Synthesis and properties of polyamides derived from systematically halogenated terephthalic acids with fluorine,chlorine, or bromine atoms

Aromatic polyamides were prepared from systematically halogenated terephthalic acids with hexamethylene diamine, piperazine, 4,4′-diaminodiphenylether and p-phenylene diamine by interfacial or low temperature solution polycondensation. The halogenated terephthalic acids used have mono-, di-, or tetra-substituted fluorine, chlorine, or bromine atoms on the benzene ring. The nonhalogenated terephthalic acid was also used for the comparison. The effects of halogen substitution on the benzene ring on the synthesis and some properties of polymers were examined. Reduced specific viscosity decreased in the order F > Cl > Br by halogen substitution. The incorporation of halogen substituents on the ring led to a decrease of crystallinity and fluoro-substituents hindered the crystallization more strongly. The melting point (T_m) decreased in the order F > Cl > Br by mono-substitution, and Br > Cl > F by di-and tetra-substitution. The change of T_m caused by the difference of the number of halogen substituents differed depending on the rigidity of polymer chains. The flame-retardancy estimated by thermogravimetry, self-ignition, and flash-ignition test increased with increasing halogen content of the polymers. Solubility increased remarkably by halogen substitution. The peak temperature of tan δ decreased by halogen substitution. Some discussion was made on these effects of halogen substitution.     

一系列水合和非水合铀酰卤族(F,Cl,Br)配合物在水溶液中的结构和紫外吸收光谱性质的密度泛函理论研究

本文考虑相对论效应并应用密度泛函理论(DFT)研究水溶液中UO2Xn(H2O)5-n(X=F,Cl,Br;n=1～4)和UO2Xn(X=F,Cl,Br;n=1～6)一系列水合和非水合铀酰化合物的结构和紫外吸收光谱性质。将这一系列物质命名为Xnm(X为F,Cl,和Br;n为卤素配体个数,m为水分子配体的个数)。在水溶液中,溶剂化效应采用类导体屏蔽模型(COSMO)并采用SAS溶剂接触曲面构造空穴模拟水溶剂对配合物的作用。配合物的紫外光谱性质采用考虑旋-轨耦合相对论效应的含时密度泛函(SO-TD-DFT)进行计算。U=O键随着F配体数目的增加而明显伸长,然而随Cl和Br配体数目的增加变化较小。随X配体数目的增加和水分子参与配位,铀与X的结合能逐渐减弱。配合物的紫外光谱计算表明铀酰氟的各种配合物并不出现特征吸收峰,而铀酰氯和铀酰溴的各种配合物均有特征吸收光谱。通过分子轨道分析可以很好解释光谱所体现的特征。     

Phase Transition and Band Gap Regulation by Halogen Substituents on the Organic Cation in Organic–Inorganic Hybrid Perovskite Semiconductors

In the last decade, hybrid materials have received widespread attention. In particular, hybrid lead halide perovskite-type semiconductors are very attractive owing to their great flexibility in band gap engineering. Here, by using precise molecular modifications, three one-dimensional perovskite-type semiconductor materials are designed and obtained: [Me₃PCH₂X][PbBr₃] (X=H, F, and Cl for compounds 1 , 2 , and 3 , respectively). The introduction of a heavier halogen atom (F or Cl) to [Me₄P]⁺ increases the potential energy barrier required for the tumbling motion of the cation, hence achieving the transformation of the phase transition temperature from low temperature (192 K) to room temperature (285 K) and high temperature (402.3 K). Moreover, the optical band gaps reveal a broadening trend with 3.176 eV, 3.215 eV, and 3.376 eV along the H→F→Cl series, which is attributed to the formation of the structural distortion.     

Coordination Polyhedra OsXn(X = F, Cl, Br, I) in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were used to perform crystal-chemical analysis of compounds containing complexes [Os _a X _b ] ^z–(X = F, Cl, Br, I). Atoms of Os(V) at X = F and Cl, of Os(IV) at X = Cl, Br, and of Os(III) at X = Br were found to exhibit a coordination number of 6 with respect to the halogen atoms and to form OsX₆octahedra. The coordination polyhedra of Os(III) for X = Cl, I are square pyramids OsX₄. Each Os(III) atom forms one Os–Os bond; as a consequence, the OsBr₆octahedra share a face in forming Os₂Br^3– ₉complexes, while the OsX₄pyramids (X = Cl, I) dimerize to produce [X₄Os–OsX₄]^2–ions. The influence of the valence state of the Os atoms and of the nature of the halogen atoms on the composition and structure of the complexes formed and some characteristics of the coordination sphere of Os were considered.     

