Theoretical study of mixed LiLnX4 (Ln = La, Dy; X = F, Cl, Br, I) rare earth/alkali halide complexes

The structure, bonding and vibrational properties of the mixed LiLnX4 (Ln = La, Dy; X = F, Cl, Br, I) rare earth/alkali halide complexes were studied using various quantum chemical methods (HF, MP2 and the Becke3-Lee-Yang-Parr exchange-correlation density functional) in conjunction with polarized triple-zeta valence basis sets and quasi-relativistic effective core potentials for the heavy atoms. Our comparative study indicated the superiority of MP2 theory while the HF and B3-LYP methods as well as less sophisticated basis sets failed for the correct energetic relations. In particular, f polarization functions on Li and X proved to be important for the Li...X interaction in the complexes. From the three characteristic structures of such complexes, possessing 1-(C3v), 2-(C2v), or 3-fold coordination (C3v) between the alkali metal and the bridging halide atoms, the bi- and tridentate forms are located considerably lower on the potential energy surface then the monodentate isomer. Therefore only the bi- and tridentate isomers have chemical relevance. The monodentate isomer is only a high-lying local minimum in the case of X = F. For X = Cl, Br, and I this structure is found to be a second-order saddle point. The bidentate structure was found to be the global minimum for the systems with X = F, Cl, and Br. However, the relative stability with respect to the tridentate structure is very small (1-5 kJ/mol) for the heavier halide derivatives and the relative order is reversed in the case of the iodides. The energy difference between the three structures and the dissociation energy decrease in the row F to I. The ionic bonding in the complexes was characterized by natural charges and a topological analysis of the electron density distribution according to Bader's theorem. Variation of the geometrical and bonding characteristics between the lanthanum and dysprosium complexes reflects the effect of "lanthanide contraction". The calculated vibrational data indicate that infrared spectroscopy may be an effective tool for experimental investigation and characterization of LiLnX4 molecules.     

Molecular structure and vibrational spectra of mixed MDyX4 (M = Li, Na, K, Rb, Cs; X = F, Cl, Br, I) vapor complexes: a computational and matrix-isolation infrared spectroscopic study

The structures, energetic, and vibrational properties of MDyX(4) (M = Li, Na, K, Rb, Cs; X = F, Cl, Br, I) mixed alkali halide/dysprosium halide complexes have been investigated by a joint computational and experimental, matrix-isolation Fourier-transform infrared spectroscopic (MI-IR), study. According to our DFT computations for the complexes with heavier halides and alkali metals the ground-state structure is the tridentate isomer; while at high temperatures the bidentate structural isomer dominates. The survey of various dissociation processes revealed the preference of the dissociation to neutral MX and DyX(3) fragments over ionic and radical dissociation products. Cationic complexes are considerably less stable at 1000 K than the neutral complexes, and they prefer to dissociate to M(+) + DyX(4)(?) fragments. The vapor species of selected mixtures of NaBr and CsBr with DyBr(3) and of CsI with DyI(3) in the temperature range 900-1000 K have been isolated in krypton and xenon matrices and investigated by infrared spectroscopy. Besides the characteristic vibrational frequencies of the monomeric and dimeric alkali halide species and of the dysprosium trihalide molecules, certain signals indicated the formation of MDyX(4) (M = Na, Cs; X = Br, I) mixed complexes. Comparison with the computed vibrational and thermodynamic characteristics of the relevant species lead to the conclusion that these complexes appear in the vapor predominantly as the C(2v)-symmetry bidentate isomer. This is the first time that this structure was identified in an experimental vibrational spectroscopic study. The signals appearing upon performing a thermal anneal cycle were tentatively assigned to the double complex M(2)DyX(5) (M = Na, Cs; X = Br, I). A structure in which one alkali atom is bound to dysprosium by three and the other by two bridges is proposed for these double complexes.     

