Can the Fluxionality in Borospherene Influence the Confinement-Induced Bonding between Two Noble Gas Atoms?

A density functional theory study is performed to determine the stability and bonding in the neon dimer inside the B₃₀N₃₀ fullerene cage, the fluxional B₄₀ cage, and within non-fluxional cages such as B₁₂N₁₂ and C₆₀. The nature of bonding in the Ne₂ encapsulated B₄₀ is compared with the that in other cages in an attempt to determine whether any possible alterations are brought about by the dynamical nature of the host cage apart from the associated confinement effects. The bonding analysis includes the natural bond order (NBO), Bader’s Atoms-in-Molecules electron density analysis (AIM), and energy decomposition analysis (EDA), revealing the non-covalent nature of the interactions between the Ne atoms and that between the Ne and the cage atoms. The formation of all the Ne₂@cage systems is thermochemically unfavourable, the least being that for the B₃₀N₃₀ cage, which can easily be made favourable at lower temperatures. The Ne-Ne distance is lowest in the smallest cage and increases as the cage size increase due to steric relaxation experienced by the dimer. The dynamical picture of the systems is investigated by performing ab initio molecular dynamics simulations using the atom-centred density matrix propagation (ADMP) technique, which shows the nature of the movement of the dimer inside the cages, and by the fact that since it moves as a single entity, a weak bonding force holds them together, apart from their proven kinetic stability.     

EPR Study of Electronic Structure of [CoF<Subscript>6</Subscript>]<Superscript>3−</Superscript>and B<Subscript>18</Subscript>N<Subscript>18</Subscript> Nano Ring Field Effects on Octahedral Complex

Density functional theory calculations (DFT), as well as hybrid methods (B3LYP) for B₁₈N₁₈-[CoF₆]³⁻ complex have been carried out to study the non-bonded interaction. The geometry of the B₁₈N₁₈ has been optimized at B3LYP method with EPR-II basis set and geometry of the [CoF₆]³⁻ have been optimized at B3LYP method with Def2-TZVP basis set and Stuttgart RSC 1997 Effective Core Potential. The electromagnetic interactions of the [CoF₆]³⁻ molecule embedded in the B₁₈N₁₈ Nano ring have been investigated at B3LYP and total atomic charges, spin densities, dipole moment and isotropic Fermi coupling constants parameters in different loops and bonds of the B₁₈N₁₈-[CoF₆]³⁻ system have been calculated. Also NBO analysis such as electronic delocalization between donor and acceptor bonds has been studied by DFT method. Then we have been investigated the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) for the lowest energy have been derived to estimate the structural stability of the B₁₈N₁₈-[CoF₆]³⁻ system, and the coefficients of s, p and d orbitals of Co-F bonds involved in B₁₈N₁₈-[CoF₆]³⁻.Thus, hybridization of Co and F atoms can be distinguished based on these NBO data. The Gaussian quantum chemistry package is used for all calculations.     

A semiempirical study of C24N4 and its boron-nitrogen analogs

The results of semiempirical calculations on the heterofullerence C₂₄N₄ and its boron-nitrogen analogs B₆N₁₀C₁₂ (the smallest CBN ball) are presented in accordance with considerations of chemical bondings and geometries. The structures and relative properties of the 28-atom cages, C₂₈, C₂₄N₄, and B₆N₁₀C₁₂, were investigated using semiempirical methods contained in the MOPAC program. C₂₄N₄ and B₆N₁₀C₁₂ have T_d and C₃ symmetry, respectively. B₆N₁₀C₁₂ has four geometric isomers, and their optimized structures were determined. The ionization energies, vibrational frequencies, IR intensities, and various thermodynamic properties (including entropy and heat capacity) for C₂₄N₄ and B₆N₁₀C₁₂ were calculated by the MNDO method. The evidence suggests that a B₆N₁₀C₁₂ cage is more stable than that of C₂₄N₄. Possible experimental methods to prepare B₆N₁₀C₁₂ are also proposed. © 1996 John Wiley & Sons, Inc.     

