, which is within the range proposed for effective CO2 storage (−0.40 to −0.80 eV). As a result, Ca and Al decorated B38 fullerenes are efficient and promising materials for high-capacity CO2 storage.

On the potential of all-boron fullerene B40 as a carrier for anti-cancer drug nitrosourea

The potential application of all-boron fullerene B40 as a drug carrier for anti-cancer nitrosourea (NU) has been explored by the means of density functional theory (DFT). Our results reveal that the NU drug tends to combine with the corner boron atom of B40 cage via its oxygen and nitrogen atoms with a moderate adsorption energy of −25.18 kcal/mol. Herein, the newly formed B-O and B-N bonds are proved to be strong polar covalent bonds by atoms in molecules (AIM) theory, localized molecular orbital (LMO), and electron localization function (ELF) analyses. A short recovery time of 52 s is predicted for the NU desorption process at 310.15 K, indicating that the desorption of NU from B40 is easy under body temperature. Moreover, it is found that B40 can simultaneously adsorb up to five NU drugs, exhibiting a high loading capacity. Finally, the substituent effect of C, N, Al, and Ga atoms on the drug delivery performance of this B40 nanocage has been considered. Our results not only suggest that B40 has a great potential to be used in drug delivery, but also signify that the substituent effect of foreign atoms can be employed to modulate the drug adsorption performance of B40.

Magneto-straintronics on a Co-coordinating metalloboronfullerene

The strain-modulated ultrafast spin dynamics of Co embedded exohedral boron fullerene $[\mathrm{Co}a{\mathrm{B}}_{40}{]}^{\ensuremath{-}}$ is investigated with high-level ab initio calculations. We find that due to its high ductility and malleability, ${\mathrm{B}}_{40}$ can retain its structure upon both the addition of a magnetic atom and the exertion of mechanical tensile or compressive strain, and that its elasticity modulus is highly anisotropic. The geometric optimization reveals that $[\mathrm{Co}a{\mathrm{B}}_{40}{]}^{\ensuremath{-}}$ prefers three different configurations. For the spin-dynamics investigation we focus on one of them, namely the configuration with the Co located near the center of a heptagon (the only geometry in which the boron cage remains intact) as an example to investigate the spin-dynamics features. Several laser-induced spin-flip scenarios are suggested, the details of which strongly depend on the magnitude and the direction of any deformations. Thus, utilizing the coupling between the external mechanical strain and the spin degree of freedom in magnetic exohedral all-boron fullerenes, we demonstrate the realizability of magnetostraintronic devices on molecular systems. The asymmetric modulation of the spin-flip process with respect to the tensile and compressive strain (tension-compression-asymmetric ultrafast spin dynamics) can provide further control of such integrated spin-logic devices.

Fe-decorated all-boron B40 fullerene serving as a potential promising active catalyst for CO oxidation: A DFT mechanistic approach

In the present research, a special boron-based catalyst was introduced for carbon monoxide oxidation using dispersion-corrected DFT calculations. The iron metal is decorated at hexagonal and heptagonal rings of B40 fullerene, which is discovered as the first experimental boron allotrope in cage form. Accordingly, the Fe atom strongly chemisorbs on top of hexagonal and heptagonal rings of this fullerene. However, the adsorption energy for Fe atom above the hexagonal ring is found to be greater than that of over the heptagonal one. Thus, this complex selected as an appropriate catalyst for investigating the CO oxidation process. The conventional Eley–Rideal (ER), Langmuir–Hinshelwood (LH) and termolecular Eley–Rideal (TER) mechanisms were explored in detail. The outcomes have revealed that the acceptable mechanism for CO oxidation over Fe@B40 substrate is TER pathway. The results might be valuable for designing promising active boron-based catalyst for the CO oxidation.

