Activation and Conversion of Molecular Nitrogen to the Precursor of Ammonia on Silicon Substituted Cyclo[18]Carbon: a DFT Design

Recent synthesis of sp-hybridized cyclo[18]carbon allotrope has attracted immense curiosity. Since then, a generous amount of theoretical studies concerning aromaticity, adsorption, and spectra of the molecule have been performed. However, very few stuides have been carried out concerning its reactivities and catalytic behaviour. In this article, a DFT-based inquisition has been reported regarding the reactivity of Si substituted cyclo[18]carbon molecule towards molecular N₂. Results show that the Si substituted derivative is effective in producing adducts with molecular nitrogen. Charge calculations and IRC trapping methods indicate that only the Si center of C₁₇Si and its (HOMO-1) level participate in N₂ addition. The N-adduct so formed, is then found to spontaneously react with molecular H₂. The addition of two H₂ molecules to the activated nitrogen molecule to give respective amine derivatives have also been studied. The successful generation of the precursor of NH₃ by C₁₇Si lays a clear emphasis on its potentiality.     

In-silico exploration of noble gas dimer enforced by noncovalent interaction

Density functional calculations have been carried out to investigate the possibility of trapping of noble gas dimers by cyclo[18]carbon dimer. Parallel-displaced conformation of the cyclo[18]carbon dimer is found to be the minimum energy structure. Noncovalent interaction is found to hold the noble gas dimers. The lighter noble gases (He, Ne) posses weaker attractive interactions while the heavier one (Ar, Kr) are held by stronger attractive interactions forming genuine bonds. Each of the noble gas atoms in turn forms noncovalent interaction with the cyclo[18]carbon monomers. The bond dissociation energy of the noble gas dimers dramatically increases inside the cyclo[18]carbon dimer. Energy decomposition analysis reveals that dispersion plays the major role toward the stabilization energy.     

Contrast of Bonding and Characters for C6, B3N3, C6H6 and B3N3H6 Molecules

Through integrative consideration of NICS, MO, MOC and NBO, we precisely investigated delocalization and bonding characters of C₆, C₆H₆, B₃N₃ and B₃N₃H₆ molecules. Firstly, we originally discovered and testified that C₆ cluster was sp² hybridization. Negative NICS values in 0 and 1 Å indicated that C₆ had δ and Π aromaticity. Secondly, B₃N₃ with sp² hybridization had obvious δ aromaticity. Finally, WBI values approved that there were delocalization in C₆, C₆H₆ and B₃N₃ molecules, but B₃N₃H₆ structure did not have delocalization with the WBI 1.0. Moreover, total WBI values of carbon, boron and nitrogen atoms were four, three and three, respectively. Namely, the electrons of B₃N₃H₆ and B₃N₃ were localized in nitrogen atoms and they did not form delocalized bonding. In a word, bonding characters of carbon, boron and nitrogen atoms were dissimilar although the molecules composed of carbon, boron and nitrogen were regarded as isoelectronic structures.     

A Density Functional Investigation of Fluorinated B12N12 Clusters

Density functional calculations have been carried out on a series of fluorinated B₁₂N₁₂ molecules. The fluorine atoms are more prone to absorb on the boron atoms than the nitrogen atoms in B₁₂N₁₂. The 1,3 addition is an energetically favorable adsorption site in one‐fluorine‐molecule adsorption. We found that the average bond energy of fluorine molecule is decreased with n increasing, but significantly larger than that of B₁₂N₁₂F. The energy gap of B₁₂N₁₂ is controllable by introducing fluorine molecules. Moreover, calculation of the Gibbs free energy of the B₁₂N₁₂+12F₂→B₁₂N₁₂F₂₄ reaction showed that this reaction is exothermic at low temperatures.     

