Substitution of halogen atom in α-halonitro compounds of the aliphatic series

Ethyl -halo--nitropropionate and -butyrate were prepared by alkylating ammonium salts of ethyl bromo- and chloronitroacetates. The addition of alkyl acrylates to alkyl chloronitroacetates or their salts gives dialkyl -chloro--nitroglutarates. Sodium salts of ethyl -nitro--sulfo--hydroxypropionate and -butyrate were obtained by the sulfodehalogenation of ethyl -chloro--nitro--hydroxypropionate and -butyrate with sodium dithionite. Esters of -amino acid hydrochlorides were prepared by the reduction of alkyl -chloro--nitrocarboxylates. The hydrogenation of alkyl nitrosulfoacetates leads to the corresponding disodium salts of alkyl aminodisulfoacetates and piperazine-2,5-dione.For communication 5 seeIvz. Akad. Nauk SSSR, Ser. Khim., 1990, 2012 [Bull. Acad. Sci. USSR, Div. Chem. Sci., 1990,39, 1826].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 872–876, May, 1994.     

Vibrational spectra of halogen substituted cyclopropanes—V. Trans-1,2-dichlorocyclopropane

The i.r. spectra of gaseous trans-1,2-dichlorocyclopropane were measured from 4000 to 400 cm⁻¹ and to 200 cm⁻¹ in the liquid phase. The Raman spectrum of the liquid was obtained from 4000 to 50 cm⁻¹. An assignment of all 21 normal vibrations was proposed on the basis of i.r. vapour phase band contours, Raman depolarization ratios, expected group frequencies and comparison with closely related molecules. There is excellent agreement with the normal modes previously assigned for the cis and trans isomers of the chloro, bromo and iodo analogues. The data indicate little interaction between the two CHCl moieties.     

New preparation method for halogenated ethanes and methanes via base-catalyzed halogen dance

Although literature abounds with examples of formation of perhaloalkanes by photo-lytic or Lewis-acid induced halogen exchange reactions involving radical or carbocationintermediates,the procedures are seldom applicable to the preparation of perhaloalkanes ingood yields under mild conditions.Recently,we have reported the spontaneous reactionsof some perhalofluoroalkanes with various types of nucleophiles.All these reactions areinitiated by the halophilic attack of nucleophiles on C—Br or C—Cl bonds,followed byanionic chain steps involving carbanion as well as olefin intermediates.Notably,the latter areformed after the β-elimination of a good leaving group from the former.On the other hand,it is well known that halogenated carbanions can effectively make halophilic attacks on theC—X bonds of other halogenated substrates,e.g.,in the“halogen dance”of Bunnett.There-     

Self-assembly of nitroxide radicals via halogen bonding—directional NO?I interactions

Novel supramolecular self-assemblies of nitroxide free radicals via noncovalent halogen bonding are synthesised. A directional NO?I interaction is observed in a one-dimensional coordination polymer consisting of alternating electron donor and acceptor molecules.     

Cocrystals assembled from iodoperfluorobenzene and flexible NTPO via halogen and π-hole bonds

Two binary cocrystals of 1,4-diiodotetrafluorobenzene (1,4-DITFB, C₆F₄I₂) and 1,3,5-trifluoro-2,4,6-triiodobenzene (1,3,5-TITFB, C₆F₃I₃) with the flexible 2-{[(naphthalen-2-yl)methyl]sulfanyl}pyridine 1-oxide (NTPO, C₁₆H₁₃NOS) molecule were successfully prepared and characterized by X-ray diffraction and quantum chemistry calculation methods. X-ray diffraction analysis reveals that the conformation of the flexible NTPO molecule has been changed significantly after introducing the 1,4-DITFB or 1,3,5-TITFB molecule into the NTPO lattice. Also the formation of the binary cocrystals is driven mainly by robust C—I…⁻O—N⁺ halogen bonds and π-hole…π-bond interactions, and they possess `sandwich' structural frameworks. Moreover, interaction energy analysis and AIM analysis were used to explore the contribution of different fragments to the structural stability and the corresponding electronic properties, which reveals that the robust halogen bonds with shorter bonding lengths [2.768 (4) and 2.789 (3) Å] are suggested to be covalent to a certain degree.     