Electronic and nonlinear optical features of first row transition metals-decorated all-boron B40 fullerene: A promising route to remarkable electro-optical response

The newly found B40 is the first experimentally observed all-boron fullerene. The electronic (energy gap and work function) as well as electrical properties (first hyperpolarizabilities) of first row transition metals decorated B40 fullerene were explored using DFT calculations. The transition metals are decorated above the hexagonal and heptagonal rings of B40 fullerene. The findings demonstrate that transition metals can remarkably decrease the HOMO-LUMO energy gap and work function values. The obtained interaction energy values indicate that the transition metals interaction with heptagonal ring is much stronger than hexagonal one. The greatest amount of first hyperpolarizability (β0) belongs to the interaction cobalt metal with heptagonal ring of B40 withβ0 = 1.35 × 105 au. The conventional two-level model through TD-DFT calculations is considered to get better insights into how transition metals decoration influences on the first hyperpolarizability of B40 fullerene.

Binary magnetic moments of all-boron fullerene B40 by positioning the Co atom

Recently, the all-boron fullerene B40 is experimentally observed and theoretically confirmed. As the second single-element fullerene after C60, further study about this novel fascinating fullerene is thus quite desirable. In this work, the structures, stability and magnetic properties of the Co-doped B40-based metallofullerenes were systematically studied. The results reveal different stable configurations of the endohedral Co@B40 and exohedral Co-B40 metallofullerenes depending on the doped sites of the Co atom. The spin-polarized calculations indicate that all the Co-doped metallofullerenes have an interesting characteristic of the magnetic properties: the magnetic moments having binary alternative between 2.98 μB and 1.00μB, corresponding to the Co atom resident inside the center of the unwoven double rings and inside the center of multiple-membered holes, respectively. This interesting finding of the binary magnetic moments implies that the Co-encapsulated B40-based metallofullerenes may be a promising candidate for the single molecular spin electronic devices.

Fe-Doped All-Boron Fullerene B40 with Tunable Electronic and Magnetic Properties as Single Molecular Devices**Supported by the National Basic Research Program of China under Grant No 2014CB931700, and the State Key Laboratory of Optoelectronic Materials and Technologies.

Systematic theoretical calculations are performed to investigate the dopant effect of Fe on stability, electronic and magnetic properties of the newly synthesized all-boron fullerene B40. The results reveal that as a typical ferromagnetic element, Fe atoms can either be chemically externally adsorbed on, or internally encapsulated in the cage of B40, with the binding energies ranging from 3.07 to 5.31 eV/atom. By introducing the dopant states from the doped Fe atom, the energy gaps of the Fe-doped B40-based metallofullerenes are decreased. Our spin-polarized calculations indicate that Fe-doped metallofullerenes have attractive magnetic properties: with alternative binary magnetic moments between 4.00μB and 2.00μB, depending on the resident sites of the doped Fe atom. The findings of the tunable electronic properties and binary magnetic moments of the Fe-doped B40-based metallofullerenes imply that this type of metallofullerene may be applied in single molecular devices.

Stability of endo- and exohedral complexes of all-boron fullerene B 40

Abstract In a recent publication [Nature Chemistry, 6, 727 (2014)] the synthesis and properties of a new all-boron fullerene analog, B40, have been reported, and a possibility of utilizing the B40 molecule as a hydrogen storage has been postulated. Therefore, in this contribution we study the stability of endo- and exohedral complexes with the hydrogen molecule and several other small molecules, such as N2, H2O, and CO2. The examination of binding and interaction energies obtained by symmetry-adapted perturbation theory and by supermolecular approaches shows that among the studied endohedral complexes only the one with H2 inside the cage is possibly weakly stabilized by the complexation, while all other molecules clearly exhibit too large repulsion, which cannot be counterweighted by attractive components of the interaction energy. An addition of the zero-point vibrational correction to the H2@B40 binding energy changes the balance of the attractive and repulsive contributions in favor of repulsion, so that finally also this endohedral complex is thermodynamically unstable at zero Kelvin. The exohedral minima are stable in all the cases, and are mostly bound by dispersion.

Ultrastable actinide endohedral borospherenes.

