Theoretical Study on the Regioselectivity of Leapfrog B18 and B30 Boron Sheets in Electrophilic and Nucleophilic Reactions Using DFT-Based Reactivity Indices.

A combined computational and interpretational DFT study is performed to investigate the regioselectivity of B18 and B30 leapfrog boron sheets upon reaction with XH3-type electrophiles and nucleophiles (X = N, P, As, B, Al). The M062X, B3LYP, and B3LYP-D3 functionals are used combined with the 6-31+G(d,p) basis. The molecular electrostatic potential (MEP), Fukui functions, and the dual descriptor are employed to predict the local reactivity of B18 and B30. Our results reveal that both clusters are hard and prefer to react with hard bases and acids, such as NH3 and BH3. Further, these leapfrog B6n clusters can play the role of catalysts as they break B-H and Al-H bonds of BH3 and AlH3 in s-BH3-B6n and s-AlH3-B6n complexes, respectively. Leapfrog B6n-XH3 complexes (X = B and Al) can be considered as an interaction between two electron-deficient systems. Therefore, the chemical reactivity between these systems cannot be interpreted in terms of the Hard-Soft-Acid-Base principle.

Theoretical insights into the binding interaction of Nirmatrelvir with SARS-CoV-2 Mpro mutants (C145A and C145S): MD simulations and binding free-energy calculation to understand drug resistance.

Mpro, the main protease and a crucial enzyme in SARS-CoV-2 is the most fascinating molecular target for pharmacological treatment and is also liable for viral protein maturation. For antiviral therapy, no drugs have been approved clinically to date. Targeting the Mpro with a compound having inhibitory properties against it can hinder viral replication. The therapeutic potential of the antiviral compound Nirmatrelvir (NMV) against SARS-CoV-2 Mpro was investigated using a systematic approach of molecular docking, MD simulations, and binding free energy calculation based on the MM-GBSA method. NMV, a covalent inhibitor with a recently revealed chemical structure, is a promising oral antiviral clinical candidate with significant in vitro anti-SARS-CoV-2 action in third-phase clinical trials. To explore the therapeutic ability and possible drug resistance, the Mpro system was studied for WT and two of its primary mutants (C145A & C145S). The protein-ligand (Mpro/NMV) complexes were further examined through long MD simulations to check the possible drug resistance in the mutants. To understand the binding affinity, the MM-GBSA method was applied to the Mpro/NMV complexes. Moreover, PCA analysis confirms the detachment of the linker region from the major domains in C145S and C145A mutants allowing for conformational alterations in the active-site region. Based on the predicted biological activities and binding affinities of NMV to WT and mutant (C145A & C145S) Mpro, it can be stipulated that NMV may have conventional potency to act as an anti-viral agent against WT Mpro, while the catalytic-dyad mutations may show substantial mutation-induced drug resistance.Communicated by Ramaswamy H. Sarma.

Bond dissociation energies of ethyl valerate and tripropionin.

CONTEXT: Due to the expected decrease in the availability of conventional oils, numerous studies are currently underway to find complementary sources of energy. Among the explored avenue is that of biofuels. Ethyl valerate (ETV) and tripropionin (TPP) are two biofuels whose thermal decomposition has not received the attention it deserves. Herein, we have evaluated the bond dissociation enthalpies (BDHs) to predict how easy it is to break some bonds in these compounds, and subsequently contribute to revealing the initiation step in their combustion reactions. Our computations consistently predict C4-C5 and C1-C2 bonds in ETV and TPP as the weakest bonds, likely to break first and initiate the thermal decomposition of these two compounds, respectively. The conformational changes in ETV and TPP have only a small influence on the BDHs of 1 kcal/mol at M06-2X/6-311 + G(3df,2p). B3LYP and ωB97XD appear to be the most affordable methods for estimating BDHs at 6-31G(d,p) as they give good results for ETV (RMSD: 2.94 kcal/mol and 3.22 kcal/mol) and performed better than CBS-QB3 (RMSD: 3.64 kcal/mol). Using a larger basis set, the M06-2X (RMSD: 3.61 kcal/mol) and ωB97XD (RMSD: 3.51 kcal/mol) functionals are found to provide the most accurate predictions at 6-311 + G(3df,2p) as compared to G4MP2. METHODS: BDHs of ETV and TPP are computed using density functional theory (DFT) and quantum chemistry composite methods at 6-31G(d,p) and 6-311 + G(3df,2p) levels. Because of its reliability and accuracy in thermochemical calculations, the G4MP2 theory is used as a reference to gauge the performance of DFT methods. All the calculations were carried out using the Gaussian 09 program.