Regioselective aminohalogenation of β-nitrostyrenes using NCS and NBS as nitrogen/halogen sources

Aminohalogenation reaction of β-nitrostyrenes with N-halosuccinimides(N-chloro and N-bromosuccinimides) has been successfully conducted by using nickel acetate as a catalyst in the presence of potassium carbonate and succinimide as co-additives.The reaction was easily performed at room temperature under nitrogen gas protection to give dihalorinaed haloamino products in good to excellent yields(60%-98%).The structure has been confirmed by X-ray crystal structure analysis.     

Thermodynamic and aromaticity studies for the assessment of the halogen⋯cyano interactions on Iodobenzonitrile

The standard (p° = 0.1 MPa) molar enthalpies of formation, in the gaseous phase, of the 2-, 3- and 4-iodobenzonitrile isomers were derived from the combination of the corresponding standard molar enthalpies of formation, in the condensed phase, at T = 298.15 K, and the standard molar enthalpies of sublimation, at the same temperature, calculated respectively from the standard molar energies of combustion in oxygen, measured by rotating-bomb calorimetry, and from the vapour-pressure study of the referred compounds, measured by mass-loss Knudsen effusion technique. The strength of the halogen-halogen and the halogen-cyano intermolecular interactions, in the crystal, are evaluated by the enthalpies and entropies of phase transition of the iodobenzonitrile derived from mass-loss Knudsen technique and differential scanning calorimetry measurements and compared with those reported to fluorobenzonitrile and bromobenzonitrile isomers. The computational calculations complement the experimental work, using different aromaticity criteria (HOMA, NICS, Shannom Aromaticity, PDI and ATI) for the analysis of the electronic behaviour of each iodobenzonitrile isomer.     

Cooperative and substitution effects in enhancing strengths of halogen bonds in FCl⋯CNX complexes

In this paper, the cooperative effect of halogen bond with hydrogen bond has been used to make a halogen bond in FCl-CNH dimer vary from a chlorine-shared one to an ion-pair one. The halogen bond is strengthened in FCl-CNH-CNH trimer and its maximal interaction energy equals to -76 kJ∕mol when the number of CNH in FCl-CNH-(CNH)(n) polymer approaches infinity. Once the free H atom in FCl-CNH-CNH trimer is replaced with alkali metals, the halogen bond becomes strong enough to be an ion-pair one in FCl-CNH-CNLi and FCl-CNH-CNNa trimers. An introduction of a Lewis acid in FCl-CNH dimer has a more prominent effect on the type of halogen bond. A prominent cooperative effect is found for the halogen bond and hydrogen bond in the trimers. FH-FCl-CNH-CNH and FH-FCl-CNH-CNLi tetramers have also been studied and the interaction energy of halogen bonding in FH-FCl-CNH-CNLi tetramer is about 12 times as much as that in the FCl-CNH dimer. The atoms in molecules and natural bond orbital analyses have been carried out for these complexes to understand the nature of halogen bond and the origin of the cooperativity.     

Computationally rational design of metal-involving halogen bonds with π-covalency: Structures and bonding analysis

Traditional π-covalent interactions have been proved in the non-metal halogen bond adducts formed by chloride and halogenated triphenylamine-based radical cations. In this study, we have rationally designed two metal-involving halogen bond adducts with π-covalency property, such as [L1-Pd···I-PTZ]⁺ (i.e., 1) and [L2-Pd···I-PTZ]⁺ (i.e., 2), in which the square-planar palladium complexes serve as halogen bond acceptor and 3,7-diiodo-10H-phenothiazine radical cation (i.e., [I-PTZ]^•+) acts as halogen bond donor. Noncovalent interaction analysis and quantum theory of atoms in molecules analysis revealed that there are notable halogen bond interactions along the Pd···I direction without genuine chemical bond formed in both designed adducts. Energy decomposition analysis together with natural orbital for chemical valence calculations were performed to gain insight into their bonding nature, which demonstrated the presence of remarkable π-covalent interactions and σ-covalent interactions in both 1 and 2. We therefore proposed a new strategy for building the metal-involving halogen bonds with π-covalency property, which will help the further development of new types of halogen bonds.     