Spark source mass spectrometric assessment of boron and nitrogen concentrations in crystalline gallium arsenide

The residual or doped element concentration [E] in GaAs measured by SSMS is only accurate with respect to the relative sensitivity coefficient RSC_E. For a trace element concentration, the RSC_E = [E]_SSMS/[E]_TRUE is set to unity, if no reference material or method is available to approximate the concentration to the true value. For boron a relative sensitivity coefficient of RSC_B = 0.94 ± 0.08 was obtained using TI-IDMS as a reference method. RSC_N = 1 is used for nitrogen determinations. A boron and nitrogen detection limit of 4.4 × 10¹³ cm^–3 is achieved. SSMS was used as reference method to calibrate the FTIR factor f_E = [E] / I_α due to the integrated local vibrational mode absorption I_α of atomic boron and nitrogen in GaAs. A factor of f_B = (12.0 × 2.7) × 10¹⁶ cm^–1 (517 cm^–1) and f_N = (7.4 ± 0.1) × 10¹⁵ cm^–1 (472 cm^–1) was obtained for a boron and nine nitrogen containing GaAs samples at 77 K and 10 K, respectively. Received: 15 December 1998 / Revised: 8 April 1999 / Accepted: 13 April 1999     

Vibrational Spectra and Molecular Vibrational Behaviors of All-Carboatomic Rings,cyclo[18]carbon and Its Analogues

The vibrational spectra of cyclo[18]carbon and its analogues, cyclo[2n]carbon (n=3 to 15), were carefully simulated and characterized. The in-plane C−C stretching vibrations shows strong rigidity, while out-of-plane motions seem to be extremely flexible. The solvation effect can enhance signal strengths of the vibrational spectra, but does not evidently change the shape of the spectral curves. The infrared and Raman spectra of cyclo[2n]carbons are quite sensitive to ring size in the range of n=3 to 7, while the size only modestly affects peak positions and strengths for larger rings. Molecular dynamic trajectories show that the fluctuation period of the skeleton of cyclo[18]carbon is basically constant at different temperatures, and they are all about 300 fs. With increase of simulation temperature, the ring distortion due to thermal motion is notable and becomes much stronger. However, neither ring breaking nor isomerization in cyclo[18]carbon is observed during the simulations untill 298.15 K.     

Spark source mass spectrometric assessment of boron and nitrogen concentrations in crystalline gallium arsenide

The residual or doped element concentration [E] in GaAs measured by SSMS is only accurate with respect to the relative sensitivity coefficient RSC_E. For a trace element concentration, the RSC_E = [E]_SSMS/[E]_TRUE is set to unity, if no reference material or method is available to approximate the concentration to the true value. For boron a relative sensitivity coefficient of RSC_B = 0.94 ± 0.08 was obtained using TI-IDMS as a reference method. RSC_N = 1 is used for nitrogen determinations. A boron and nitrogen detection limit of 4.4 × 10¹³ cm^–3 is achieved. SSMS was used as reference method to calibrate the FTIR factor f_E = [E] / I_α due to the integrated local vibrational mode absorption I_α of atomic boron and nitrogen in GaAs. A factor of f_B = (12.0 × 2.7) × 10¹⁶ cm^–1 (517 cm^–1) and f_N = (7.4 ± 0.1) × 10¹⁵ cm^–1 (472 cm^–1) was obtained for a boron and nine nitrogen containing GaAs samples at 77 K and 10 K, respectively. Received: 15 December 1998 / Revised: 8 April 1999 / Accepted: 13 April 1999     

A DFT study on electronic and optical properties of aspirin-functionalized B<Subscript>12</Subscript>N<Subscript>12</Subscript> fullerene-like nanocluster

In this work, the interaction of an aspirin (AS) molecule with the external surface of a boron nitride fullerene-like nanocage (B₁₂N₁₂) is studied by means of density functional theory (DFT) calculations. Equilibrium geometry, electronic properties, adsorption energy and thermodynamic stability are identified for all of the adsorbed configurations. Four stable configurations are obtained for the interaction of AS molecule with the B₁₂N₁₂ nanocage, with adsorption energies in the range of ?10.1 to ?37.7 kcal/mol (at the M06-2X/6-31 + G** level). Our results clearly indicate that Al-doping of the B₁₂N₁₂ tends to increase the adsorption energy and thermodynamic stability of AS molecule over this nanocage. We further study the adsorption of AS over the B₁₂N₁₂ and B₁₁N₁₂Al in the presence of a protic (water) or aprotic (benzene) solvent. It is found that the calculated binding distances and adsorption energies by the PCM and CPCM solvent models are very similar, especially for the B₁₂N₁₂ complexes. According to time-dependent DFT calculations, the Al-doping can shift estimated λ _max values toward longer wavelengths (redshift). Solvent effects also have an important influence on the calculated electronic absorption spectra of AS-B₁₂N₁₂ complexes.     

