Effect of substitutionally boron‐doped single‐walled semiconducting zigzag carbon nanotubes on ammonia adsorption

We investigate the binding of ammonia on intrinsic and substitutionally doped semiconducting single‐walled carbon nanotubes (SWCNTs) on the side walls using density functional calculations. Ammonia is found to be weakly physisorbed on intrinsic semiconducting nanotubes while on substitutional doping with boron its affinity is enhanced considerably reflected with increase in binding energies and charge transfer. This is attributed to the strong chemical interaction between electron rich nitrogen of ammonia and electron deficient boron of the doped SWCNT. On doping, the density of states are changed compared to the intrinsic case and additional levels are formed near the Fermi level leading to overlap of levels with that of ammonia indicating charge transfer. The doped SWCNTs thus are expected to be a potential candidate for detecting ammonia. © 2014 Wiley Periodicals, Inc.     

A density functional theory study of the dimers of HX (X = F,Cl, and Br)

The geometries, interaction energies, and vibrational properties of (HF)₂, (HCl)₂, and (HBr)₂ have been investigated using a variety of hybrid density functional methods and the 6‐311+G(2df,p) basis set. Although most of the density functional methods predict geometries in reasonable agreement with experiment, methods containing the LYP correlation functional yield geometrical parameters in slightly better agreement. The (HF)₂ interaction energy, predicted by the hybrid density functional methods, is in reasonable agreement with experiment, but the (HCl)₂ and (HBr)₂ interaction energies are underestimated substantially. The frequency shift for the X? H donor bond correlates linearly with the elongation of the X? H bond upon complexation, and is predicted reasonably well by methods containing the LYP functional. Overall, the hybrid density functional methods adequately predict the properties of the halide dimers. It is interesting to note that the BHandHLYP and B1LYP density functional methods offer a competitive alternative to the popular B3LYP method. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1590–1597, 2001     

Competition between halogen bond and hydrogen bond in complexes of superalkali Li3S and halogenated acetylene XCCH (X = F,Cl, Br,and I)

Complexes of superalkali Li₃S and XCCH (X = F, Cl, Br, and I) have been studied with theoretical calculations at the MP2/aug‐cc‐pVTZ level. Three types of structures are found: (A) the X atom combines with the S atom through a halogen bond; (B) the X atom interacts with the π electron of Li₃S by a π halogen bond; (C) the H atom combines with the S atom through a hydrogen bond. For A and B, a heavier halogen atom makes the interaction stronger, while for C, the change of interaction energy is not obvious, showing a small dependence on the nature of the X atom in HCCX. A is more stable than B and their difference in stability decreases as X varies from Cl to I. For the F and Cl complexes, A is weaker than C, however, the former is stronger than the latter in the Br and I complexes. The above three types of interactions have been analyzed by means of electron localization function, electron density difference, and energy decomposition, and the results show that they have similar nature and features with conventional interactions. © 2014 Wiley Periodicals, Inc.     

Synthese,Eigenschaften und Kristallstruktur von Cu3Mo8O23X2 (X = Cl,Br, I)

Synthesis, Properties, and Crystal Structure of Cu₃Mo₈O₂₃X₂ (X = Cl, Br, I) Single crystals of the Cu₃Mo₈O₂₃X₂ compounds were grown by chemical transport reactions at the lower temperature of a gradient 873–823 K without extra transport agent (auto transport). As DTA/TG measurements indicate, the gaseous compounds, necessary for chemical transport reactions, are formed by partial decomposition of Cu₃Mo₈O₂₃X₂ at 873 K. Cu₃Mo₈O₂₃Br₂ crystallizes with the orthorombic space group Pbcm (a = 4.021(1), b = 22.978(2), c = 21.673(2) Å, Z = 4). The crystal structure consists of pentagonal columns ¹_∞[Mo₆O₇O_20/2] linked by additional MoO_6/2 octahedra. All the polyhedra(pentagonal bipyramide, octahedra) are distorted. Infinite chains ¹_∞[Cu₃Br₂] along [100] are arranged in tunnels with s‐like square shape, left open by the pentagonal columns. Cu₃Mo₈O₂₃Cl₂ (a = 4.010(1), b = 22.942(2), c = 21.639(2) Å) and Cu₃Mo₈O₂₃I₂ (a = 4.052(1), b = 23.075(2), c = 21.719(2) Å) are isotypic.     