Theoretical study on tetranuclear boron clusters: B4X4 (X = H, F, Cl, Br, I)

The molecular orbitals for B4H4, B4F4, B4Cl4, B4Br4 and B4I4 have been calculated by using all-electron or effective core potential ab initio method at the self-consistent field level using basis sets with diffuse and polarization functions. The boron-boron and boron-halide (-hydrogen) distances of these cage compounds are optimized with three kinds of basis sets constrained to a tetrahedral symmetry. According to the localization scheme of Boys, four three-centered two-electron (3c2e) B-B-B bonds localized on each of the faces of the B4 tetrahedron are derived for B4X4 clusters. The HOMO-LUMO energy gaps, atomization energies and Mulliken overlap populations of these compounds indicate that the stabilities of the clusters decrease in the sequence of B4F4 > B4Cl4, B4H4 > B4Br4 > B4I4.     

GeH4与HX(X＝F,Cl,Br)间二氢键复合物的理论研究

对GeH4与HX形成的二氢键复合物的结构特征及本质进行了探讨.在MP2/6-311 ++G(3 d,3p)水平优化、频率验证得到复合物的分子结构,通过分子的几何参数及电子密度拓扑分析,确认GeH4与卤化氢已形成了二氢键复合物.MP2/6-311 ++ G(3d,3p)水平下进行BSSE校正后的结合能为3.281到4.5...     

卤代氰基卡宾自由基XCCN(X=F,Cl,Br)的理论研究

在C_s对称性和ANO-S基组下, 使用全活化空间自洽场方法(CASSCF), 研究了卤代氰基卡宾自由基及其阴离子的低能电子激发态性质. 为了进一步考虑电子的动态相关效应,采用多组态二级微扰理论(CASPT2)获得更加精确的能量值. 计算结果表明, XCCN的基态是三重态. 单重态和三重态的能隙差ΔE_S-T(kJ/mol): 7.4(FCCN)<13.4(ClCCN)<16.6(BrCCN). 计算得到, XCCN(X=F, Cl, Br)最低垂直激发能分别为408.3, 385.4和 345.2 kJ/mol, 这归因于π(a′) →n_xy 的电子跃迁; XCCN的电子亲和势分别为235.7, 233.0和 237.2 kJ/mol, 与HCCN相比, 其电子亲和势变大.     

Schwingungs-Raman-Spektren von Hexahalogenokomplexen von OsIV (X = Cl,I) und IrIV (X = Cl,Br) bei 80 K

Vibrational Raman Spectra of Hexahalo Complexes of Os^IV (X = Cl, I) and Ir^IV (X = Cl, Br) at 80 K The Resonance-Raman (RR) spectra of the tetrabutyl- resp. tetraethylammonium salts of [OsCl₆]^2?, [OsI₆]^2?, [IrCl₆]^2?, and [IrBr₆]^2? have been investigated with the excitation-lines of an Ar⁺ and Kr⁺ laser. Devices with a movable sample holder for low-temperature experiments (80 K) are described. The anormal intensities of some of the Ra-active fundamentals are attributed to the RR effect. As a rule the deformation vibration υ₅(T_2g) is RR enhanced if excited within a π—π*(dt_2g)-CT-transition and the stretching vibration υ₂(E_g) is RR-enhanced within a π—σ*(de_g)-CT-transition. The dispersion of the degree of depolarisation of the three Ra-active fundamentals of [IrBr₆]^2? demonstrates, that this rule cannot only be applicated to the symmetrical but also to the antisymmetrical part of the scattering tensor.     

Structure and bonding in coinage metal halide clusters M(n)X(n), M = Cu, Ag, Au; X = Br, I; n = 1-6

Ab initio calculations in the framework of density functional theory (DFT) were performed to study the lowest-energy isomers of noble metal halide clusters M(n)Br(n) and M(n)I(n), for M = Cu, Ag, or Au and n = 1-6. For all species, the most stable structures were found to be cyclic arrangements. Calculated bond lengths and infrared frequencies were compared with the available experimental data. The nature of the ionocovalent bonding was characterized. The stability and fragmentation were also investigated. The present work confirms previous observations on the particular stability of the trimer.     

