Theoretical study of cooperativity between hydrogen bond‒hydrogen bond,halogen bond‒halogen bond and hydrogen bond‒halogen bond in ternary FX…diazine…XF (X = H and Cl) complexes

ABSTRACT

In the present work, the cooperativity between hydrogen bond?hydrogen bond, halogen bond?halogen bond and hydrogen bond?halogen bond in ternary FX…diazine…XF (X = H and Cl) complexes is theoretically investigated. The sign of cooperative energy (E_coop) obtained in all of the triads is positive which indicates that the ternary complex is less stable than the sum of the two isolated binary complexes. Moreover, our calculations show that E_coop value in triads increases as FX…pyridazine…XF > FX…pyrimidine…XF > FX…pyrazine…XF. In agreement with energetic, geometrical and topological properties, electrostatic potentials and coupling constants across ¹⁵N…X?¹⁹F (X = ¹H or ³⁵Cl) hydrogen and halogen bonds indicate that hydrogen and halogen bonds are weakened in the considered complexes where two hydrogen and halogen bonds coexist. As compared to N…H hydrogen bond, it is also observed that cooperativity has greater effect on N…Cl halogen bond.     

Cooperativity effects between σ-hole interactions: a theoretical evidence for mutual influence between chalcogen bond and halogen bond interactions in F2S···NCX···NCY complexes (X = F,Cl, Br,I; Y = H,F, OH)

Quantum chemical calculations are performed to study the cooperativity effects between chalcogen bond and halogen bond interactions in F₂S···NCX···NCY complexes, where X = F, Cl, Br, I and Y = H, F, OH. These effects are investigated in terms of geometric and energetic features of the complexes, which are computed by second-order Møller–Plesset perturbation theory (MP2). For each F₂S···NCX···NCY complex studied, the effect of cooperativity on the chalcogen bond is dependent on the strength of halogen bond. The results indicate that the interaction energies of chalcogen and halogen bonds in the triads are more negative relative to the respective dyads. The interaction energy of chalcogen bond is increased by 31%–49%, whereas that of halogen bond by 28%–62%. The energy decomposition analysis reveals that electrostatic force plays a main role in the cooperativity effects between the chalcogen bond and halogen bond interactions. The topological analysis, based on the quantum theory of atoms in molecules, is used to characterise the interactions and analyse their enhancement with varying electron density at bond critical points.     

Computational study of non-covalent interactions in oxirane…XF complexes (X = H,F, Cl,Br, Li) and their F-/Li-substituted analogues

A computational study found oxirane^…XF (X = H, Cl, Br, F, Li) dimers to be energetically stable, with their interaction energies increasing with the magnitude of the XF dipole moment in the order XF = LiF > BrF ～ HF > ClF > F₂. Their relative stabilities roughly correlate with the amount of charge transferred from the lone pairs on the O atom of oxirane to the antibonding σ* orbital of XF. However, the most strongly bound dimer, oxirane^…LiF, is stabilised by the largest dipole but involves the smallest charge transfer. The variation in the strength of the oxirane^…XF interaction was subsequently investigated by the sequential substitution of the protons on oxirane by either electron-donating Li or electron-withdrawing F atoms.     

Tuning of tetrel bonds interactions by substitution and cooperative effects in XH3Si···NCH···HM (X = H,F, Cl,Br; M = Li,Na, BeH and MgH) complexes

In this work, the interplay between the tetrel bond and the dihydrogen bond is investigated in ternary XH₃Si···NCH···HM complexes, where X = H, F, Cl, Br and M = Li, Na, BeH, MgH. The nature of Si···N and H···H interactions is studied by molecular electrostatic potential (MEP), noncovalent interaction and electron localisation function analyses. All binding distances in the ternary complexes are shorter than those of isolated XH₃Si···NCH and NCH···HM systems. That is, the two types of interactions have a cooperative effect on each other. The results of the MEP analysis indicate that the enhancement of the Si···N and H···H bonds can mainly be attributed to the electrostatic interaction. The plot of the reduced density gradient versus sign (λ₂)ρ indicates that the location of the spike associated with each interaction in the ternary systems moves slightly towards the negative (λ₂)ρ values with respect to the binary systems. This confirms that both Si···N and H···H interactions in the ternary complexes are strengthened by the presence of other. Besides, cooperative effects lead to a considerable change in the ¹⁴N nuclear quadrupole coupling constant values of the ternary complexes relative to the XH₃Si···NCH complexes.     