Structure,stability, and nature of bonding in carbon monoxide bound complexes (E = group 14 element; X = H,F, Cl,Br, I)

A density functional theory study is performed to predict the structures and stability of carbon monoxide (CO) bound (E = C, Si, Ge, Sn, Pb; X = H, F, Cl, Br, I) complexes. The possibility of bonding through both C‐ and O‐sides of CO is considered. Thermochemical analysis reveals that all the dissociation processes producing CO and are endothermic in nature whereas most of the dissociation reactions are endergonic in nature at room temperature. The nature of bonding in E? C/O bonds is analyzed via Wiberg bond index, natural population analysis, electron density, and energy decomposition analyses in conjunction with natural orbitals for chemical valence scheme. In comparison to C? O stretching frequency ( ) in free CO, while a red shift is noted in O‐side binding, the C‐side binding results in a blue shift in . The relative change in values in CO bound complexes on changing either E or X is scrutinized and possible explanation is provided in terms of polarization in the σ‐ and π‐orbitals and the relative strength of C→E or O→E σ‐donation and E→C or E→O π‐back‐donation. © 2016 Wiley Periodicals, Inc.     

Characterization and cytotoxicity studies of thiol‐modified polystyrene microbeads doped with [{Mo6X8}(NO3)6]2– (X = Cl,Br, I)

Halide octahedral molybdenum clusters [{Mo₆X₈}L₆]^n– possess luminescence properties that are highly promising for biological applications. These properties are rather dependent on the nature of both the inner ligands X (i.e. Cl, Br, or I) and the apical organic or inorganic ligands L. Herein, the luminescence properties and the toxicity of thiol‐modified polystyrene microbeads (PS‐SH) doped with [{Mo₆X₈}(NO₃)₆]^2– (X = Cl, Br, I) were studied and evaluated using human epidermoid larynx carcinoma (Hep2) cell cultures. According to our data, the photoluminescence quantum yield of {Mo₆I₈}@PS‐SH is significantly higher (0.04) than that of {Mo₆Cl₈}@PS‐SH (<0.005) and {Mo₆Br₈}@PS‐SH (<0.005). Treatment of Hep2 cells with {Mo₆X₈}@PS‐SH showed that all three types of doped microbeads had no significant effect on the viability and proliferation of the cells. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface studies of magnesium oxide‐based catalysts modified with X2 or MgX2 (X = Br,I)

The introduction of a halide (Br, I) onto MgO leads to obtaining catalysts whose catalytic activity in transfer hydrogenation of acrolein with ethanol is significantly higher than that of unmodified MgO. In data found in literature, there is no concise view on how the modification of the surface of MgO with a halide affects its surface properties. Although most of the literature studies indicate a dependence of activity on the initial halide‐containing compound and type of halide, no study comprising both these aspects has been performed. The aim of the present study was to conduct measurements of MgO modified with two halides and with two types of initial halide‐containing compounds with surface‐sensitive techniques to determine how each of these factors influences the surface properties of the catalyst. Titration experiments showed that all of the modified catalysts have a smaller diversity of basic site strengths than unmodified MgO. They also revealed that for all studied systems, the modification of the surface leads to the formation of Brønsted acidic sites, which MgO does not possess. XPS spectra indicate that bromine‐modified catalysts give a broader range of surface species than the appropriate iodine‐modified ones. Moreover, they showed that in the case of both iodine‐modified and bromine‐modified catalysts, the one that exhibited the higher concentration of the appropriate halogen on the surface showed a lower activity in catalytic transfer hydrogenation of acrolein with ethanol. Copyright © 2015 John Wiley & Sons, Ltd.     