同核双卤分子X2(X=F,CI,Br,I)与C2H2相互作用本质的量子化学研究

用对称性匹配微扰理论(SAPT)对C2H2与X2(X=F,CI,Br,I)相互作用进行了量子化学研究.优化所得的4个稳定复合物相互作用能在-3.276 8～-10.639 5 kJ/mol之间.自然键轨道(NBO)理论分析表明,形成复合物分子间的电荷转移量都很少,在0.002 3～0.013 2之间.SAPT2能量分析显示,从F到I,静电能和诱导能先增大后减小,交换能和色散能逐渐增强,相互作用能依次增强.复合物稳定构型的相互作用能中静电能占主导作用,对吸引能的贡献比例在C2H2…F2中最大(57.3％),在C2H2…I2中最小(49.7％);其次为色散能,在吸引能中所占的比例在21.9％(C2H2…F2)～31.2％(C2H2…I2)之间;诱导能在吸引能中所占的比例最小,均小于20.7％.     

Zweiwertiges Samarium: AISmX5 (AI = K,Rb; X = Cl,Br, I)

Divalent Samarium: A^ISm X₅ (A^I = K, Rb; X = Cl, Br, I) Ternary halides with divalent Samarium ASm₂X₅ were prepared and investigated by X-ray techniques. The paramagnetic susceptibility of Sm²⁺ has been measured with a Faraday balance and calculated theoretically.     

Neue Halogenozinkate(II) MZnX4 (MI = Li,Na; X = Cl,Br) mit Olivinstruktur

New Halogenozincates M ZnX₄ (M^I = Li, Na; X = Cl, Br) of Olivine Type The hitherto unknown tetrabromozincates Li₂ZnBr₄ and Na₂ZnBr₄ have been prepared. Quaternary halides Li₂Zn(Cl, Br)₄ and Li₂Zn(Br, I)₄ have been not obtained due to decomposition to mixtures of LiCl and ZnBr₂, and LiBr and ZnI₂. The crystal structures of the olivine-type bromides and of the high-temperature polymorph of Li₂ZnCl₄ have been determined by neutron powder diffraction using the Rietveld method (space group Pnma, Z = 4, a = 1 360.41(4), b = 788.47(2), c = 647.07(2) pm, R_I = 9.07% (Li₂ZnBr₄), a = 1 446.32(5), b = 853.02(3), c = 676.61(2) pm, R_I = 9.29% (Na₂ZnBr₄), a = 1 277.60(3), b = 741.76(2), c = 611.10(1) pm, R_I = 7.63% (Li₂ZnCl₄)). The Raman spectra as well as the results of thermal analyses (DSC) and conductivity measurements (impedance spectroscopy) are presented and discussed. Contrary to Li₂ZnCl₄, Li₂ZnBr₄ and Na₂ZnBr₄ do not undergo any phase transition between 20°C and their melting points.     

Theoretical study of structure, stability and infrared spectra of CH3X-SO3 (X = F, Cl, Br) complexes

Ab initio computational study of the electronic structure and infrared spectra of donor-acceptor complexes formed between SO3 and CH3X (X = F, Cl, Br) molecules was carried out at the MP2(full)/6-31G(d) level of theory. The calculated complexation energy at G2MP2 level shows that stability of complexes decrease, as CH3Cl-SO3 > CH3Br-SO3 > CH3F-SO3. The NBO partitioning scheme show that the lengthening of the C-F, C-Cl, and C-Br bond lengths, upon complexation, is due to an decreasing "s" character in these bonds.     

Synthesis and structures of five-coordinate bis-o-iminobenzosemiquinone complexes M(ISQ-R)2X (X = Cl, Br, I, or SCN; M = CoIII, FeIII, or MnIII)

