Complexes H2CO:PXH2 and HCO2H : PXH2 for X=NC,F, Cl,CN, OH,CCH, CH3, and H: Pnicogen Bonds and Hydrogen Bonds

Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to investigate H₂CO : PXH₂ pnicogen-bonded complexes and HCO₂H : PXH₂ complexes that are stabilized by pnicogen bonds and hydrogen bonds, with X=NC, F, Cl, CN, OH, CCH, CH₃, and H. The binding energies of these complexes exhibit a second-order dependence on the O−P distance. DFT-SAPT binding energies correlate linearly with MP2 binding energies. The HCO₂H : PXH₂ complexes are stabilized by both a pnicogen bond and a hydrogen bond, resulting in greater binding energies for the HCO₂H : PXH₂ complexes compared to H₂CO : PXH₂. Neither the O−P distance across the pnicogen bond nor the O−P distance across the hydrogen bond correlates with the binding energies of these complexes. The nonlinearity of the hydrogen bonds suggests that they are relatively weak bonds, except for complexes in which the substituent X is either CH₃ or H. The pnicogen bond is the more important stabilizing interaction in the HCO₂H : PXH₂ complexes except when the substituent X is a more electropositive group. EOM-CCSD spin-spin coupling constants ^1pJ(O−P) across pnicogen bonds in H₂CO:PXH₂ and HCO₂H : PXH₂ complexes increase as the O−P distance decreases, and exhibit a second order dependence on that distance. There is no correlation between ^2hJ(O−P) and the O−P distance across the hydrogen bond in the HCO₂H : PXH₂ complexes. ^2hJ(O−P) coupling constants for complexes with X=CH₃ and H have much greater absolute values than anticipated from their O−P distances.     

The HRuCCH, RuCCH2, and Ru-η2-C2H2 molecules: infrared spectra and density functional calculations

Laser-ablated ruthenium atoms undergo reaction with acetylene during condensation in excess neon and argon matrices to form a metallacycle complex, insertion into the C-H bond, and rearrangement to the vinylidene complex. The subject molecules were identified by (13)C(2)H(2) and C(2)D(2), isotopic substitutions and density functional theory (DFT) frequency calculations. The HRuCCH molecule is described by Ru-H, CH, and CC stretching modes and CCH deformation modes. A very strong CC double bond stretching, weak CH stretching, and CCH deformation frequencies were observed for the Ru═C═CH(2) complex. The metallacycle Ru-η(2)-(C(2)H(2)) is characterized through CC double bond stretching, CH stretching and CCH deformation modes. The reaction mechanism for formation of the Ru═C═CH(2) complex was investigated by B3LYP internal reaction coordinate calculations, and the hydrido-alkyny complex is the rate-determining step. The delocalized three-center-four-electron π bond using the Ru 4d(xz) electron pair contributes to the C-C π* orbital and provides stabilization energy (ΔE((2)), second-order perturbation) for the vinylidene Ru═C═CH(2) complex.     

Aggregation Stability of SiO2, FeOOH, ZrO2, CeO2, and Natural Diamond Sols and Their Binary Mixtures: 2. The Photometric Study of Heterocoagulation of SiO2–FeOOH, SiO2–ZrO2, SiO2–CeO2, and CeO2–Natural Diamond Binary Systems in KCl Solutions

The aggregation stability of 1 : 1 and 3 : 1 (by volume) binary mixtures of two hydrophobic (SiO₂–FeOOH), one hydrophobic and one hydrophilic (SiO₂–ZrO₂, SiO₂–CeO₂), and two hydrophilic (CeO₂–natural diamond) sols was studied by photometry over a wide range of KCl concentrations at pH 6 and 3. The stability of the mixed binary sols was determined by the stability of the sol with a predominant particle number concentration. In the SiO₂–FeOOH system, the phenomenon of heteroadagulation stabilization was caused by the electrostatic factor of the stability of adsorbed SiO₂ particles and, in the SiO₂–ZrO₂ system, by the structural factor of the stability of adsorbed hydrophilic ZrO₂ particles. The stability of binary mixtures containing one or two hydrophobic components is qualitatively explained in terms of the Derjaguin theory of heterocoagulation of hydrophobic colloids. The stability of the binary system of two hydrophilic components (CeO₂–natural diamond) is determined by the structural component of the interaction energy of particles.     