How does halogen bonding behave in solution? A theoretical study using implicit solvation model

A systematic study of halogen bonding interactions in gas phase and in solution was carried out by means of quantum chemical DFT/B3LYP method. Three solvents with different polarities (chloroform, acetone, and water) were selected, and solvation effects were considered using the polarized continuum model (PCM). For charged halogen-bonded complexes, the strength of the interactions tends to significantly weaken in solution, with a concomitant elongation of intermolecular distances. For neutral systems, halogen bond distances are shown to shorten and the interaction energies change slightly. Computations also reveal that in the gas phase the binding affinities decrease in the order Cl(-) > Br(-) > I(-), while in solution the energy gaps of binding appear limited for the three halide anions. According to free energy results, many systems under investigation are stable in solution. Particularly, calculated free energies of formation of the complexes correlate well with halogen-bonding association constants determined experimentally. The differences of the effects of solvent upon halogen and hydrogen bonding were also elucidated. This study can establish fundamental characteristics of halogen bonding in media, which would be very helpful for applying this noncovalent interaction in medicinal chemistry and material design.     

Gas-phase molecular halogen formation from NaCl and NaBr aerosols: when are interface reactions important?

Unique interface reactions at the surface of sea-salt particles have been suggested as an important source of photolyzable gas-phase halogen species in the troposphere. Many factors influence the relative importance of interface chemistry compared to aqueous-phase chemistry. The Model of Aerosol, Gas, and Interfacial Chemistry (MAGIC 2.0) is used to study the influence of interface reactions on gas-phase molecular halogen production from pure NaCl and NaBr aerosols. The main focus is to identify the relative importance of bulk compared to interface chemistry and to determine when interface chemistry dominates. Results show that the interface process involving Cl-(surf) and OH(g) is the main source of Cl2(g). For the analogous oxidation of bromide by OH, gaseous Br2 is formed mainly in the bulk aqueous phase and transferred across the interface. However, the reaction of Br-(surf) with O3(g) at the interface is the primary source of Br2(g) under dark conditions. The effect of aerosol size is also studied. Potential atmospheric implications and effects of interface processes on aerosol pH are discussed.     

Importance of halogen···halogen contacts for the structural and magnetic properties of CuX2(pyrazine-N,N′-dioxide)(H2O)2 (X = Cl and Br)

The structural and magnetic properties of the newly crystallized CuX(2)(pyzO)(H(2)O)(2) (X = Cl, Br; pyzO = pyrazine-N,N'-dioxide) coordination polymers are reported. These isostructural compounds crystallize in the monoclinic space group C2/c with, at 150 K, a = 17.0515(7) ?, b = 5.5560(2) ?, c = 10.4254(5) ?, β = 115.400(2)°, and V = 892.21(7) ?(3) for X = Cl and a = 17.3457(8) ?, b = 5.6766(3) ?, c = 10.6979(5) ?, β = 115.593(2)°, and V = 950.01(8) ?(3) for X = Br. Their crystal structure is characterized by one-dimensional chains of Cu(2+) ions linked through bidentate pyzO ligands. These chains are joined together through OH···O hydrogen bonds between the water ligands and pyzO oxygen atoms and Cu-X···X-Cu contacts. Bulk magnetic susceptibility measurements at ambient pressure show a broad maximum at 7 (Cl) and 28 K (Br) that is indicative of short-range magnetic correlations. The dominant spin exchange is the Cu-X···X-Cu supersuperexchange because the magnetic orbital of the Cu(2+) ion is contained in the CuX(2)(H(2)O)(2) plane and the X···X contact distances are short. The magnetic data were fitted to a Heisenberg 1D uniform antiferromagnetic chain model with J(1D)/k(B) = -11.1(1) (Cl) and -45.9(1) K (Br). Magnetization saturates at fields of 16.1(3) (Cl) and 66.7(5) T (Br), from which J(1D) is determined to be -11.5(2) (Cl) and -46.4(5) K (Br). For the Br analog the pressure dependence of the magnetic susceptibility indicates a gradual increase in the magnitude of J(1D)/k(B) up to -51.2 K at 0.84 GPa, suggesting a shortening of the Br···Br contact distance under pressure. At higher pressure X-ray powder diffraction data indicates a structural phase transition at ～3.5 GPa. Muon-spin relaxation measurements indicate that CuCl(2)(pyzO)(H(2)O)(2) is magnetically ordered with T(N) = 1.06(1) K, while the signature for long-range magnetic order in CuBr(2)(pyzO)(H(2)O)(2) was much less definitive down to 0.26 K. The results for the CuX(2)(pyzO)(H(2)O)(2) complexes are compared to the related CuX(2)(pyrazine) materials.     