New five-coordinate complexes Co(ISQ-Prⁱ)₂Cl, Co(ISQ-Me)₂Cl, Co(ISQ-Me)₂I, Co(ISQ-Me)₂(SCN), Mn(ISQ-Prⁱ)₂Cl, and Fe(ISQ-Me)₂Br (ISQ-Prⁱ and ISQ-Me are the 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-and 4,6-di-tert-butyl-N-(2,6-dimethylphenyl)-o-iminobenzosemiquinone radical anions, respectively) were synthesized. The complexes were characterized by UV-Vis and IR spectroscopy and magnetochemistry. The molecular structures of the Fe(ISQ-Me)₂Br and Mn(ISQ-Prⁱ)₂Cl complexes were established by X-ray diffraction. The singlet ground state (S = 0) of the cobalt complexes is caused by antiferromagnetic coupling between the unpaired electrons of the radical ligands (S = 1/2) through the fully occupied atomic orbitals of low-spin cobalt(III) (d⁶, S = 0). The effective magnetic moments of the complexes at 10 K are 0.18 μ_B for Co(ISQ-Prⁱ)₂Cl and 0.16 μ_B for Co(ISQ-Me)₂I. The ground state of the manganese complex is triplet (S = 1). Two unpaired electrons of the o-iminobenzosemiquinone ligands are strongly antiferromagnetically coupled with two of four unpaired electrons of high-spin manganese(III) (d⁴, S = 2). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 43–51, January, 2006.     

Theoretical investigation of the weakly dihydrogen bonded complexes FArCCH...HBeX (X = H, F, Cl, Br)

An ab initio computational study of the properties of four linear dihydrogen-bonded complexes formed between the first compound with an Ar-C chemical bond (FArCCH) and HBeX (X = H, F, Cl, and Br) molecules was undertaken at the MP2/6-311++G(2d,2p) level of theory. The calculated complexation energy at MP2 and G2(MP2) levels decreases in the order HBeH...HCCArF > BrBeH...HCCArF > ClBeH...HCCArF > FBeH...HCCArF. The intermolecular stretching frequency, and shifts within the monomers, are compared with the energetic strength of complexation.     

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.     

HCHO+X(X=F、Cl、Br)的反应机理

采用CCSD/6-311++G(d,p)//B3LYP/6-311++G(d,p)方法研究了HCHO与卤素原子X(X=F、Cl、Br)的反应机理. 计算结果表明, 卤素原子X(X=F、Cl、Br)主要通过直接提取HCHO中的H原子生成HCO+HX(X=F、Cl、Br). 另外还可以生成稳定的中间体, 中间体再通过卤原子夺氢和氢原子直接解离两个反应通道分别生成HCO+HX(X=F、Cl、Br)和H+XCHO(X=F、Cl、Br). 其中卤原子夺氢通道为主反应通道, HCO和HX(X=F、Cl、Br)为主要的反应产物; 且三个反应的活化能均较低, 说明此类反应很容易进行, 计算结果与实验结果符合很好. 电子密度拓扑分析显示, 在HCHO+X反应通道(b)中出现了T型结构过渡态, 结构过渡态(STS)位于能量过渡态(ETS)之后. 并且按F、Cl、Br的顺序, 结构过渡态出现得越来越晚.     

A coordinatively flexible hexadentate ligand gives structurally isomeric complexes M2(L)X3 (M = Cu,Zn; X = Br,Cl)

Polypyridyl multidentate ligands based on ethylenediamine backbones are important metal‐binding agents with applications in biomimetics and homogeneous catalysis. The seemingly hexadentate tpena ligand [systematic name: N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetate] reacts with zinc chloride and zinc bromide to form trichlorido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dizinc(II), [Zn₂(C₂₂H₂₄N₅O₂)Cl₃], and tribromido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dizinc(II), [Zn₂Br₃(C₂₂H₂₄N₅O₂)]. One Zn^II ion shows the anticipated N₅O coordination in an irregular six‐coordinate site and is linked by an anti carboxylate bridge to a tetrahedral ZnX₃ (X = Cl or Br) unit. In contrast, the Cu^II ions in aquatribromido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dicopper(II)–tribromido[μ‐N,N,N′‐tris(pyridin‐2‐ylmethyl)ethylenediamine‐N′‐acetato]dicopper(II)–water (1/1/6.5) [Cu₂Br₃(C₂₂H₂₄N₅O₂)][Cu₂Br₃(C₂₂H₂₄N₅O₂)(H₂O)]·6.5H₂O, occupy two tpena‐chelated sites, one a trigonal bipyramidal N₃Cl₂ site and the other a square‐planar N₂OCl site. In all three cases, electrospray ionization mass spectra were dominated by a misleading ion assignable to [M(tpena)]⁺ (M = Zn²⁺ and Cu²⁺).     