XPS primary excitation spectra of Zn 2p,Fe 2p,and Ce 3d from ZnO, α-Fe2O3, and CeO2

Metal oxides are important for current development in nanotechnology. X-ray photoelectron spectroscopy(XPS) is a widely used technique to study the oxidation states of metals, and a basic understanding of the photoexcitation process is important to obtain the full information from XPS. We have studied core level excitations of Zn 2p, Fe 2p, and Ce 3d photoelectron emissions from ZnO, α-Fe₂O₃, and CeO₂. Using an effective energy-differential XPS inelastic-scattering cross section evaluated within the semiclassical dielectric response model for XPS, we analysed the experimental spectra to determine the corresponding primary excitation spectra, ie, the initial excitation processes. We find that simple emission (Zn 2p) as well as complex multiplet photoemission spectra (Fe 2p and Ce 3d) can be quantitatively analysed with our procedure. Moreover, for α-Fe₂O₃, it is possible to use the software package CTM4XAS (Charge Transfer Multiplet program for X-ray Absorption Spectroscopy) to calculate its primary excitation spectrum within a quantum mechanical model, and it was found to be in good agreement with the spectrum determined by analysis of the experiment.     

Enthalpies of Dilution of Aqueous Solutions of HCl, MgCl2}, CaCl2, and BaCl2 at 300, 325, and 350°C

Dilution enthalpies, measured using isothermal flow calorimetry, are reported for aqueous solutions of BaCl₂ at 300°C and 11.0 MPa, MgCl₂, CaCl₂, and BaCl₂ at 325°C and 14.8 MPa, and at 350°C and 17.6 MPa. Previously collected dilution enthalpies for aqueous solutions of MgCl₂ and CaCl₂ at 300°C and 10.3 MPa and for aqueous solutions of HCl at 250, 275, and 300°C at 10.3 MPa and 320°C at 12.8 MPa were included with the new data at 300°C and 11.0 MPa and at 350°C and 17.6 MPa when fitting the Pitzer parameters. The concentration range of the chloride solutions was 0.5 to 0.02 molal. Parameters for the Pitzer excess Gibbs ion–interaction equation were determined from the fits of the experimental heat data. Equilibrium constants, enthalpy changes, entropy changes, and heat-capacity changes for the association of alkaline earth metal ions and H⁺ with chloride ion were estimated from the heat data. For all systems, the enthalpy and entropy changes are positive and show accelerating increases with temperature. The resulting equilibrium constants show significant, but smaller, increases with temperature.     

Syntheses,Crystal Structures,Visible, and Near-Infrared Luminescence Properties of 3d–4f Coordination Polymers Cu2Er2 and Eu2Ni2

Russian Journal of Coordination Chemistry - Solvothermal condition reaction of Ln(NO3)3 ? 6H2O (Ln = Er, Eu) with 5-nitroisophthalate (Nipt2–) and mononuclear macrocyclic oxamide...     

Structures and bonding situation of Pb2X2 (X?=?H, F, Cl, Br and I)

Quantum chemical calculations using DFT (BP86) and ab initio methods (MP2, MP4 and CCSD(T)) have been carried out for the title compounds. The nature of the Pb?CPb interactions has been investigated with an energy decomposition analysis. The energy minimum structures of the halogen substituted Pb₂X₂ molecules possess a doubly bridged butterfly geometry A like the parent system Pb₂H₂. The unusual geometry can be explained with the interactions between PbX fragments in the X ²?? ground state which leads to one Pb?CPb electron-sharing ?? bond and two donor?Cacceptor bonds between the Pb?CX bonds as donor and vacant p(??) AOs of Pb. The energy difference between the equilibrium form A and the linear structure XPb??PbX (E) which is a second-order saddle point is much higher when X is a halogen atom than for X?=?H. This is because the a ⁴??^?????X ²?? excitation energies of PbX (X?=?F?CI) are higher than for PbH. The structural isomers B, D1, D2, E, F1, F2 and G of Pb₂X₂ are no minima on the potential energy surface.     

Synthesis, Single-crystal Structure, and Optical and Magnetic Properties of CaEr2S4

Brown needle-like crystals of CaEr2S4 were isolated as the major product from a reaction of elements and binary sulfides by a two-step flux technique. CaEr2S4 crystallizes in the orthorhombic space group Pnma with a = 12.845(4), b = 3.862(4), c = 13.001(2) , V = 645.0(7) 3, Z = 4, F(000) = 880, μ(MoKα) = 27.794 mm-1, the final R = 0.0528 and wR = 0.0562 for 1070 observed reflections with I > 3σ(I). The CaEr2S4 structure forms a three-dimensional framework that consists of interconnected tetra-octahedral Er4S18 fragments. Ca2+ cations, in a monocapped trigonal prism geometry, are stuffed in two parallel rows into the one-dimensional channels along the b direction. CaEr2S4 is an infrared-transparent semiconductor with a band gap of 1.81 eV. Magnetic susceptibility measurements over 6～300 K indicate a Curie-Weiss paramagnetic behavior for the phase, with an effective magnetic moment of 9.64(1) μB per Er3+ ion.     