Supramolecular arrangement and photophysical properties of a dinuclear cyanophenylboronic acid ester

Boronic esters are useful building blocks for crystal engineering and the generation of supramolecular architectures, including macrocycles, cages and polymers (one‐, two‐ and three‐dimensional), with potential utility in diverse fields such as separation, storage and luminescent materials. The novel dinuclear cyanophenylboronic ester described herein, namely 4,4′‐(2,4,8,10‐tetraoxa‐3,9‐diboraspiro[5.5]undecane‐3,9‐diyl)dibenzonitrile, C₁₉H₁₆B₂N₂O₄, was prepared by condensation of 4‐cyanophenylboronic acid and pentaerythritol and fully characterized by elemental analysis, IR and NMR (¹H and ¹¹B) spectroscopy, single‐crystal X‐ray diffraction analysis and TG‐DSC (thermogravimetry–differential scanning calorimetry) studies. In addition, the photophysical properties were examined in solution and in the solid state by UV–Vis and fluorescence spectroscopies. Density functional theory (DFT) calculations with ethanol as solvent reproduced reasonably well the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) of the title compound. Hirshfeld surface and fingerprint plot analyses are presented to illustrate the supramolecular connectivity in the solid state.     

The properties and possible transformation path for C12B24N24

The structure and frequencies of C₁₂B₂₄N₂₄ have been calculated by means of an ab initio method. By comparing the average bond energies with C₆₀, the calculated results predict that the cage C₁₂B₂₄N₂₄ is a stable molecule. The calculated results indicate that the cage molecule C₁₂B₂₄N₂₄ has a relative large HOMO–LUMO energy gap and a low rigidity. The structures and stability of six possible isomers of C₂B₄N₄ are used to suggest a possible transformation path from the pentagon CB₂N₂ to the C₁₂B₂₄N₂₄ materials. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 363–368, 2001     

Tuning Hydrogen Storage in Lithium‐Functionalized BC2N Sheets by Doping with Boron and Carbon

First‐principles calculations are used to explore the strong binding of lithium to boron‐ and carbon‐doped BC₂N monolayers (BC₂NB_C and BC₂NC_N, respectively) without the formation of lithium clusters. In comparison to BC₂N and BC₂NC_B, lithium‐decorated BC₂NB_C and BC₂NC_N systems possess stronger s–p and p–p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC₂NB_C–Li and BC₂NC_N–Li complexes can serve as high‐capacity hydrogen‐storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt %, respectively.     

Experimental and theoretical studies on bis[<Emphasis Type="Italic">μ</Emphasis>-2-methoxy-<Emphasis Type="Italic">N</Emphasis>′-(2-oxidobenzoyl)benzohydrazidato(3-)]dipyridinetricopper(II)

A novel homotrinuclear pyridine Schiff base copper(II) compound, [Cu₃(C₁₅H₁₁N₂O₄)₂(C₅H₅N)₂], has been synthesized and characterized by elemental analysis and X-ray single crystal deterimination. X-ray structural determination reveals that each copper(II) ion has a distorted square-planar geometry. The central copper ion is coordinated by two O and two N atoms from two Schiff base ligands, while each terminal copper ion is coordinated by one N and two O atoms of one Schiff base ligand and by one N atom of a pyridine molecule. Density funcational theory (DFT) method calculations of the structure, atomic charges distribution and natural bond orbital (NBO) analyses have been performed. The coordinate stabilization energies show that the trinuclear copper(II) compound is very stable.     