A comparison of structure and stability between the group 11 halide tetramers M4X4 (M = Cu, Ag, or Au; X = F, Cl, Br, or I) and the group 11 chloride and bromide phosphanes (XMPH3)4

The tetramers of the group 11 (I) halides, M(4)X(4) (M = Cu, Ag, or Au; X = F, Cl, Br, or I), and corresponding group 11 (I) phosphanes, chloride and bromide (XMPH(3))(4) (X = Cl or Br), are investigated by the density functional theory. All coinage metal(I) halide tetramers adopt squarelike ring structures with an out-of-plane distorted (butterfly) D(2d) symmetry. These structures are much lower in energy than the more compact cubelike T(d) arrangements, which maximize dipole-dipole interactions and more closely resemble the solid-state structures of the copper and silver halides. Phosphine coordination completely changes the structures of these M(4)X(4) clusters. The copper(I) and silver(I) phosphane chloride and bromide tetramers adopt a heterocubane structure, slightly preferred over a step (ladder-type)-cluster structure well-known in the coordination chemistry of such compounds. In stark contrast, gold(I) phosphane chloride and bromide tetramers prefer assemblies of linear XAuPH(3) units with direct gold-gold contacts, resulting in a square planar, centered trigonal planar, or tetrahedral gold core.     

Spectrochemical studies on the ethylthiourea complexes of palladium (II) and platinum (II): M2(Etu)2X4(X = Cl,Br, I) and M(Etu)4A2(A = Cl,Br, I,ClO4, BF4, CF3COO).

The ethylthiourea complexes of Pd(II) and Pt(II): M₂(Etu)₂X₄ (X = Cl, Br, I) and M(Etu)₄A₂ (A = Cl, Br, I, ClO₄, BF₄, CF₃COO) have been studied by i.r. and electronic spectra and the halide-bridged M₂(Etu)₂X₄ complexes by bridge-splitting reactions with nitrogen ligands. Ethylthiourea is S-coordinated to the metal. Far i.r. spectra show ν(MS) bands at 270–300 cm⁻¹ and, for the M₂(Etu)₂X₄ complexes ν(MX) bands corresponding to terminal and bridging MX bonds. From the electronic spectra of the Pd(Etu)₄A₂ (A = ClO₄, BF₄) complexes the Δ₁ ( = 22120 cm⁻¹) spectral parameter was obtained.     

Theoretical study of XPO (X=H,F,Cl,Br) molecules: Structural and molecular properties

A theoretical study has been performed on the ground state of XPO systems, where X=H, F, Cl, and Br. Structural and molecular properties have been calculated at high level of theory: the CCSD(T) method in conjunction with a hierarchical series of correlation consistent basis sets has been employed. Extrapolation to complete basis set as well as core-valence and scalar relativistic effects have been considered.     

Ternäre Halogenide der Seltenen Erden vom Typ A2MX5 (A = K,In, NH4, Rb,Cs; X = Cl,Br, I)

Ternary Rare-Earth Halides of the A₂MX₅ Type (A = K, In, NH₄, Rb, Cs; X = Cl, Br, I) Ternary rare-earth (=M) chlorides, bromides, and iodides In₂MCl₅, (NH₄)₂MCl₅, Rb₂MCl₅, Cs₂MCl₅, CsRbMCl₅, K₂MBr₅, Rb₂MBr₅, K₂MI₅, and Rb₂MI₅ have been synthesized. Single crystals of In₂PrCl₅, Rb₂PrCl₅, K₂PrBr₅, and K₂PrI₅ were grown and the structures refined. The other halides were characterized by x-ray powder patterns. They are isotypic either with K₂PrCl₅(orthorhombic, Pnma, Z = 4, hexagonal arrangement of chains of edge-connected polyhedra [PrX₇]) or with Cs₂DyCl₅ (orthorhombic, Pbnm, Z = 4, hexagonal arrangement of cis-corner-connected octahedra [DyCl₆]) which may be discriminated in structure field diagrams. The thermal expansion was investigated für Cs₂LuCl₅ and Rb₂PrX₅ (X = Cl, Br, I).