Coherent Vibrational Dynamics and High-resolution Nonlinear Spectroscopy： A Comparison with the Air/DMSO Liquid Interface

We present a comparative study on the C-H stretching vibrations at air/DMSO （dimethyl sulfoxide） interface with both the free-induction decay （FID） coherent vibrational dynamics and the sub-wavenumber high resolution sum-frequency generation vibrational spectroscopy measurements. In principle the frequency-domain and time-domain spectroscopic measurements should generate identical information for a given molecular system. However, when the molecular systems are with several coupled or overlapping vibrational modes, obtain- ing detailed spectroscopic and coherent dynamics information is not as straightforward and rather difficult from either the time-domain or the frequency domain measurements. For the case of air/DMSO interface that is with moderately complex vibrational spectra, we show that the frequency-domain measurement with sub-wavenumber high-resolution sum-frequency generation vibrational spectroscopy is probably more advantageous than the time- domain measurement in obtaining quantitative understanding of the structure and coherent dynamics of the molecular interface.     

Can stimulated Raman pumping cause large population transfers in isolated molecules?

When stimulated Raman pumping (SRP) is applied to a stream of isolated molecules, such as found in a supersonic molecular beam expansion, we show that SRP can neither saturate nor power broaden a molecular transition connecting two metastable levels that is resonant with the energy difference between the pump and Stokes laser pulses. Using the optical Bloch-Feynman equations, we discuss the pumping of the hydrogen molecule from H(2) (v = 0, J = 0, M = 0) to H(2) (v = 1, J = 2, M = 0) as an illustration of how coherent population return severely reduces the SRP pumping efficiency unless the pump and Stokes laser pulses are applied with an appropriate relative delay and ratio of intensities.     

A 3D Ba(Ⅱ) Inorganic-organic Hybrid Framework Based on 1,3,5-Benzenetricarboxylic Acid Ligand: Synthesis and Characterization

A three-dimensional(3D) barium complex with 1,3,5-benzenetricarboxylic acid(H3BTC), {[Ba1.5(BTC)(H2O)]·(H2O)}n(1), was synthesized in DMF/EtOH/H2 O mixed solution under solvothermal conditions, and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric analyses, and photoluminescence measurement. In complex 1, the 2D I2O0 type inorganic layer is constructed by {Ba1O10} and {Ba2O9} polyhedra. Moreover, the solid-state fluorescence measurement reveals a fluorescence emission band at 465 nm under 344 nm excitation, assigned to a charge-transfer transition.     

Structure cristalline et conformation en solution aqueuse de la carnosine (β-alanyl-L-histidine)

Carnosine (β-alanyl-L-histidine) is a biologically active molecule involved in muscular metabolism. It crystallises in the C; space group with a = 24.725 Å b = 5,427 Å c = 8,004 Å β = 100,2° (Z = 4)

In the crystal, acid and basic groups are engaged in hydrogen bonds whose strength is evaluated through IR frequencies. Molecular conformation in the solid state is defined by τ₁ = /t-177° τ₂ = −38° φ = −96° ψ = +131° χ₁ = 181° χ₂₁ = 62°

NMR study of carnosine in aqueous solution indicates that rotation about CH₂-CH₂ is free and that the other angles take the following values: Ø −150° or −90° and X₁ = 165° or 315°. Infrared and Raman spectra suggest that τ₂ undergoes small changes when going from crystal to solution while ψ is close to +150°.     

Calibration of conductance cells at various temperatures

Precise conductance measurements on aqueous potassium chloride solutions at 0, 10, 18, and 25°C have been made under various conditions over a concentration range 10^?4?2 mole-dm^?3, yielding the conductance equations $$\begin{gathered} 25^\circ C:\Lambda = 149.873 - 95.01\sqrt c + 38.48c log c + 183.1c - 176.4c^{3/2} \hfill \\ 18^\circ C:\Lambda = 129.497 - 80.38\sqrt c + 32.87c log c + 154.3c - 143.0c^{3/2} \hfill \\ 10^\circ C:\Lambda = 107.359 - 64.98\sqrt c + 27.07c log c + 125.4c - 110.3c^{3/2} \hfill \\ 0^\circ C:\Lambda = 81.700 - 47.80\sqrt c + 20.60c log c + 93.8c - 79.3c^{3/2} \hfill \\ \end{gathered} $$ which are proposed for calibration of conductance cells.     

Dipole polarizability pseudospectra and C6 dispersion coefficients for H2–H2

Pseudostate decomposition of static dipole polarizabilities for ground state H₂⁺ from a Givens-Householder diagonalization of the excitation operator (

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H" height="17" width="20">₀−E₀) over an N-term basis of appropriate symmetry allows for a rapidly convergent evaluation of C₆ dispersion coefficients for H₂⁺–H₂⁺. 27-term pseudospectra of hypergeneralized James functions with a 30-term GGJ⁺ unperturbed wavefunction with an optimized scale factor δ=0.918 at R=2₀ give C₆ and γ₆ values that are accurate to no less than nine significant figures.     