Density functional investigations of endohedral metallofullerenes TM@C24 (TM = Mn,Fe, Co,Ni, Cu,and Zn)

The theoretical investigations on TM@C₂₄ (TM = Mn, Fe, Co, Ni, Cu, and Zn) with different spin configurations have been performed by using the hybrid DFT‐B3PW91 functional in conjunction with 6‐31G(d) basis sets. The results show that the ground states of Fe@C₂₄ and Ni@C₂₄ are their spin triplet states, whereas the ground state of Co@C₂₄ is spin quartet state. Moreover, three Fe@C₂₄ isomers are favorable in energy. The HOMO and LUMO of Zn@C₂₄ indicates that there is no hybridization between Zn atomic orbitals and the C₂₄ cage orbitals. Natural population analysis shows that the charges always transfer from the TM atoms to the C₂₄ cage. In going from isolated TM atom to TM@C₂₄, the occupation of the 4s orbital is strongly reduced. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Predicting adsorption behavior of Triacanthine anticancer drug with pure B12N12 nano-cage: A theoretical study

Predicting adsorption behavior of the Triacanthine (TRC) anticancer drug on the surface of B₁₂N₁₂ nano-cage was investigated using DFT and TD-DFT methods by B3LYP/6-311+G(d) level in the water solution. The adsorption energies of the TRC-B₁₂N₁₂ complexes (A-C) were shown that the adsorption process is exothermic. The UV/Vis absorption and IR spectra analysis were calculated to investigate the changes happening in adsorption of TRC over nano-cage. According to the results, the interaction of the TRC drug from the N9 atom on the B₁₂N₁₂ nano-cage (model A) has the most chemical stability rather than models B and C. Based on NBO analysis, the charge transfer process has happened between the TRC drug and B₁₂N₁₂ nano-cage. Recovery time, charge difference (ΔN), and ELF analysis were calculated. It was understood that the B₁₂N₁₂ nano-cage can be a good carrier for the delivery of TRC anticancer medicine.     

A theoretical prediction of the molecular and electronic structures,thermodynamic properties,and stability of 1,3-diazido-2-methyl-2-nitropropane (DAMNP)

1,3-Diazido-2-methyl-2-nitropropane (DAMNP) is a newly synthesized azido compound and may be a potential candidate of the plasticizer of propellants. For better understanding its properties, the molecular conformations, electronic structure, IR spectrum, thermodynamic properties, pyrolysis mechanism, and specific impulse (I _S) were studied using the B3LYP/6-31++G** method of density functional theory (DFT). The electronic structure of DAMNP was analyzed by the natural atomic charges, bond orders, donor–acceptor interactions, and molecular electrostatic potential (MEP). Results show that the main contributions to the highest occupied molecular orbital and the lowest unoccupied molecular orbital are from –N₃ and –NO₂, respectively. The most negative area on the MEP locates at the O atoms of –NO₂, which agrees with the atomic charges distributions. The pyrolysis mechanism was investigated by considering three possible bond dissociations (C–N₃, C–NO₂, and N–N₂). Results show that the pyrolysis of DAMNP starts from the rupture of N–N₂ finished cooperatively via the H-transfer process to eliminate N₂. The lowest energy needed for pyrolysis is 165.13 kJ mol^?1. To verify the reliability of the method, the organic azido compound CH₃N₃ was also considered. DAMNP has a slightly higher thermal stability than CH₃N₃. However, using DAMNP to replace the plasticizer nitroglycerin of the nitramine modified double-base propellant leads to a decrease in I _S. Therefore, whether DAMNP can be really used as a plasticizer or not is worth further considerations.     

Phthalocyanine‐Based Organometallic Nanocages: Properties and Gas Storage

Phthalocyanine (Pc) molecules are well‐known flexible structural units for 1D nanotubes and 2D nanosheets. First‐principles calculations combined with grand canonical Monte Carlo simulations are used to obtain the geometries, electronic structures, optical properties, and hydrogen‐storage capacities of nanocages consisting of six Pc molecules with six Mg or Ca atoms. The primitive Pc cage has T_h symmetry with twofold degeneracy in the highest occupied molecular orbital (HOMO), and threefold degeneracy in the lowest unoccupied molecular orbital (LUMO); the corresponding HOMO–LUMO gap is found to be 0.97 eV. The MgPc and CaPc cages have O_h symmetry with a HOMO–LUMO gap of 1.24 and 1.13 eV, respectively. Optical absorption spectra suggest that the Pc‐based cages can absorb infrared light, which is different from the visible‐light absorption in Pc molecules. We further show that the excess uptake of hydrogen on MgPc and CaPc cages at 298 K and 100 bar (1 bar=0.1 MPa) is about 3.49 and 4.74 wt %, respectively. The present study provides new insight into Pc‐based nanostructures with potential applications.     

