H2O, H2S与双卤分子间相互作用的电子密度拓扑研究

运用量子化学微扰理论MP2和密度泛函B3LYP方法, 采用6-311＋＋G(d,p)基组, 对H₂O, H₂S与双卤分子XY (XY＝F₂, Cl₂, Br₂, ClF, BrF, BrCl)形成的卤键复合物进行构型全优化, 并计算得到了这些体系的分子间相互作用能. 利用电子密度拓扑分析方法对卤键复合物的拓扑性质进行了分析研究, 探讨了该类分子间卤键的作用本质. 结果表明, 形成卤键后, 作为电子受体的双卤分子X—Y键长增长, 振动频率减小. 复合物体系中的卤键介于共价键与离子键之间, 偏于静电作用成分为主.     

Computational studies of σ-type weak interactions between NCO/NCS radicals and XY(X = H,Cl;Y = F,Cl,and Br)

The triatomic radicals NCO and NCS are of interest in atmospheric chemistry,and both the ends of these radicals can potentially serve as electron donors during the formation of σ-type hydrogen/halogen bonds with electron acceptors XY(X = H,Cl;Y = F,Cl,and Br).The geometries of the weakly bonded systems NCO/NCS···XY were determined at the MP2/aug-cc-pVDZ level of calculation.The results obtained indicate that the geometries in which the hydrogen/halogen atom is bonded at the N atom are more stable than those where it is bonded at the O/S atom,and that it is the molecular electrostatic potential(MEP)-not the electronegativity-that determines the stability of the hydrogen/halogen bond.For the same electron donor(N or O/S) in the triatomic radical and the same X atom in XY,the bond strength decreases in the order Y = F > Cl > Br.In the hydrogen/halogen bond formation process for all of the complexes studied in this work,transfer of spin electron density from the electron donor to the electron acceptor is negligible,but spin density rearranges within the triatomic radicals,being transferred to the terminal atom not interacting with XY.     

The Role of Molecular Electrostatic Potentials in the Formation of a Halogen Bond in Furan⋅⋅⋅XY and Thiophene⋅⋅⋅XY Complexes

The halogen bonding of furan???XY and thiophene???XY (X=Cl, Br; Y=F, Cl, Br), involving σ‐ and π‐type interactions, was studied by using MP2 calculations and quantum theory of “atoms in molecules” (QTAIM) studies. The negative electrostatic potentials of furan and thiophene, as well as the most positive electrostatic potential (V_S,max) on the surface of the interacting X atom determined the geometries of the complexes. Linear relationships were found between interaction energy and V_S,max of the X atom, indicating that electrostatic interactions play an important role in these halogen‐bonding interactions. The halogen‐bonding interactions in furan???XY and thiophene???XY are weak, “closed‐shell” noncovalent interactions. The linear relationship of topological properties, energy properties, and the integration of interatomic surfaces versus V_S,max of atom X demonstrate the importance of the positive σ hole, as reflected by the computed V_S,max of atom X, in determining the topological properties of the halogen bonds.     

NCO/NCS自由基与XY（X=H,Cl;Y=F,Cl,Br）间σ-型弱作用的理论研究

NCO和NCS是大气化学中非常引人关注的自由基,它们均有三个原子并且两个端基原子均可作为电子给体形成σ-型氢/卤键.本文在MP2/aug-cc-pVDZ水平上研究了NCO/NCS...XY（X=H,Cl;Y=F,Cl,Br）体系中的弱化学键.计算结果表明,氢/卤原子与N原子相连形成的复合物比与O/S原子相连形成的复合物稳定;氢/卤键的稳定性由分子静电势决定,而非原子电负性;对相同的电子给体B（B=N,O/S）和相同的卤原子来说,化学键的强度按Y=F,Cl,Br的顺序逐渐减弱.在氢/卤键形成过程中,自旋电子密度在电子给体和电子受体间的转移较少,但它在自由基内部发生重排,就本文研究的所有复合物而言,自旋电子密度均转移向XY分子的相反位置.     