Metallorganische lewissäuren : XX. Reaktionen von (π-C5H5)(CO)2LM-X (L = CO, PR3; M = Mo, W; X = BF4, PF6, AsF6, SbF6) mit Schwefel-haltigen liganden

The compounds (π-C₅H₅)(CO)₂LM-X (L = CO, PR₃; M = Mo, W; X = BF₄, PF₆, AsF₆, SbF₆) react with H₂S, p-MeC₆H₄SH, Ph₂S and Ph₂SO(L′) to give ionic complexes [(π-C₅H₅)(CO)₂LML′]⁺ X⁻. Also sulfur-bridged complexes, [(π-C₅H₅)(CO)₃W---SH---W(CO)₃(π-C₅H₅)]⁺ AsF₆⁻ and [(π-C₅H₅)(CO)₃M-μ-S₂C=NCH₂Ph-M(CO)₃(π-C₅H₅)], have been obtained. Reactions with SO₂ and CS₂ have been examined.     

Intermodulated fluorescence spectroscopy of caf AΠ-XΠ

The A ²Π-X²∑⁺ 0-0 transition of CaF has been examined by the technique of intermodulated fluorescence spectroscopy (“Lamb dip”). The hyperfine structure due to ¹⁹F and the spin-rotation fine structure of the X ²∑⁺ state was determined. Parameter values of b = 104.0 (9) MHz, c = 58(6) MHz and γ = 38.6(2) MHz were found for v = 0 of X²∑⁺     

MRD CI study on the low-lying states of AlP

Large-scale MRD CI calculations assign to AlP the ground state X ³Σ⁻ (9σ²3π²) and a close-lying state 1 ³Π (9σ3π³) (T_e = 0.08 eV). Up to transition energies of 2.0 eV, other states are described by the configurations 9σ3π³ (1¹Π), 8σ²3π⁴ (1 ¹Σ⁺), 9σ²3π² (1 ¹Δ and 2 ¹Σ⁺) and 9σ3π²4π (1 ⁵Π). The 2 ³Π state, located at ≈ 2.30 eV, shows a shallow double minimum. Numerous perturbations are expected to induce predissociation upon 2 ³Π. Multiplets arising from the occupation 8σ²3π³4π are clustered in the 3.25–3.50 eV region. Quintet states with the configuration 8σ9σ3π³4π are bound, with T_e values (in eV) of 3.80 (1 ⁵Σ⁺), 4.44 (1 ⁵Δ) and 4.88 (3 ⁵Σ⁻), respectively. The 9σ → 4s Rydberg members ⁵Σ⁻ and ³Σ⁻ lie in the 4.58–4.72 eV energy region. The first ionization potential (ionization to X⁴Σ⁻ of AlP⁺, 9σ → ∞) is estimated to be 7.65 eV. Ionization to the 1 ²Σ⁻ and 1 ²Π states of AlP⁺ is suggested to occur between 8.0 and 8.8 eV. The dipole moments of X ³Σ⁻, 1 ¹Δ and 2 ¹Σ⁺ are close to 1.0 D, whereas the 1 ¹Σ⁺ state has μ = 3.49 D; 1 ³Π and 1 ¹Π have dipole moments from 2.45 to 2.91 D. All low-lying states show a polarity Al⁺P⁻. Finally, the electronic structure and transition energies of AlP are compared with those of the isoelectronic species BN, AIN, and SiP⁺.     

Asymmetric higher-order [10 + n] cycloadditions of palladium-containing 10π-cycloaddends

We uncovered an asymmetric higher-order [10 + 2] cycloaddition reaction between diverse activated alkenes and a new type of π-allylpalladium complex-containing dipole-type 10π-cycloaddend, which was generated in situ from 2-methylene-1-indanols via a dehydrative insertion and deprotonation strategy under double activation of Pd(0) and phosphoric acid. A similar strategy was applied to an asymmetric higher-order [10 + 8] cycloaddition reaction or [10 + 4] cycloaddition reaction by using a heptafulvene derivative or a cyclic enone, respectively, as the acceptor. A variety of polycyclic frameworks imbedding an indene core were generally furnished in moderate to excellent yields with high levels of enantioselectivity by employing a newly designed chiral phosphoramidite ligand.

A type of π-allylpalladium complex-containing 10π-cycloaddend generated from 2-methylene-1-indanols under double activation of Pd(0) and phosphoric acid undergoes asymmetric higher-order [10 + 2] cycloadditions with diverse activated alkenes.     