Electrochemically activated reaction of nucleophilic substitution in polyfluorovinyl halides under the action of the cyclopentadienylirondicarbonyl anion [CpFe(CO)2]−

The reaction of polyfluorovinyl halides RCF=CFX (R =t-C₄F₉, X = F, CI, or Br; R = Ph, X = F, Cl) with the [CpFe(CO)₂]^– anion has been studied by cyclic voltammetry and preparative-scale electrolysis. The electrochemical activation of vinyl halides made it possible to obtain the products of nucleophilic substitution for all substrates investigated independently of their configuration and the nature of the halogen.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1523–1528, June, 1996.     

Magnitude and origin of the attraction and directionality of the halogen bonds of the complexes of C6F5X and C6H5X (X = I, Br, Cl and F) with pyridine

The geometries and interaction energies of complexes of pyridine with C₆F₅X, C₆H₅X (X=I, Br, Cl, F and H) and R_FI (R_F=CF₃, C₂F₅ and C₃F₇) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (E_int) 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 E_int 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 E_int estimated for the R_FI–pyridine (R_F=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.     

Four-Center Nodes: Supramolecular Synthons Based on Cyclic Halogen Bonding

The isocyanide trans-[PdBr₂(CNC₆H₄-4-X′)₂] (X′=Br, I) and nitrile trans-[PtX₂(NCC₆H₄-4-X′)₂] (X/X′=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four-center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C−X′⋅⋅⋅X−M halogen-bonding contacts and include one Type I M−X⋅⋅⋅X−M interaction, thus giving the rhombic-like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6–2.9 kcal mol⁻¹.     

Density functional theory study on the reactions of X− with CH3SY (X,Y = F,Cl, Br,I)

Gas‐phase anionic reactions X^? + CH₃SY (X, Y = F, Cl, Br, I) have been investigated at the level of B3LYP/6‐311+G (2df,p). Results show that the potential energy surface (PES) of gas‐phase reactions X^? + CH₃SY (X, Y = Cl, Br, I) has a quadruple‐well structure, indicating an addition–elimination (A–E) pathway. The fluorine behaves differently in many respects from the other halogens and the reactions F^? + CH₃SY (Y = F, Cl, Br, I) correspond to deprotonation instead of substitution. The gas‐phase reactions X^? + CH₃SF (X = Cl, Br, I), however, follow an A–E pathway other than the last two out going steps (COM2 and PR) that proceeds via a deprotonation. The polarizable continuum model (PCM) has been used to evaluate the solvent effects on the energetics of the reactions X^? + CH₃SY (X, Y = Cl, Br, I). The PES is predicted to be unimodal in the solvents of high polarity. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Halogen bonding in mono- and dihydrated halobenzene

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•••O_w internuclear separation (where O_w is the water oxygen). For all XPh-H₂O systems hydrogen-bonded systems exist, containing a combination of CH•••O_w and O_wH_w•••X hydrogen bonds. For all systems except X = At the X•••H_w hydrogen-bonding interaction is stronger than the X•••O_w 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.     

Redistribution reactions in the ion source of a mass spectrometer of complexes of titanium (iv), tin (iv) and germanium (iv) with 8-quinolinolato and halo or ethoxy ligands

The relative intensities of peaks in the mass spectra of the compounds MX_4?nox_n (oxH = 8-quinolinol; n = 2; M = Ti; X = F, Cl, Br or OEt; M = Sn; X = F, Cl, Br or I; M = Ge; X = Cl or Br; n = 1; M = Ti; X = OEt) depend on the insertion temperature and the residence time of the sample in the mass spectrometer. In most cases ions which cannot arise by fragmentation of the respective molecular ions are observed. These ions arise from the ionisation and fragmentation of species which are due to redistribution reactions in the mass spectrometer. The fragmentation pattern of the compounds MX₂ox₂ (X = halogen), mainly involving loss of ligand radicals, is related to the common oxidation states of the metals and reflects the metal-halogen bond strength. The molecular ions of the compounds Ti(OEt)_4?nox_n (n = 0, 1 or 2) fragment by loss of intact ligand radicals.     