Halogen bonding: a theoretical study based on atomic multipoles derived from quantum theory of atoms in molecules

Atomic multipole moments derived from quantum theory of atoms in molecules are used to study halogen bonds in dihalogens (with general formula YX, in which X refers to the halogen directly interacted with the Lewis base) and some molecules containing C–X group. Multipole expansion is used to calculate the electrostatic potential in a vicinity of halogen atom (which is involved in halogen bonding) in terms of atomic monopole, dipole, and quadrupole moments. In all the cases, the zz component of atomic traceless quadrupole moments (where z axis taken along Y–X or C–X bonds) of the halogens plays a stabilizing role in halogen bond formation. The effects of atomic monopole and dipole moments on the formation of a halogen bond in YX molecules depend on Y and X atoms. In Br₂ and Cl₂, the monopole moment of halogens is zero and has no contribution in electrostatic potential and hence in halogen bonding, while in ClBr, FBr, and FCl it is positive and therefore stabilize the halogen bonds. On the other hand, the negative sign of dipole moment of X in all the YX molecules weakens the corresponding halogen bonds. In the C–X-containing molecules, monopole and dipole moments of X atom are negative and consequently destabilize the halogen bonds. So, in these molecules the quadrupole moment of X atom is the only electrostatic term which strengthens the halogen bonds. In addition, we found good linear correlations between halogen bonds strength and electrostatic potentials calculated from multipole expansion.     

Ab initio and AIM studies on typical π‐type and pseudo‐π‐type halogen bonds: Comparison with hydrogen bonds

Series of typical π‐type and pseudo‐π‐type halogen‐bonded complexes B ··· ClY and B ··· BrY and hydrogen‐bonded complex B ··· HY (B = C₂H₄, C₂H₂, and C₃H₆; Y = F, Cl, and Br) have been investigated using the MP2/aug‐cc‐pVDZ method. A striking parallelism was found in the geometries, vibrational frequencies, binding energies, and topological properties between B ··· XY and B ··· HY (X = Cl and Br). It has been found that the lengths of the weak bond d(X ··· π)/d(H ··· π), the frequencies of the weak bond ν(X ··· π)/ν(H ··· π), the frequency shifts Δν(X? Y)/Δν(H? Y), the electron densities at the bond critical point of the weak bonds ρ_c(X ··· π)/ρ_c(H ··· π), and the electron density changes Δρ_c(X? Y)/Δρ_c(H? Y) could be used as measures of the strengths of typical π‐type and pseudo‐π‐type halogen/hydrogen bonds. The typical π‐type and pseudo‐π‐type halogen bond and hydrogen bond are noncovalent interactions. For the same Y, the halogen bond strengths are in the order B ··· ClY < B ··· BrY. For the same X, the halogen bond strength decreases according to the sequence F > Cl > Br that is in agreement with the hydrogen bond strengths B ··· HF > B ··· HCl > B ··· HBr. All of these typical π‐type and pseudo‐π‐type hydrogen‐bonded and halogen‐bonded complexes have the “conflict‐type” structure. Contour maps of the Laplacian of π electron density indicate that the formation of B ··· XY halogen‐bonded complex and B ··· HY hydrogen‐bonded complex is very similar. Charge transfer is observed from B to XY/HY and both the dipolar polarization and the volume of the halogen atom or hydrogen atom decrease on B ··· XY/B ··· HY complex formation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

A computational study on the nature of the halogen bond between sulfides and dihalogen molecules

The characteristics and nature of the halogen bonding in a series of B···XY (B = H₂S, H₂CS, (CH₂)₂S; XY = ClF, Cl₂, BrF, BrCl, Br₂) complexes were analyzed by means of the quantum theory of “atoms in molecules” (QTAIM) and “natural bond orbital” (NBO) methodology at the second-order Møller-Plesset (MP2) level. Electrostatic potential, bond length, interaction energy, topological properties of the electron density, the dipole moment, and the charge transfer were investigated systematically. For the same electron donor, the interaction energies follows the B···BrF > B···ClF > B···BrCl > B···Br₂ > B···Cl₂ > B···ClBr order. For the same electron acceptor, the interaction energies increase in the sequence of H₂S, H₂CS, and (CH₂)₂S. Topological analyses show these halogen bonding interactions belong to weak interactions with an electrostatic nature. It was found that the strength of the halogen-bonding interaction correlates well with the electrostatic potential associated with halogen atom and the amount of charge transfer from sulfides to dihalogen molecules, indicating that electrostatic interaction plays an important role in these halogen bonds. Charge transfer is also an important factor in the halogen bonds involved with dihalogen molecules.     