Since the discovery of the first all-boron fullerenes B40-/0, metal-doped borospherenes have received extensive attention. So far, in spite of theoretical efforts on metalloborospherenes, the feasibility of actinide analogues remains minimally explored. Here we report a series of actinide borospherenes AnBn (An = U, Th; n = 36, 38, and 40) using DFT-PBE0 calculations. All the AnBn complexes are found to possess endohedral structures (An@Bn) as the global minima. In particular, U@B36 (C2h, 3Ag) and Th@B38 (D2h, 1Ag) exhibit nearly ideal endohedral borospherene structures. The C2h U@B36 and D2h Th@B38 complexes are predicted to be highly robust both thermodynamically and dynamically. In addition to the actinide size match to the cage, the covalent character of the metal-cage bonding in U@B36 and Th@B38 affords further stabilization. Bonding analysis indicates that U@B36 and Th@B38 can be qualified as 32-electron systems, and Th@B38 exhibits 3D aromaticity with σ plus π double delocalization bonding. The results demonstrate that doping with appropriate actinide atoms is promising to stabilize diverse borospherenes, and may provide routes for borospherene modification and functionalization.

All-boron fullerene B40: a superatomic structure

By means of the first-principles calculations, we reveal that B40 presents superatomic properties. It not only has superatomic 1S, 1P, 1D and 1F orbitals, but also has superatomic orbitals 2S, 2P, 2D and 2F. The superatomic 2F orbital of B40 is partially occupied, thus adding six electrons to the cluster leads to a superatomic structure of fully occupied shells. The computed nucleus-independent chemical shift values suggest that the B406− is of higher electron delocalization than B40 itself. Our work opens up a new perspective for the superatomic physics in boron fullerene family.

Bonding the superalkali M3O (M = Li and K): An effective strategy to improve the electronic and nonlinear optical properties of the inorganic B40 nanocage

Inspired by the fascinating finding of all-boron fullerene B40 (Nat Chem, 2014, 6, 727), we propose a new and effective strategy to construct a series of typical Donor-Acceptor (D-A) frameworks via linking the superalkali M3O (M = Li and K) unit with the low ionization potential to the B40 nanocage with large electron affinity. By means of the density functional theory computations, we have systematically investigated the structures, electronic properties, the first and second hyperpolarizabilities of these modified B40 nanocage systems. Owing to the formation of a B–O chemical bond, these composite systems (M3O)n-B40 (M = Li and K, n = 1 and 2) can possess the considerably large binding energy ranging from 57.0 to 99.8kcal/mol, indicating their high structure stabilities. Compared with the pristine B40 nanocage, linking the superalkali M3O can effectively narrow the wide energy gap from the original 2.86eV to 0.61–1.11eV, and significantly increase the first and second hyperpolarizabilities to as large as 5.00 × 104–2.46 × 105 au and 1.48 × 107–4.85 × 108 au, respectively, owing to the occurrence of evident electron transfer process in this kind of typical D-A framework. These fascinating findings will be advantageous for promoting the potential applications of the inorganic boron-based nanosystems in the new type of electronic nanodevices and high-performance nonlinear optical materials.

Computational prediction of the endohedral metalloborofullerenes Ti n @B40 (n = 1, 2)

The recent discovery of the B40−/0 borospherenes (Zhai et al. in Nat Chem 6:727–731, 2014) has stimulated a large number of experimental/theoretical studies on the small all-boron fullerenes. At the same time, their capabilities to accommodate various metal species are predicted by calculations. However, the simultaneous encapsulation of two metal atoms has never been touched probably due to the limited cavities of these boron cages. In this work, systematic density functional theory calculations reveal that B40 tends to entrap one and even two titanium atoms. The formed Tin@B40 (n = 1, 2) complexes possess large binding energies and sizable HOMO–LUMO gap energies, and are highly robust at different temperatures (300–1000 K), suggesting their excellent stabilities. Interestingly, Ti2@B40 features two filled pentagonal (B@B5) motifs with protruding central atom, which are reminiscent of the B12 icosahedral unit in bulk boron. The analysis on the electronic properties and bonding patterns of Tin@B40 reveal that both of them have σ plus π double electron delocalization. Furthermore, various spectroscopies were simulated for the future experimental characterization.

