Si‐Doped B12N12 Nanocage as an Adsorbent for Dissociation of N2O to N2 Molecule

Adsorption of N₂O molecule by using density functional theory calculations at the B3LYP/6–31G* level onto pristine and Si‐doped B₁₂N₁₂ nanocage in terms of energetic, geometric, and electronic properties was investigated. The results of calculations showed that the N₂O molecule is physically adsorbed on the pristine and Si‐doped B₁₂N₁₂ (Si_N) models, releasing energies in the range of –1.13 to –2.02 kcal mol⁻¹. It was found that the electronic properties of the models have not changed significantly upon the N₂O adsorption. On the other hand, the adsorption energy of N₂O on the Si‐doped B₁₂N₁₂ (Si_B model) was about –67.20 kcal mol⁻¹and the natural bond orbital charge of 0.58|e| is transferred from the nanocage to the N₂O molecule. In the configuration, the O atom of N₂O molecule is bonded to the Si atom of the nanocage, so that an N₂ molecule escapes from the wall of the nanocage. The results showed that the Si_B model can be an adsorbent for dissociation of the N₂O molecule.     

Theoretical studies of O2−:(H2O)n clusters

The interaction of superoxide ion O₂^? with up to four water molecules [O₂^?: (H₂O)_n, n = 1, 2, 4] has been investigated using ab initio molecular orbital theory. The binding energy of O₂^?: H₂O is calculated to be ?20.6 kcal/mol in good agreement with gas phase experimental data. At the MP3/6-31G^* level the O₂^?:H₂O complex has a C_2v structure with a double (cyclic) hydrogen bond between O₂^? and H₂O. A C_s structure with a single hydrogen bond is only 0.7 kcal/mol less stable. Interaction of H₂O with the doubly occupied π^* orbital of O₂^? is preferred slightly over interaction with the singly occupied π^* orbital. Natural bond orbital analysis suggests that both electrostatic and charge transfer interactions are important in anionic complexes. The charge transfer occurs predominantly in the O₂^? → H₂O direction and is important in determining the relative stabilities of the different structures and states. Singly and doubly hydrogen-bonded structures for the O₂^?: (H₂O)₂ and O₂^?: (H₂O)₄ clusters were found to be similar in stability and the increase in binding of the cluster becomes smaller as each additional water molecule is added to the cluster.     

A DFT study of H2O dissociation on metal‐precovered Fe (100) surface

The H₂O adsorption and dissociation on the Fe (100) surface with different precovered metals are studied by density functional theory. On both kinds of metal‐precovered surface, H₂O molecules prefer adsorb on hollow sites than bridge and top sites. The impurity energy difference is proportional to the adsorption energy, but the adsorbates are not sensitive to the adsorption orientation and height relative to the surface. The Hirshfeld charge analysis shows that water molecules act as an electron donor while the surface Fe atoms act as an electron acceptor. The rotation and dissociation of H₂O molecule occur on the Co‐ and Mn‐precovered surfaces. Some H₂O molecules are dissociated into OH and H groups. The energy barriers are about 0.5 to 1.0 eV, whose are consistence with the experimental data. H₂O molecules can be dissociated more easily at the top site on Co‐precovered surface 1 than that at bridge site on Mn‐precovered surface 2 because of the lower reaction barrier. The dispersion correction effects on the energies and adsorption configurations on Co‐precovered surface 1 were calculated by OBS + PW91. The dispersion contributions can improve a bit of the bond energy of adsorbates and weaken the hydrogen bond effect between adsorption molecules a little.     

Ab initio SCF MO study of hydrogen bonds between H2S and H2O molecules

The hydrogen bonds between H₂S and H₂O molecules are calculated through anab initio, LCAO MO SCF method using a Gaussian type orbital double-zeta basis set. The capacity of the H₂S molecule to act as an electron acceptor is confirmed. Consultant of the Instituto Mexicano del Petróleo.     