Molecular and Crystal Structure of 2, 3, 5, 6-dipropylene-r-pyrone

11NTRODUCT1ONWeattemptedtosynthesizeanextractant(1)bythereactionofadipylchloridewithcyclopentanonepiperidineenamineaccordingtoHunig'sprocedure"',however,wemainlyobtainedthetitlecompound,whichmaybepossiblyapotentialmedicinet2'3i.Itsmolecularstructurewasfinallyconfirmedbythesingle-crystalstructuredeterminationafterconventionalUV,IR,lHNMR,MSandelementana-lyticalworks.2EXPER1MENTALSECT1ON2.1SynthesisToastirredsolutioncontaining8Omlofchloroform,2.8mloftri-ethylamineand1.51g(O-Olmol)…     

Adsorption isotherms of CO2, CO,N2, CH4, Ar and H2 on activated carbon and zeolite LiX up to 1.0 MPa

The adsorption isotherms of CO₂, CO, N₂, CH₄, Ar, and H₂ on activated carbon and zeolite LiX were measured using a volumetric method. Equilibrium experiments were conducted at 293, 308, and 323 K and pressures up to 1.0 MPa. The adsorption isotherm and heat of adsorption were analyzed for two pressure regions of experimental data: pressures up to 0.1 MPa and up to 1.0 MPa. Each experimental isotherm was correlated by the Langmuir, Sips, Toth and temperature dependent Sips isotherm models, and the deviation of each model was evaluated. The Sips and Toth models showed smaller deviation from the experimental data of adsorbents than the Langmuir model. Isosteric heats of adsorption were calculated by the temperature dependent Sips model and are presented along with surface loading. From deviation analysis, it is recommended that the isotherm in the proper pressure range be used to appropriately design adsorptive processes.     

First-principles study of structural,elastic, electronic and optical properties of rutile GeO2 and α-quartz GeO2

Structural parameters, elastic, electronic, bonding and optical properties of rutile GeO₂ and α-quartz GeO₂ have been investigated using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory (DFT). The ground-state properties obtained by minimizing the total energy are in favorable agreement with the previous work. Two phases of GeO₂ are found to be elastically stable and we have derived the bulk, shear and Young’s modulus, Poisson coefficient for rutile GeO₂ and α-quartz GeO₂. We estimated the Debye temperature of rutile GeO₂ and α-quartz GeO₂ from the acoustic velocity. Electronic and chemical bonding properties have been studied from the calculation of band structure, density of states and charge densities. Furthermore, in order to clarify the mechanism of optical transitions for rutile GeO₂ and α-quartz GeO₂, the complex dielectric function, refractive index, extinction coefficient, optical reflectivity, absorption coefficient, energy-loss spectrum and the complex conductivity function are calculated, which show the significant optical anisotropy in the components of polarization directions (100) and (001) for rutile GeO₂ and α-quartz GeO₂.     

Spectral and electrochemical properties of mono-, bi-, and tetranuclear cyclopalladized complexes based on 2-(2-thienyl)pyridine and 2-phenylpyridine with pyridine and 4,4′-bipyridyl

Mono-, bi-, and tetranuclear cyclopalladized complexes based on 2-(2-thienyl)pyridine and 2-phenylpyridine with pyridine and 4,4′-bipyridyl were prepared and characterized by the methods of ¹H NMR, electron absorption and emission spectroscopy, and also by the voltammetry method. The values of the coordination-induced shifts of proton in the ligands of the complexes were determined; the upfield displacement of chemical shifts of protons of the cyclopalladized ligand nearest to the metal was assigned to the anisotropic action of a ring current of the pyridine rings orthogonal to the coordination plane in 4,4′-bipyridyl and pyridine. Long-wave absorption bands of the complexes were assigned to the spin-allowed optical d-π charge-transfer transitions, and the bands of the low-temperature phosphorescence, to the intraligand π-π_NyyC^* transitions. Three waves of the reduction of the complexes were assigned to the ligand-centered processes of successive electron transfer on π* orbitals preferentially localized on coordinated pyridine and cyclopalladized ligands.     

