Computational study of the cooperative effects between tetrel bond and halogen bond in XCN⋅⋅⋅F2CO⋅⋅⋅YCN complexes (X = H,F, Cl,Br; Y = F,Cl, Br)

ABSTRACT

Ab initio calculations have been accomplished to study the cooperativity between the halogen bond and tetrel bond in the XCN???F2CO???YCN (X = H, F, Cl, Br; Y = F, Cl, Br) complexes. F₂CO at the same time plays the role of Lewis acid with the π-hole on the C atom and Lewis base with the O atom to participate in the tetrel bond and in halogen bond, respectively. According to the geometry survey, the effect of a tetrel bond on a halogen bond is more pronounced than that of a halogen bond on a tetrel bond and the intermolecular distances in the triads are always smaller than the corresponding values in the dyads. In all cases, the halogen bond and tetrel bond in the termolecular complexes are stronger compared with those in the bimolecular complexes. So, from the intermolecular distances, interaction energies and many-body interactions demonstrate that there is positive cooperativity between the halogen bond and tetrel bond. The molecular electrostatic potential, atoms in molecules and natural bond orbital methodologies are used to analyse the nature of interactions of the complexes.     

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.     

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。     

HX(X=F,Cl,Br)酸性强度的理论计算

本文用Gibbs自由能ΔGacid定义了HX(g)的酸性强度.研究表明,用MP2、QCISD和B3LYP三种量化方法计算所得的HX酸性强度与文献值对比,其最大的相对误差仅为2.45%.其中,B3LYP方法的计算结果与文献值最为接近,其误差在0.37-1.09%范围内.HF气态分子有明显的氢键作用,其二聚体分子酸性强度ΔGacid与单体分子的ΔGacid值相比降低了约-5～-11%,此时氟化氢气体的酸性强度已不能单从HF单体分子的ΔGacid值来衡量,而应考虑HF分子的氢键作用.     

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.     

Ionic conductivity of ZrF4BaF2MX (M = Li,Na;X = F,Cl) glasses

Glasses were prepared in a wide range of compositions for the two systems oof mixed-cation, ZrF₄BaF₂LiFNaF, and mixed-anion, ZrF₄BaF₂LiFLiCl. Ionic conductivities were measured for these glasses and it was found that these glasses were not only cationic but also anionic conductors depending on the total alkali halide content. Four types of mixed-cation and mixed-anion effects on ionic conductivity were demonstrated for the cation-conducting and anion-conducting glasses. In cation conduction, the cation mixing caused the conductivity decline, whereas the anion mixing led to the conductivity enhancement. In anion conduction, on the other hand, the cation mixing led to the conductivity enhancement, whereas the anion mixing caused the conductivity decline.     

Relativistic density functional investigation of UX6（X=F,Cl,Br and I）

The molecular structures and the vibrational frequencies of uranium hexahalides UX 6(X=F,Cl,Br and I) molecules are investigated by using local density approximation(LDA) and generalised gradient approximation(GGA) functions(BP,BLYP and RPBE) in combination with two different relativistic methods(scalar and scalar+spin-orbit relativistic effects).The calculated results show that the differences are trivial between scalar and scalar+spin-orbit relativistic methods.The vibrational frequencies are also compared with existing experimental values,and overall,the RPBE approach gives the smallest error.The bond dissociation energies(BDEs) of UX 6 are computed by using the RPBE function,thereby obtaining exact vibrational frequencies.In addition,the calculated magnitudes of the spin-orbit effect on the BDE of UX 6(X=F,Cl,Br,and I) are found to be approximately-0.3198,-0.3218,-0.3609 and-0.4415 eV,respectively.     

HOX(X=F,Cl)二聚体红移氢键的理论研究

用理论方法研究了二聚体HOX(X=F,Cl)分子间氢键,在B3LYP/6-31+G(d,p)、 B3LYP/6-311++G(d,p)、MP2/6-31+G(d,p)和MP2/6-311++G(d,p)水平上,利用标准方法和均衡校正方法对二聚体进行了几何优化、振动频率和相互作用能的计算。同时,利用电子密度拓扑分析和自然键轨道分析对红移氢键的本质进行了分析。研究表明：分子间O—H…O和O—H…X(X=F,Cl)氢键的形成使二聚体中O—H键伸长,伸缩振动频率减小,形成红移氢键。NBO分析表明,电荷转移效应占优势,因此形成O—H…O和O—H…X(F,Cl)红移氢键。     

Prediction and characterisation of a chalcogen···π interaction with acetylene as a potential electron donor in XHS···HCCH and XHSe···HCCH (X = F,Cl, Br,CN, OH,OCH3, NH2, CH3) σ-hole complexes