Ab initio valence-bond calculations of H2O

The first and second bond dissociation energies for H₂O have been calculated in anab initio manner using a multistructure valence-bond scheme. The basis set consisted of a minimal number of non-orthogonal atomic orbitals expressed in terms of gaussian-lobe functions. The valence-bond structures considered properly described the change in the molecular system as the hydrogen atoms were individually removed to infinity. The calculated equilibrium geometry for the H₂O molecule has an O-H bond length of 1.83 Bohrs and an HOH bond angle of 106.5°. With 49 valence-bond structures the energy of H₂O at this geometry was ?76.0202 Hartrees. The calculated equilibrium bond length for the OH radical was 1.86 Bohrs and the energy, using the same basis set, was ?75.3875 Hartrees. After correction for zero point energies the calculated bond dissociation energies are: H₂O → OH + H, D₁=75.38 kcal/mole and OH → O+H, D₂=54.79 kcal/mole.     

Effect of Hydrogen on O2 Adsorption and Dissociation on a TiO2 Anatase (001) Surface

The effect of hydrogen on the adsorption and dissociation of the oxygen molecule on a TiO₂ anatase (001) surface is studied by first‐principles calculations coupled with the nudged elastic band (NEB) method. Hydrogen adatoms on the surface can increase the absolute value of the adsorption energy of the oxygen molecule. A single H adatom on an anatase (001) surface can lower dramatically the dissociation barrier of the oxygen molecule. The adsorption energy of an O₂ molecule is high enough to break the O?O bond. The system energy is lowered after dissociation. If two H adatoms are together on the surface, an oxygen molecule can be also strongly adsorbed, and the adsorption energy is high enough to break the O?O bond. However, the system energy increases after dissociation. Because dissociation of the oxygen molecule on a hydrogenated anatase (001) surface is more efficient, and the oxygen adatoms on the anatase surface can be used to oxidize other adsorbed toxic small gas molecules, hydrogenated anatase is a promising catalyst candidate.     

Electronic Response of Nano-sized Cages of ZnO and MgO to Presence of Nitric Oxide

We have performed a comparative theoretical study on the adsorption of nitric oxide (NO) on Zn₁₂O₁₂ and Mg₁₂O₁₂ nanocages in terms of their energetic, geometric, and electronic properties. It has been found that NO adsorption on the MgO nanocage is energetically more favorable than that on the ZnO one. In contrast to the ZnO nanocage, HOMO-LUMO energy gap (Eg) of MgO one is dramatically decreased in the presence of NO molecule so that it is transformed from an intrinsic semiconductor (Eg≈5.00 eV) to a p-type one (Eg≈1.93 eV). We have predicted that electronic and conductance properties of the Mg₁₂O₁₂ nanocage are sensitive toward NO molecule, thus it may be potential candidate in detection of NO molecules.     

ZnO Nanocluster as a Potential Catalyst for Dissociation of H2S Molecule

Adsorption of hydrogen sulfide (H₂S) on the external and internal surface of Zn₁₂O₁₂ nanocluster was studied by using density functional calculations. The results indicate that the H₂S molecule is physically adsorbed or chemically dissociated by the nanocluster. It was found that the H₂S molecule can dissociate into –H and–SH fragments, suggesting that the nanocluster might be a potential catalyst for dissociation of the H₂S molecule. Also, dissociation of H₂S to S species in internal surface of the Zn₁₂O₁₂ nanocluster is energetically impossible. The HOMO–LUMO energy gap of H₂S dissociation configuration is changed about 27.68 %, indicating that the electronic properties of the nanocluster by dissociation process have strongly changed.     

Effect of aluminum vacancies on the H2O2 or H2O interaction with a gamma-AlOOH surface. A solid-state DFT study

The adsorption of a single H₂O₂ or H₂O molecule on a family of periodic slab models of γ-AlOOH is studied by solid-state DFT. The single H₂O₂ or Н₂О molecule interacts with the perfect (010) slab by intermolecular hydrogen bonds (H-bonds). In the models of γ-AlOOH with oxygen and aluminum vacancies, H₂O₂ or Н₂О also forms covalent O∙∙∙Al bonds. The energies of covalent O∙∙∙Al and H-bonds are estimated by a combined approach based on simultaneous consideration of the total binding energies with BSSE correction and empirical schemes of the Н-bond energy evaluation. The O∙∙∙Al bond energy ranges from ~75 to ~156 kJ mol⁻¹. The total energy of H-bond interactions in the case of H₂O₂ exceeds that of Н₂О by ~30 kJ mol⁻¹ for all considered slab models. In contrast to Н₂О, a H₂O₂ molecule always forms two H-bonds as the proton donor. The energy of these bonds noticeably increase on defect γ-AlOOH surfaces in comparison with the perfect slab due to formation of short (strong) H-bonds by adsorbed H₂O₂.     