Zn~Ⅱ, Ni~Ⅱ, and Mn~Ⅱ Complexes Supported by N-Hydroxy-pyridine-2-carboxamidine: Syntheses,Structures, and Luminescent and Magnetic Properties

The employment of N-hydroxy-pyridine-2-carboxamidine in the coordination chemistry of zinc(Ⅱ), nickel(Ⅱ) and manganese(Ⅱ) under solvothermal conditions is reported. Four complexes of compositions, [Zn2(O2CMe)3{(py)C(NH2)NOH}4](OH)(1), [Zn4(OH)2{(py)C(NH2)-NO}4Cl2]·3MeCN(2), [Ni(SO4)(H2O){(py)C(NH2)NOH}2]·H2O(3) and [Mn(SO4){(py)C(NH2)-NOH}2]n(4), have been synthesized by rationally choosing different metal salts and dexterously employing acetate and sulfate ions as the bridging groups. Luminescent properties for 2 suggested strong emission in the solid state at room temperature. Variable temperature(2.0~300 K) magnetic studies for the linear chain complex 4 indicate weak antiferromagnetic Mn(Ⅱ)···Mn(Ⅱ) exchange interactions.     

Vibrational spectroscopic study of the hypophosphite and phosphite anions,H2PO2−2 and HPO2−3, and of their deuteriated analogues in the solid state and in aqueous solution

A full vibrational spectroscopic study of sodium hypophosphite, sodium phosphite and their deuteriated analogues has been made. The vibrations characteristic of the hypophosphite anion have been assigned and the presence of a previously unreported band has been established for the Raman spectrum of the aqueous solution. The first Raman study of deuteriated sodium phosphite has been undertaken and a full vibrational assignment is given.     

Hydrothermal synthesis, structure and photocatalytic property of nano-TiO_2-MnO_2

TiCI4 and MnSO4.H2O as raw materials are hydrolyzed stiochiometrically, following the intermediate of oxide hydrating reacts at 150℃, 0.5 MPa in high-pressure reactor, after filtering, washing and drying, nanometric TiO2-MnO2 (Ti1-xMnxO2) is prepared. The effects of the reaction temperature and time on nanometric TiO2-MnO2 are also discussed. XRD shows that the product is TiO2-MnO2 with amorphous phase. After being sintered at above 780℃, it transfers into Ti1-xMnxO2 with a rutile structure. TEM shows that TiO2-MnO2 is the spherical particle. And the average diameter of the particles is 20 nm. The optical absorbance was determined by UV-265 spec-trophotometer after dispersing the sample in the mixture of water and glycerol with the ratio of 1 : 1 equably. It is found that the nano-material possesses the advantages of both nano-TiO2 and nano-MnO2, and it has strong absorption in the UV and visible region. Photodegradation of dyes in an aqueous solution is investigated using nanometricTiO2-MnO2 as a pho     

Coupled cluster,MP2, and DFT study of structures,stabilities, vibrations,and bonding properties of XXeOH (X = F,Cl, Br,and I)

The optimized geometries, molecular properties, and stabilities of new noble gas molecules, XXeOH (X = F, Cl, Br, and I), were studied using CCSD, MP2, CAM-B3LYP, and WB97XD methods and large basis sets. All XXeOH molecules showed equilibrium structures with Cs symmetry. The results also showed that some bonds in XXeOH could be presented as a typical ionic bond. An alteration in ion-pair character was observed for IXeOH, showing two OH ^? and IXe ⁺ parts, while in other molecules, they could be presented as XeOH ⁺ and X ^? . Two decomposition routes were proposed for these molecules that showed high exothermic reactions. However, despite their low thermodynamic stabilities, their decomposition rate constants were small and all molecules (except BrXeOH) had high kinetic stabilities, indicating the possibility for identification and characterization of these molecules. However, in addition to the calculation of their vibrational frequencies, NBO atomic charges, and hybridizations, the bonding properties of XXeOH molecules were studied by AIM calculations (to calculate electron densities, bond elipticities, and Laplacian of electron densities) and second-order intramolecular perturbation energies using NBO calculations. Moreover, the ease of formations and relative stabilities of XXeOH molecules were compared using heats of formations, Gibbs free energies of formations and isodesmic reactions. These calculations showed that the stability of XXeOH molecules was decreased from F to I.     

