共查询到20条相似文献,搜索用时 390 毫秒
1.
Guillermo Mínguez Espallargas Dr. Fiorenzo Zordan Dr. Luis Arroyo Marín Harry Adams Kenneth Shankland Dr. Jacco van de Streek Dr. Lee Brammer Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(31):7554-7568
A family of 16 isomolecular salts (3‐XpyH)2[MX′4] (3‐XpyH=3‐halopyridinium; M=Co, Zn; X=(F), Cl, Br, (I); X′=Cl, Br, I) each containing rigid organic cations and tetrahedral halometallate anions has been prepared and characterized by X‐ray single crystal and/or powder diffraction. Their crystal structures reflect the competition and cooperation between non‐covalent interactions: N? H???X′? M hydrogen bonds, C? X???X′? M halogen bonds and π–π stacking. The latter are essentially unchanged in strength across the series, but both halogen bonds and hydrogen bonds are modified in strength upon changing the halogens involved. Changing the organic halogen (X) from F to I strengthens the C? X???X′? M halogen bonds, whereas an analogous change of the inorganic halogen (X′) weakens both halogen bonds and N? H???X′? M hydrogen bonds. By so tuning the strength of the putative halogen bonds from repulsive to weak to moderately strong attractive interactions, the hierarchy of the interactions has been modified rationally leading to systematic changes in crystal packing. Three classes of crystal structure are obtained. In type A (C? F???X′? M) halogen bonds are absent. The structure is directed by N? H???X′? M hydrogen bonds and π‐stacking interactions. In type B structures, involving small organic halogens (X) and large inorganic halogens (X′), long (weak) C? X???X′? M interactions are observed with type I halogen–halogen interaction geometries (C? X???X′ ≈ X???X′? M ≈155°), but hydrogen bonds still dominate. Thus, minor but quite significant perturbations from the type A structure arise. In type C, involving larger organic halogens (X) and smaller inorganic halogens (X′), stronger halogen bonds are formed with a type II halogen–halogen interaction geometry (C? X???X′ ≈180°; X???X′? M ≈110°) that is electrostatically attractive. The halogen bonds play a major role alongside hydrogen bonds in directing the type C structures, which as a result are quite different from type A and B. 相似文献
2.
The ability of the “bird-like” halogenabenzene molecule, referred to as X-bird (XCl to At), to form halogen-bonded complexes with the nucleophiles H2O and NH3 was investigated using double-hybrid density functional theory and the aug-cc-pVTZ/aug-cc-pVTZ-PP basis set. The structures and interaction energies were compared with 5-halocyclopenta-1,3-diene (halocyclopentadiene; an isomer of halogenabenzene) and halobenzene, also complexed with H2O and NH3. The unusual structure of the X-bird, with the halogen bonded to two carbon atoms, results in two distinct σ-holes, roughly at the extension of the C-X bonds. Based on the behavior of the interaction energy (which increases for heavier halogens) and van der Waals (vdW) ratio (which decreases for heavier halogens), it is concluded that the X-bird forms proper halogen bonds with H2O and NH3. The interaction energies are larger than those of the halogen-bonded complexes involving halobenzene and halocyclopentadiene, presumably due to the presence of a secondary interaction. © 2019 Wiley Periodicals, Inc. 相似文献
3.