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.     

Two scandium–biuret complexes: [Sc(C2H5N3O2)(H2O)5]Cl3·H2O and [Sc(C2H5N3O2)4](NO3)3

The scandium(III) cations in the structures of pentaaqua(biuret‐κ²O,O′)scandium(III) trichloride monohydrate, [Sc(C₂H₅N₃O₂)(H₂O)₅]Cl₃·H₂O, (I), and tetrakis(biuret‐κ²O,O′)scandium(III) trinitrate, [Sc(C₂H₅N₃O₂)₄](NO₃)₃, (II), are found to adopt very different coordinations with the same biuret ligand. The roles of hydrogen bonding and the counter‐ion in the establishment of the structures are described. In (I), the Sc³⁺ cation adopts a fairly regular pentagonal bipyramidal coordination geometry arising from one O,O′‐bidentate biuret molecule and five water molecules. A dense network of N—H...Cl, O—H...O and O—H...Cl hydrogen bonds help to establish the packing, resulting in dimeric associations of two cations and two water molecules. In (II), the Sc³⁺ cation (site symmetry 2) adopts a slightly squashed square‐antiprismatic geometry arising from four O,O′‐bidentate biuret molecules. A network of N—H...O hydrogen bonds help to establish the packing, which features [010] chains of cations. One of the nitrate ions is disordered about an inversion centre. Both structures form three‐dimensional hydrogen‐bond networks.     

Chemische,thermoanalytische und röntgenorgraphische Untersuchungen zur Bildung des β-Ca2[P2O7] aus dem Ca2[P4O12] · 4 H2O

Chemical, Thermoanalytical, and X-ray Investigations to the Formation of the β-Ca₂[P₂O₇] from the Ca₂[P₄O₁₂] · 4 H₂O The formation of β-Ca₂[P₂O₇] from Ca₂[P₄O₁₂] · 4 H₂O (modification I) proceeds crystallographically oriented in several steps: In one of these steps an X-ray amorphous phase is formed and simultaneously cyclotetraphosphate reorganizes to polyphosphate. The dehydration proceeds in 2 steps: At 120°C 3 molecules and at 220°C 1 molecule are lost, respectively. The formation of diphosphate from polyphosphate, which is connected with the loss of P₂O₅, takes place at 850°C according to high temperature Guinier.     

Synthesis and magnetic properties of nickel(II) triazamacrocyclic complexes. Crystal structure of [Ni(Me3[12]N3)(O2N)(H2O)]-(ClO4)·2H2O

Summary The synthesis, properties and X-ray crystal structure of [Ni(Me₃[12]N₃)(O₂N)(H₂O)](ClO₄)·2H₂O, in which Me₃[12]N₃ is 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene, are described. The Ni atom is octahedrally coordinated to three N atoms of the macrocycle, two O atoms of the nitrito group and one H₂O molecule. Monomeric units are linked by hydrogen bonds through one of the water of crystallization molecules, forming a chain. Magnetic measurements between 290 and 4 K reveal slight antiferromagnetic behaviour.     

Preparation,Crystal Structure and Vibrational Spectra of Ca2P2O6·2H2O and [Ca(H2O)3(H2P2O6)]·0.5(C12H24O6)·H2O

The calcium salts Ca₂P₂O₆ · 2H₂O ( 1 ) and [Ca(H₂O)₃(H₂P₂O₆)] · 0.5(C₁₂H₂₄O₆) · H₂O ( 2 ) were prepared and structurally characterized by single‐crystal X‐ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pbca and compound 2 in the monoclinic space group P2₁/n. The crystal structure of compound 1 consists of chains of edge‐sharing [CaO₇] polyhedra linked by hypodiphosphate(IV) anions to form a three‐dimensional network. The crystal structure of compound 2 consists of alternated layers of crown ether and water molecules and respective ionic units. Within the layers of ionic units the Ca²⁺ cations are octahedrally coordinated by three monodentate dihydrogenhypodiphosphate(IV) anions and three water molecules. The IR/Raman spectra of the title compounds were recorded and interpreted, especially with respect to the [P₂O₆]^4– and [H₂P₂O₆]^2– groups. The phase purity of 2 was verified by powder diffraction measurements.     