Comparison of triel bonds with different chalcogen electron donors: Its dependence on triel donor and methyl substitution

The complexes between R₃Tr (Tr = B, Al, and Ga; R = H, F, Cl, and Br) and H₂X (X = O, S, and Se) were theoretically studied. The interaction energies of R₃Al⋯H₂X and R₃Ga⋯H₂X are consistent with the electronegativity of the halogen atom R (R ≠ H), but an opposite dependence is found for R₃B⋯H₂X. The triel bond of R₃Tr⋯H₂X is weaker for the heavier chalcogen donor. The dependence of triel bonding strength on the triel atom is complicated, depending on the nature of R and X. The methyl substitution of H₂X causes a substantial increase in the interaction energy from −5.74 kcal/mol to −22.88 kcal/mol, and its effect is relevant to the nature of Tr, X, and R groups. For the S and Se donors, the increased percentage of interaction energy is almost the same due to the methyl substitution, which is larger than that of the O analogue. In most triel-bonded complexes, electrostatic dominates and polarization has comparable contribution. However, polarization plays a dominant role in R₃B⋯ and R₃B⋯ (R = Cl and Br; R′ = H and Me).     

Triel Bonds with Au Atoms as Electron Donors

The novel triel bonds of BX₃ (X=H, F, Cl, Br, and I) and C₅H₅B as electron acceptors and AuR₂ (R=Cl and CH₃) as an electron donor were explored. The triel bond is a primary driving force for most complexes, while the contribution from a halogen-chlorine interaction in BX₃−AuCl₂ (X=Cl, Br, and I) and an iodine-Au interaction in BI₃−Au(CH₃)₃ is also very important. Interestingly, the positively charged Au atom of AuCl₂ can attractively bind with the holes of BX₃ and C₅H₅B. The interaction energy lies in the range of 1 and 80 kcal/mol, in the order X=F<H<Cl<Br<I. In most cases, the triel bond of C₅H₅B is stronger than the triel bond of BX₃. In the formation of B−Au triel bond, electrostatic energy is not dominant, while polarization energy including orbital interaction has the largest contribution for the strongly bonded complexes and dispersion energy for the weak triel bond.     

Comparison of σ-/π-Hole Tetrel Bonds between TH3F/F2TO and H2CX (X=O,S, Se)

Several σ-hole and π-hole tetrel-bonded complexes with a base H₂CX (X=O, S, Se) have been studied, in which TH₃F (T=C−Pb) and F₂TO (T=C and Si) act as the σ-hole and π-hole donors, respectively. Generally, these complexes are combined with a primary tetrel bond and a weak H-bond. Only one minimum tetrel-bonded structure is found for TH₃F, whereas two minima tetrel-bonded complexes for some F₂TO. H₂CX is favorable to engage in the π-hole complex with F₂TO relative to TH₃F in most cases, and this preference further expands for the Si complex. Particularly, the double π-hole complex between F₂SiO and H₂CX (X=S and Se) has an interaction energy exceeding 500 kJ/mol, corresponding to a covalent-bonded complex with the huge orbital interaction and polarization energy. Both the σ-hole interaction and the π-hole interaction are weaker for the heavier chalcogen atom, while the π-hole interaction involving F₂TO (T=Ge, Sn, and Pb) has an opposite change. Both types of interactions are electrostatic in nature although comparable contributions from dispersion and polarization are respectively important for the weaker and stronger interactions.     

Theoretical Studies on the Halogen Bond between Propargyl Radical and Dihalogen Molecules

MP2/aug‐cc‐pVDZ calculations are carried out on the geometries, vibrational frequencies, interaction energies and topological properties for the π‐type halogen‐bonded complexes between propargyl radical and dihalogen molecules ClF, BrF and BrCl. There are two kinds of geometries: complex ( a ) involves the interaction between the X (X=Cl, Br) atom and the midpoint of C(1) –C(2) bond, complex ( b ) involves the interaction between the X atom and C(3) atom. The lengths of the halogen bond, the frequencies of the halogen bond, the elongation extent of the X–Y (XY=ClF, BrF, BrCl) bond, topological parameters at the BCPs of the halogen bond and X–Y bond are all well consistent with the interaction energies. The interaction of complex ( a ) is stronger than that of complex ( b ); the interaction of propargyl···BrF is stronger than that of propargyl···ClF and propargyl···BrCl. For the complexes ( a ) and ( b ), the charge transfer is observed from propargyl radical to XY, the atomic energy, the dipolar polarization, and the volume of the halogen atom X decrease upon complex formation.     