Computational study on the reactions of XO (X = F, Cl and Br) with CH3SO and CH3SO2

Potential energy surface (PES) for the reactions of XO (X = F, Cl and Br) with CH₃SO and CH₃SO₂ have been calculated at MP2/6-311++G(d, p)//B3LYP/6-311++G(d, p) level. It is revealed that all the reactions take place on both singlet and triplet surfaces. The reaction mechanisms of XO (X = F, Cl and Br) with CH₃SO and CH₃SO₂ are similar: the hydrogen abstraction channel of singlet-state PES, which has the overall negative activation energy, should be the dominant channel and CH₂SO (CH₂SO₂) + HOX should be the main products. The reactions of CH₃SO (CH₃SO₂) with XO become thermodynamically favored in the sequence of FO, ClO and BrO. The topological analysis of electronic density shows that a four-member-ring structure appears in the dominant reaction pathway, it turns to three-member-ring structure via a T-shaped structure and the ring structure disappears as the reaction proceeds. Furthermore, the scope of the structure transition region, the appeared position of the four-member-ring structure and the position of T-shaped structure correlated well to the atom which linked to the four-member-ring structure.     

Compounds with Cluster Cations together with Cluster Anions [(M6X12)(EtOH)6]2+ besides [(Mo6Cl8)Cl4X2]2– (M = Nb,Ta; X = Cl,Br) – Synthesis and Crystal Structures

Compounds consisting of both cluster cations and cluster anions of the composition [(M₆X₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₄X₂] · n EtOH · m Et₂O (M = Nb, Ta; X = Cl, Br) have been prepared by the reaction of (M₆X₁₂)X₂ · 6 EtOH with (Mo₆Cl₈)Cl₄. IR data are given for three compounds. The structures of [(Nb₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 3 EtOH · 3 Et₂O 1 and [(Ta₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 6 EtOH 2 have been solved in the triclinic space group P1 (No. 2). Crystal data: 1 , a = 10.641(2) Å, b = 13.947(2) Å, c = 15.460(3) Å, α = 65.71(2)°, β = 73.61(2)°, γ = 85.11(2)°, V = 2005.1(8) ų and Z = 1; 2 , a = 11.218(2) Å, b = 12.723(3) Å, c = 14.134(3) Å, α = 108.06(2)°, β = 101.13(2)°, γ = 91.18(2)°, V = 1874.8(7) ų and Z = 1. Both structures are built of octahedral [(M₆Cl₁₂)(EtOH)₆]²⁺ cluster cations and [(Mo₆Cl₈)Cl₆]^2– cluster anions, forming distorted CsCl structure types. The Nb–Nb and Ta–Ta bond lengths of 2.904 Å and 2.872 Å (mean values), respectively, are rather short, indicating weak M–O bonds. All O atoms of coordinated EtOH molecules are involved in H bridges. The Mo–Mo distances of 2.603 Å and 2.609 Å (on average) are characteristic for the [(Mo₆Cl₈)Cl₆]^2– anion, but there is a clear correlation between the number of hydrogen bridges to the terminal Cl and the corresponding Mo–Cl distances.     

Homonuclear chalcogen–chalcogen bond interactions in complexes pairing YO3 and YHX molecules (Y = S,Se; X = H,Cl, Br,CCH, NC,OH, OCH3): Influence of substitution and cooperativity

MP2/aug‐cc‐pVTZ calculations are performed on complexes of YO₃ (Y = S, Se) with a series of electron‐donating chalcogen bases YHX (X = H, Cl, Br, CCH, NC, OH, OCH₃). These complexes are formed through the interaction of a positive electrostatic potential region (π‐hole) on the YO₃ molecule with the negative region in YHX. Interaction energies of the binary O₃Y???YHX complexes are in the range of ?4.37 to ?12.09 kcal/mol. The quantum theory of atoms in molecules and the natural bond orbital analysis were applied to characterize the nature of interactions. It was found that the formation and stability of these binary complexes are ruled mainly by electrostatic effects, although the electron charge transfer from YHX to YO₃ unit also seems to play an important role. In addition, mutual influence between the Y???N and Y???Y interactions is studied in the ternary HCN???O₃Y???YHX complexes. The results indicate that the formation of a Y???N interaction tends to weaken Y???Y bond in the ternary systems. Although the Y???Y interaction is weaker than the Y???N one, however, both types of interactions seem to compete with each other in the HCN???O₃Y???YHX complexes. © 2016 Wiley Periodicals, Inc.     

