Comparison of aromatic NH···π, OH···π, and CH···π interactions of alanine using MP2, CCSD, and DFT methods

A comparison of the performance of various density functional methods including long‐range corrected and dispersion corrected methods [MPW1PW91, B3LYP, B3PW91, B97‐D, B1B95, MPWB1K, M06‐2X, SVWN5, ωB97XD, long‐range correction (LC)‐ωPBE, and CAM‐B3LYP using 6‐31+G(d,p) basis set] in the study of CH···π, OH···π, and NH···π interactions were done using weak complexes of neutral (A) and cationic (A⁺) forms of alanine with benzene by taking the Møller–Plesset (MP2)/6‐31+G(d,p) results as the reference. Further, the binding energies of the neutral alanine–benzene complexes were assessed at coupled cluster (CCSD)/6‐31G(d,p) method. Analysis of the molecular geometries and interaction energies at density functional theory (DFT), MP2, CCSD methods and CCSD(T) single point level reveal that MP2 is the best overall performer for noncovalent interactions giving accuracy close to CCSD method. MPWB1K fared better in interaction energy calculations than other DFT methods. In the case of M06‐2X, SVWN5, and the dispersion corrected B97‐D, the interaction energies are significantly overrated for neutral systems compared to other methods. However, for cationic systems, B97‐D yields structures and interaction energies similar to MP2 and MPWB1K methods. Among the long‐range corrected methods, LC‐ωPBE and CAM‐B3LYP methods show close agreement with MP2 values while ωB97XD energies are notably higher than MP2 values. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

Isodimorphism of the salts 2RbCl · MIICl2 · 2H2O (MII = Mn,Fe, Co,Cu)

The three-component systems RbClMnCl₂H₂O, 2RbCl · CoCl₂ · 2H₂O2RbCl · CuCl₂ · 2H₂OH₂O, 2RbCl · CoCl₂ · 2H₂O2RbCl · MnCl₂ · 2H₂OH₂O have been studied at 25°C. In the 2RbCl · CoCl₂ · 2H₂O2RbCl · CuCl₂ · 2H₂OH₂O system, a discontinuous series of mixed crystals is formed and in the 2RbCl · CoCl₂ · 2H₂O2RbCl · MnCl₂ · 2H₂OH₂O system, a continuous series is present.The unit cell parameters of the 2RbCl · CoCl₂ · 2H₂O double salt were determined: a = 5.586(2) Å, b = 6.469(3) Å, c = 6.988(2) Å, α = 65.31(3)°, β = 87.69(3)°, γ = 84.65(4)°, volume 228.4 ų, Z = 1.The results obtained and discussed in conjunction with the crystal structure data suggest that for 2M^ICl · M^IICl₂ · 2H₂O type salts the triclinic structure is stable only when the large rubidium and cesium ions participate in combinations with non-Jahn-Teller metal(II) ions. In the cases of Jahn-Teller metal(II) ions or with potassium or ammonium ions a tetragonal structure is always stable.     

Heat capacities of 15Na2O·10(MgO,CaO, TiO2, ZrO2)·75SiO2 glasses

Heat capacitiesC _p of title glasses were measured for temperature ranging from 50 to 550°C. True linear temperature dependences were observed for all studied glasses at temperatures sufficiently lower than the glass transition temperature. The temperature-compositionalC _p dependence was described by the linear model with only statistically significant coefficients retained. The parameters were estimated using the standard least squares procedure. The results obtained may be used for evaluation of viscosity values according to Adam and Gibbs theory.This work was supported by the Slovak Grant Agency for Science under the grant No. 1171/95.     