The competition of Y⋯o and X⋯n halogen bonds to enhance the group V σ‐hole interaction in the NCY⋯oPH3⋯NCX and OPH3⋯NCX⋯NCY (X,YF,Cl, and Br) complexes

The positive electrostatic potentials (ESP) outside the σ‐hole along the extension of O? P bond in O?PH₃ and the negative ESP outside the nitrogen atom along the extension of the C? N bond in NCX could form the Group V σ‐hole interaction O?PH₃?NCX. In this work, the complexes NCY?O?PH₃?NCX and O?PH₃?NCX?NCY (X, Y?F, Cl, Br) were designed to investigate the enhancing effects of Y?O and X?N halogen bonds on the P?N Group V σ‐hole interaction. With the addition of Y?O halogen bond, the V _{S, max} values outside the σ‐hole region of O?PH₃ becomes increasingly positive resulting in a stronger and more polarizable P?N interaction. With the addition of X?N halogen bond, the V _{S, min} values outside the nitrogen atom of NCX becomes increasingly negative, also resulting in a stronger and more polarizable P?N interaction. The Y?O halogen bonds affect the σ‐hole region (decreased density region) outside the phosphorus atom more than the P?N internuclear region (increased density region outside the nitrogen atom), while it is contrary for the X?N halogen bonds. © 2015 Wiley Periodicals, Inc.     

Magnesium–halobenzene bonding: mapping the halogen sigma-hole with a Lewis-acidic complex

Complexes of the Lewis base-free cations (^MeBDI)Mg⁺ and (^tBuBDI)Mg⁺ with Ph–X ligands (X = F, Cl, Br, I) have been studied (^MeBDI = HC[C(Me)N-DIPP]₂ and ^tBuBDI = HC[C(tBu)N-DIPP]₂; DIPP = 2,6-diisopropylphenyl). For the smaller β-diketiminate ligand (^MeBDI) only complexes with PhF could be isolated. Heavier Ph–X ligands could not compete with bonding of Mg to the weakly coordinating anion B(C₆F₅)₄⁻. For the cations with the bulkier ^tBuBDI ligand, the full series of halobenzene complexes was structurally characterized. Crystal structures show that the Mg⋯X–Ph angle strongly decreases with the size of X: F 139.1°, Cl 101.4°, Br 97.7°, I 95.1°. This trend, which is supported by DFT calculations, can be explained with the σ-hole which increases from F to I. Charge calculation and Atoms-In-Molecules analyses show that Mg⋯F–Ph bonding originates from electrostatic attraction between Mg²⁺ and the very polar C^δ+–F^δ− bond. For the heavier halobenzenes, polarization of the halogen atom becomes increasingly important (Cl < Br < I). Complexation with Mg leads in all cases to significant Ph–X bond activation and elongation. This unusual coordination of halogenated species to early main group metals is therefore relevant to C–X bond breaking.

Complexes of a highly Lewis acidic Mg cation and the full series of Ph–X (X = F, Cl, Br, I) have been structurally characterized. The Mg⋯X–Ph angle decreases with halogen size on account of the growing halogen σ-hole.     

Halogen bonding between substituted chlorobenzene and trimethylamine: Decisive role of σ–hole and C?Cl bond breaking energy

Theoretical studies have been carried out on the halogen bonding interaction between para substituted chlorobenzene (Y C₆H₄Cl, Y = H, NH₂, CH₃, F, CN, NO₂) and N(CH₃)₃ using ab initio MP2/aug‐cc‐pVDZ and DFT based wB97XD/6‐311++G(d,p) methods. The positive electrostatic potential (V_S,max) on the Cl atom and the heterolytic bond breaking enthalpy of the C Cl bond have been calculated and their role on halogen bonding is discussed. The heterolytic bond breaking enthalpy of the C Cl bond is proposed as a measure of the strength of the σ‐hole on Cl atom. The binding strength of the complexes ranging between −6.13 kJ mol⁻¹ and −9.29 kJ mol⁻¹ are linearly related to the V_S,max of the Cl atom and the bond breaking enthalpy of the C Cl bond. In addition, energy decomposition analysis was performed on the halogen bonded complexes via symmetry adapted perturbation theory (SAPT) to predict the dominant energy component and the nature of the N···Cl interaction.     

Comparison between Hydrogen and Halogen Bonds in Complexes of 6-OX-Fulvene with Pnicogen and Chalcogen Electron Donors

Quantum chemical calculations are applied to complexes of 6-OX-fulvene (X=H, Cl, Br, I) with ZH₃/H₂Y (Z=N, P, As, Sb; Y=O, S, Se, Te) to study the competition between the hydrogen bond and the halogen bond. The H-bond weakens as the base atom grows in size and the associated negative electrostatic potential on the Lewis base atom diminishes. The pattern for the halogen bonds is more complicated. In most cases, the halogen bond is stronger for the heavier halogen atom, and pnicogen electron donors are more strongly bound than chalcogen. Halogen bonds to chalcogen atoms strengthen in the order O<S<Se<Te, whereas the pattern is murkier for the pnicogen donors. In terms of competition, most halogen bonds to pnicogen donors are stronger than their H-bond analogues, but there is no clear pattern with respect to chalcogen donors. O prefers a H-bond, while halogen bonds are favored by Te. For S and Se, I-bonds are strongest, followed Br, H, and Cl-bonds in that order.     

