Some measures for making halogen bonds stronger than hydrogen bonds in H2CS-HOX (X = F, Cl, and Br) complexes

The properties and applications of halogen bonds are dependent greatly on their strength. In this paper, we suggested some measures for enhancing the strength of the halogen bond relative to the hydrogen bond in the H(2)CS-HOX (X = F, Cl, and Br) system by means of quantum chemical calculations. It has been shown that with comparison to H(2)CO, the S electron donor in H(2)CS results in a smaller difference in strength for the Cl halogen bond and the corresponding hydrogen bond, and the Br halogen bond is even stronger than the hydrogen bond. The Li atom in LiHCS and methyl group in MeHCS cause an increase in the strength of halogen bonding and hydrogen bonding, but the former makes the halogen bond stronger and the latter makes the hydrogen bond stronger. In solvents, the halogen bond in the Br system is strong enough to compete with the hydrogen bond. The interaction nature and properties in these complexes have been analyzed with the natural bond orbital theory.     

N—H…X (X = Cl and Br) hydrogen bonds in three isomorphous 3,5‐dichloropyridinium salts

Specific short contacts are important in crystal engineering. Hydrogen bonds have been particularly successful and together with halogen bonds can be useful for assembling small molecules or ions into crystals. The ionic constituents in the isomorphous 3,5‐dichloropyridinium (3,5‐diClPy) tetrahalometallates 3,5‐dichloropyridinium tetrachloridozincate(II), (C₅H₄Cl₂N)₂[ZnCl₄] or (3,5‐diClPy)₂ZnCl₄, 3,5‐dichloropyridinium tetrabromidozincate(II), (C₅H₄Cl₂N)₂[ZnBr₄] or (3,5‐diClPy)₂ZnBr₄, and 3,5‐dichloropyridinium tetrabromidocobaltate(II), (C₅H₄Cl₂N)₂[CoBr₄] or (3,5‐diClPy)₂CoBr₄, arrange according to favourable electrostatic interactions. Cations are preferably surrounded by anions and vice versa ; rare cation–cation contacts are associated with an antiparallel dipole orientation. N—H…X (X = Cl and Br) hydrogen bonds and X …X halogen bonds compete as closest contacts between neighbouring residues. The former dominate in the title compounds; the four symmetrically independent pyridinium N—H groups in each compound act as donors in charge‐assisted hydrogen bonds, with halogen ligands and the tetrahedral metallate anions as acceptors. The M —X coordinative bonds in the latter are significantly longer if the halide ligand is engaged in a classical X …H—N hydrogen bond. In all three solids, triangular halogen‐bond interactions are observed. They might contribute to the stabilization of the structures, but even the shortest interhalogen contacts are only slightly shorter than the sum of the van der Waals radii.     

Automated potentiostatic microdetermination of Cl,Br and I in organic compounds

The automation of a rapid microdetermination of Cl, Br and/or I in organic compounds is described. A combustion furnace, a buret and a titrator are modified and assembled to an apparatus. A solid state programmer using monostable multivibrator circuits to generate various time delays completes a halogen determination automatically in less than 4 min. The following steps in a determination are automated: combustion with sample injection and retraction; feed of reductive flush solution; filling of the titration vessel; titration.Quantitative oxidation of organic samples (about 2–10 mg) in an Ingram-type combustion tube at 1000 °C can be accomplished in two ways: in pure oxygen only or with the aid of an additional layer of a specially prepared $\text{WO}{}_3\text{V}{}_2\text{O}{}_5$ catalyst. A continuously renewed solution of SO₂ or bisulfite assures quantitative reduction to halides. They are flushed into the titration vessel, absorbed in a vigorously stirred absorption solution and titrated immediately with 0.01 N silver nitrate. The titrator is used in potentiostatic mode. End points are set individually for each halogen. Several flush and absorption solutions were investigated and used successfully.     

New coordination motifs of melamine directed by N-H---X (X = Cl or Br) hydrogen bonds

Unusual mu(2)- and mu(3)-coordination modes of melamine are found in two organic-inorganic hybrid copper halides, [Cu(2)Br(2)(MA)](n) (1) and [Cu(3)Cl(3)(MA)](n) (2) (MA = melamine), in which the MA ligand affords two N-heterocycle N atoms to link (Cu(2)Br(2))infinity stairs and serves as a novel mu(3) bridge to give a 3D framework, respectively.     