Strengthening of the halogen-bonding by an aerogen bond interaction: substitution and cooperative effects in O3Z···NCX···NCY (Z = Ar,Kr, Xe; X = Cl,Br, I; Y = H,F, OH) complexes

The geometry, interaction energy and bonding properties of ternary complexes O₃Z···NCX···NCY (Z= Ar, Kr, Xe; X = Cl, Br, I and Y = H, F, OH) are investigated with ab initio calculations at the MP2/aug-cc-pVTZ level. Two different types of intermolecular interactions are present in these complexes, namely, aerogen bond (Z···N) and halogen bond (X···N). The formation mechanism and bonding properties of these complexes are analysed with molecular electrostatic potentials, quantum theory of atoms in molecules and non-covalent interaction index. It is found that the cooperativity energies in the ternary complexes are all negative; that is, the interaction energy of the ternary complex is greater (more negative) than the sum of the interaction energies of the corresponding binary systems. Also, the cooperativity energies increase with the increase of the interaction energies. The cooperative effects in the ternary complexes make a decrease in the total spin–spin coupling constants across the aerogen bonding, J(Z–N), which can be regarded as a proof for the reinforce of Z···N interactions in the ternary complexes with respect to the binary systems.     

Effect of electron-donating and electron-withdrawing atoms on the C–H…Y hydrogen bond in model X3CH…YZ (X = B,F; YZ = BF,CO, N2) complexes

A computational study of model complexes X₃CH…YZ (X = B, F; YZ = BF, CO, N₂) was undertaken to assess the effect of electron-donating and electron-withdrawing X atoms on the properties of the C–H…Y hydrogen bond. Sequential substitution of the B atoms in B₃CH by F atoms to produce F₃CH allowed for the elucidation of interesting trends in the corresponding hydrogen-bonded complexes. The dipole moments and the dipole moment derivative with respect to C–H bond displacement for the proton donors and the chemical hardness of the Y atom of the proton acceptor YZ were found to be useful parameters for understanding these trends. It was found that a positive dipole derivative favours red-shifted hydrogen bonds, whereas a negative dipole derivative favours blue-shifted hydrogen bonds. However, decreasing hardness of Y (which correlates with increasing intermolecular attraction) modifies the interaction such that either greater C–H bond extensions/red shifts or smaller C–H bond compressions/blue shifts are obtained.     

SCF Xα — SW ionization energies of XNO (X = Cl,F and Br) and XON (X = Cl,and F)

Ionization energies of the nitrosyl halides XNO (X = Cl, F, and Br) have been obtained using the SCF Xα scattered-wave method and transition state procedure. The results are comapred to other theoretical and experimental ionization energies as well as among themselves. Ionization energies of nitrogen hypohalides XON (X = Cl and F) have also been computed and compared to those of XNO (X = Cl and F). It was found that the present results yield a good agreement with the experimental ionization energies.     

Cooperative effects between F … Ag bonded and X … Br (Cl) halogen-bonded interaction in BrF(ClF) … AgX … BrF(ClF) (X = F,Cl, Br) complexes: a theoretical study

The equilibrium structures, interaction energies and binding properties of ternary BrF(ClF)?… AgX?…?BrF(ClF)(X?=?F, Cl, Br) complexes and the corresponding binary systems have been studied by DFT method at the X3LYP/aug-cc-pVQZ level. Cooperative effects are probed by analysing charge transfer, electronic properties and orbital interactions when F?…?Ag bond and X?…?Br (Cl) halogen bond coexist in the same complex. The results indicate that the X?…?Br (Cl) halogen bond has a greater enhancing effect than the F?…?Ag bond does, resulting in a shorter binding distances, larger interaction energies and greater electron densities for the ternary complexes than for the corresponding binary ones. In addition, the origins of both the F?…?Ag bond and X?…?Br (Cl) halogen bond have been deduced via energy decomposition.     

A comparative study of model halogen-bonded, π-hole-bonded and cationic complexes involving NCX AND H2O (X = F,Cl, Br)

A MP2/6-311+ +G(d,p) study of NCX (X = F, Cl, Br) has shown that it is possible to attach an electrophile (H⁺, Be²⁺) to the positive halogen X surface of NCX. The stability and properties of model halogen-bonded and π-hole carbon-bonded NCX/H₂O complexes were found to be significantly affected by H⁺ or Be²⁺ cationic attachment at the N atom. The halogen-bonded complexes are destabilised by binding at the N, while an attached proton enhances the binding in the π-hole bonded dimers. For the attached Be²⁺, an unusual complex was obtained with the NCF subunit, whereas the complexes containing Cl and Br were destabilised by the interaction.     