Chemical interaction in the B-BN system at high pressures and temperatures.: Synthesis of novel boron subnitrides

Chemical interaction and phase transformations in the B-BN system have been in situ studied by X-ray diffraction with synchrotron radiation at pressures up to 5.3 GPa and temperatures up to 2800 K using multianvil press. New rhombohedral boron subnitride B₁₃N₂ has been synthesized by crystallization from the B-BN melt at 5 GPa. The structure of B₁₃N₂ belongs to the R-3m space group (a=5.4455(2) Å, c=12.2649(9) Å) and represents a new structural type. The subnitride is an individual compound and not a solid solution, in contrast to boron carbide. Besides, the formation of two other boron-rich B-N phases denoted as “B₆N” and “B₅₀N₂” has been observed. Their structures seem to be much more sophisticated and have not been even resolved to present time.     

Boron complexes of S-trityl- -cysteine and S-tritylglutathione

S-Trityl- -cysteine and S-tritylglutathione have been converted to 1,3,2-oxazaborolidine-5-ones by reaction with B-methoxydialkylborane derivatives. The synthesis of dicyclohexyl[S-trityl-(R)-cysteinato-O,N]boron (2), diisopinocampheyl[S-trityl-(R)-cysteinato-O,N]boron (3) and 9-borabicyclo[3.3.1]non-9-yl[S-tritylglutathionato-O,N]boron (5), dicyclohexyl[S-tritylglutathionato-O,N]boron (6) and diisopinocampheyl[S-tritylglutathionato-O,N]boron (7) from S-trityl- -cysteine and S-tritylglutathione, respectively, with potential application in boron neutron capture therapy is reported. The structure of 9-borabicyclo[3.3.1]non-9-yl[S-trityl-(R)-cysteinato-O,N]boron 1 has been determined by X-ray diffraction.     

Penicillamine functionalized B12N12 and B12CaN12 nanocages act as potential inhibitors of proinflammatory cytokines: A combined DFT analysis,ADMET and molecular docking study

The adsorption of penicillamine (PCA) on pure B₁₂N₁₂ and B₁₂CaN₁₂ nanocages in aqueous and chloroform solvents has been evaluated using density functional theory (DFT) calculations. The interaction of PCA on B₁₂N₁₂ nanocages is chemisorption through its four nucleophilic sites: amine, carbonyl, hydroxyl and thiol. The most stable adsorption configuration was achieved when zwitterionic PCA adsorbs via its carbonyl group in water with value of ?1.723 eV, in contrast, when neutral PCA adsorbs via its amine group in chloroform with value of ?1.68 eV. Intercalated calcium ion within B₁₂N₁₂ nanocage (B₁₂CaN₁₂) was shown to attract PCA onto nanocage surface, resulting in higher solubility and adsorption energy after their complexation in water and chloroform. The adsorption of multiple PCA molecules from their amine and carbonyl groups on pure and B₁₂CaN₁₂ nanocages were also evaluated where two and three molecules can be chemisorbed on boron atoms of the nanocage surfaces with the adsorption energy per PCA reduces slightly with the increasing the amount of drugs due to the curvature effects. Molecular docking study indicates that PCA from its NH₂ group on B₁₂CaN₁₂ nanocage has the best binding affinity and inhibition potential of tumor necrosis factor-alpha (TNF-α) and Interleukin-1 (IL-1) receptors as compared with the other adsorption systems. Molecular docking and ADMET analysis displayed that the chosen compounds pass Lipinski Rule and have appropriate pharmacokinetic features suitable as models for developing anti-inflammatory agents.     