Halogen Bonding or Hydrogen Bonding between 2,2,6,6-Tetramethyl-piperidine-noxyl Radical and Trihalomethanes CHX3 (X=Cl,Br, I)

The halogen and hydrogen bonding complexes between 2,2,6,6-tetramethylpiperidine-noxyl and trihalomethanes (CHX₃, X=Cl, Br, I) are simulated by computational quantum chem-istry. The molecular electrostatic potentials, geometrical parameters and interaction energy of halogen and hydrogen bonding complexes combined with natural bond orbital analysis are obtained. The results indicate that both halogen and hydrogen bonding interactions obey the order Cl相似文献   

Synthesis,Crystal Structure,and Optical Properties of (CH3NH3)2CoX4 (X = Cl,Br, I,Cl0.5Br0.5, Cl0.5I0.5, Br0.5I0.5)

The reaction of methylammonium halides and cobalt halides yielded the organic‐inorganic hybrid compounds of general formula (CH₃NH₃)₂CoX₄. By varying the different halides, we were able to synthesize the whole row from Cl to I as well as some mixed halides compounds and to determinate the crystal structures. (CH₃NH₃)₂CoX₄ (X = Cl, Br, Cl_0.5Br_0.5, Br_0.5I_0.5) crystallize isotypic to (CH₃NH₃)₂HgCl₄ in space group P2₁/c with Z = 4 [X = Cl: a = 7.6483(9), b = 12.6885(18), c = 10.8752(12) Å, β = 96.639(9)°; X = Cl_0.5Br_0.5: a = 7.8271(9), b = 12.9543(9), c = 11.1007(11) Å, β = 96.320(8)°; X = Br: a = 7.9782(2), b = 13.1673(2), c = 11.2602(2) Å, β = 96.3260(10)° and X = Br_0.5I_0.5: a = 8.2435(12), b = 13.645(2), c = 11.5856(18) Å, β = 95.54(2)°]. The mixed halides show a statistic distribution in both cases. In (CH₃NH₃)₂CoCl₂I₂ an ordered variant is realized representing a new structure type [C2/m, Z = 4, a = 18.808(4), b = 7.3604(7), c = 10.4109(17) Å, β = 120.364(13)°]. (CH₃NH₃)₂CoI₄ crystallizes again isotypic to the respective mercury compound [(CH₃NH₃)₂HgCl₄] [Pbca, Z = 8, a = 10.9265(5), b = 12.1552(5), c = 20.9588(9) Å]. All structures are build up by inorganic tetrahedral [CoX₄]^2– anions and organic (CH₃NH₄)⁺ cations. Additionally the Raman spectra as well as the optical reflectance spectra are discussed.     

Complexes of HArF and AuX (X = F,Cl, Br,I). Comparison of H-bonds,halogen bonds,F-shared bonds and covalent bonds

The various sorts of complexes in which HArF and AuX (X = F, Cl, Br, I) can engage are probed by MP2/aug-cc-pVTZ calculations. The most weakly bound are those containing a halogen bond (XB) of the AuX⋯FArH sort, with binding energies less than 8 kcal/mol. H-bonded dimers FArH⋯XAu are a little stronger, held together by some 12 kcal/mol. Being the most strongly bound places the F atom of HArF roughly midway between Ar and Au in an F-shaped structure, bound by some 43–54 kcal/mol. The last sort of product involves atomic rearrangements wherein the H atom migrates from Ar to Au, followed by formation of a covalent Ar–Au bond. The resulting molecular unit is stabilized by 30–40 kcal/mol relative to the original HArF and AuX reactants. The H-bonded dimers are held together by an unusually large polarization component, surpassing electrostatic attraction, while dispersion predominates for the halogen bonds. Perturbations of the geometries and stretching frequencies offer a ready means of distinguishing the different types of complexes by spectroscopic techniques.     

Nonconventional hydrogen bonds: a theoretical study of [uracil-L](-) (L = F, Cl, Br, I, Al, Ga, In) complexes

The interaction of L (-) (L = F, Cl, Br, I, Al, Ga and In) with a uracil molecule has been studied with B3LYP density-functional geometry optimizations and electron-propagator calculations of vertical electron detachment energies. Because the extra electron of the anion is localized on L, nonconventional hydrogen bonds are formed. The interactions of halide anions with uracil are similar to the interactions of uracil with Cu (-), Ag (-) and Au (-) that were reported previously. Whereas halide and transition metal anion complexes with uracils are singlets, the anions formed with Al, Ga and In are triplets. Vertical electron detachment energies (VEDEs) are higher for (uracil-L) (-) than the analogous values for isolated L (-) anions. Predicted VEDEs are assigned to Dyson orbitals that may be localized on L (-) or uracil.     