Molecular insights to the binding interactions of APNS containing HIV-protease inhibitors against SARS-CoV-2 Mpro: an in silico approach towards drug repurposing.

SARS-CoV-2 Mpro is one of the most vital enzymes of the new coronavirus-2 (SARS-CoV-2) and is a crucial target for drug discovery. Unfortunately, there is not any potential drugs available to combat the action of SARS-CoV-2 Mpro. Based on the reports HIV-protease inhibitors can be applied against the SARS by targeting the SARS-CoV-1 Mpro, we have chosen few clinically trialed experimental and allophenylnorstatine (APNS) containing HIV-protease inhibitors (JE-2147, JE-533, KNI-227, KNI-272 & KNI-1931), to examine their binding affinities with SARS-CoV-2 Mpro and to assess their potential to check for a possible drug candidate against the protease. Here, we have chosen a methodology to understand the binding mechanism of these five inhibitors to SARS-CoV-2 Mpro by merging molecular docking, molecular dynamics (MD) simulation and MM-PBSA based free energy calculations. Our estimations disclose that JE-2147 is highly effective (ΔGBind = -28.31 kcal/mol) due to an increased favorable van der Waals (ΔEvdw) interactions and decreased solvation (ΔGsolv) energies between the inhibitor and viral protease. JE-2147 shows a higher level of interactions as compared to JE-533 (-6.85 kcal/mol), KNI-227 (-18.36 kcal/mol), KNI-272 (-15.69 kcal/mol) and KNI-1931 (-21.59 kcal/mol) against SARS-CoV-2 Mpro. Binding contributions of important residues (His41, Met49, Cys145, His164, Met165, Glu166, Pro168, Gln189, etc.) from the active site or near the active site regions with ≥1.0 kcal/mol suggest a potent binding of the inhibitors. It is anticipated that the current study of binding interactions of these APNS containing inhibitors can pitch some valuable insights to design the significantly effective anti-SARS-CoV-2 Mpro drugs.Communicated by Ramaswamy H. Sarma.

Temporally Resolved Electrochemical Interrogation for Stochastic Collision Dynamics of Electrogenerated Single Polybromide Droplets.

In this article, we present electrochemical interrogation for collision dynamics of electrogenerated individual polybromide ionic liquid (PBIL) droplets through chronoamperometry combined with fast scan cyclic voltammetry (CA-FSCV). In the CA mode of CA-FSCV, a Pt ultramicroelectrode (UME) acts as the electrochemical generator for PBIL droplets by holding the oxidation potential for Br- in a given time, while FSCV is repetitively performed at a certain frequency. In the FSCV mode of CA-FSCV, a Pt UME serves as the probe to electrochemically monitor Br3- reduction for an adsorbed PBIL droplet during collision with a high temporal resolution. Based on the newly introduced CA-FSCV, we can estimate the dynamic changes in the following parameters for a short collision time: the contact radius of a PBIL droplet on a Pt UME, the concentration of Br- in the droplet, and the apparent charge transfer rate constant for electro-reduction of Br3- to Br- in the droplet, koapp. Moreover, a computational calculation using molecular dynamics is presented that can explain the change in koapp as a function of time for Br- electrolysis in a PBIL droplet. Based on the quantitative estimation of the above parameters, we suggest a more advanced mechanism for the stochastic electrochemical collision process of a PBIL droplet. These findings are important for understanding QBr2n+1/QBr half redox reactions in aqueous energy storage systems, such as Zn-Br redox flow batteries and Br-related redox enhanced electrochemical capacitors.