Theoretical investigation on icosahedral C60(FeCp)12: A hybrid of C60 and ferrocene

A perfect hybrid complex C₆₀(FeCp)₁₂ is predicted using density functional theory method_. This fullerene derivative could be view as a C₆₀ cage of which each C₅ ring coordinates a (FeCp) ligand. Theoretical calculation reveals that it has a large lowest unoccupied molecular orbital–highest unoccupied molecular orbital gap (2.53 eV) and keeps the I_h symmetry of C₆₀. But the C? C bond length of its inner C₆₀ cage trends to be uniform, which is quite different from the bonding character of C₆₀ fullerene. Further investigation reveals that the chemical bonding, TDOS and the aromaticity of the (C₅FeCp) unit in C₆₀(FeCp)₁₂ are similar as those of ferrocene molecule, which indicates the similarity of their electronic properties. So, this compound could be viewed as the combination of ferrocene molecules. Thus, its unconventional formation process from 12 Fe(Cp)₂ is proposed and the reaction energy is calculated. As the C₆₀(FeCp)₁₂ compound has the geometry framework as C₆₀ and the electronic characters as ferrocene, it would inherit the outstanding properties from both two molecules and have wild potential applications in nanochemistry. We hope our study could give some references for the further investigation and experimental synthesis research of the C₆₀(FeCp)₁₂ compound. © 2015 Wiley Periodicals, Inc.     

Optical properties of (Z)‐2‐(2‐phenylhydrazinylidene)acenaphthen‐1(2H)‐one: a potential electron donor in organic solar cells

Electron‐donating molecules play an important role in the development of organic solar cells. (Z )‐2‐(2‐Phenylhydrazinylidene)acenaphthen‐1(2H )‐one (PDAK), C₁₈H₁₂N₂O, was synthesized by a Schiff base reaction. The crystal structure shows that the molecules are planar and are linked together forming `face‐to‐face' assemblies held together by intermolecular C—H…O, π–π and C—H…π interactions. PDAK exhibits a broadband UV–Vis absorption (200–648 nm) and a low HOMO–LUMO energy gap (1.91 eV; HOMO is the highest occupied molecular orbital and LUMO is the lowest unoccupied molecular orbital), while fluorescence quenching experiments provide evidence for electron transfer from the excited state of PDAK to C₆₀. This suggests that the title molecule may be a suitable donor for use in organic solar cells.     

4‐(3,5‐Dimethyl‐1H‐pyrazol‐4‐ylmethyl)‐3,5‐dimethyl‐1H‐pyrazol‐2‐ium dihydrogen phosphate: a combined X‐ray and DFT study

The molecular structure of the title salt, C₁₁H₁₇N₄⁺·H₂PO₄⁻, has been determined from single‐crystal X‐ray analysis and compared with the structure calculated by density functional theory (DFT) at the BLYP level. The crystal packing in the title compound is stabilized primarily by intermolecular N—H...O, O—H...N and O—H...O hydrogen bonds and π–π stacking interactions, and thus a three‐dimensional supramolecular honeycomb network consisting of R₄²(10), R₄⁴(14) and R₄⁴(24) ring motifs is established. The HOMO–LUMO energy gap (1.338 eV; HOMO is the highest occupied molecular orbital and LUMO is the lowest unoccupied molecular orbital) indicates a high chemical reactivity for the title compound.     

Electronic and Chemical Characterization of Aluminum–Nitrogen (AlN) Substituted Fullerenes: C58AlN to C24Al12N12

Density functional theory calculations (B3LYP/6-311G*) are applied to devise a series of AlN-substituted C₆₀ fullerenes, avoiding weak homonuclear Al–Al and N–N bonds. The substitutional structures, energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, ionization potentials, binding energies, as well as dipole moments have been systematically investigated. The band gap (HOMO–LUMO gap) is larger for all the AlN-substituted fullerenes than C₆₀. The properties of heterofullerenes, especially, the HOMO–LUMO strongly depend on the number of AlN units. Natural charge analyses indicate that doping of fullerene with AlN units exerts electronic environment diversity to the cage. High charge transfer on the surfaces of our heterofullerenes provokes more studies on their possible application for hydrogen storage.     