The crystal structure of phenoxatellurine dinitrate,C12H8O7N2Te

The crystal structure of phenoxatellurine dinitrate, C₁₂H₈O₇N₂Te, has been determined by x-ray diffractometer methods. The crystals are monoclinic, C2/c, a = 12.916(3), b = 14.050(5), c = 7.532(2) Å; β = 96.65(3)° at t = 22°. The molecule is nearly planar (175°), with the Te and O atoms of the central ring in special positions on the twofold symmetry axis. The bond distances for the central ring are: Te-C = 2.068(4) Å, C-O = 1.366(5), C-C = 1.388(6) with C-Te-C = 93.5(2)° and C-O-C = 128.2(5). The bond distances and angles in the phenyl rings do not differ significantly from the normally accepted values of 1.40 Å and 120°. The two nitrate groups are close to Te and are related by the twofold axis of symmetry. The independent distances and angles are: Te-O1 = 2.201(3), O1-N = 1.325(5), N-02 = 1.229(6), N-O3 = 1.204(6) Å, O2-N-O3 = 126.3(4), O1-N-02 = 117.1(4), O1-N-03 = 116.6(4)°. All hydrogen atoms were located at or near their calculated positions. The final R value for 1679 independent reflections was 0.031. The planarity of the molecule is discussed qualitatively in terms of simple molecular orbital theory.     

[Mn12O12(O2CMe)12(NO3)4(H2O)4]: facile synthesis of a new type of Mn12 complex

The title dodecanuclear Mn complex, namely dodeca‐μ₂‐acetato‐κ²⁴O:O′‐tetraaquatetra‐μ₂‐nitrato‐κ⁸O:O′‐tetra‐μ₄‐oxido‐octa‐μ₃‐oxido‐tetramanganese(IV)octamanganese(III) nitromethane tetrasolvate, [Mn₁₂(CH₃COO)₁₂(NO₃)₄O₁₂(H₂O)₄]·4CH₃NO₂, was synthesized by the reaction of Mn²⁺ and Ce⁴⁺ sources in nitromethane with an excess of acetic acid. This compound is distinct from the previously known single‐molecule magnet [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄], synthesized by Lis [Acta Cryst. (1980), B 36 , 2042–2044]. It is the first Mn₁₂‐type molecule containing nitrate ligands to be directly synthesized without the use of a preformed cluster. Additionally, this molecule is distinct from all other known Mn₁₂ complexes due to intermolecular hydrogen bonds between the nitrate and water ligands, which give rise to a three‐dimensional network. The complex is compared to other known Mn₁₂ molecules in terms of its structural parameters and symmetry.     

Crystal structure of the cyclotetraphosphate Ca2[P4O12] · 4 H2O

Ca₂[P₄O₁₂] · 4 H₂O crystallizes in the monoclinic space group P2₁/n, a = 7.668, b = 12.895, c = 7.144 Å, β 107.00°, D_x = 2.28 g · cm^?3, Z = 2. In the structure there are ringlike anions, which are composed of 4 PO₄ tetrahedra connected by oxygen bridges. The Ca²⁺ are surrounded by 7 oxygen atoms. Each two cation polyhedra are connected by a common edge to pairs which are isolated from one another. The water molecules form hydrogen bridges with one another and with the anion rings.     

Zoledronate complexes. III. Two zoledronate complexes with alkaline earth metals: [Mg(C5H9N2O7P2)2(H2O)2] and [Ca(C5H8N2O7P2)(H2O)]n