A comparison of the chemical bonding and reactivity of Si8H8O12 and Ge8H8O12: A theoretical study.

We have analyzed the chemical bonding and reactivity in the cubic molecule octahydridosilsesquioxane, Si8H8O12, and its counterpart Ge8H8O12 by means of ab initio quantum chemical methods and group theory. Density functional theory and MP2 methods combined with the basis sets 6-311+G(d) and 6-311++G(2d,p) were used for geometry optimization and vibrational frequency analysis. The geometries of Si8H8O12 and Ge8H8O12 are unstable under Oh symmetry and distort to the rare Th molecular symmetry. The energy gained from this pseudo-Jahn-Teller distortion ranges from 0.78 to 6.14 kcal mol-1 depending on methodological treatment. The Fukui functions and the molecular electrostatic potential were both used as DFT-based reactivity descriptors. Our study shows that Si8H8O12 and Ge8H8O12 are both hard amphoteric molecules. The cavity within each cage is acidic and able to encapsulate hard small bases such as F-. The exterior of the cages is basic and can form stable exohedral complexes with hard acids, as in the case of H+. The insertion of F- in Si8H8O12 and Ge8H8O12 cages gives the most stable endohedral complexes of the series studied, characterized by formation energies of -3.50 and -3.45 eV at CAM-B3LYP/6-311+G(d) and -3.61 and -3.68 eV at the MP2/6-311++G(d,p) level, respectively. The calculated formation energies of the exohedral and endohedral complexes align with the DFT reactivity descriptor analysis.

Structure, stability and bonding of the leapfrog B24 0 ,±1,±2.

Two new structural motifs of the B24 clusters are constructed by use of the leapfrog transformation. The resulting leapfrog B24 has either a bowl shape with a square vacancy or a quasi-planar 2D close-packed triangular boron sheet. The neutral and ionic forms of the latter are found to be more stable than their homologous leapfrog bowl clusters, with the exception of the dicationic B24 +2 . While the leapfrog isomer is less stable than the tubular double ring in the neutral state, it becomes competitive in some ionic states. The nucleus independent chemical shift, electron localization function, ring current maps and the electronic structure of leapfrog B24 clusters reveal them to behave as aromatics.

Interplay between σ Holes, Anion···H-C, and Cation-π Interactions in Dibromo[2,2]paracyclophane Complexes.

Theoretical calculations were performed to investigate the interplay between σ-hole, anion-HC and cation-π interactions in the complexes of dibromo[2,2]paracyclophane (DBr[2,2]PCP) with alkali (Li+, Na+, K+), alkaline earth metal cations (Be2+, Mg2+, and Ca2+), and halogen anions (F-, Cl-, and Br-) using the wave function (MP2) and density functional theory (M06-2X and B3LYP) methods with the 6-311++G(d,p) basis set. The study reveals that DBr[2,2]PCP behaves as amphoteric molecule with a predominance of basic character. It prefers to interact with hard cations and hard anions such as Be2+ and F- through cation-π and anion···HC interactions, respectively. Substitution of Br by F and Cl atoms in DBr[2,2]PCP decreases slightly the interaction energies of DX[2,2]PCP-halogen complexes (X = F, Cl, and Br) by 2.0 and 0.3 kcal/mol (M06-2X), respectively. The anion-HC interactions in DBr[2,2]PCP complexes are ∼10 kcal/mol stronger (B3LYP; ∼15 kcal/mol at M06-2X and 7 kcal/mol at MP2) than the σ-hole interactions.

