Ab initio Study of H2O–HCl (1:1, 1:2, 2:1) Complexes

This paper reports on an ab initio (6-31G**) study of 1:1, 1:2, and 2:1 (H₂O) _n (HCl) _m complexes. Stable configurations of the 1:2 and 2:1 (H₂O) _n (HCl) _m complexes and their geometrical and energy characteristics were determined. The vibrational analysis of the complexes was carried out. The effect of hydrogen bonding due to S₁S₀ and T₀T₁ electronic excitations is considered.     

1:1 and 1:2 Inclusion Complexes of Di-tert-butyl l-tartrate with α-Cyclodextrin: A Diffusion Study

The diffusion properties at two overall compositions of a ternary aqueous system containing α-cyclodextrin and a double-functional guest molecule, namely di-tert-butyl l-tartrate, have been studied by means of the Gouy interferometry. The experimental data are interpreted in terms of two independent chemical equilibria involving inclusion compounds. The elements of the diffusion coefficient matrix have been expressed as functions of the two equilibrium constants as well as of the diffusivities of the actual species occurring in solution. The reliability of the diffusion coefficients obtained through the Fujita–Gosting–Revzin procedure is also discussed in terms of its dependence on the composition of solutions used in the Gouy experiments.     

Ruthenium hydrazone complexes with 1:1 and 1:2 metal–ligand stoichiometry: a comparison of biomolecular interactions and in vitro cytotoxicities

Transition Metal Chemistry - Two ruthenium(II) complexes [RuIICl(PPh3)2(L)] (1) and [RuII(L)2] (2) were synthesized by reacting [RuCl2(PPh3)3] and thiophene-2-carboxylic acid...     

NixZry(x:y=1∶2或2∶1)团簇的量子化学研究

根据化学键理论和拓扑学原理,设计了非晶态团簇NixZry(x:y=1∶2 或2∶1, x+y≤9)的几十种可能的构型,并应用量子化学从头算方法对它们的几何构型进行了优化,分析比较了这些构型的能量和稳定性。结果表明对于NixZry(x:y=1∶2)低对称性的平面构型最稳定,而NixZry(x:y=2∶1)三棱柱构型最稳定。这可能是由于两者外层价电子的数量差异所致： Zr仅有4个价电子,较适宜配位数低的平面构型,而Ni（4s23d8),更适宜立体构型。     

Competition and interplay between σ-hole and π-hole interactions: a computational study of 1:1 and 1:2 complexes of nitryl halides (O2NX) with ammonia

Quantum calculations at the MP2/cc-pVTZ, MP2/aug-cc-pVTZ, and CCSD(T)/cc-pVTZ levels have been used to examine 1:1 and 1:2 complexes between O(2)NX (X = Cl, Br, and I) with NH(3). The interaction of the lone pair of the ammonia with the σ-hole and π-hole of O(2)NX molecules have been considered. The 1:1 complexes can easily be differentiated using the stretching frequency of the N-X bond. Thus, those complexes with σ-hole interaction show a blue shift of the N-X bond stretching whereas a red shift is observed in the complexes along the π-hole. The SAPT-DFT methodology has been used to gain insight on the source of the interaction energy. In the 1:2 complexes, the cooperative and diminutive energetic effects have been analyzed using the many-body interaction energies. The nature of the interactions has been characterized with the atoms in molecules (AIM) and natural bond orbital (NBO) methodologies. Stabilization energies of 1:1 and 1:2 complexes including the variation of the zero point vibrational energy (ΔZPVE) are in the ranges 7-26 and 14-46 kJ mol(-1), respectively.     

键函数法与Be2体系的稳定性1: Be2的基态

采用价电子全CI(FCI)方法对Be2的基态(X^1∑g^+)进行了研究, 仔细考察了键函数在弱键体系计算中的作用。对引入键函数的不同方式分别按Boys方法计算了基组重叠误差(BSSE)。键函数的运用使得Be2基态性质的计算结果大为改善。研究结果表明键函数方法在相互作用能小的体系的计算中十分可取。     

键函数法与Be2体系的稳定性1: Be2的基态

采用价电子全CI(FCI)方法对Be2的基态(X^1∑g^+)进行了研究, 仔细考察了键函数在弱键体系计算中的作用。对引入键函数的不同方式分别按Boys方法计算了基组重叠误差(BSSE)。键函数的运用使得Be2基态性质的计算结果大为改善。研究结果表明键函数方法在相互作用能小的体系的计算中十分可取。     