Diaquabis[dihydrogen 1‐hydroxy‐2‐(imidazol‐3‐ium‐1‐yl)ethylidene‐1,1‐diphosphonato‐κ²O,O′]magnesium(II), [Mg(C₅H₉N₂O₇P₂)₂(H₂O)₂], consists of isolated dimeric units built up around an inversion centre and tightly interconnected by hydrogen bonding. The Mg^II cation resides at the symmetry centre, surrounded in a rather regular octahedral geometry by two chelating zwitterionic zoledronate(1−) [or dihydrogen 1‐hydroxy‐2‐(imidazol‐3‐ium‐1‐yl)ethylidene‐1,1‐diphosphonate] anions and two water molecules, in a pattern already found in a few reported isologues where the anion is bound to transition metals (Co, Zn and Ni). catena‐Poly[[aquacalcium(II)]‐μ₃‐[hydrogen 1‐hydroxy‐2‐(imidazol‐3‐ium‐1‐yl)ethylidene‐1,1‐diphosphonato]‐κ⁵O:O,O′:O′,O′′], [Ca(C₅H₈N₂O₇P₂)(H₂O)]_n, consists instead of a Ca^II cation in a general position, a zwitterionic zoledronate(2−) anion and a coordinated water molecule. The geometry around the Ca^II atom, provided by six bisphosphonate O atoms and one water ligand, is that of a pentagonal bipyramid with the Ca^II atom displaced by 0.19 Å out of the equatorial plane. These Ca^II coordination polyhedra are `threaded' by the 2₁ axis so that successive polyhedra share edges of their pentagonal basal planes. This results in a strongly coupled rhomboidal Ca₂–O₂ chain which runs along [010]. These chains are in turn linked by an apical O atom from a –PO₃ group in a neighbouring chain. This O‐atom, shared between chains, generates strong covalently bonded planar arrays parallel to (100). Finally, these sheets are linked by hydrogen bonds into a three‐dimensional structure. Owing to the extreme affinity of zoledronic acid for bone tissue, in general, and with calcium as one of the major constituents of bone, it is expected that this structure will be useful in modelling some of the biologically interesting processes in which the drug takes part.     

Opposing Electronic and Nuclear Quantum Effects on Hydrogen Bonds in H2O and D2O

The effect of extending the O−H bond length(s) in water on the hydrogen-bonding strength has been investigated using static ab initio molecular orbital calculations. The “polar flattening” effect that causes a slight σ-hole to form on hydrogen atoms is strengthened when the bond is stretched, so that the σ-hole becomes more positive and hydrogen bonding stronger. In opposition to this electronic effect, path-integral ab initio molecular-dynamics simulations show that the nuclear quantum effect weakens the hydrogen bond in the water dimer. Thus, static electronic effects strengthen the hydrogen bond in H₂O relative to D₂O, whereas nuclear quantum effects weaken it. These quantum fluctuations are stronger for the water dimer than in bulk water.     

Syntheses,Crystal Structures,and Properties of the Isotypic Pair [Cr(H2O)6]2[B12H12]3·15H2O and [In(H2O)6]2[B12H12]3·15H2O

Single crystals of [Cr(H₂O)₆]₂[B₁₂H₁₂]₃ · 15H₂O and [In(H₂O)₆]₂[B₁₂H₁₂]₃ · 15H₂O were obtained by reactions of aqueous solutions of the acid (H₃O)₂[B₁₂H₁₂] with chromium(III) hydroxide and indium metal shot, respectively. The title compounds crystallize isotypically in the trigonal system with space group R$\bar{3}$ c (a = 1157.62(3), c = 6730.48(9) pm for the chromium, a = 1171.71(3), c = 6740.04(9) pm for the indium compound, Z = 6). The arrangement of the quasi‐icosahedral [B₁₂H₁₂]^2– dianions can be considered as stacking of two times nine layers with the sequence …ABCCABBCA… and the metal trications arrange in a cubic closest packed …abc… stacking sequence. The metal trications are octahedrally coordinated by six water molecules of hydration, while another fifteen H₂O molecules fill up the structures as zeolitic crystal water or second‐sphere hydrating species. Between these free and the metal‐bonded water molecules, bridging hydrogen bonds are found. Furthermore, there is also evidence of hydrogen bonding between the anionic [B₁₂H₁₂]^2– clusters and the free zeolitic water molecules according to B–H^δ– ··· ^δ+H–O interactions. Vibrational spectroscopy studies prove the presence of these hydrogen bonds and also show slight distortions of the dodecahydro‐closo‐dodecaborate anions from their ideal icosahedral symmetry (I_h). Thermal decomposition studies for the example of [Cr(H₂O)₆]₂[B₁₂H₁₂]₃ · 15H₂O gave no hints for just a simple multi‐stepwise dehydration process.