Li interactions with the B40 fullerene and its application in Li-ion batteries: DFT studies

The interaction of Li and Li+ with a B40 all-boron fullerene was theoretically investigated at the B3LYP, and Minnesota 2006 levels of theory. It was found that, unexpectedly, the interaction Li+ cation with the electron deficient B40 fullerene is stronger than the Li atom. It indicates that the B40 fullerene does not act as a conventional Lewis acid because of its highly correlated structure. Frontier molecular orbitals, partial density of states, and natural bond orbital analyses were used to discuss this unusual behavior. Our calculations indicate that this behavior makes the B40 fullerene more appropriate for application in the Li-ion batteries as anode material. The calculated cell voltage is about 530mV. Also, it was found that Hartree Fock (HF) exchange percentage of density functionals has a reverse effect on the adsorption energies of Li and Li+. This energy is increased and decreased, respectively, for Li+ and Li adsorptions by increasing %HF exchange. Finally, a potential energy surface for Li and Li+ penetration into B40 fullerene was predicted.

All-boron fullerene exhibits a strong affinity to inorganic anions

Experimentally observed all-boron fullerene, B-80, inspires systematic investigation of its physical chemical properties and search for possible applications. We hereby report density functional theory calculations to characterize interactions of B-80 with the selected imidazolium room-temperature ionic liquids (RTILs), dimethylimidazolium nitrate and dimethylimidazolium hexafluorophosphate. Whereas the imidazolium cation exhibits a rather poor affinity to B-80, the inorganic anions form polar covalent bonds with the boron atom occupying a central position within a B-6 hexagon. Attachment of the RTIL ion pairs leads to a significant alteration of the electronic spectra, charge density distribution, valence and conduction molecular orbitals. The total binding energies keeping the RTIL@B80 complexes together range 200–250kcalmol−1, being higher than the energies of many interactions in chemistry. The observed phenomenon predicts an excellent solubility of B-80 in the considered RTILs, but may also reveal a poor stability of B-80 in the polar media. Our results motivate further efforts in studying the behavior of the all-boron fullerene in polar environments.

Ground state properties and spectral properties of borospherene B40 under different external electric fields

The recent discovery of borospherene B40 marks the onset of a new class of all-boron fullerenes. External electric field can influence the structure and property of molecule. It is necessary to understand the electrostatic field effect in the borospherene B40. In this work, density functional theory method at the PBE0 level with the 6-31G* basis set is used to investigate the ground state structures, mulliken atomic charges, the highest occupied molecular orbital (HOMO) energy levels, the lowest unoccupied molecular orbital (LUMO) energy levels, energy gaps, electric dipole moments, infrared spectra and Raman spectra of borospherene B40 under the external electric field within the range of values F=0-0.06 a.u.. The electronic spectra (the first 18 excited states contain excited energies, excited wavelengths and oscillator strengths) of borospherene B40 are calculated by the time-dependent density functional theory method (TD-PBE0) with the 6-31G* basis set under the same external electric field. The results show that borospherene B40 can be elongated in the direction of electric field and B40 molecule is polarized under the external electric field. Meanwhile, the addition of external electric field results in lower symmetry (C2v), however, electronic state of borospherene B40 is not changed under the external electric field. Moreover, the calculated results show that the electric dipole moment is proved to be increasing with the increase of the external field intensity, but the total energy and energy gap are proved to decrease with the increase of external field intensity. The addition of external electric field can modify the infrared and Raman spectra, such as the shift of vibrational frequency and the strengthening of infrared and Raman peaks. Furthermore, the calculated results indicate that the external electric field has a significant effect on the electronic spectrum of borospherene B40. The increase of the electric field intensity can lead to the redshift of electronic spectrum. With the change of the electric field intensity, the strongest excited state (with the biggest oscillator strength) can become very weak (with the small oscillator strength) or optically inactive (with the oscillator strength of zero). Meanwhile, the weak excited state can become the strongest excited state by the external field. The ground state properties and spectral properties of borospherene B40 can be modified by the external electric field. Our findings can provide theoretical guidance for the application of borospherene B40 in the future.