Ruimin Wang Janine George Shannon Kimberly Potts Marius Kremer Richard Dronskowski Ulli Englert 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(9):1190-1201
Experimental electron‐density studies based on high‐resolution diffraction experiments allow halogen bonds between heavy halogens to be classified. The topological properties of the electron density in Cl…Cl contacts vary smoothly as a function of the interaction distance. The situation is less straightforward for halogen bonds between iodine and small electronegative nucleophiles, such as nitrogen or oxygen, where the electron density in the bond critical point does not simply increase for shorter distances. The number of successful charge–density studies involving iodine is small, but at least individual examples for three cases have been observed. (a) Very short halogen bonds between electron‐rich nucleophiles and heavy halogen atoms resemble three‐centre–four‐electron bonds, with a rather symmetric heavy halogen and without an appreciable σ hole. (b) For a narrow intermediate range of halogen bonds, the asymmetric electronic situation for the heavy halogen with a pronounced σ hole leads to rather low electron density in the (3,?1) critical point of the halogen bond; the properties of this bond critical point cannot fully describe the nature of the associated interaction. (c) For longer and presumably weaker contacts, the electron density in the halogen bond critical point is only to a minor extent reduced by the presence of the σ hole and hence may be higher than in the aforementioned case. In addition to the electron density and its derived properties, the halogen–carbon bond distance opposite to the σ hole and the Raman frequency for the associated vibration emerge as alternative criteria to gauge the halogen‐bond strength. We find exceptionally long C—I distances for tetrafluorodiiodobenzene molecules in cocrystals with short halogen bonds and a significant red shift for their Raman vibrations. 相似文献
4.
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. 相似文献
5.
Comparative Study of Halogen‐ and Hydrogen‐Bond Interactions between Benzene Derivatives and Dimethyl Sulfoxide
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The halogen bond, similar to the hydrogen bond, is an important noncovalent interaction and plays important roles in diverse chemistry‐related fields. Herein, bromine‐ and iodine‐based halogen‐bonding interactions between two benzene derivatives (C6F5Br and C6F5I) and dimethyl sulfoxide (DMSO) are investigated by using IR and NMR spectroscopy and ab initio calculations. The results are compared with those of interactions between C6F5Cl/C6F5H and DMSO. First, the interaction energy of the hydrogen bond is stronger than those of bromine‐ and chlorine‐based halogen bonds, but weaker than iodine‐based halogen bond. Second, attractive energies depend on 1/rn, in which n is between three and four for both hydrogen and halogen bonds, whereas all repulsive energies are found to depend on 1/r8.5. Third, the directionality of halogen bonds is greater than that of the hydrogen bond. The bromine‐ and iodine‐based halogen bonds are strict in this regard and the chlorine‐based halogen bond only slightly deviates from 180°. The directional order is iodine‐based halogen bond>bromine‐based halogen bond>chlorine‐based halogen bond>hydrogen bond. Fourth, upon the formation of hydrogen and halogen bonds, charge transfers from DMSO to the hydrogen‐ and halogen‐bond donors. The CH3 group contributes positively to stabilization of the complexes. 相似文献
6.
Theoretical study on the interactions of halogen‐bonds and pnicogen‐bonds in phosphine derivatives with Br2, BrCl,and BrF
下载免费PDF全文
![点击此处可从《International journal of quantum chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yinchun Jiao Yi Liu Wenjing Zhao Zhaoxu Wang Xunlei Ding Hexiu Liu Tian Lu 《International journal of quantum chemistry》2017,117(22)
The MP2 ab initio quantum chemistry methods were utilized to study the halogen‐bond and pnicogen‐bond system formed between PH2X (X = Br, CH3, OH, CN, NO2, CF3) and BrY (Y = Br, Cl, F). Calculated results show that all substituent can form halogen‐bond complexes while part substituent can form pnicogen‐bond complexes. Traditional, chlorine‐shared and ion‐pair halogen‐bonds complexes have been found with the different substituent X and Y. The halogen‐bonds are stronger than the related pnicogen‐bonds. For halogen‐bonds, strongly electronegative substituents which are connected to the Lewis acid can strengthen the bonds and significantly influenced the structures and properties of the compounds. In contrast, the substituents which connected to the Lewis bases can produce opposite effects. The interaction energies of halogen‐bonds are 2.56 to 32.06 kcal·mol?1; The strongest halogen‐bond was found in the complex of PH2OH???BrF. The interaction energies of pnicogen‐bonds are in the range 1.20 to 2.28 kcal·mol?1; the strongest pnicogen‐bond was found in PH2Br???Br2 complex. The charge transfer of lp(P) ? σ*(Br? Y), lp(F) ? σ*(Br? P), and lp(Br) ? σ*(X? P) play important roles in the formation of the halogen‐bonds and pnicogen‐bonds, which lead to polarization of the monomers. The polarization caused by the halogen‐bond is more obvious than that by the pnicogen‐bond, resulting in that some halogen‐bonds having little covalent character. The symmetry adapted perturbation theory (SAPT) energy decomposition analysis showes that the halogen‐bond and pnicogen‐bond interactions are predominantly electrostatic and dispersion, respectively. 相似文献
7.