固相配位化学反应研究 LV.FeCl_2·4H_2O,CoCl_2·6H_2O,NiCl_2·6H_2O,CuCl_2·2H_2O与邻菲咯啉的低热固相化学反应研究

邻菲咯啉(Phen)与过渡金属离子在液相中的反应速度很快,瞬间即可完成,形成稳定的配合物。过渡金属氯化物在水溶液中反应时,一般是以水合离子[M(H_2O)_6]~(2+)的形式参加反应。而在固相中参加反应物质的形式是其物质本身的凝聚态分子。因此,尽管是同一反应物,但在固相,液相反应中,参加反应物质的形式不同,可能产生两种不同的反应结果。为了比较固、液相反应的差别,寻找固相反应的规律性。我们研究了FeCl2_·4H_2O,CoCl_2·6H_2O,NiCl_2     

Concerted halogen and hydrogen bonding in [RuI2(H2dcbpy)(CO)2]···I2···(CH3OH)···I2···[RuI2(H2dcbpy)(CO)2

A new type of concerted halogen bond-hydrogen bond interaction was found in the solid state structure of [RuI(2)(H(2)dcbpy)(CO)(2)]···I(2)···(MeOH)···I(2)···[RuI(2)(H(2)dcbpy)(CO)(2)]. The iodine atoms of the two I(2) molecules interact simultaneously with each other and with the OH group of methanol of crystallization. The interaction was characterized by single crystal X-ray measurements and by computational charge density analysis based on DFT calculations.     

S···X halogen bonds and H···X hydrogen bonds in H2CS-XY (XY = FF, ClF, ClCl, BrF, BrCl, and BrBr) complexes: cooperativity and solvent effect

Using ab initio calculations, we have studied the structures, properties, and nature of halogen bonds in H(2)CS-XY (XY = FF, ClF, ClCl, BrF, BrCl, and BrBr) complexes. The results show that the ring-shaped complexes are formed by a halogen bond (S···X) and a secondary hydrogen bond (H···X). We also analyzed the H(2)CS-ClF-ClF and FCl-H(2)CS-ClF complexes to investigate the cooperative and diminutive halogen bonding. The cooperative effect of halogen bonding is found in the former, while the diminutive effect is present in the latter. We finally considered the solvent effect on the halogen bond in H(2)CS-BrCl complex and found that the solvent has a prominent enhancing effect on it. The complexes have also been analyzed with natural bond orbital, atoms in molecules, and symmetry adapted perturbation theory method.     

209Bi NQR in Mixed Oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3

It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that -Bi₂O₃, Bi₃O₄Br and mixed oxides Bi₂O₃· 2Al₂O₃, Bi₂O₃· 2Ga₂O₃, Bi₂O₃· 3GeO₂, and 2Bi₂O₃· 3GeO₂exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi₂O₃· B₂O₃, 3Bi₂O₃· 5B₂O₃, and Bi₂O₃· 3B₂O₃were prepared and studied using ²⁰⁹Bi NQR. The quadrupole interactions of the ²⁰⁹Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the ²⁰⁹Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal ²⁰⁹Bi NQR in external magnetic fields.     

Interaction in the ternary complexes of HNO3···HCl···H2O: a theoretical study on energetics, structure, and spectroscopy

Ternary complexes of HNO(3)···HCl···H(2)O were investigated by ab initio calculations with aug-cc-pVDZ and aug-cc-pVTZ basis sets. The results are analyzed in terms of structures, energetics, and infrared vibrational frequencies. In all minima, neither HNO(3) nor HCl becomes ionized. The contribution of the nonadditivity effect, which is significant for hydrogen-bonded clusters, is bigger for the cyclic structures in which HNO(3) acts as a proton donor to HCl, although the global minimum contains HNO(3) donating its proton to a H(2)O molecule.     

Polyoxometalate-based supramolecular hybrids composed of Cu/2, 2′-dimethyl-4, 4′-bithiazole fragments extended via non-bonding S···O interactions

Four polyoxometalate-based complexes, namely [Cu^I(dm4bt)₂]₃[PMo₁₂O₄₀] (1), H₂[Cu^I(dm4bt)₂]₂{[Cu ₂ ^I (dm4bt)₃]₂[SiW₁₂O₄₀]}[SiW₁₂O₄₀] (2), [Cu^I(dm4bt)₂]₅ {[Cu^I(dm4bt)][P₂W₁₈O₆₂]} (3) and {Cu ₂ ^II (dm4bt)₂[Mo₆O₂₀]} (4) (dm4bt = 2,2′-dimethyl-4,4′-bithiazole), were synthesized hydrothermally from copper nitrate and various polyoxoanions. X-ray crystal structural analysis reveals that all four complexes have supramolecular structures, in which the dm4bt ligands coordinate with the Cu atoms to give different Cu/dm4bt fragments, which are further connected into supramolecular structures via non-bonding S···O interactions between Cu/dm4bt fragments and polyoxoanions. The crystal structures also reveal the crucial role of S···O interactions in the packing structures of complexes 1–4. The electrochemical and electrocatalytic properties of 1–3 with respect to bromate reduction were investigated.     