Electronic Structure and Photoluminescence Properties of Eu(η9-C9H9)2.

The electronic structure of Eu2+ compounds results from a complex combination of strongly correlated electrons and relativistic effects as well as weak ligand-field interaction. There is tremendous interest in calculating the electronic structure as nowadays the Eu2+ ion is becoming more and more crucial, for instance, in lighting technologies. Recently, interest in semiempirical methods to qualitatively evaluate the electronic structure and to model the optical spectra has gained popularity, although the theoretical methods strongly rely upon empirical inputs, hindering their prediction capabilities. Besides, ab initio multireference models are computationally heavy and demand very elaborative theoretical background. Herein, application of the ligand-field density functional theory (LFDFT) method that is recently available in the Amsterdam Modeling Suite is shown: (i) to elucidate the electronic structure properties on the basis of the multiplet energy levels of Eu configurations 4f7 and 4f65d1 and (ii) to model the optical spectra quite accurately if compared to the conventional time-dependent density functional theory tool. We present a theoretical study of the molecular Eu(η9-C9H9)2 complex and its underlying photoluminescence properties with respect to the Eu 4f-5d electron transitions. We model the excitation and emission spectra with good agreement with the experiments, opening up the possibility of modeling lanthanides in complex environment like nanomaterials by means of LFDFT at much-reduced computational resources and cost.

Viologen-Bromide Dual-Redox Ionic Solid Complexes: Understanding Their Electrochemical Formation and Proton-Accompanied Redox Chemistry.

The inhibition of self-discharge in a redox-enhanced electrochemical capacitor (Redox-EC) is crucial for excellent energy retention. Heptyl viologen dibromide (HVBr2) was chosen as a strong candidate of a dual-redox species in Redox-EC due to its solid complexations during the charging process, at which HV2+ is electrochemically reduced to HV+• and form a solid complex, [HV+•·Br-], on an anode while Br- is electro-oxidized to Br3- and renders [HV2+·2Br3-] on a cathode. The solid complexes could not transfer across the separator, resulting in significant diminution of the self-discharge. In this Article, we present detailed electrochemical studies of formation of [HV2+·2Br3-] and [HV+•·Br-], their redox features, and galvanic exchange reactions between the two types of dual-redox ionic solids on a Pt ultra-microelectrode (UME) in neutral (0.33 M Na2SO4) and acidic (1 M H2SO4) solutions. Most importantly, through voltammetric and particle-impact electrochemical analyses, we found that the redox and galvanic exchange reactions of the two dual-redox ionic solid complexes involve H+ transfer, which is the key process to limit the overall kinetics of the electrochemical reactions. We also rationalize the proton-accompanied galvanic exchange reaction based on computational simulation.

Unraveling V(V)-V(IV)-V(III)-V(II) Redox Electrochemistry in Highly Concentrated Mixed Acidic Media for a Vanadium Redox Flow Battery: Origin of the Parasitic Hydrogen Evolution Reaction.

We present a mechanistic understanding of the full redox electrochemistry of V(V)-V(IV)-V(III)-V(II) and the origin of the parasitic hydrogen evolution reaction (HER) during electroreduction of either V3+ or VO2+ in a highly concentrated mixed acidic solution based on both electroanalytical and computational approaches. First, we found that the VO2+/VO2+ redox reaction is well explained by the EC/EC square scheme. We also found that V3+ is electrochemically oxidized to V4+ and subsequently undergoes a transition to stable VO2+ via hydrolysis. In the V3+/V2+ redox reaction via voltammetric analysis at scan rates greater than 0.05 V/s, the voltammograms are well explained based on a simple 1e- transfer reaction scheme. However, at the longer time scale observed in the chronoamperograms with constantly applied potentials where V3+ is electrochemically reduced to V2+, we found that a significant HER occurs because of possible formation of an electrocatalyst related to the V(II)O species, V(II)catalyst. We suggest that V(II)O is kinetically formed from V2+ via hydrolysis only when a local concentration of V2+ is high in the vicinity of a GC electrode surface, and V(II)O is adsorbed on a GC surface to form V(II)catalyst. To extend our mechanistic pathway, electroreduction of VO2+ to V(II) was also analyzed, revealing that VO2+ is electroreduced to VO+ and further reduced to VO in addition to disproportionation of VO+. Eventually, V(II)catalyst forms on a GC electrode, resulting in a significant HER. The computational calculation strongly supports the possible formation of V(II)catalyst. The calculation shows that neither V3+ nor V2+ can form stable intermediates during the HER, while V(II)O has the highest proton affinity compared with V(III)O+ and V(IV)O2+, indicating a plausible electrocatalytic property of V(II)O for the HER.