An ab initio evaluation of the role of p,π interaction: II. Molecules of the CH3COX series

The RHF/6-311G(d) and MP2/6-311G(d) calculations with full geometry optimization were performed for CH₃COX molecules (X = F, Cl, Br, CH₃). Variations in the populations of the p _y orbitals of their halogen and carbon atoms (orbitals whose symmetry axes are perpendicular to the molecular plane) from X = F to X = Cl, Br, and CH₃ are not associated with variations in the extent of the p,π conjugation between the lone electron pair of the halogen atom and the π-electron system of the carbonyl group. The bonding molecular orbitals formed by these atomic p _y orbitals are not determined by this interaction. The RHF/6-311G(d) and MP2/6-311G(d) calculations give similar results.     

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.     

Structure and Conformational Stability of 1,3-Dihalo-2,2,4,4-tetrachloro-1λ3,3λ3-diphosphetidines

The optimal geometry of isomeric molecules of (XP-CCl₂)₂ with X = F, Cl, Br was determined by RHF/6-31G(d) calculations. With X = F and Cl, the electronic correlation was considered on the MP2/6-31G(d) level. The P₂C₂ ring is nonplanar. With X = Cl and Br, the trans conformation is energetically preferable compared to the two possible cis conformations: by 7.8 and 14.2 kJ mol^{- 1} for X = Cl and by 7.5 and 14.1 kJ mol^{- 1} with X = Br. respectively. With X = F, the calculated energies of the cis and trans forms are very close.     

Predicting the halogen-n (n = 3–6) synthons to form the “windmill” pattern bonding based on the halogen-bonded interactions

The “windmill” pattern cyclic halogen polymers (XBr)3 (X = Cl, Br, I) and (BrY)n (n = 3–6, Y = Cl, Br, I) have been investigated using the density functional theory. Due to the anisotropic distribution of its electron density, the halogen atom can form halogen-bonded interactions by functioning as both electron donor sites and electron acceptor sites. For (XBr)3 (X = Cl, Br, I) trimers, the Cl···Cl interaction is the weakest, and the I···I interaction is the strongest. For (BrY)n (n = 3–6, Y = Cl, Br, I), the Br···Br halogen bonds are the strongest in (BrY)₄ tetramers. We predict that the iodine-4 synthon may allow creation of a self-assembled island during crystal growth. The angle formed by the electron-depleted sigma-hole, the halogen atom and the electron-rich equatorial belt perpendicular to the bond direction, together with the halogen-bond angle, can be used to explain the geometries and strength of the halogen-bond interactions. © 2018 Wiley Periodicals, Inc.     

Theoretical study on the substituent effect of halogen atom at different position of 7-azaindole-water derivatives: relative stability and excited-state proton-transfer mechanism

We have theoretically investigated the substituted effect on the first excited-state proton-transfer process of nX7AI-H₂O (n?=?2~6, X?=?F, Cl, Br) complex at the TD-M06-2X/6-31?+?G(d, p) level. Here X is the substituted halogen atom, and n value denotes the substituted position of X, such as C₂, C₃, C₄, C₅, or C₆. For the substituted 7-azaindole clusters, 6X7AI-H₂O molecule is the most stable structure in water. The replacement of halogen atom X does not affect the characters of the HOMO and LUMO, but influence the S₀?→?S₁ adiabatic transition energies of nX7AI-H₂O (n?=?2~6, X?=?F, Cl, Br). Our calculated results show that the double proton transfer occurs in a concerted but asynchronous protolysis pathway no matter which H atom is replaced by halogen atom. The halogen substitution changes the structural parameters evidently and leads to amply the asynchronousity during the proton-transfer process. The ESPT barrier height increases or decreases due to the halogen atom and substituted position.     

Theoretical investigation on identical anionic halide‐exchange SN2 reaction processes on N‐haloammonium cation NH3X+ (X = F,Cl, Br,and I)

CCSD(T) calculations have been used for identically nucleophilic substitution reactions on N‐haloammonium cation, X^? + NH₃X⁺ (X = F, Cl, Br, and I), with comparison of classic anionic S_N2 reactions, X^? + CH₃X. The described S_N2 reactions are characterized to a double curve potential, and separated charged reactants proceed to form transition state through a stronger complexation and a charge neutralization process. For title reactions X^? + NH₃X⁺, charge distributions, geometries, energy barriers, and their correlations have been investigated. Central barriers ΔE for X^? + NH₃X⁺ are found to be lower and lie within a relatively narrow range, decreasing in the following order: Cl (21.1 kJ/mol) > F (19.7 kJ/mol) > Br (10.9 kJ/mol) > I (9.1 kJ/mol). The overall barriers ΔE relative to the reactants are negative for all halogens: ?626.0 kJ/mol (F), ?494.1 kJ/mol (Cl), ?484.9 kJ/mol (Br), and ?458.5 kJ/mol (I). Stability energies of the ion–ion complexes ΔE_comp decrease in the order F (645.6 kJ/mol) > Cl (515.2 kJ/mol) > Br (495.8 kJ/mol) > I (467.6 kJ/mol), and are found to correlate well with halogen Mulliken electronegativities (R² = 0.972) and proton affinity of halogen anions X^? (R² = 0.996). Based on polarizable continuum model, solvent effects have investigated, which indicates solvents, especially polar and protic solvents lower the complexation energy dramatically, due to dually solvated reactant ions, and even character of double well potential in reactions X^? + CH₃X has disappeared. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Evidence for Interfacial Halogen Bonding