A convenient approach towards boron cluster modifications with adenosine and 2′-deoxyadenosine

New 2′-deoxyadenosine and adenosoine modifications: 8-[(2-dimethylaminoethyl)amino]-2′-deoxyadenosine and 8-[(2-dimethylaminoethyl)amino]adenosine were prepared and their reactivity towards cyclic oxonium adducts of closo-dodecaborate and cobalt-bis-dicarbollide was studied. The cleavage reactions of clusters oxonium rings by N,N-dimethylanio group of modified nucleosides led to the first [B₁₂H₁₂]²⁻ and new [Co(C₂B₉H₁₁)₂]⁻ conjugates with adenosine and 2′-deoxyadenosine respectively. The proposed methodology provides a convenient route for the synthesis of libraries of boron cluster modified adenosine and 2′-deoxyadenosine derivatives for biological screening.     

Solid-state synthesis of boron subnitride, B6N: myth or reality?

Solid-state synthesis of boron subnitride, B₆N, as a result of chemical interaction between boron and boron nitride at 7.5 GPa and 1700 °C has been previously reported by Hubert et al. However, a critical analysis of the results has shown that the evidence for the formation of boron subnitride with B₆O-like structure is inconclusive. We have studied in situ the interaction between boron and BN at the same p–T conditions using X-ray diffraction with synchrotron radiation. At 7.4 GPa and 1700 °C the formation of a new phase has not been observed. At the same time, HP–HT treatment has resulted in strong and unpredictable preferred orientation of boron crystallites. This leads to the rise of some weak boron reflections that might be erroneously attributed to the appearance of a new phase. To cite this article: V.L. Solozhenko et al., C. R. Chimie 9 (2006).     

Synthesis and characterization of 18- and 20-membered hexaaza macrocycles containing pyridine manganese(II) complex nanoparticles dispersed within nanoreactors of zeolite-Y

Manganese(II) complexes of [18]py₂N₄: 3,6,14,17,23,24-hexaazatricyclo[17.3.1.1^8,12]tetracosa-1(23),2,6,8(24),9,11,13,17,19,21-decane; [20]py₂N₄: 3,7,15,19,25,26-hexaazatricyclo[19.3.1.1^9,13]hexacosa-1(25),2,7,9(26),10,12,14,19,21,23-decaene; Bzo₂[18]py₂N₄: 3,10,18,25,31,32-hexaazapentacyclo[25.3.1.1.^12,16.0^4,9.0^19,24]dotriaconta 1(31),2,4(9),5,7,10,12(32),13,15,17,19,21,23,25,29-hexadecane and Bzo₂[18]py₂N₄: 2,10,16,24,30,32-hexaazapentacyclo[23.3.1.1^4,8.1^1,1,151^18,22otriaconta-1(29),2,4,6,8(32),9,11,13,15(31),16,18(30),19,21,23,25,27-hexadecane have been encapsulated in the nanopores of zeolite-Y by the template condensation reaction. Mn(II) complexes with macrocyclic ligand were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) the adsorption of [bis(diamine)manganese(II)]; [Mn(diamine)₂]²⁺@NaY; in the supercages of the zeolite, and (ii) in situ condensation of the manganese(II) precursor complex with 2,6-diacetylpyridine. The new complex nanoparticles entrapped in the nanoreactor of zeolite-Y have been characterized by FT-IR, diffuse reflectance (DRS), X-ray photoelectron (XPS), thermal analysis, UV–Vis spectroscopic techniques, X-ray diffraction (XRD) and elemental analysis as well as by nitrogen adsorption.     

O3 and SO2 sensing concept on extended surface of B12N12 nanocages modified by Nickel decoration: A comprehensive DFT study

Adsorption of SO₂ and O₃ molecules on pristine boron nitride (B₁₂N₁₂) and Ni-decorated B₁₂N₁₂ nano-cages has been systemically investigated through density functional theory (DFT) methods. Adsorption energies (thermodynamics), bond distances, charge analysis, dipole moments, orbital analysis and density of states are calculated by van der Waals DFT method (MPW1PW91) functional. The adsorption energies of O₃ and SO₂ on pristine B₁₂N₁₂ are about −143.8 and −14.0 kJ mol⁻¹, respectively. The interaction energies of O₃ and SO₂ with pristine B₁₂N₁₂ are indicative of chemisorption and physisorption, respectively. Ni-decorated B₁₂N₁₂ (Ni@BN) enhances adsorption of both O₃ and SO₂ species. The interaction energies for adsorption of SO₂ are about −166 and −277 kJ mol⁻¹ whereas the corresponding energies for O₃ are −362 and −396 kJ mol⁻¹ for configuration A and B, respectively. These observations show that functionalized B₁₂N₁₂ are highly sensitive toward SO₂ and O₃ molecules.     