Comparative study of ionic interactions of 1 : 1 and 1 : 2 electrolytes of nitrates salts solutions with water analysed with physicochemical data

Densities (ρ), viscosities (η) and surface tension (γ) as function of the molarity of 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 for LiNO₃, NaNO₃, KNO₃, Sr(NO₃)₂, Ba(NO₃)₂ and Pb(NO₃)₂ electrolytes are reported at 32°C. Data were regressed for limiting values for solute–solvent interactions and effects of shell numbers and electronic configurations. A confidence variance of 95.5% at Gaussian distribution was noted. Densities explained ionic forces and sizes, and viscosities defined frictional forces while the surface tension focused surface energies of hydrated ions. Slopes of densities, viscosities and surface tensions explained the concentration effects on ionic interactions. Limiting densities from Li⁺ to Ba²⁺ increased with increase in sizes. Pb²⁺ smaller in size than the Ba²⁺ had lower limiting densities. The ρ ⁰ are Ba^2+?>?Sr^2+?>?Pb^2+?>?K^+?>?Na^+?>?Li⁺ with 3.24, 2.98, 4.53, 2.109, 2.257 and 2.38?×?10^3?kg?m^?3 densities of nitrate salts, respectively, in the solid state.     

Inclusion of α-phenyl-N-p-methylphenyl Nitrone in β- Cyclodextrin: Formation of 1G : 1H and 1G : 2H Complexes and the Remarkably Fast 1,3-Dipolar Cycloaddition of the 1G : 2H Complex with Olefins in the Solid State

The nitrone is found to be included in the -cyclodextrin cavity in two different stoichiometries viz., 1G : 1H and 1G : 2H – the existence of which is proved by physical methods. The 1G : 2H complex of the nitrone serves as a good potent dipolarophile in the 1,3-dipolar cycloaddition reactions with olefins resulting in rate acceleration and regioselection.     

ReO(N2O2)X] complexes: "4 + 1"?

[ReO(ppme)X] (where ppme(2-) is 2,5-diazo-N,N'-dimethylhexyl-1,6-bis(phenylphosphinate), X = Br0.3Cl0.7) has been synthesized via a substitution reaction and structurally characterized. The coordination geometry is a distorted octahedron and one phosphinate coordinates cis and the other trans to the oxo O atom. This coordination mode is conserved in all [ReOppmeX] complexes synthesized in this study. [ReO(ppme)Cl] has been prepared by a reduction/complexation reaction from [NH4][ReO4]. [ReO(ppme)Cl] reacts with thiocyanate and benzene thiolate forming [ReO(ppme)X] (X = (-)NCS, (-)SC6H5), but the one-pot synthesis of the respective ternary thiolate complexes from perrhenate was not successful. The reduction/complexation reaction of a thiol, H2ppmeCl4, and perrhenate resulted in the formation of [H3ppme][ReO(SR)4], the reaction of which with [ReO(ppme)Cl] does not lead to [ReO(ppme)SR] in high yields.     

Stereo-isomerism controls surface reactivity: 1-chloropentane-pairs on Si(100)-2×1

Chloropentane forms asymmetric ('A') and symmetric ('S') pairs on Si(100)-2×1, differing in the direction of curvature of one pentane tail. Surprisingly this renders the rate of thermal reaction of 'A' fifteen times greater than 'S' in chlorinating room-temperature silicon. Correspondingly, for electron-induced reaction the energy threshold for A is 1 eV less than for S.     

Liquid–liquid equilibria of two binary systems: water+1-pentanol and water+2-methyl-2-butanol and two ternary systems: water+1-pentanol+2-butyloxyethanol and water+2-methyl-2-butanol+2-butyloxyethanol

Liquid–liquid equilibrium phase diagrams for two binary systems: water+1-pentanol and water+2-methyl-2-butanol and two ternary systems: water+1-pentanol+2-butyloxyethanol and water+2-methyl-2-butanol+2-butyloxyethanol at 20°C and 30°C are presented in this paper. The experimental results were correlated with the UNIQUAC model by fitting the effective UNIQUAC binary interaction parameters as a function of temperature. Agreement between the calculated and experimental data was very good.     