Qingzhong Li Dr. Qingquan Lin Wenzuo Li Jianbo Cheng Baoan Gong Jiazhong Sun 《Chemphyschem》2008,9(15):2265-2269
Ab initio calculations are used to provide information on H3N???XY???HF triads (X, Y=F, Cl, Br) each having a halogen bond and a hydrogen bond. The investigated triads include H3N???Br2‐HF, H3N???Cl2???HF, H3N???BrCI???HF, H3N???BrF???HF, and H3N???ClF???HF. To understand the properties of the systems better, the corresponding dyads are also investigated. Molecular geometries, binding energies, and infrared spectra of monomers, dyads, and triads are studied at the MP2 level of theory with the 6‐311++G(d,p) basis set. Because the primary aim of this study is to examine cooperative effects, particular attention is given to parameters such as cooperative energies, many‐body interaction energies, and cooperativity factors. The cooperative energy ranges from ?1.45 to ?4.64 kcal mol?1, the three‐body interaction energy from ?2.17 to ?6.71 kcal mol?1, and the cooperativity factor from 1.27 to 4.35. These results indicate significant cooperativity between the halogen and hydrogen bonds in these complexes. This cooperativity is much greater than that between hydrogen bonds. The effect of a halogen bond on a hydrogen bond is more pronounced than that of a hydrogen bond on a halogen bond. 相似文献
8.
Mehdi D. Esrafili Soheila Asadollahi Yousef Dadban Shahamat 《Structural chemistry》2016,27(5):1439-1447
Using ab initio calculations, the geometries, interaction energies and bonding properties of chalcogen bond and halogen bond interactions between YOX4 (Y = S, Se; X = F, Cl, Br) and NH3 molecules are studied. These binary complexes are formed through the interaction of a positive electrostatic potential region (σ-hole) on the YOX4 with the negative region in the NH3. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level, through analysis of molecular electrostatic potentials, quantum theory of atoms in molecules and natural bond orbital methods. Our results indicate that even though the chalcogen and halogen bonds are mainly dominated by electrostatic effects, but the polarization and dispersion effects also make important contributions to the total interaction energy of these complexes. The examination of interaction energies suggests that the chalcogen bond is always favored over the halogen bond for all of the binary YOX4:NH3 complexes. 相似文献
9.
10.
Yuchen Zhang Yunxiang Lu Zhijian Xu Hairong Ding Weihong Wu Honglai Liu 《Structural chemistry》2016,27(3):907-917
Intramolecular halogen bonds have been the subject of several current experimental and theoretical studies. In this work, intramolecular halogen bonds in a series of 1,2-aryldiyne molecules were investigated using density functional theory calculations at the M06-2x level of theory. For comparison, some dimeric complexes between halogenated aryldiynes and quinolinyl compounds were also considered. The calculated interatomic distances and interaction angles of intramolecular halogen bonds compare fairly well with those determined experimentally, and the triangle motifs retain almost perfectly planar in all the studied molecules. Many of the well-known properties of conventional halogen bonds are reproduced in intramolecular halogen bonds: the interaction strength tends to increase with the enlargement of the atomic radius of halogens (I > Br > Cl); the attachment of electron-withdrawing moieties to halogens leads to much stronger intramolecular halogen bonds; the X···N (quinolinyl) interactions are stronger than the X···O (carbonyl) halogen bonds. On the basis of the shorter interatomic distances and the larger values of electron densities at the bond critical points, intramolecular halogen bonds become stronger in strength than corresponding intermolecular halogen bonds. However, these interactions have similar structural, energetic, atoms in molecules (AIM), and noncovalent interaction index (NCI) characteristics to traditional halogen bonds. Therefore, these interactions can be recognized as halogen bonds that are primarily electrostatic in nature. Particularly, the formation of intramolecular halogen bonds gives rise to the essential coplanarity of the molecules, whereas the two subunits in the dimeric complexes deviate from planarity to a large degree. In addition, a small number of crystal structures containing intramolecular halogen bonds were retrieved from the Cambridge Structural Database (CSD), to provide more insights into these interactions in crystals. This work not only will extend the knowledge of noncovalent interactions involving halogens as electrophilic centers but also could be very useful in molecular design and synthetic chemistry. 相似文献
11.