Achieving Adaptive Aromaticity in Cyclo[10]carbon by Screening Cyclo[n]carbon (n=8−24)

Discovery of species with adaptive aromaticity (being aromatic in both the lowest singlet and triplet states) is particularly challenging as cyclic species are generally aromatic either in the ground state or in the excited state only, according to Hückel's and Baird's rules. Inspired by the recent realization of cyclo[18]carbon, here we demonstrate that cyclo[10]carbon possesses adaptive aromaticity by screening cyclo[n]carbon (n=8?24), which is supported by nucleus‐independent chemical shift (NICS), anisotropy of the current‐induced density (ACID), π contribution of electron localization function (ELF_π) and electron density of delocalized bonds (EDDB) analyses. Further study reveals that the lowest triplet state of cyclo[10]carbon is formed by in‐plane ππ* excitation. Thus, the major contribution to the aromaticity from out‐of‐plane π molecular orbitals does not change significantly in the lowest singlet state. Our findings highlight a crucial role of out‐of‐plane π orbitals in maintaining aromaticity for both the lowest singlet and triplet states as well as the aromaticity dependence on the number of the carbon in cyclo[n]carbon.     

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.     

Adsorption separation of carbon dioxide,methane, and nitrogen on Hβ and Na-exchanged β-zeolite

Adsorption isotherms of carbon dioxide （CO2）, methane （CH4）, and nitrogen （N2） on Hβand sodium exchanged β-zeolite （Naβ） were volumetrically measured at 273 and 303 K. The results show that all isotherms were of Brunauer type I and well correlated with Langmuir-Freundlich model. After sodium ions exchange, the adsorption amounts of three adsorbates increased, while the increase magnitude of CO2 adsorption capacity was much higher than that of CH4 and N2. The selectivities of CO2 over CH4 and CO2 over N2 enhanced after sodium exchange. Also, the initial heat of adsorption data implied a stronger interaction of CO2 molecules with Na＋ ions in Naβ . These results can be attributed to the larger electrostatic interaction of CO2 with extraframework cations in zeolites. However, Naβ showed a decrease in the selectivity of CH4 over N2, which can be ascribed to the moderate affinity of N2 with Naβ. The variation of isosteric heats of adsorption as a function of loading indicates that the adsorption of CO2 in Naβ presents an energetically heterogeneous profile. On the contrary, the adsorption of CH4 was found to be essentially homogeneous, which suggests the dispersion interaction between CH4 and lattice oxygen atoms, and such interaction does not depend on the exchangeable cations of zeolite.     

A [Fe(CB6)] platform for binding of small molecules: Insights from DFT calculations

The viability of making [Fe(CB₆)L] (L = H₂, N₂, O₂, nitric oxide [NO^?, NO, and NO⁺], CO₂, and hydrocarbons [CH₄, C₂H₆, C₂H₄, and C₆H₆]) has been investigated by density functional theory (DFT) calculations. The complexes 2 – 18 are thermodynamically stable and may be synthesized. The small molecules are activated to some extent after complexation. Molecular orbital and ΔG calculation revealed that the molecular hydrogen and hydrocarbons can be chemically adsorbed and desorbed on [Fe(CB₆)] without any significant chemical modification and therefore [Fe(CB₆)] may serve as a storage material. The N₂, O₂, and nitric oxide (NO^?, NO, and NO⁺) can be activated using [Fe(CB₆)]. Proton, carbon, boron, and nitrogen NMR chemical shift calculation predicts drastic chemical shift difference before and after the complexation of [Fe(CB₆)] with small molecules. This new findings suggest that the CB₆^2? ligand‐based complex may provide several applications in the future. © 2012 Wiley Periodicals, Inc.