It is well-known that many covalently bonded atoms of group VI have specific positive regions of electrostatic potential (σ-holes) through which they can interact with Lewis bases. This interaction is called ‘chalcogen bond’ by analogy with halogen bond and hydrogen bond. In this study, ab initio calculations are performed to predict and characterise chalcogen···π interactions in XHS···HCCH and XHSe···HCCH complexes, where X = F, Cl, Br, CN, OH, OCH₃, NH₂, CH₃. For the complexes studied here, XHS(Se) and HCCH are treated as a Lewis acid and a Lewis base, respectively. The CCSD(T)/aug-cc-pVTZ interaction energies of this type of σ-hole bonding range from ?1.18 to ?4.83 kcal/mol. The calculated interaction energies tend to increase in magnitude with increasing positive electrostatic potential on the extension of X–S(Se) bond. The stability of chalcogen···π complexes is attributed mainly to electrostatic and correlation effects. The nature of chalcogen···π interactions is unveiled by means of the atoms in molecules, natural bond orbital, and electron localisation function analyses.     

范德华分子He—X（X=F,Cl,I）的解析势能函数

范德华分子势能函数的研究在原子分子领域具有重要的意义。此文应用Ｇａｕｓｓｉａｎ９２计算程序，计算了ＨｅＦ，ＨｅＣｌ和ＨｅＩ三个范德华分子的势能函数值，并通过最小二乘的方法拟合出了它们的解析势能函数。     

HXCO（X=F,Cl）解离和异构通道中的取代基效应

本文在２００－１３００Ｋ温度范围内，计算了ＨＸＣＯ、ＸＣＯＨ和ＨＣＯＸ解离和异构化反应的Ｇｉｂｂｓ自由能改变、热效应、速度常数以及Ｗｉｇｎｅｒ校正系数，讨论了取代基对反应的热力学和动力学参量的影响。结果表明：（１）取代基对反应的热力学量和速度常数影响较大，但影响结果因反应机理不同而异；（２）当反应所断裂化学键不直接连接取代基，则取代基对隧道效应影响较小；（３）仅用电子能量判断分子的稳定性是不可靠的     

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.     

CnH2n(n=2,3,4)与BX3(X=H,F,Cl)作用的DFT研究

用量子化学的密度泛函理论方法对BX3(X=H,F,Cl)与烯烃CnH2n(n=2,3,4)形成的复合物进行了研究,结果表明,复合物的构型皆为BX3位于烯烃π键的上方,并且偏向氢原子数较多的碳原子一侧.C-C双键中的π电子通过向BH3中B的空p轨道转移电子而形成复合物,但BF3和BCl3与烯烃分子只是通过微弱的分子间作用力结合,复合物的形成使分子的振动光谱随作用的强弱而出现一定的红移现象.     

GeX2(X=F,Cl)与甲醛环加成反应机理的理论研究

在从头算方法HF/6311+G水平上研究了单重态GeX2(X=F,Cl)与甲醛的环加成反应,找到了反应的中间配合物和过渡态,并在MP4(SDTQ)/6311+G计算水平上进一步进行单点算,对得到的复合物以振动频率确认其驻点性质(过渡态和稳定态),讨论了其反应机理.结果表明,二氟锗烯与甲醛的环加成反应分两步进行,第一步生成中间配合物,是一个无势垒的放热反应;第二步是中间配合物异构化为产物%D二氟锗杂环氧甲烷,计算的反应势垒为196.4kJ/mol,是整个反应发生的控速步骤.而在二氯锗烯与甲醛环加成反应中,对应的控速步骤的能垒仅为125.7kJ/mol.与二氟硅烯与甲醛环加成反应相比,二氟锗烯与甲醛的环加成反应速率要慢一些,而二氯锗烯与甲醛环加成反应速率则与其相当.     

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.     

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.     

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.     

Cooperative interaction between π-hole and single-electron σ-hole interactions in O2S···NCX···CH3 and O2Se···NCX···CH3 complexes (X = F,Cl, Br and I)

Ab initio calculations are performed to analyse the cooperative effects between π-hole and single-electron σ-hole interactions in O₂S···NCX···CH₃ and O₂Se···NCX···CH₃ complexes, where X = F, Cl, Br and I. These effects are investigated in terms of geometric and energetic features of the complexes, which are computed by UMP2/aug-cc-pVTZ(-PP) method. Our results indicate that the shortening of the each π-hole bond distance in the complexes is dependent on the strength of the σ-hole interaction. The maximum and minimum energetic cooperativity values correspond to the most and least stable complexes studied in the present work. The cooperativity between both types of interaction is chiefly caused by the electrostatic effects. 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.