Intramolecular SN2 reaction α- to a trifluoromethyl group: preparation of 1-cyano-2-trifluoromethylcyclopropane

The first intramolecular S_N2 reaction of α-trifluoromethylated secondary alcohols by a carbanion is described. A stereoselective intramolecular cyclization of 3-substituted-3-cyano-1-trifluoromethylpropyl sulfonate via the cyano stabilized carbanion provides 1-substituted-1-cyano-2-trifluoromethylcyclopropanes in good yields. The product has the opposite configuration to the starting alcohol at the carbon attached to trifluoromethyl group, revealing the reaction takes place in S_N2 manner with Walden inversion at the reaction center.     

Reaction of 1, 1-Di-p-methoxyphenyl-2, 2-dinitroethylene and 1, 1-Di-O-methoxyphenyl-2, 2-dinitroethylene with 1-Benzyl-1, 4-dihydronicotinamide： Evidence for Concerted Electron-hydrogen Atom Transfer Mechanism

1,1-Di-p-methoxyphenyl-2, 2-dinitroethylene reacts with 1-benzyl-1, 4-dihydronicotinamide (BNAH) in deaerated acetonitrile to give 1,1-di-p-methoxyphenyl-2, 2-dinitroethane,while 1,1-di-O-methoxyphenyl-2, 2-dinitroethylene fails to react with BNAH under the same conditions, which provides evidence for a concerted electron-hydrogen atom transfer mechanism.     

Spectra and Thermodynamics: Is the Phototautomerisation of 1-Hydroxy-2-Pyridone or 1-Hydroxy-2-Pyridinethione Possible in the Triplet State?

The reproted [1] phototautomerisation of 1-hydroxy-2-pyridone (HP) and 1-hydroxy-2-pyridinethione (HPT) in their triplet states at 77 K seems to result from a misinterpretation of the phosphorescence spectra. Application of the thermodynamic Föster-type cycle to the described spectra of the HP and HPT proves a contrary : the phototautomerisation in the triplet states of HP and HPT is not possible. The thermodynamic and spectral criteria are given.     

The Crystal Structure of the 2 : 1 Cholic Acid – Benzophenone Clathrate

The 2 : 1 cholic acid – benzophenone clathratecrystallizes in the space group P2_1 withthe unit-cell parameters a = 25.498(6),b = 7.942(1), c = 28.309(6) Å, = 101.85(2)°. There are four symmetricallyindependent host molecules in the unit cell: two ofthem with the steroidal side chain assuminggauche and the remaining two with the side chain in thetrans conformation. Pairs of the host moleculesadopting similar conformations alternate along the[201] direction of the bilayer. The guestmolecules are accommodated in two crystallographicallyindependent but topologically similar channelsrunning parallel to [010]. Benzophenone molecules aredisordered and included in each channel in twodifferent conformations.     

Computational studies of 1:2 complex between retinol propionate and β cyclodextrin

[M05-2X/6-31G*:PM3MM] and [B3LYP/6-31G*:PM3] ONIOM2 methods have been used to investigate the vitamin A propionate/β cyclodextrin complex with 1:2 stoichiometry. Both methods give almost the same lowest energy minimum. The minimum energy structure of the complex is found in good agreement with experimental data. In this configuration, the major structure of propionate of vitamin A (PVA) is embedded inside the two cavities of βCD while the propionate group is kept outside. However, the three methyl groups of PVA are positioned in the free space between both βCD molecules. The driving forces for complexation are dominated by Van der Waals interactions between PVA and the βCD molecules assisted with multiple hydrogen bond interactions between the two cyclodextrin molecules. These interactions were investigated using the natural bond orbital approach.     

Haloduracin α binds the peptidoglycan precursor lipid II with 2:1 stoichiometry

The two-peptide lantibiotic haloduracin is composed of two post-translationally modified polycyclic peptides that synergistically act on gram-positive bacteria. We show here that Halα inhibits the transglycosylation reaction catalyzed by PBP1b by binding in a 2:1 stoichiometry to its substrate lipid II. Halβ and the mutant Halα-E22Q were not able to inhibit this step in peptidoglycan biosynthesis, but Halα with its leader peptide still attached was a potent inhibitor. Combined with previous findings, the data support a model in which a 1:2:2 lipid II:Halα:Halβ complex inhibits cell wall biosynthesis and mediates pore formation, resulting in loss of membrane potential and potassium efflux.