A homologous series of donor–π–acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye‐X (X=F, Cl, Br, and I) was immobilized on a TiO₂ surface to investigate how the halogen substituents affect the reaction between the light‐induced charge‐separated state, TiO₂(e^?)/ Dye‐X⁺ , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye‐F < Dye‐Cl < Dye‐Br < Dye‐I . Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ‐hole on the heavier halogens, the differences in dye regeneration kinetics for Dye‐Cl , Dye‐Br , and Dye‐I are ascribed to the extent of halogen bonding with the nucleophilic solution species.     

The Prominent Enhancing Effect of the Cation–π Interaction on the Halogen–Hydride Halogen Bond in M1⋅⋅⋅C6H5X⋅⋅⋅HM2

We designed M¹???C₆H₅X???HM² (M¹=Li⁺, Na⁺; X=Cl, Br; M²=Li, Na, BeH, MgH) complexes to enhance halogen–hydride halogen bonding with a cation–π interaction. The interaction strength has been estimated mainly in terms of the binding distance and the interaction energy. The results show that halogen–hydride halogen bonding is strengthened greatly by a cation–π interaction. The interaction energy in the triads is two to six times as much as that in the dyads. The largest interaction energy is ?8.31 kcal mol^?1 for the halogen bond in the Li⁺???C₆H₅Br???HNa complex. The nature of the cation, the halogen donor, and the metal hydride influence the nature of the halogen bond. The enhancement effect of Li⁺ on the halogen bond is larger than that of Na⁺. The halogen bond in the Cl donor has a greater enhancement than that in the Br one. The metal hydride imposes its effect in the order HBeH<HMgH<HNa<HLi for the Cl complex and HBeH<HMgH<HLi<HNa for the Br complex. The large cooperative energy indicates that there is a strong interplay between the halogen–hydride halogen bonding and the cation–π interaction. Natural bond orbital and energy decomposition analyses indicate that the electrostatic interaction plays a dominate role in enhancing halogen bonding by a cation–π interaction.     

Thermodynamics of vinyl ethers—XV : Halogen-containing vinyl ethers

Thermodynamics of geometrical and prototropic isomerization reactions on some halogen-containing vinyl ethers of the types ROCH–CHX (X = Cl, Br), ROC(CH₂X)CH₂ (X = F, Cl, Br), and ROC(CHMeCl)CH₂ (R = Me, Et, Et₂CH) have been studied. In ROCH_αCH_βX the cis (or Z) isomer is thermodynamically the more stable isomer, the higher stability of the Z isomer being due to its lower enthalpy. The relative stability of the E and Z forms is, however, reversed if the α H atom is replaced by a Me group. In systems like OCCX the double-bond stabilizing ability of the halogen atom decreases in the order Cl > Br > F, in contrast to the case in haloalkenes, where the corresponding order is F > Cl > Br.     

Tris-1-adamantylcyclotriphosphin und Tetrakis-1-adamantylcyclotetraphosphin: zwei Peradamantylierte Vertreter der Cyclopolyphosphinreihe (RP)n

Tris-1-adamantylcyclotriphosphine and Tetrakis-1-adamantylcyclotetraphosphine: Two Peradamantylated Examples from the Cyclopolyphosphine Series (RP)_n Depending on the halogen substitution at the phosphorus atom, 1-adamantyldihalophosphines of the type 1-AdPX₂ (X = Cl, Br) react with sodium to give tris-1-adamantylcyclotriphosphine 1 (X = Cl) or tetra-kis-1-adamantylcyclotetraphosphine 2 (X = Br). The latter is also formed in the reaction of approximately equimolar quantities of 1-adamantylphosphine and phosgene. The ³¹P-NMR-parameters are discussed and compared with those of the analogous ^tbutyl compounds.