Formation of the quasi-planar B50 boron cluster: topological path from B10 and disk aromaticity.

The lowest-lying isomer of the B50 boron cluster is confirmed to have a quasi-planar shape with two hexagonal holes. By applying a topological (leap-frog) dual operation followed by boron capping, we demonstrated that such a quasi-planar structure actually comes from the smallest elongated B102-, and its high thermodynamic stability is due to its inherent disk aromaticity arising from its 32 valent π electrons that fully occupy a disk configuration of [(1σ)2(1π)4(1δ)4(2σ)2(1φ)4(2π)4(1γ)4(2δ)4(1η)4]. The aromatic character of the quasi-planar B50 is further supported by a strong diatropic magnetic current flow. The sudden appearance of a quasi-planar B50 again points out that the growth pattern of pure boron clusters is still far from being completely understood.

Theoretical investigation on the ground state properties of the hexaamminecobalt(iii) and nitro-nitrito linkage isomerism in pentaamminecobalt(iii) in vacuo.

Nitro-nitrito isomerization in Co(NH3)5NO2 2+ linkage isomers was investigated with a focus on the geometries, relative stabilities and chemical bonding using ωB97XD/6-31+G(d,p) to elucidate the photo-salient effect in [Co(NH3)5NO2]NO3Cl. Different techniques like atoms in molecules (AIM), electron localization function (ELF) and natural bonding orbital (NBO) were used to gain insight into the chemical bonds of the isomers and to identify the key factors influencing their relative stabilities. The study of the ground-state potential energy surface of [Co(NH3)5NO2]2+ reveals that the nitro/exo-nitrito isomerization reaction can proceed via the following two paths: (1) nitro → TS1 (38.16 kcal mol-1) → endo-nitrito → TS2 (9.68 kcal mol-1) → exo-nitrito and (2) nitro → TS3 (41.76 kcal mol-1) → exo-nitrito. Pathway (1) through endo-nitrito is the most likely isomerization mechanism because of a lower energy barrier than pathway (2). The intramolecular-resonance-assisted hydrogen bonds (N-H⋯O and N-H⋯N), the orientation of NO2, and the difference between Co-N and Co-O bond energies are identified as the key factors determining the relative stabilities of the linkage isomers. Co(NH3)6 3+ is less stable compared to Co(NH3)5NO2 2+ and undergoes a slight geometrical distortion from D 3d to either D 3 or S 6 characterized by a stabilization energy of ∼750 cm-1 at CCSD(T)/6-31+G(d,p).

Hydrogen bonded and stacked geometries of the temozolomide dimer.

Dispersion-corrected density functional theory (DFT) and MP2 quantum chemical methods are used to examine homodimers of temozolomide (TMZ). Of the 12 dimer configurations found to be minima, the antarafacial stacked dimer is the most favored, it is lower in energy than coplanar dimers which are stabilized by H-bonds. The comparison between B3LYP and B3LYP-D binding energies points to dispersion as a primary factor in stabilizing the stacked geometries. CO(π) → CO(π*) charge transfers between amide groups in the global minimum are identified by NBO, as well as a pair of weak CH∙∙N H-bonds. AIM analysis of the electron density provides an alternative description which includes N∙∙O, N∙∙N, and C∙∙C noncovalent bonds.