Substitution effect on the intermolecular halogen and hydrogen bonds of the σ‐bonded fluorinated pyridine···XY/HX complexes (XY = F2, Cl2, ClF; HX = HF,HCl)

Optimal structures, electronic and thermodynamic properties of the title complexes are presented. The stability of the hydrogen bonded systems is enhanced by the increasing dipole moments whereas in the halogen bonded systems it is also affected by the atom size in the diatomics. The consecutive addition of fluorine atoms to the pyridine moiety results in the decrease of the interaction energy for both types of the investigated bonds. The substitution on the meta sites in pyridine leads to more stable complexes than the substitution in the ortho position. The role of substitution on electric polarization and electrostatic forces is estimated by the symmetry‐adapted perturbation theory energy decomposition. The predicted Gibbs free energies of the complexes of mono fluorinated pyridines with HCl, HF, and ClF are from ?12 to ?22 kJ mol^?1 at 200 K. The possible experimental identification of the complexes with respect to the vibrational modes is discussed. © 2014 Wiley Periodicals, Inc.     

Geometries,vibrational frequencies,and excitation energies of a series of fluorine‐substituted carbenes,FCX (X = H,F, Cl,Br, and I): A high‐level multireference configuration interaction study

High‐level calculations using internally contracted multireference configuration interaction including Davidson correction (icMRCI+Q) method have been carried out for the ground singlet states, the first excited states, and the lowest triplet states of a series of fluorine‐substituted carbenes FCX (X = H, F, Cl, Br, and I). Equilibrium geometries and vibrational frequencies of the three electronic states, adiabatic transition energy of the first excited singlet state, as well as the ground singlet—lowest triplet energy gap (S‐T gap) of each of FCX carbenes have been obtained. Effects of the basis set of icMRCI+Q calculation on the geometries and energies have been investigated. In addition, various corrections, including the scalar relativistic effect, spin‐orbit coupling, and core‐valence correlation, have been studied in calculating the transition energies and the S‐T gaps, especially for heavy‐atom carbenes. This results have been compared with previous calculations using a variety of methods. Our icMRCI+Q results are in very good agreement with the high‐resolution laser‐based spectroscopic results where available. Some structure and spectroscopic constants of the fluorine‐substituted carbenes which are void in the literature have been provided with consistent high‐level calculations. © 2013 Wiley Periodicals, Inc.     

Competitive interaction between halogen and hydrogen bonds in NH2Br‐HOX (X = F,Cl, and Br) complex

The NH₂Br‐HOX (X = F, Cl, and Br) complexes have been investigated with quantum chemical calculations at the MP2/aug‐cc‐pVTZ level. Five isomers are observed for the Cl and Br complexes, whereas only two isomers are found for the F complex. The geometrical, energetic, and spectroscopic parameters have been analyzed for these complexes. The hydrogen‐bonded complexes are more stable than the halogen‐bonded ones. In most complexes, the associated O? H and O? X bonds are elongated and show a red shift, whereas the distant bonds are contracted and exhibit a blue shift. The complexes have been analyzed with natural bond orbital and atoms in molecules. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Zur Reaktion der Alkin‐Kupfer(I)‐Komplexe [CuX(S‐Alkin)] (X = Cl,Br, I; S‐Alkin = 3,3,6,6‐Tetramethyl‐1‐thia‐4‐cycloheptin) mit den Phosphanen PMe3 und Ph2PCH2CH2PPh2 (dppe)