Strahlenchemie von alkoholen—IX Die UV-photolyse (λ = 185 nm) von methanol in flüssiger phase

The UV photolysis (λ = 185 nm) of liquid methanol yields hydrogen, glycol, formaldehyde, methane and traces of ethane in quantum yields of 0·83, 0·78, 0·058, 0·05 and 0·002 resp. (related to φ(H₂) = 0·4 of the ethanol-actinometer (5 mole/1 in water)). The isotopic distribution of the hydrogen (85% HD) formed in the photolysis of CH₃OD shows, that as in the gasphase² the scission of the O---H-bond (1) is the major process. CH₃OH + hv (λ = 185 nm) → CH₃O^• + H^• (1)

In methanoi-water mixtures (nearly all the light of the wavelength λ = 185 nm is absorbed by methanol) the quantum yields of hydrogen, glycol, methane and ethane are greatly reduced, while the formaldehyde yield remains unaffected. In 1 molar solution φ(H₂) = 0·42, φ(glycol) = 0·32 and φ(CH₄) = 6 x 10⁻⁴ is obtained. Ethane cannot be detected.     

Spin-forbidden c 3Sigma1+<--X 1Sigma+ band system of YF

Optical spectra of jet-cooled diatomic YF have been recorded using resonant two-photon ionization spectroscopy. A vibrational progression corresponding to the c 3Sigma1+<--X 1Sigma+ system has been identified. The vibrational frequency omegae' and anharmonicity omegae'xe' of the c 3Sigma+ state are 546.70 and 2.45 cm-1, respectively. The 0-0, 1-0, and 2-0 bands of the c 3Sigma1+<--X 1Sigma+ system were rotationally resolved and analyzed, allowing the v'=0, 1, and 2 levels of the c 3Sigma1+ substate to be characterized. From these studies, Be'=0.269 81(3) cm-1, alphae'=0.001 72(3) cm-1, and re'=1.9979(1) A were obtained (1sigma error limits). For these levels the spin-spin coupling constant lambdav is identical within experimental error, as lambda=-22.5 cm-1. The spin-forbidden c 3Sigma1+<--X 1Sigma+ transition is made allowed by spin-orbit interaction between the c 3Sigma1+ and the B 1Pi states. Excited state lifetimes of the c 3Sigma1+ and the B 1Pi states have been measured as 7.11(41) and 0.133(15) micros, respectively. A spin-orbit analysis shows that the c 3Sigma1+ state is contaminated with 2% B 1Pi character, which is approximately sufficient to explain the 7 micros lifetime of the c 3Sigma1+ state.     

Study of the N2 bΠu state via 1 + 1 multiphoton ionization

Medium-resolution spectra of the N₂ b¹Π_u-X¹Σ_g⁺ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b ¹Π_u state: Δν₀ = 0.50 ± 0.05 cm⁻¹, Δν₁ = 0.28 ± 0.02 cm⁻¹, Δν₂ = 0.65 ± 0.06 cm⁻¹, Δν₃ = 3.2 ± 0.5 cm⁻¹, Δν₄ = 0.60 ± 0.07 cm⁻¹, and Δν₅ = 0.28 ± 0.02 cm⁻¹. From these linewidths, predissociation lifetimes τ_ν were obtained: τ₀ = 16 ± 3 ps, τ₁ > 150 ps, τ₂ = 10 ± 2 ps, τ₃ = 1.6 ± 0.3 ps, τ₄ = 9 ± 2 ps, and τ₅ > 150 ps. Band origins and rotational constants for the b ¹Π_uν = 0 and 1 levels were determined for the ¹⁴N₂ and ¹⁴N¹⁵N molecules.     

Investigation of the Interaction between Isoflavonoids and Bovine Serum Albumin by Fluorescence Spectroscopy

The interactions of bovine serum albumin （BSA） with three structurally related isoflavonoids, genistein, puerarin and daidzein, were studied under physiological conditions by fluorescence spectroscopic technique. The quenching mechanism of these compounds with BSA was suggested as static quenching and the binding constants were determined at different temperatures based on the fluorescence quenching results. The transfer efficiency of energy and distance between the acceptor and BSA were investigated on the basis of the mechanism of the Forster energy transference. According to the thermodynamic parameters it has been suggested that the acting force be mainly hydrophobic force. The comparison of binding potency of the three isoflavonoids to BSA showed that the substitution by 5-OH and 8-Glc could enhance the binding affinity. All these obtained in the work can make us better understand the mode of the action and pharmacological activities of the isoflavonoids.     

Bounds for total π-electron energy of polymethines

The introduction of a -CH=CH- fragment into an arbitrary alternant ,ω-disubstituted polymethine increases the total Hückel π-electron energy at least by 2(√5 − 1) = 2.472 β and at most by 2(√3 + 1 − √2) = 2.636 β. These bounds are the best possible. With increasing length of the polymethine chain, the energy difference tends to 8/π = 2.546 β.     