The boron conundrum: which principles underlie the formation of large hollow boron cages?

Extensive optimisation calculations are performed for the B(80) isomers in order to find out which principles underlie the formation of large hollow boron cages. Our analysis shows that the most stable isomers contain triangular B(10) or rhombohedral B(16) building blocks. The lowest-energy isomer has C(3v) symmetry and is characterised by a belt of three interconnected B(16) units and two separate B(10) units. At the B3LYP/6-31G(d) level of theory, this newly discovered isomer is 2.29, 1.48, and 0.54 eV below the leapfrog B(80) of Szwacki et al., the T(h) -B(80) of Wang, and the D(3d) -B(80) of Pochet et al., respectively. Our C(3v) isomer is therefore identified as the most stable hollow cage isomer of B(80) presently known. Its HOMO-LUMO gap of 1.6 eV approaches that of the leapfrog B(80). The leapfrog principle still remains a reliable scheme for producing boron cages with larger HOMO-LUMO gaps, whereas the thermodynamically most stable B(80) cages are formed when all pentagonal faces are capped. We show that large hollow cages of boron retain a preference for fullerene frames. The additional capping is in accordance with the following rules: preference for capping of pentagonal faces, formation of B(10) and/or B(16) units, homogeneous distribution of the hexagonal caps, and hole density approaching 1/9. Although our most stable B(80) isomer still remains higher in energy than the B(80) core-shell structure, we show that by applying the bonding principles to larger structures it is possible to construct boron cages with higher stabilisation energy per boron atom than the core-shell structure; a prototypical example is B(160). This clearly shows the continuous competition between the two suggested construction schemes, namely, the formation of multiple-shell structures and hollow cages.

Jahn-Teller instability in cationic boron and carbon buckyballs B80+ and C60+: a comparative study.

This paper investigates the Jahn-Teller effect in the icosahedral cation B(80)(+) and compares the descent in symmetry with that in C(60)(+). For both cations the icosahedral ground state is a (2)H(u) state, which exhibits a H ⊗ (g ⊕ 2h) Jahn-Teller instability. A detailed construction of the potential energy surface of B(80)(+) using different DFT methods including B3LYP/6-31G(d), VWN/6-31G(d), PBE/TZP and PBE/6-31G(d) shows that, contrary to C(60)(+), which prefers D(5d) symmetry, the ground state of B(80)(+) adopts S(6) point group symmetry. A D(3d) structure is identified as a saddle point among the S(6) minima of B(80)(+). The distortion of D(3d) to S(6) in B(80)(+) is attributed to a superposition of Jahn-Teller and pseudo-Jahn-Teller effects. Imaginary modes, transforming as the g(g) representation, which are present in neutral icosahedral B(80), form the dominant symmetry breaking active modes. The pronounced difference between the JT effects in the boron and carbon buckyball cations is due to the plasticity of the boron caps. The calculated Jahn-Teller stabilization of B(80)(+) is nearly 1549 cm(-1) (PBE/TZP), which exceeds the stabilization of 596 cm(-1) computed for C(60)(+) at the same level.

Theoretical study of the regioselectivity of the interaction of 3-methyl-4-pyrimidone and 1-methyl-2-pyrimidone with Lewis acids.