Organometallic Compounds of Copper. XVIII. On the Reaction of the Alkyne Copper(I) Complexes [CuX(S‐Alkyne)] (X = Cl, Br, I; S‐Alkyne = 3,3,6,6‐Tetramethyl‐1‐thiacyclohept‐4‐yne) with the Phosphanes PMe₃ and Ph₂PCH₂CH₂PPh₂ (dppe) The alkyne copper(I) halide complexes [CuX(S‐Alkyne)]_n ( 2 ) ( 2 a : X = Cl, 2 b : X = Br, 2 c : X = I; S‐Alkyne = 3,3,6,6‐tetramethyl‐1‐thiacyclohept‐4‐yne; n = 2, ∞) add the phosphanes PMe₃ and Ph₂PCH₂CH₂PPh₂ (dppe) to form the mono‐ and dinuclear copper compounds [(S‐Alkyne)CuX(PMe₃)] ( 6 ) ( 6 a : X = Cl, 6 b : X = Br) and [(S‐Alkyne)CuX(μ‐dppe)CuX(S‐Alkyne)] ( 7 a : X = Cl, 7 b : X = Br, 7 c : X = I), respectively. By‐product in the reaction of 2 a with dppe is the tetranuclear complex [(S‐Alkyne)Cu(μ‐X)₂Cu(μ‐dppe)₂Cu(μ‐X)₂Cu(S‐Alkyne)] ( 8 ). In case of the compounds 7 prolonged reaction times yield the alkyne‐free dinuclear copper complexes [Cu₂X₂(dppe)₃] ( 9 ) ( 9 a : X = Cl, 9 b : X = Br, 9 c : X = I)). X‐ray diffraction studies were carried out with the new compounds 6 a , 6 b , 7 b , 8 , and 9 c .     

Ab initio and AIM Theoretical Analysis of Hydrogen‐Bond Radius of HD (D: F,Cl, Br,CN, HO,HS and CCH) Donors and Some Acceptors.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Highly accurate benchmark calculations of the interaction energies in the complexes C6H6···C6X6 (X = F,Cl, Br,and I)

Different from the case of the benzene dimer, the differences between the interaction energies are always less than 0.50 kcal/mol for face‐to‐face eclipsed, face‐to‐face staggered, and parallel‐displaced configurations of all investigated complexes C₆H₆···C₆X₆ (X = F, Cl, Br, and I). Hence, it is a great challenge for quantum chemists to accurately calculate the interaction energies for the three configurations of the complexes C₆H₆···C₆X₆. This work demonstrates that results obtained with the PBE0 density functional combined with the D3 dispersion correction (PBE0‐D3) and the basis set def2‐TZVPP are in excellent agreement with the estimates of the coupled‐cluster singles, doubles, and perturbative triples [CCSD(T)] complete basis set (CBS) limit. The other finding in this study is that, in comparison with the gold‐standard CCSD(T)/CBS benchmark, the spin‐component scaled (SCS) zeroth‐order symmetry‐adapted perturbation theory (SAPT0), when paired with the basis set aug‐cc‐pVDZ, performs also very well, and its performance is even better than that of the PBE0‐D3/def2‐TZVPP method or the conventional SAPT/aug‐cc‐pVQZ method. The findings of this study are very significant because both PBE0‐D3/def2‐TZVPP and SCS‐SAPT0/aug‐cc‐pVDZ can deal with the systems with more than 200 atoms.     

Darstellung,Kristallstrukturen und Schwingungsspektren von trans‐[Pt(N3)4X2]2–, X = Cl,Br, I