Cooperativity between the hydrogen bonding and halogen bonding in F3CX ··· NCH(CNH) ··· NCH(CNH) complexes (X=Cl,Br)

MP2 calculations with the cc-pVTZ basis set were used to analyse the intermolecular interactions in F₃CX?···?NCH(CNH)?···?NCH(CNH) triads (X=Cl, Br), which are connected via hydrogen and halogen bonds. Molecular geometries, binding energies, and infrared spectra of the dyads and triads were investigated at the MP2/cc-pVTZ computational level. Particular attention was given to parameters such as the cooperative energies, cooperative dipole moments, and many-body interaction energies. All studied complexes, with the simultaneous presence of a halogen bond and a hydrogen bond, show cooperativity with energy values ranging between ?1.32 and ?2.88?kJ?mol^?1. The electronic properties of the complexes were analysed using the Molecular Electrostatic Potential (MEP), electron density shift maps and the parameters derived from the Atoms in Molecules (AIM) methodology.     

Structures and stabilities of the donor–acceptor complexes HXPY (X=Al,B; Y=H,F, OH)

The optimized geometries, complexation energies, etc. of HXPY (X?=?Al, B; Y?=?H, F, OH) donor–acceptor complexes have been investigated at the B3LYP/6-311+G(d,p), MP2/6-311+G(d,p) and/or CCSD(T)/6-311+G(d,p) levels. The results show that HBPY (Y?=?H, F, OH) is more stable than the corresponding HAlPY (Y?=?H, F, OH), F (or OH) substitution on phosphorus results in decreasing complex stability, and the stronger the electron-attracting nature of the substitution atom, the more stable the complex. Moreover, the thermodynamic and kinetic properties of the formation reaction of these donor–acceptor complexes were also examined within the temperature range 200–800?K using the general statistical thermodynamics and Eyring transition state theory with Wigner correction. It is concluded that the formation of HBPY is thermodynamically favoured over that of the corresponding HAlPY, especially at low temperature, and is kinetically favoured over that of the relevant HAlPY (Y?=?H, F, OH), especially at high temperature.     

UX(X=H,F,Cl,Br)的分子结构与稳定性

用密度泛函B3LYP方法对UX(X=H,F,Cl,Br)分子体系进行了理论研究,结果表明, 这些分子的基态电子状态分别是X4Ⅱ、X6∑、X2∑、X6∑,且都能稳定存在,其中UBr最 稳定,UH稳定性最差;势能函数为Murrell-Sorbie势函数,并得到了相应的几何性质、力 学性质和光谱数据。     

Competition between σ-hole pnicogen bond and π-hole tetrel bond in complexes of CF2=CFZH2 (Z = P,As, and Sb)

ABSTRACT

A computational study of the complexes formed by F₂C=CFZH₂ (Z?=?P, As, and Sb) and F₂C=CFPF₂ with two Lewis bases (NH₃ and NMe₃) has been carried out. In general, two minima complexes are found, one with a σ-hole pnicogen bond and the other one with a π-hole tetrel bond in most complexes but two σ-hole pnicogen bonded complexes are obtained for F₂C=CFZH₂ and NH₃. They have similar stability though F₂C=CFSbH₂ engages in a much stronger σ-hole pnicogen bond with NMe₃. The –PF₂ substitution makes the π-hole on the terminal carbon form a tetrel bond with NH₃. A heavier –ZH₂ group engages in a stronger σ-hole pnicogen bond but results in a weaker π-hole tetrel bond. Other than electrostatic interaction, the stability of both complexes is attributed to the charge transfer from the N lone pair into the C–Z/H–Z anti-bonding orbital in the pnicogen bond and the C=C anti-bonding orbital in the tetrel bond.

The σ-hole pnicogen bonded and π-hole tetrel bonded complexes between F₂C=CFZH₂ (Z = P, As, and Sb) and two Lewis bases (NH₃ and NMe₃) have been compared. The results indicate that both interactions can compete, dependent on the nature of the N base.     

Interplay and competition between the lithium bonding and halogen bonding: R3C···XCN···LiCN and R3C···LiCN···XCN as a working model (R = H,CH3; X = Cl,Br)

UMP2 calculations with aug-cc-pVDZ basis set were used to analyse intermolecular interactions in R₃C···XCN···LiCN and R₃C···LiCN···XCN triads (R = H, CH₃; X = Cl, Br) which are connected via lithium bond and halogen bond. To understand the properties of the systems better, the corresponding dyads are also studied. Molecular geometries and binding energies of dyads, and triads are investigated at the UMP2/aug-cc-pVDZ computational level. Particular attention is paid to parameters such as cooperative energies, and many-body interaction energies. All studied complexes, with the simultaneous presence of a lithium bond and a halogen bond, show cooperativity with energy values ranging between ?1.20 and ?7.71 kJ mol^?1. A linear correlation was found between the interaction energies and magnitude of the product of most positive and negative electrostatic potentials (V_S,maxV_S,min). The electronic properties of the complexes are analysed using parameters derived from the atoms in molecules (AIM) methodology. According to energy decomposition analysis, it is revealed that the electrostatic interactions are the major source of the attraction in the title complexes.     