Theoretical study of the interaction of fluorinated dimethyl ethers and the ClF and HF molecules. Comparison between halogen and hydrogen bonds
下载免费PDF全文
![点击此处可从《International journal of quantum chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dipankar Sutradhar Asit K. Chandra Thérèse Zeegers‐Huyskens 《International journal of quantum chemistry》2016,116(9):670-680
A theoretical study of the halogen‐bonded complexes formed between fluorinated dimethyl ethers (nF = 0–4) and ClF is carried out using the wB97XD method combined with the 6‐311++G(d,p) basis set. The properties of the complexes are compared with the corresponding properties of the hydrogen‐bonded complexes formed between the same electron donors and HF. The optimized geometries, the interaction energies, relevant natural bonding orbital characteristics along with some vibrational data are calculated. The analyzed properties also include the symmetry adapted perturbation theory decomposition of the energies along with the atoms‐in molecule analysis. For both the halogen and hydrogen bonds, the interaction energies are ruled by the intermolecular hyperconjugation energies. In contrast, the correlations between the binding energies and the basic properties of the ethers or the charge transfer are different for the halogen and hydrogen bonds. The applicability of the Bent's rule to these systems is discussed. © 2016 Wiley Periodicals, Inc. 相似文献
12.
Xin Ren Zhouyang Luo Jinpei Du Shi Wu 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(5):826-830
Theoretical investigation on the stabilities and spectroscopic properties of the complexes formed by cyciobis(paraquat-p-anthracene) with pharmaceutical molecules were performed using the semi-empirical PM3 and B3LYP/3-21G methods. Based on the
B3LYP/3-21G optimized geometries, the energies of the complexes were calculated at B3LYP/6-31G(d) level. The binding energies of the complexes were computed after the correction of basis set superposition error (BSSE).
The energy gaps of the complexes are decreased due to the formation of the hydrogen bonds. The stretching vibrations of the
C-H bonds adjacent to the hydrogen bonds in the IR spectra of the complexes calculated with PM3 method are red-shifted compared
with those of the host. The chemical shifts of α-C and β-C atoms in the complexes calculated at B3LYP/3-21G level are shifted
downfield due to the formation of the hydrogen bonds and the electron-withdrawing effect of the nitrogen atoms. The aromaticities
of the complexes are improved because of the enlargement of the conjugation system and the overlap of electron cloud based
on the nuclear independent chemical shifts (NICS) calculated at B3LYP/3-21G level. 相似文献
13.
Tsuzuki S Wakisaka A Ono T Sonoda T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):951-960
The geometries and interaction energies of complexes of pyridine with C6F5X, C6H5X (X=I, Br, Cl, F and H) and RFI (RF=CF3, C2F5 and C3F7) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (Eint) for the C6F5X–pyridine (X=I, Br, Cl, F and H) complexes at the basis set limit were estimated to be ?5.59, ?4.06, ?2.78, ?0.19 and ?4.37 kcal mol?1, respectively, whereas the Eint values for the C6H5X–pyridine (X=I, Br, Cl and H) complexes were estimated to be ?3.27, ?2.17, ?1.23 and ?1.78 kcal mol?1, respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C6F5X. The values of Eint estimated for the RFI–pyridine (RF=CF3, C2F5 and C3F7) complexes (?5.14, ?5.38 and ?5.44 kcal mol?1, respectively) are close to that for the C6F5I–pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short‐range (charge‐transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C6F5I– and C2F5I–pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water–formaldehyde complex. The calculations suggest that the C? I and C? Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C? Cl bonds play a less important role and that C? F bonds have a negligible impact. 相似文献
14.