Synthesis, Crystal Structures, and Vibrational Spectra of trans ‐[Pt(N₃)₄X₂]^2–, X = Cl, Br, I By oxidative addition to (n‐Bu₄N)₂[Pt(N₃)₄] with the elemental halogens in dichloromethane trans‐(n‐Bu₄N)₂[Pt(N₃)₄X₂], X = Cl, Br, I are formed. X‐ray structure determinations on single crystals of trans‐(Ph₄P)₂[Pt(N₃)₄Cl₂] (triclinic, space group P1, a = 10.352(1), b = 10.438(2), c = 11.890(2) Å, α = 91.808(12), β = 100.676(12), γ = 113.980(10)°, Z = 1), trans‐(Ph₄P)₂[Pt(N₃)₄Br₂] (triclinic, space group P1, a = 10.336(1), b = 10.536(1), c = 12.119(2) Å, α = 91.762(12), β = 101.135(12), γ = 112.867(10)°, Z = 1) and trans‐(Ph₄P)₂[Pt(N₃)₄I₂] (triclinic, space group P1, a = 10.186(2), b = 10.506(2), c = 12.219(2) Å, α = 91.847(16), β = 101.385(14), γ = 111.965(18)°, Z = 1) reveal, that the compounds crystallize isotypically with octahedral centrosymmetric complex anions. The bond lengths are Pt–Cl = 2.324, Pt–Br = 2.472, Pt–I = 2.619 and Pt–N = 2.052–2.122 Å. The approximate linear Azidoligands with N^α–N^β–N^γ‐angles = 172.1–176.8° are bonded with Pt–N^α–N^β‐angles = 116.2–121.9°. In the vibrational spectra the platinum halogen stretching vibrations of trans‐(n‐Bu₄N)₂[Pt(N₃)₄X₂] are observed in the range of 327–337 (X = Cl), at 202 (Br) and in the range of 145–165 cm^–1 (I), respectively. The platinum azide stretching modes of the three complex salts are in the range of 401–421 cm^–1. Based on the molecular parameters of the X‐ray determinations the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f_d(PtCl) = 1.90, f_d(PtBr) = 1.64, f_d(PtI) = 1.22, f_d(PtN^α) = 2.20–2.27 and f_d(N^αN^β, N^βN^γ) = 12.44 mdyn/Å.     

Three closely‐related cyclohexanols (C35H27X2N3O3; X = F,Cl or Br): similar molecular structures but different crystal structures

Three highly‐substituted cyclohexanol derivatives have been prepared from 2‐acetylpyridine and 4‐halogenobenzaldehydes under mild conditions. (1RS,2SR,3SR,4RS,5RS)‐3,5‐Bis(4‐fluorophenyl)‐2,4‐bis(pyridine‐2‐carbonyl)‐1‐(pyridin‐2‐yl)cyclohexanol, C₃₅H₂₇F₂N₃O₃, (I), (1RS,2SR,3SR,4RS,5RS)‐3,5‐bis(4‐chlorophenyl)‐2,4‐bis(pyridine‐2‐carbonyl)‐1‐(pyridin‐2‐yl)cyclohexanol acetone 0.951‐solvate, C₃₅H₂₇Cl₂N₃O₃·0.951C₃H₆O, (II), and (1RS,2SR,3SR,4RS,5RS)‐3,5‐bis(4‐bromophenyl)‐2,4‐bis(pyridine‐2‐carbonyl)‐1‐(pyridin‐2‐yl)cyclohexanol, C₃₅H₂₇Br₂N₃O₃, (III), all crystallize in different space groups, viz. Pbca, Fdd2 and P, respectively. In compound (II), the acetone molecule is disordered over two sets of atomic sites having occupancies of 0.690 (13) and 0.261 (13). Each of the cyclohexanol molecules contains an intramolecular O—H...N hydrogen bond and their overall molecular conformations are fairly similar. The molecules of (I) are linked by two independent C—H...O hydrogen bonds to form a C(5)C(10)[R₂²(15)] chain of rings, and those of (III) are linked by a combination of C—H...O and C—H...N hydrogen bonds, forming a chain of alternating R₂²(16) and R₂²(18) rings. The cyclohexanol molecules in (II) are linked by a single C—H...N hydrogen bond to form simple C(4) chains and these chains are linked by a π–π stacking interaction to form sheets, to which the disordered acetone molecules are weakly linked via a number of C—H...O contacts.     

ChemInform Abstract: Lewis Acidities and Hydride,Fluoride, and X‐ Affinities of the BH3‐nXn Compounds for (X: F,Cl, Br,I, NH2, OH,and SH) from Coupled Cluster Theory.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.