Substituent effects on CL···N, S···N, and P···N noncovalent bonds

Cl, S, and P atoms have previously been shown as capable of engaging in a noncovalent bond with the N atom on another molecule. The effects of substituents B on the former atoms on the strength of this bond are examined, and it is found that the binding energy climbs in the order B = CH(3) < NH(2) < CF(3) < OH < Cl < NO(2) < F. However, there is some variability in this pattern, particularly for the NO(2) group. The A···N bonds (A = Cl, S, P) can be quite strong, amounting to as much as 10 kcal/mol. The binding energy arises from approximately equal contributions from its induction and electrostatic components, although the former becomes more dominant for the stronger bonds. The induction energy is due in large measure to the transfer of charge from the N lone pair to a B-A σ* antibonding orbital of the electron-acceptor molecule containing Cl, S, or P. These A···N bonds typically represent the lowest-energy structure on each potential energy surface, stronger than H-bonds such as NH···F, CH···N, or SH···N.     

Infrared and Raman spectra of CuCl2·2(H,D)2O and K2CuCl4·2(H,D)2O. Vibrational modes,assignment and coupling of the water librations

The i.r. and Raman spectra of CuCl₂·2H₂O and K₂CuCl₄·2H₂O and of deuterated samples of these compounds are presented in the range 50–1700 cm⁻¹ at liquid helium, liquid nitrogen, and ambient temperatures. The spectra obtained are discussed and compared with the literature data in terms of both bonding structure of the water molecules and vibrational modes, assignment, intermolecular coupling, and combination bands of the H₂O, HDO, and D₂O librations. The i.r. and Raman bands of the librational modes of CuCl₂·2H₂O are very broad even at liquid helium temperature indicating orientational disorder of the water molecules.     

2MgO·2B2O3·MgCl2·14H2O-MgCl2-H2O体系30℃相平衡

用相平衡方法研究2MgO@2B2O3@MgCl2@14H2O在30℃不同质量分数MgCl2水溶液中的溶解转化产物及其溶解度.结果表明,该复盐在MgCl2的质量分数0～2%浓度范围,发生不同步溶解并转化为多水硼镁石(2MgO@3B2O3@15H2O);在MgCl2的质量分数2%～13.8%浓度范围,转化为柱硼镁石(MgO@B2O3@3H2O),这一结果比文献报导的该硼酸盐的形成温度低了13℃,为盐湖硼酸镁矿物柱硼镁石形成的解释提供了物理化学依据;而在MgCl2质量分数大于13.8%时,同步溶解,不发生转化.提出了溶解相转化反应机理.     

Prediction and characterization of halogen–hydride interaction in Cu n H n ···ClC2Z and Cu n H···ClC2Z complexes (n = 2–5; Z = H, F, CH3)

Halogen–hydride interactions between the lowest energy structure of Cu _n H _n and Cu _n H clusters (n = 2–5) as halogen acceptor and ClC₂Z (Z = H, F, CH₃) as halogen donor have been investigated at the MP2/6-311++G(d,p) level of theory. Different approaches based on structural parameters, energetic analysis, shift in vibrational frequencies, and molecular electrostatic potential were used to characterize the resultant halogen–hydride bonds. Upon complexation, the Cl–C bonds tend to elongate, concomitant with red shifts of the Cl–C vibrational frequencies. Interaction energies of this type of halogen bonds vary from ?2.34 to a maximum ?7.38 kJ mol^?1. The calculated interaction energies were found to be increased in magnitude with increasing of the negative electrostatic potential at a point on the outer side of hydrogen atom of halogen acceptor units. Moreover, decomposition of the interaction energies reveals that the electrostatic interaction plays a main role in the formation of the complexes. The quantum theory of atoms in molecules analysis has also been applied to provide more insight into the nature and properties of these interactions. Our results indicate pure closed-shell interactions in these systems with similar characteristics to the conventional halogen bonds.     