Fe48Co52 Alloy Nanowire Arrays： Effects of Magnetic Field Annealing

The effects of magnetic field annealing on the properties of Fe48Co52 alloy nanowire arrays with various interwire distances （Di=30-60 nm） and wire diameters （Dw=22-46 nm） were investigated in detail. It was found that the array＇s best annealing temperature and crys- talline structure did not show any apparent dependence on the treatment of applying a 3 kOe magnetic field along the wire during the annealing process. For arrays with small Dw or with large Di, the treatment of magnetic field annealing also had no obvious influence on their magnetic performances. However, such a magnetic field annealing constrained the shift of the easy magnetization direction and improved the coercivity and the squareness obviously for arrays with large Dw or with small Di. The difference in the intensity of the effective anisotropic field within the arrays was believed to be responsible for this different variation of the array＇s magnetic properties after magnetic field annealing.     

Laser Flash Photolysis on Electron Transfer Reactions between 1,8-Dihydroxyanthraquinone with Adenine and Cytosine

Electron transfer （ET） reactions between 1,8-dihydroxyanthraquinone （DHAQ） and two DNA bases, adenine （A） and cytosine （C）, have been investigated in CH3CN/H20 solution with nanosecond time-resolved laser flash photolysis. After irradiation at 355 nm, the triplet DHAQ is produced via intersystem crossing and reacts with two nucleobases. ET processes for both reactions have been definitely identified, in which two bases play a significant role of electron donor. Based on the measured decay dynamics of various intermediates and the corresponding quenching rates, an initial ET process followed by a secondary proton-transfer reaction is suggested for both the overall reactions. By plotting the observed quenching rate against the concentration of two DNA bases, the bimolecular quenching rate constants are determined as 9.0-10s L/（mol.s） for the 3DHAQ＊＋C reaction and 3.3x10^8 L/（mol.s） for the 3DHAQ＊＋A reaction, respectively.     

Synthesis and Crystal Structure of Tianagliflozin Triacetate

The title compound tianagliflozin triacetate 1 was synthesized and its crystal structure was determined by single-crystal X-ray diffraction.The crystal belongs to monoclinic system(C27H31ClO8,Mr = 518.97),space group P21 with a = 5.3913(11),b = 16.137(2),c = 15.411(3) ,β = 94.15(3)°,V = 1337.3(5) 3,Z = 2,Dc = 1.289 g/cm3,F(000) = 548,μ = 0.190 mm-1,the final R = 0.0374 and wR = 0.0809 for 3981 observed reflections(I 2σ(I)).The structure of 1,triacetate of a highly potent SGLT2 inhibitor tianagliflozin,was unambiguously determined by single-crystal X-ray diffraction,which helped to confirm the desired β configuration at the anomeric center and the position where the deoxylation occurred.The two benzene rings in the lattice are basically orthogonal to each other.There are four intermolecular hydrogen bonds in the crystal,which helps to further stabilize the crystal.     

Improved Photovoltaic Performance of MEH-PPV/PCBM Solar Cells via Incorporation of Si Nanocrystals

We have studied the effect of silicon nanocrystals （SiNCs） as a third component on performance of organic bulk heterojunction solar cells composed of poly[2-methoxy,5-（2＇-ethylhexyloxy）-l,4-phenylene vinylene] （MEH- PPV）：[6,6]-phenyI-C61-butyric acid methyl ester （PCBM） blend film. By adding suitable amounts of SiNCs into MEH-PPV：PCBM blend, the device performance such as external quantum efficiency, short circuit current density （Js（）, and power conversion efficiency （PCE） improved. Incorporation of 2.5% SiNCs in the blend led to 13.6% improvement of Jsc, which in turn resulted in 18% improvement of PCE up to 2.28%. The improved performance was mainly due to the improvements both in the charge generation from the interface of MEH-PPV/SiNCs and the charge collection at the cathode.     

Theoretical Investigation on Interaction between Guanine and Luteolin

The interacting patterns of the luteolin and guanine have been investigated by using the density functional theory B3LYP method with 6-31＋G＊ basis set. Eighteen stable structures for the luteolin-guanine complexes have been found respectively. The results indicate that the complexes are mainly stabilized by the hydrogen bonding interactions. Meanwhile, both the number and strength of hydrogen bond play important roles in determining the stability of the complexes which can form two or more hydrogen bonds. Theories of atoms in molecules and natural bond orbital have also been utilized to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes which were corrected by basis set superposition error are 6.04-56.94 kJ/mol. The calculation results indicate that there are strong hydrogen bonding interactions in the luteolin-guanine complexes. We compared the interaction between luteolin and four bases of DNA, and found luteolin-thymine was the strongest and luteolin-adenine was the weakest. The interaction between luteolin and DNA bases are all stronger than luteolin-water.