Group 12 Carbonates and their Binary Complexes with Nitrogen Bases and FH2Z Molecules (Z=P,As, Sb): Synergism in Forming Ternary Complexes

MCO₃ (M=Zn, Cd, Hg) forms a spodium bond with nitrogen-containing bases (HCN, NHCH₂, NH₃) and a pnicogen bond with FH₂Z (Z=P, As, Sb). The spodium bond is very strong with the interaction energy ranging from −31 kcal/mol to −56 kcal/mol. Both NHCH₂ and NH₃ have an equal electrostatic potential on the N atom, but the corresponding interaction energy is differentiated by 1.5–4 kcal/mol due to the existence of spodium and hydrogen bonds in the complex with NHCH₂ as the electron donor. The spodium bond is weakest in the HCN complex, which is not consistent with the change of the binding distance. The spodium bond becomes stronger in the CdCO₃<ZnCO₃<HgCO₃ sequence although the positive electrostatic potential on the Hg atom is smallest. This is because the electrostatic interaction is dominant in the spodium-bonded complexes of CdCO₃ and ZnCO₃ but the polarization interaction in that of HgCO₃. The pnicogen bond is much weaker than the spodium bond and the former has a larger enhancement than the latter in the FH₂Z⋅⋅⋅OCO₂M⋅⋅⋅N-base ternary complexes.     

A new unconventional halogen bond C?X···H?M between HCCX (X = Cl and Br) and HMH (M = Be and Mg): An ab initio study

In this article, a new type of halogen‐bonded complex YCCX···HMY (X = Cl, Br; M = Be, Mg; Y = H, F, CH₃) has been predicted and characterized at the MP2/aug‐cc‐pVTZ level. We named it as halogen‐hydride halogen bonding. In each YCCX···HMY complex, a halogen bond is formed between the positively charged X atom and the negatively charged H atom. This new kind of halogen bond has similar characteristics to the conventional halogen bond, such as the elongation of the C? X bond and the red shift of the C? X stretch frequency upon complexation. The interaction strength of this type of halogen bond is in a range of 3.34–10.52 kJ/mol, which is smaller than that of dihydrogen bond and conventional halogen bond. The nature of the electrostatic interaction in this type of halogen bond has also been unveiled by means of the natural bond orbital, atoms in molecules, and energy decomposition analyses. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010     

Alkoxy,amido and thiolato complexes of tris (3, 5-dimethylpyrazolyl)borato(nitrosyl) molybdenum fluoride,chloride and bromide

The complexes Mo{HB(Me₂pyz)₃}(NO)XY {HB(Me₂pyz)₃  HB(3, 5-Me₂C₃HN₂)₃; X=Y=F, Cl or Br; X=F, Y=OEt, NHMe or SBuⁿ; X=Cl, Y=NHR (R=Me Et, Buⁿ, Ph, p-MeC₆H₄), NMe₂ and SR (R=Buⁿ, C₆H₁₁, CH₂Ph, Ph); X=Br, Y=NHMe, NMe₂ and SBuⁿ} have been prepared and characterised spectroscopically. Their properties are generally similar to those of their iodo-analogues.     

Using Ylide Functionalization to Stabilize Boron Cations

The metalated ylide YNa [Y=(Ph₃PCSO₂Tol)⁻] was employed as X,L‐donor ligand for the preparation of a series of boron cations. Treatment of the bis‐ylide functionalized borane Y₂BH with different trityl salts or B(C₆F₅)₃ for hydride abstraction readily results in the formation of the bis‐ylide functionalized boron cation [Y−B−Y]⁺ ( 2 ). The high donor capacity of the ylide ligands allowed the isolation of the cationic species and its characterization in solution as well as in solid state. DFT calculations demonstrate that the cation is efficiently stabilized through electrostatic effects as well as π‐donation from the ylide ligands, which results in its high stability. Despite the high stability of 2 [Y−B−Y]⁺ serves as viable source for the preparation of further borenium cations of type Y₂B⁺←LB by addition of Lewis bases such as amines and amides. Primary and secondary amines react to tris(amino)boranes via N−H activation across the B−C bond.