Rhodium-Catalyzed Chemo-, Regio-, Diastereo-, and Enantioselective Intermolecular [2+2+2] Cycloaddition of Three Unsymmetric 2π Components

We have developed the Rh⁺/H₈-binap-catalyzed chemo-, regio-, diastereo-, and enantioselective intermolecular [2+2+2] cycloaddition of three unsymmetric 2π components. Thus, two arylacetylenes react with a cis-enamide to yield a protected chiral cyclohexadienylamine. Moreover, replacing one arylacetylene with a silylacetylene enables the [2+2+2] cycloaddition of three distinct unsymmetric 2π components. These transformations proceed with excellent selectivity (complete regio- and diastereoselectivity and up to >99 % yield and >99 % ee). Mechanistic studies suggest the chemo- and regioselective formation of a rhodacyclopentadiene intermediate from the two terminal alkynes.     

Phosphotungstic acid mediated,microwave assisted solvent-free green synthesis of highly functionalized 2ˈ-spiro and 2, 3-dihydro quinazolinone and 2-methylamino benzamide derivatives from aryl and heteroaryl 2-amino amides

Phosphotungstic acid has been found as green catalyst for the synthesis of spiro and cyclized quinazolinones and 2-amino substituted carboxamide under microwave irradiation and solvent-free condition has been developed. The scope of the reaction has been demonstrated for a variety of aldehydes and ketones with O-amino amides such as 2-amino-benzamide, 2-amino-5-iodo benzamide, 3-aminothiophene-2-carboxamide, 3-aminobenzofuran-2-carboxamide and 2-aminopyridine-3-carboxamides. The reaction afforded spiro-, cyclized quinazolinones and 2-amino substituted carboxamide derivatives within few minutes of irradiation in excellent yield. Plausible mechanism for the formation of products is provided. Synthetic utility of 1′H-spiro[fluorene-9,2′-quinazolin]-4′(3′H)-one 3a has been demonstrated by synthesis of 1,4-di(1′H-spiro[fluorene-9,2′-quinazolin]-4′(3′H)-one) buta-1,3-diyne 12, 1′-((1-benzyl-1H-1,2,3-triazol-4-yl) methyl)-1′H-spiro[fluorene-9,2′-quinazolin]-4′(3′H)-one 13 and 1′-phenyl-1′H-spiro[fluorene-9,2′-quinazolin]-4′(3′H)-one 14 under standard protocols.     

Ab Initio Study of the Acetylene–Allene Rearrangement in 2-Propargylpyrrole, 2-Propargylfuran, and 2-Propargylthiophene

Ab initio (MP4/6-31G*//RHF/6-31+G*) calculations have been performed to study the acetylene–allene rearrangement in X–CH₂–CCH propargyl systems, where X = ethenyl, E-1-butadienyl, 2-pyrrolyl, 2-furanyl, and 2-thienyl. The spatial and electronic structures, as well as the relative stability, of the initial and final acetylene structures and the corresponding allenes are examined. Migration of the triple bond from the terminal position into the chain, including the stage of allene structure formation, is shown to be thermodynamically favorable for the whole series of compounds. The propargyl substituents of heterocycles isomerize as readily as open diene systems. The differences in the isomerization energies in the series of allenyl- and 1-propynyl-substituted pyrrole, furan, and thiophene are mainly due to the differences in the nature of long-range interactions between heteroatoms and the tricarbon system.     

Syntheses,structures, and properties of transition metal complexes with 2-( n -pyridyl)benzimidazole ( n = 2, 3, and 4)

Three pyridylbenzimidazoles (2-PBIM, 3-PBIM, and 4-PBIM) have been prepared (2-PBIM: 2-(2-pyridyl)-benzimidazole, 3-PBIM: 2-(3-pyridyl)-benzimidazole, 4-PBIM: 2-(4-pyridyl)-benzimidazole). Reactions of several transition metals (Cd²⁺, Cu²⁺, Fe²⁺) with the three ligands gave four new coordination complexes, [(Cd)₂(2-PBIM)₂(CH₃COO)₄] (1), [Cu(3-PBIM)₂(CH₃COO)₂]?·?2H₂O (2), [Cu(4-PBIM)₂(CH₃COO)₂(H₂O)]?·?H₂O (3), and [Fe(4-PBIM)₂(Cl)₂(H₂O)₂] (4), respectively. These four complexes have been characterized by X-ray crystallography, IR spectroscopy, and UV absorption spectroscopy. Thermogravimetric properties of 2 and 4 were also measured. X-ray crystallographic studies reveal that these four complexes are very different, although the ligands are similar in structure. The role of hydrogen-bonding and π–π interactions in extending dimensionality of simple complexes has been discussed.