Structure,chemical bonding and electrochemical behavior of heteroatom-substituted carbons prepared by arc discharge and chemical vapor deposition

The structural characteristics, chemical bonding and electrochemical properties of the heteroatom-substituted carbons synthesized by arc discharge and chemical vapor deposition have been investigated. C_xN was prepared only as a soot by arc discharge in nitrogen atmosphere; BC_x and B_xC_yN_z were obtained both as soot and cathode deposits by arc discharge of graphite rods having B₄C and boron nitride (BN) in argon and nitrogen atmospheres, respectively. Transmission electron microscopic study showed that C_xN, BC_x and B_xC_yN_z soots were composed of nanoparticles with diameters of 20–100 nm, while cathode deposits contained nanotubes with diameters of ca. 20 nm or less and nanoparticles with diameters less than 100 nm. It was found from XPS study that C_xN contained a large amount of pyridine type nitrogen atoms at the edge of graphene layer; the BBC₂ structure was dominant in BC_x; and B₃N, B₂NC and BNC₂ structures might exist in B_xC_yN_z. Carbon- and C_xN-coated graphite were prepared by deposition of carbon and C_xN onto natural graphite powder, respectively. The concentrations of coated C_xN layers were between C₂₁N and C₆₂N. Charge–discharge profiles of C_xN, BC_x and B_xC_yN_z soots prepared by arc discharge were similar to each other, giving linearly increasing potential with lithium ion deintercalation. C_xN soot heat-treated at 3000°C showed a similar profile for charge–discharge curves to that of graphite with a charge capacity of 334 mAh g⁻¹. On the other hand, C_xN-coated graphite exhibited as high as 397 mAh g⁻¹ larger than ∼365 mAh g⁻¹ for carbon-coated graphite and that of heat-treated C_xN soot.     

Computational studies of the corrosion‐inhibition efficiency of iron by triazole surfactants

The corrosion‐inhibition efficiency of N‐decyl‐1,2,4‐triazole, N‐undecyl‐1,2,4‐triazole, and N‐dodecyl‐1,2,4‐triazole surfactants and the corresponding protonated molecules have been studied computationally using density functional theory and second‐order Møller–Plesset calculations. Corrosion‐inhibition properties and the strength of the affinity of the iron‐surfactant molecules were estimated by using an appropriate cluster model. The iron‐surfactant complexes were constructed by attaching the triazole ring to the iron surface modeled by one and five iron atoms, respectively. Relations between molecular properties and corrosion‐inhibition efficiency were determined by using linear regression and quantitative structure–activity relationship (QSAR). The QSAR analysis yielded significant correlations between the corrosion‐inhibition activity of the studied molecules with molecular properties such as the highest occupied molecular orbital, the lowest unoccupied molecular orbital, dipole moments (μ), and the total atomic charges. Fukui indexes were also calculated for assessing correlations between them and experimental corrosion‐inhibition efficiencies. Solvent effects were investigated by using the polarized continuum model. The effects of the acidity medium and the local reactivity of the triazole derivatives with iron were also analyzed. The calculated binding energy of 276 kJ/mol for the Fe₅‐N‐dodecyl‐1,2,4‐triazole cluster shows that the surfactant molecules bind strongly to iron surfaces, which is in agreement with experimental data. © 2012 Wiley Periodicals, Inc.     