The matrix-isolated molecular complexes CO/XF (X=Cl,Br,I) and the molecular structure of FC(O)Br

FC(O)Br has been synthesized, and its IR spectrum in the gas phase and isolated in an Ar matrix, as well as, its Raman spectrum in the solid state at -196 degrees C has been analyzed. Its molecular structure has been determined and its UV has been measured. FC(O)Br and FC(O)Cl has been photodissociated in an argon matrix at 17 K with a 193 nm laser. The photolysis produces CO and XF which recombine to form CO/XF complexes. The formation of complexes are followed by the shift of the normal vibration modes with respect to CO and XF isolated in argon matrix. In the case of FC(O)Br, three isomers are identified, OC...BrF, OC...FBr, and CO...BrF, whereas for FC(O)Cl only one isomer is observed, OC...ClF. High level quantum chemical calculations are used to help the assignment of the different isomers.     

Competitive interaction between halogen and hydrogen bonds in NH2Br‐HOX (X = F,Cl, and Br) complex

The NH₂Br‐HOX (X = F, Cl, and Br) complexes have been investigated with quantum chemical calculations at the MP2/aug‐cc‐pVTZ level. Five isomers are observed for the Cl and Br complexes, whereas only two isomers are found for the F complex. The geometrical, energetic, and spectroscopic parameters have been analyzed for these complexes. The hydrogen‐bonded complexes are more stable than the halogen‐bonded ones. In most complexes, the associated O? H and O? X bonds are elongated and show a red shift, whereas the distant bonds are contracted and exhibit a blue shift. The complexes have been analyzed with natural bond orbital and atoms in molecules. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

On three-electron bonds and hydrogen bonds in the open-shell complexes [H2X2]+ for X = F, Cl, and Br

The [H2X2]+ (X = Cl, Br) formula could refer to two possible stable structures, namely, the hydrogen-bonded complex and the three-electron-bonded one. In contrary to the results published by other authors, we claim that for the F-type structures the hydrogen-bonded form is the only possible one and the [HFFH]+ complex is an artifact as its wave function is unstable. For all analyzed molecules, the IR anharmonic spectra have been simulated, which enabled a deeper analysis of other authors' published results of IR low-temperature matrix experiments. Topological atoms in molecules and electron localization function investigations have revealed that the nature of the bond in three-electron-bonded structures is similar to the covalent-depleted one in F2 or HOO molecules, but the effect of removing electrons from the bond area is stronger.     

The heI photoelectron spectra of the halogen azides,XN3(X = Cl and Br) and the halogen isocyanates,XNCO(X = Cl,Br and I)

High yield routes to the unstable halogen azides and isocyanates have permitted vacuum ultraviolet photoelectron spectra to be obtained for the chlorine and bromine azides, and the chlorine, bromine and iodine isocyanates. The results are compared with ab initio and semi-empirical calculations, leading to a reassignment of the photoelectron spectra of the parent acids, HN₃ and HNCO in the high energy region. The halogen azide and isocyanate photoelectron spectra provide an interesting investigation into how the orbitals of a linear pseudohalide grouping are perturbed by an off-azis halogen atom. A photoelectron spectrum for the unknown molecule FNCO is predicted.     

[Pd(en)2Pd(en)2X2]4+n(X=Cl,Br,I)链的畸变研究

对一维卤桥过渡金属化合物〔Ｐｄ（ｅｎ）２Ｐｄ（ｅｎ）２Ｘ２〕ｎ＾４＋（Ｘ＝Ｃｌ,Ｂｒ,Ｉ）应用量子化学从头算及ＥＨＴ能带计算进行了研究,发现Ｐｅｉｅｒｌｓ畸变的产生及程度取决于填充轨道能量的降低与核间及电子间相互作用。     

Computational investigation of the weakly bound dimers HOX...SO(3) (X = F, Cl, Br)

The electronic structure and thermochemical stability of the HOX-SO(3) (X = F, Cl, Br) complexes is studied using second-order M?ller-Plesset perturbation theory (MP2). The calculated dissociation energies of the HOF-SO(3), HOCl-SO(3), and HOBr-SO(3) complexes are 5.43, 6.02, and 5.98 kcal mol(-1) at MP2/6-311++G(3df,3pd) level, respectively. Anharmonic OH stretching frequencies of the HOX (X = F, Cl, Br) moieties along with the frequency shifts upon complex formation are calculated at the MP2/6-311++G(2df,2p) level. AIM and NBO analyses were also performed. Theoretical data strongly encourage performing of matrix-isolation studies of the title complexes and their spectroscopic identification.     

Single-crystal absorption spectra of CsVX3 (X = Cl,Br, I)

Polarized single-crystal absorption spectra of CsVCl₃, CsVBr₃ and CsVI₃ have been measured between 5000 and 30000 cm^?1 at temperatures ranging from 6 to 273 K. Spin-allowed transitions arise through a vibronic single-ion mechanism. Spin-forbidden transitions are strongly enhanced through an exchange intensity mechanism.