X. L. Zeng W. H. Chen J. C. Liu J. L. Kan 《Journal of Thermal Analysis and Calorimetry》2008,91(2):359-363
This paper presents calorimeter measurement for the thermal decomposition of n-propyl nitrate (NPN), isopropyl nitrate (IPN) and 2-ethylhexyl nitrate (EHN). Similar experimental results of triethylene
glycol dinitrate (tri-EGDN) and tetraethylene glycol dinitrate (tetra-EGDN) are included for comparison. The potential energy
surfaces (PESs) along O-NO2 bond stretch are investigated using the DFT (B3P86, B3PW91 and B3LYP), ab initio Hartree-Fock and PM3 methods. The good coincidence
of experimental with theoretical results indicates that initial stage in the thermal decomposition of five nitrates is only
unimolecular homolytical dissociation of the O-NO2 bonds and the activation energies of thermolysis by DSC correspond to the energies of O-NO2 bond scission of nitrates. 相似文献
15.
Klaus Gundertofte Jonas Palm Ingrid Pettersson Anders Stamvik 《Journal of computational chemistry》1991,12(2):200-208
Conformational energies of different conformers have been calculated for a series of molecules using various molecular mechanics and semiempirical methods. The quality of the force fields has also been tested by calculating barriers to rotation about carbon-carbon bonds. The molecular mechanics force fields used are MM2(85), Sybyl 5.1, Sybyl 5.21, and ChemX, ver. Jan 89. The semiempirical methods used are AM1 and PM3. Molecules with different functional groups, for which good experimental data exist, have been selected. The semiempirical methods generally calculate barriers to rotation which are lower than the experimentally determined. The conformational energies for hydrocarbons are reasonably well reproduced by all tested methods although MM2(85) gives the quantitatively best agreement with experiments. For compounds containing oxygen, nitrogen and halogens MM2(85) gives results which are in best agreement with the experimentally determined values. 相似文献
16.
N. A. Anikin V. L. Bugaenko M. B. Kuz’minskii A. S. Mendkovich 《Russian Chemical Bulletin》2014,63(2):346-349
The fundamentally new method NESE is proposed for quantum chemical calculations of large molecules, which employs the approximation of the Hamiltonian of the commonly used DFT method and is as fast as the AM1 and PM3 semi-empirical methods or the DFTB method. The parameters for the new method were chosen by the least-squares method based on the comparison of its matrix elements with the reference DFT/PBE Hamiltonian. The initial non-iterative version NESE-0 was computer-implemented and approved on many thousands of various molecules containing H, C, N, and O atoms. The NESE-0 method moderately outperforms the DFTB approach and is an order of magnitude better than the AM1, PM3, and PM6 levels in reproducing the one-electron energies calculated in terms of the DFT/PBE. 相似文献
17.
Density functional theory calculations were performed on halogen-bonded and hydrogen-bonded systems consisting of a halobenzene (XPh; X = F, Cl, Br, I, and At) and one or two water molecules, using the M06-2X density functional with the 6-31+G(d) (for C, H, F, Cl, and Br) and aug-cc-pVDZ-PP (for I, At) basis sets. The counterpoise procedure was performed to counteract the effect of basis set superposition error. The results show halogen bonds form in the XPh-H2O system when X > Cl. There is a trend toward stronger halogen bonding as the halogen group is descended, as assessed by interaction energy and X•••Ow internuclear separation (where Ow is the water oxygen). For all XPh-H2O systems hydrogen-bonded systems exist, containing a combination of CH•••Ow and OwHw•••X hydrogen bonds. For all systems except X = At the X•••Hw hydrogen-bonding interaction is stronger than the X•••Ow halogen bond. In the XPh-(H2O)2 system halogen bonds form only for X > Br. The two water molecules prefer to form a water dimer, either located around the C H bond (for X = Br, At, and I) or located above the benzene ring (for all halogens). Thus, even in the absence of competing strong interactions, halogen bonds may not form for the lighter halogens due to (1) competition from cooperative weak interactions such as C H•••O and OH•••X hydrogen bonds, or (2) if the formation of the halogen bond would preclude the formation of a water dimer. © 2018 Wiley Periodicals, Inc. 相似文献
18.