A density functional theory (DFT) study is performed to determine the stability of the complexes formed between either the N or O site of 3-methyl-4-pyrimidone and 1-methyl-2-pyrimidone molecules and different ligands. The studied ligands are boron and alkali Lewis acids, namely, B(CH(3))(3), HB(CH(3))(2), H(2)B(CH(3)), BH(3), H(2)BF, HBF(2), BF(3), Li(+), Na(+), and K(+). The acids are divided into two groups according to their hardness. The reactivity predictions, according to the molecular electrostatic potential (MEP) map and the natural bond orbital (NBO) analysis, are in agreement with the calculated relative stabilities. Our findings reveal a strong regioselectivity with borane and its derivatives preferring the nitrogen site in both pyrimidone isomers, while a preference for oxygen is observed for the alkali acids in the 3-methyl-4-pyrimidone molecule. The complexation of 1-methyl-2-pyrimidone with these hard alkali acids does not show any discrimination between the two sites due to the presence of a continuous delocalized density region between the nitrogen and the oxygen atoms. The preference of boron Lewis acids toward the N site is due to the stronger B-N bond as compared to the B-O bond. The influence of fluorine or methyl substitution on the boron atom is discussed through natural orbital analysis (NBO) concentrating on the overlap of the boron empty p-orbital with the F lone pairs and methyl hyperconjugation, respectively. The electrophilicity of the boron acids gives a good overall picture of the interaction capabilities with the Lewis base.

Ring currents in boron and carbon buckyballs, B80 and C60.

The ipsocentric method at the coupled Hartree-Fock level is used for the calculation of magnetically induced ring currents in the boron buckyball B(80), for both I(h) and distorted T(h) geometries. A close similarity between the current patterns in boron and carbon buckyballs is noted, but with a higher current density in B(80). Paratropic currents on the pentagons are predominant in the boron buckyball, and the central NICS value is positive. These observations support the conclusion that B(80) should be considered (weakly) anti-aromatic. The largest orbital contributions to the ring currents in both molecules are identified and related to specific excitations in the frontier orbital region.

Theoretical study on the regioselectivity of the B80 buckyball in electrophilic and nucleophilic reactions using DFT-based reactivity indices.

Density functional theory calculations at the B3LYP/SVP and B3LYP/6-311G(d) levels were carried out for a series of XH(3)B(80) complexes with X = {N, P, As, B, Al}. To probe the regioselectivity of B(80), the electronic Fukui function, the molecular electrostatic potential (MEP), and the natural bond orbital (NBO) were determined. These indices were shown to provide reliable guides to predict the relative reactivities of the boron buckyball sites. Thermodynamic stabilities of the complexes formed by the reaction of B(80) with nucleophiles (NH(3), PH(3), AsH(3)) and electrophiles (BH(3), AlH(3)) are in good agreement with the prediction of regioselectivity indicated on the basis of Fukui and MEP indices. The qualitative results suggest the boron buckyball to be an amphoteric and hard molecule. It has two distinct reactive sites localized on caps and frame, which act as acids and bases, respectively. Most of the complexes are stable with formation energies comparable to that of the analogous complexes of the borane molecule, BH(3)BH(3), BH(3)NH(3), and BH(3)AlH(3). The B-H-B bond characteristics of diborane are recovered in B(80)BH(3). Exohedral complexes are more stable than endohedral complexes. The most stable complexes are those with NH(3) on the caps and BH(3) on the pentagonal ring of B(80).

Encapsulation of small base molecules and tetrahedral/cubane-like clusters of group V atoms in the boron buckyball: a density functional theory study.

A density functional theory study of small base molecules and tetrahedral and cubane-like group V clusters encapsulated in B(80) shows that the boron buckyball is a hard acid and prefers hard bases like NH(3) or N(2)H(4) to form stable off-centered complexes. In contrast, tetrahedral and cubane-like clusters of this family are metastable in the cage. The most favorable clusters are the mixed tetrahedral and cubane clusters formed by nitrogen and phosphorus atoms such as P(2)N(2)@B(80), P(3)N@B(80), and P(4)N(4)@B(80). The boron cap atoms are electrophilic centers, and prefer mainly to react with electron rich nucleophilic sites. The stability of the complexes will be governed by the size and electron donating character of the encapsulated clusters. B(80) forms stable complexes with hard materials where a bidentate interaction of the encapsulated molecule with two boron cap atoms is preferred over a single direct complex toward a single endohedral boron.