SYNTHESIS, CHARACTERIZATION AND STRUCTURE OF [Co(DBP)_2·3Py]_2·2CHCl_3

The mixed ligand complex of cobalt with dibutylphosphate (HDBP) and pyridine has been synthesized. Elemental analysis yields the result that the formula of this compound is Co(DBP)_2·3Py·CHCl_3 (Py=pyridine). The thermal analsyis, visible spectra and magnetic properties of it have been studied as well. Single crystal structural analysis shows that the crystal is triclinic with space group P and the unit cell parameters are as follows:a=14.490(10), α=90.37(4)°,b=15.721(7), β=96.04(5)°,c=20.109(12), γ=105.63(4)°.The final R factor is 0.0773. Two Co atoms are connected by two bridging DBP groups to form a dinuclear molecule [Co(DBP)_2·3Py]_2 which has a C_s, symmetry. Each cell contains two dinuclear molecules and four chloroform molecules. The cobalt is coordinated in an octahedral arrangement by three oxygen atoms and three nitrogen atoms, of which one oxygen atom comes from a monodentate DBP group, two oxygen atoms from two bridging DBP groups, and the three nitrogen atoms from the three pyridi     

Li2Mg(ZrF6)2 · 4H2O: Synthesis, X-ray crystallographic, thermal, and MAS NMR study

A new zirconate with lithium and magnesium cations of composition Li₂Mg(ZrF₆)₂ · 4H₂O (I) has been synthesized and studied by different methods (X-ray crystallography, differential thermal analysis, IR spectroscopy, and NMR (¹H, ⁷Li, ¹⁹F, including ¹⁹F MAS NMR). The framework structure of I is composed of edge- and vertex-sharing ZrF₈ dodecahedra, Mg(O_w)₂F₄ octahedra, and Li(O_w)F₄ square pyramids. The structure is additionally stabilized by O-H...F and O-H...O hydrogen bonds. Compound is dehydrated in one stage in the temperature range 105–200°C to form Li₂Mg(ZrF₆)₂ (II). The latter undergoes irreversible phase transition at 365°C leading to its decomposition into a mixture of MgZrF₆ (cubic) and Li₂ZrF₆ (hexagonal). According to IR and NMR data, the structure of fluorozirconate chains of compound I is retained after dehydration.     

ZnSO4·CO(NH2)2·2H2O和MgCl2·NH4Cl·6H2O的热分解动力学研究

采用TG-DSC研究了ZnSO4·CO(NH2)2·2H2O和MgCl2·NH4Cl·6H2O的热分解反应,并对其中的脱水过程及部分分解过程进行了动力学计算,由Fridman、Ozawa-Flynn-Wall、ASTME698三种方法得出峰温时的活化能值与指前因子值,通过优化选择出了热分解过程最佳机理函数.     

水相中·OH, ·H和e-aq与2-氯酚反应机理研究

利用脉冲电子束辐解水产生*OH自由基、 *H及水合电子(e-aq), 研究了这些活性粒子在多种条件下与水相中2-氯酚的微观反应机理, 对其瞬态光谱中的主要吸收峰做了归属, 并初步考察了这些瞬态物种的生长、衰减等行为. 研究表明, *OH自由基与2-氯酚在碱性条件下可直接反应生成邻氯代酚氧自由基, 速率常数为1.0×109 L*mol-1*s-1, 也有部分*OH自由基与2-氯酚反应先生成OH-加合物, 再进一步消除水分子生成邻氯代酚氧基; 在酸性条件下要经过OH-加合物. *H则与2-氯酚反应生成H-加合物; e-aq可直接从2-氯酚分子夺氯, 在近中性和碱性环境中, 该反应的速率常数分别为1.25×109 L*mol-1*s-1和6.3×108 L*mol-1*s-1.