Geometries and Electronic Structures of Boron Clusters: Planar Structures and All-boron Fullerenes

Geometries and Electronic Structures of Boron Clusters: Planar Structures and All-boron Fullerenes

Computational study on the fullerene-like B40 borospherene properties and its interaction with ammonia

Ammonia adsorption and dissociation on an all-boron B40 fullerene were investigated using density functional theory calculations in terms of structures, work function, Fermi level, energetics, and so on. We predicted six different boron atoms in the structure of B40 fullerene. An NH3 molecule prefers to be adsorbed on the different boron atoms of the cage, releasing energy in the range of 19.76 to 26.90kcal/mol at B3LYP-D/6-311++G (2d,p). We showed that an NH3 molecule dissociation into an H2 molecule and –NH fragment may be energetically possible on the surface of B40 cluster. Upon the NH3 adsorption, the HOMO-LUMO energy gap of the cage is dramatically decreased, enhancing the electrical conductivity. Electron emission density from the B40 surface will be significantly increased upon the NH3 adsorption based on the work function calculations. Thus, this cluster may be employed in the NH3 detectors.

“W-X-M” transformations in isomerization of B39− borospherenes

The Stone-Wales transformation plays an important role in the isomerization of fullerenes and graphenic systems. The continuous conversions between neighboring six- and seven-membered rings in the borospherene (all-boron fullerene) B40 had been discovered (Martínez-Guajardo et al. Sci. Rep. 5, 11287 (2015)). In the first axially chiral borospherenes C3 B39− and C2 B39−, we identify three active boron atoms which are located at the center of three alternative sites involving five boron atoms denoted as “W”, “X”, and “M”, respectively. The concerted movements of these active boron atoms and their close neighbors between neighboring six- and seven-membered rings define the “W-X-M” transformation of borospherenes. Extensive first-principles molecular dynamics simulations and quadratic synchronous transit transition-state searches indicate that, via three transition states (TS1, TS2, and TS3) and two intermediate species (M1 and M2), the three-step “W-X-M” transformations convert the C3 B39− global minimum into its C2 isomer at room temperature (300 K) and vice versa. The maximum barriers are only 3.89 kcal/mol from C3 to C2 B39− and 2.1 kcal/mol from C2 to C3 B39−, rendering dynamic fluxionalities to these borospherenes. Therefore, the “W-X-M” transformation plays an important role in the borospherenes and borospherene-based nanostructures.

Cage-like B40 (+): a perfect borospherene monocation.

The recent discovery of perfect cage-like D 2d B40 (-) and D 2d B40 (all-boron fullerenes) has led to the emergence of a borospherene family. However, the geometrical and electronic structures of their cationic counterpart B40 (+), previously detected in gas phase, remain unknown to date. Based on extensive first-principles theory calculations, we present herein the possibility of a perfect cage-like D 2d B40 (+) (1) ((2)A1) for the monocation, which turns out to be the global minimum of the system similar to B40 (-) and B40, adding a new member to the borospherene family. Molecular dynamics simulations indicate that D 2d B40 (+) (1) is dynamically stable at 300K, whereas it starts to fluctuate at 500K between the two lowest-lying isomers D 2d B40 (+) (1) (W) and C s B40 (+) (3) (M) in concerted W-X-M mechanisms via the transition state of C 1 B40 (+) (X), with forward (W → X → M) and backward (M → X → W) activation energies (Ea) of 14.6 and 6.9kcalmol(-1), respectively. The spectra from IR, Raman, and UV-vis analyses were simulated to facilitate future characterization of this important borospherene monocation.