Mutual influence between covalent and noncovalent interactions in H3N–MCN–XF (X = H,Li, Cl,Br; M = Ag,Cu, Au)

The interplay between covalent and noncovalent interactions has been investigated in H₃N–MCN–XF (X = H, Li, Cl, Br; M = Ag, Cu, Au) complexes using ab initio calculations at the MP2 level of theory. The coinage metal as a substituent has an irregular enhancing effect (Au < Cu < Ag) on the strength of noncovalent interaction in MCN–XF, while the covalent interaction in H₃N–MCN becomes stronger with the reverse order. Interesting cooperativity effects were observed when covalent and noncovalent interactions coexist in the same complex, and they become more prominent for the stronger covalent and noncovalent interactions. These effects have been characterised in detail with the structural, spectroscopic, energetic, and charge transfer features of the complexes.     

Potential energy curve study on the ^3Π electronic states of GaX （X=F,Cl, and Br） molecules

The potential energy curves （PECs） of the 3Π states of GaX （X=F, Cl, and Br） molecules are calculated using the multireference configuration interaction method with a large contracted basis set aug-cc-pV5Z. The PECs are accurately fitted to analytical potential energy functions （APEFs） using the Murrell–Sorbie potential function. The spectroscopic parameters for the states are determined using the obtained APEFs, and compared with the theoretical and experimental data available presently in the literature.     

A computational study of C?X (X = H,C, F,Cl) bond dissociation enthalpies (BDEs) in polyhalogenated methanes and ethanes

Bond dissociation enthalpies (BDEs) play a significant role in the photolysis of Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), which lead to the depletion of stratospheric ozone. In this work, we estimate the performance of Density Functional Theory (DFT) methods in calculating BDEs of CFCs and HCFCs, and find that DFTs are unreliable for this system. The reasons for the unreliability of DFT methods in this system are also concluded. Furthermore, composite ab initio methods G3 and G3B3 are demonstrated to accurately estimate BDEs of polyhalogenated lower alkanes. Eighty two experimental values from Comprehensive Handbook of Chemical Bond Energies (2007, 2nd edition) are re‐evaluated. Eight of them are doubted as having a deviation exceeding 20.0 kJ/mol between the theoretical and experimental values. We also systematically predict the BDEs in polyhalogenated methanes and ethanes. A further study is conducted on their relationships of structures and properties. Copyright © 2010 John Wiley & Sons, Ltd.     

Computational study of the perhalogenated methyl nitrates CX3ONO2, CX x Y3−x ONO2 (X,Y = F,Cl)

Ab initio and density functional theory methods are employed to study the structures, harmonic frequencies, energetics and thermodynamic properties of the perhalogenated methyl nitrates, CX₃ONO₂, CX _x Y_3?x ONO₂ (X, Y =?F, Cl), which may be formed as secondary reactive intermediates in the coupling of the halogenated methylperoxy radicals with NO. Reaction energies are computed with respect to CX₃O₂ +?NO, CX _x Y_3?x O₂ +?NO and CX₃O +?NO₂, CX _x Y_3?x O +?NO₂ radical pair decomposition species. The large heat of formation values calculated indicate the high stabilization achieved upon halogenation of the methyl radical, particularly for the fluorinated compounds. Thus, the halogenated methyl nitrates which appear in the oxidation chain of halomethanes can be thermally deactivated under suitable temperature and pressure conditions and act as reservoir compounds for the halogenated methylperoxy radicals, CX₃O₂, CX _x Y_3?x O₂ and NO, in the troposphere. The computational investigation also demonstrates the significant structural changes caused by the halogen electron withdrawing effect, compared with the methyl analogue, CH₃ONO₂.     

Abnormal synergistic effects between Lewis acid–base interaction and halogen bond in F3B···NCX···NCM

An abnormal synergistic effect was found between the Lewis acid–base interaction and halogen bond in triads F₃B···NCX···NCM (X and M are halogen atoms), where the strong Lewis acid–base interaction between F₃B and NCX has a larger enhancement than the weak halogen bond between NCX and NCM. This is in contrast with the traditional cooperative effect. It is interesting that the alkali-metal substituent as well as the heavier halogen atom play a more remarkable role in the enhancement of the interaction F₃B···NCX than that of NCX···NCM, particularly, the alkali-metal substituent makes the abnormal synergistic effect be the traditional cooperative one.