The characteristics and structures of single-electron halogen bond complexes [H3C?Br-Y (Y = H, CCH, CN, NC, C2H3)] have been investigated by theoretical calculation methods. The geometries were optimized and frequencies calculated at the B3LYP/6-311++G** level. The interaction energies were corrected for basis set superposition error (BSSE) and the wavefunctions obtained by the natural bond orbital (NBO) and atom in molecule (AIM) analyses at the MP2/6-311++G** level. For each H3C?Br-Y complex, a single-electron Br bond is formed between the unpaired electron of the CH3 (electron donor) radical and the Br atom of Br-Y (electron acceptor); this kind of single-electron bromine bond also possesses the character of a “three-electron bond”. Due to the formation of the single-electron Br bond, the C-H bonds of the CH3 radical bend away from the Br-Y moiety and the Br-Y bond elongates, giving red-shifted single-electron Br bond complexes. The effects of substituents, hybridization of the carbon atom, and solvent on the properties of the complexes have been investigated. The strengths of single-electron hydrogen bonds, single-electron halogen bonds and single-electron lithium bonds have been compared. In addition, the single-electron halogen bond system is discussed in the light of the first three criteria for hydrogen bonding proposed by Popelier. 相似文献
19.
Prof. Dr. Ibon Alkorta Prof. Dr. José Elguero Prof. Dr. Janet E. Del Bene 《Chemphyschem》2016,17(19):3112-3119
MP2/aug′‐cc‐pVTZ calculations were performed to investigate boron as an electron‐pair donor in halogen‐bonded complexes (CO)2(HB):ClX and (N2)2(HB):ClX, for X=F, Cl, OH, NC, CN, CCH, CH3, and H. Equilibrium halogen‐bonded complexes with boron as the electron‐pair donor are found on all of the potential surfaces, except for (CO)2(HB):ClCH3 and (N2)2(HB):ClF. The majority of these complexes are stabilized by traditional halogen bonds, except for (CO)2(HB):ClF, (CO)2(HB):ClCl, (N2)2(HB):ClCl, and (N2)2(HB):ClOH, which are stabilized by chlorine‐shared halogen bonds. These complexes have increased binding energies and shorter B?Cl distances. Charge transfer stabilizes all complexes and occurs from the B lone pair to the σ* Cl?A orbital of ClX, in which A is the atom of X directly bonded to Cl. A second reduced charge‐transfer interaction occurs in (CO)2(HB):ClX complexes from the Cl lone pair to the π* C≡O orbitals. Equation‐of‐motion coupled cluster singles and doubles (EOM‐CCSD) spin–spin coupling constants, 1xJ(B‐Cl), across the halogen bonds are also indicative of the changing nature of this bond. 1xJ(B‐Cl) values for both series of complexes are positive at long distances, increase as the distance decreases, and then decrease as the halogen bonds change from traditional to chlorine‐shared bonds, and begin to approach the values for the covalent bonds in the corresponding ions [(CO)2(HB)?Cl]+ and [(N2)2(HB)?Cl]+. Changes in 11B chemical shieldings upon complexation correlate with changes in the charges on B. 相似文献
20.
The trends in the properties of prereactive or charge-transfer complexes formed between the simple amines NH3, CH3NH2, (CH3)2NH, and (CH3)3N and the halogens F2, ClF, Cl2, BrF, BrCl, and Br2 were investigated by the ab initio restricted Hartree–Fock approach, the Møller–Plesset second-order method, and with several density functional theory variants using extended polarized basis sets. The most important structural parameters, the stabilization energies, the dipole moments, and other quantities characterizing the intermolecular halogen bond in these complexes are monitored, discussed, and compared. A wide range of interaction strengths is spanned in these series. Successive methyl substitution of the amine as well as increasing polarities and polarizabilities of the halogen molecules both systematically enhance the signature of charge-transfer interaction. These trends in halogen bonds of varying strength, in many aspects, parallel the features of hydrogen bonding. 相似文献