Ab initio calculations on low-lying electronic states of TeO2 and Franck-Condon simulation of the (1)1B2 <-- X1A1 TeO2 absorption spectrum including anharmonicity

Ab initio calculations have been carried out on low-lying singlet and triplet states of TeO2 at different levels of theory with basis sets of up to the augmented-polarized valence-quintuple-zeta quality. Equilibrium geometrical parameters, harmonic vibrational frequencies, and relative electronic energies of the X1A1, 1B1, 1B2, 1A2, 3A1, 3B1, 3B2, and 3A2 states of TeO2 have been calculated. Potential energy functions (PEFs) of the X1A1 and the (1)1B2 states were computed at the complete-active-space self-consistent-field multireference configuration interaction level, with a basis set of augmented-polarized valence-quadruple-zeta quality. Franck-Condon factors (FCFs) for the electronic transition between the X1A1 and (1)1B2 states of TeO2 were calculated with the above-mentioned ab initio PEFs. The (1)1B2 <-- X1A1 absorption spectrum of TeO2 was simulated employing the computed FCFs, which include Duschinsky rotation and anharmonicity, and compared with the recently published laser-induced fluorescence (LIF) spectrum of Hullah and Brown [J. Mol. Spectrosc. 200, 261 (2000)]. The ab initio results and spectral simulation reported here confirm the upper electronic state involved in the LIF spectrum to be the (1)1B2 state of TeO2 and also confirm the vibrational assignments of Hullah and Brown. However, our simulated spectrum suggests that the reported LIF spectrum from 345 to 406 nm represents only a portion of the full (1)1B2 <-- X1A1 absorption spectrum of TeO2, which extends from ca. 406 to 300 nm. Another dye other than the two used by Hullah and Brown is required to cover the 345-300 nm region of the LIF band. Ab initio calculations show strong configuration mixing of the (1)1B2 electronic surface with higher 1B2 states in a region of large TeO bond length (> or = 2.0 A) and OTeO bond angle (> or = 135.0 degrees).     

Crystal and molecular structure of bis(N,N-dipropyl-N′-diphenoxythiophosphoryl-thioureato) nickel(II) [(C6H5O)2P(S)NC(S)N(C3H7)2]2Ni

The Ni complex [C₆H₅O₂P(S)N(C₃H₇₂]₂Ni is monoclinic, space group P2₁/n with a = 8.890(3), b = 21.692(5), c = 11.670(4) Å, β = 108.35(5)°, V = 2136(1) ų, F(000) = 916, M_r = 534.01, Z = 2, D_m = 1.318, D_x = 1.358 Mg m^?3, graphite monochromatized MoKα ^? radiation, π = 0.7107 Å, μ = 0.76 mm^?1, T = 293 K. The structure was solved by a heavy atom method and refined to R = 0.044 for 3095 independent reflexions. The Ni atom lies in the centre of symmetry and is coordinated by four S atoms of the two molecules of the ligand in a planar arrangement. Ni? S bond lengths are 2.205 and 2.226 Å resp., the angles S? Ni? S are 97.65 and 82.35° resp.     

Determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and environmental samples by gas chromatography with helium microwave plasma atomic emission detection

A highly sensitive and specific method is described for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and environmental samples by gas chromatography–plasma atomic emission detection (GC–AED). The procedure is simple, rapid and free from interferences. The absolute limit of detection is 0.5 fg of MMT (0.5×10⁻¹⁵ g) expressed as Mn. The precision for replicate injections ( n =5) of an MMT solution (10 pg Mn) was 2.8% relative standard deviation (RSD ). Applications of the method to analysis of gasoline (petrol), and preliminary results of the analyses of environmental samples such as air and roadside dirt, are given. © 1997 by John Wiley & Sons, Ltd.     

Alternative moving window factor analysis for comparison analysis between complex chromatographic data

In this investigation, a novel chemometric method is developed for the analysis of five possible relationships of components or spectral features between two correlative but different hyphenated chromatographic systems. It is very helpful for comparison study of components present in different complex systems in both chemistry and systems biology. The proposed method, named alternative moving window factor analysis (AMWFA), could be utilized to determine the number of common components between different samples and then to identify their corresponding spectra half-automatically. AMWFA can alternatively be employed to mind for the selective information hiding in anyone of the two compared data X and Y, and to self-verify the resolution results by changing the extracted target matrices in analysis. From the results of comparison of simulated hyphenated chromatographic data, volatile chemical components in drug pair rhizoma ligustici chuanxiong-radix paeoniae rubra (RLC-RPR) and its single herbal medicines, and analysis of Angelica oral solution and its plasma sample after oral intake to rabbit, powerful ability of the proposed method is shown.     

A Practical Route to Chiral Phenylalanine via the Condensation of Keto Acids with Amides and Asymmetric Hydrogenation

The condensation of β-phenylpyruvic acid with amides gave olefinic intermediates in good yields (75-80%). The asymmetric catalytic hydrogenation of α-acetamidocinnamic acid with high enantioselectivity is described.     

Multidimensional optimization of structural changes of molecules upon lonization in Franck-Condon factor calculations

Two different iterative methods, namely, the conjugate gradients method and the pattern search method, are applied to Franck-Condon factor calculations using the Coon et al. method (J. B. Coon, R. E. DeWames, and C. M. Loyd, J. Mol. Spectrosc.8, 235–299 (1962)) and the generating function method (T. E. Sharp and H. M. Rosenstock, J. Chem. Phys.41, 3453–3463 (1964); R. Botter, V. H. Dibeler, J. A. Walker, and H. M. Rosenstock, J. Chem. Phys.44, 1271–1278 (1966)). In such treatment, either the changes in normal coordinates or the changes in internal symmetry displacement coordinates are refined automatically until the weighted sum of square deviation between the calculated and the observed Franck-Condon factors is minimized. Some properties of the methods used are given and their applications to several cases are discussed in detail.