Counterion influence on the N–I–N halogen bond

A detailed investigation of the influence of counterions on the [N–I–N]⁺ halogen bond in solution, in the solid state and in silico is presented. Translational diffusion coefficients indicate close attachment of counterions to the cationic, three-center halogen bond in dichloromethane solution. Isotopic perturbation of equilibrium NMR studies performed on isotopologue mixtures of regioselectively deuterated and nondeuterated analogues of the model system showed that the counterion is incapable of altering the symmetry of the [N–I–N]⁺ halogen bond. This symmetry remains even in the presence of an unfavorable geometric restraint. A high preference for the symmetric geometry was found also in the solid state by single crystal X-ray crystallography. Molecular systems encompassing weakly coordinating counterions behave similarly to the corresponding silver(i) centered coordination complexes. In contrast, systems possessing moderately or strongly coordinating anions show a distinctly different behavior. Such silver(i) complexes are converted into multi-coordinate geometries with strong Ag–O bonds, whereas the iodine centered systems remain linear and lack direct charge transfer interaction with the counterion, as verified by ¹⁵N NMR and DFT computation. This suggests that the [N–I–N]⁺ halogen bond may not be satisfactorily described in terms of a pure coordination bond typical of transition metal complexes, but as a secondary bond with a substantial charge-transfer character.     

Interplay between halogen bonds and π-π stacking interactions: CSD search and theoretical study

According to our survey of the Cambridge Structural Database (CSD), a great number of crystal structures, in which halogen bonds and aromatic stacking interactions are present and play an important role in crystal packing, have been extracted. In this work, ab initio calculations at the MP2 level of theory were performed to investigate the mutual influence between halogen bonds and π-π stacking interactions. Different energetic effects are observed in the studied complexes where the two kinds of noncovalent interactions coexist, which can be rationalized by the direction of charge transfer for the two interactions. These effects have been analyzed in detail in terms of the structural, energetic, and charge transfer properties of the complexes. In addition, the quantum theory of atoms in molecules (QTAIM) was also employed to characterize the interactions and to examine the strengthening or weakening of the interactions, depending on the variations of electron density on the bond and cage critical points. Finally, certain crystal structures retrieved from the CSD have been selected to provide experimental evidence of the combination of the two interactions.     

Energetic effects between halogen bonds and anion-π or lone pair-π interactions: a theoretical study

Energetic effects between halogen bonds and anion-π or lone pair-π interactions have been investigated by means of ab initio MP2 calculations. 1,4-diiodo-perfluorobenzene, a very effective building block for crystal engineering based on halogen bonding, is selected in this work both as electron-deficient π aromatic ring and as halogen bond donor. Additive and diminutive effects are observed when halogen bonds and anion-π/lone pair-π interactions coexist in the same complex, which can be ascribed to the same direction of charge transfer for the two interactions. These effects have been analyzed in detail by the structural, energetic, and AIM properties of the complexes. Finally, experimental evidence of the combination of the interactions has been obtained from the Cambridge Structural Database.