Cationic Closo Carboranes—Promising Weakly Coordinating Ions

The unexplored carbon rich cationic closo carboranes, C₃B_n?3H_n⁺¹ (n=5, 6, 7, 10, 12) are investigated theoretically. The position isomers were calculated at the B3LYP/6‐31G* level, and the charge distribution in the cluster is estimated by NBO analysis. The criterion of ring‐cap orbital overlap compatibility along with the number of B? C, C? C, and B? B bonds help in explaining the stability order in each category. The most stable isomer is the one with maximum ring‐cap orbital overlap and largest number of B? C bonds. The order of relative stability among the trigonal bipyramid is 1c > 1b > 1a ′, where the stability is proportional to the number of CH caps over the small three‐membered ring. The C₃B₃H₆⁺ isomer with the one allyl C3 group ( 2b ) is more favorable than the one with a cyclopropenyl group ( 2a ). Among the C₃B₄H₇⁺ isomers the stability order is 3e > 3d > 3c > 3b > 3a , which mostly depends on the ring‐cap orbital overlap. In the bicapped square antiprism (4) where there is large number of isomers, the order follows the rule of ring cap compatibility and the number of B? C bonds. The order of 5e > 5d > 5c > 5b > 5a obtained from the calculations is in perfect agreement with the above sited rules. Equations (1) – (5) devised for estimating the stability of isomers of C₃B_n?3H_n⁺ indicate an increase in stability with cage size. The mono‐positive charge of the isomers is distributed throughout the cage, making them suitable candidates as weakly electrophillic cations. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1542–1551, 2001     

Structural and static electric response properties of highly symmetric lithiated silicon cages: Theoretical predictions

It is shown by density functional theory calculations that high symmetry silicon cages can be designed by coating with Li atoms. The resulting highly symmetric lithiated silicon cages (up to D_5d symmetry) are low‐lying true minima of the energy hypersurface with binding energies of the order of 4.6 eV per Si atom and moderate highest occupied molecular orbital–lowest unoccupied molecular orbital gaps. Moreover, relying on a systematic study of the electric response properties obtained by ab initio (Hartree–Fock, MP2, and configuration interaction singles (CIS)) and density functional (B3LYP, B2PLYP, and CAM‐B3LYP) methods, it is shown that lithium coating has a large impact on the magnitude of their second hyperpolarizabilities resulting to highly hyperpolarizable species. Such hyperpolarizable character is directly connected to the increase in the density of the low‐lying excited states triggered by the interaction between the Si cage and the surrounding Li atoms. © 2012 Wiley Periodicals, Inc.     

Theoretical Investigation on the Effect of Different Nitrogen Donors on Intramolecular Se⋅⋅⋅N Interactions

The effect of different donor nitrogen atoms on the strength and nature of intramolecular Se ??? N interactions is evaluated for organoselenium compounds having N,N‐dimethylaminomethyl (dime), oxazoline (oxa) and pyridyl (py) substituents. Quantum chemical calculations on three series of compounds [2‐(dime)C₆H₄SeX ( 1 a – g ), 2‐(oxa)C₆H₄SeX ( 2 a – g ), 2‐(py)C₆H₄SeX ( 3 a – g ); X=Cl, Br, OH, CN, SPh, SePh, CH₃] at the B3LYP/6‐31G(d) level show that the stability of different conformers depends on the strength of intramolecular nonbonded Se ??? N interactions. Natural bond orbital (NBO), NBO deletion and atoms in molecules (AIM) analyses suggest that the nature of the Se ??? N interaction is predominantly covalent and involves nN→σ*_{Se? X} orbital interaction. In the three series of compounds, the strength of the Se ??? N interaction decreases in the order 3 > 2 > 1 for a particular X, and it decreases in the order Cl>Br>OH>SPh≈CN≈SePh>CH₃ for all the three series 1 – 3 . However, further analyses suggest that the differences in strength of Se ??? N interaction in 1 – 3 is predominantly determined by the distance between the Se and N atoms, which in turn is an outcome of specific structures of 1 , 2 and 3 , and the nature of the donor nitrogen atoms involved has very little effect on the strength of Se ??? N interaction. It is also observed that Se ??? N interaction becomes stronger in polar solvents such as CHCl₃, as indicated by the shorter r_{Se ??? N} and higher E_{Se ??? N} values in CHCl₃ compared to those observed in the gas phase.