Günther Bauer

All electron density functional study of neutral and ionic polybromine clusters

The structural and electronic properties of homoatomic chains consisting of up to five Br-atoms are studied by means of the linear combination of Gaussian-type orbitals–local spin density method including nonlocal corrections to the exchange and correlation energy. A highly flexible basis set is used and the effects of introducing additional diffuse basis functions are examined. By comparison of the results for atomic Br and Br2 with those from very accurate correlated ab initio calculations the quality of the present method is established. Based on these results neutral and singly charged Br3, Br4 and Br5 are investigated, for which very few accurate data exist in literature. Geometries, harmonic vibrational frequencies, ionization potentials, electron affinities and charge distributions are reported and found in satisfactory agreement with available experimental data.

DFT study of hydrogen-bonded dimers and tetramer of glyoxilic acid oxime

Abstract DFT study of hydrogen-bonded dimers and tetramer of glyoxilic acid oxime (GAO) has been performed at B3LYP/6-31G* and B3LYP/6-31++G** levels of the theory. The N⋯Hue5f8O and O⋯Hue5f8O hydrogen bondings in the self-assembling structures studied have been estimated from intermolecular distances, enthalpy of stabilization, hydrogen-bonding energies and AIM electron density at the hydrogen bond critical points. The calculated hydrogen-bonding energies of various GAO dimers suggested a cooperative interaction in the cyclic dimers and tetramer. The comparative study of chain aggregate with both head-to-head and tail-to-tail bondings and chain aggregate only with head-to-tail bondings, showed that the latter is enthalpically preferred in agreement with the crystal structure of GAO. Harmonic frequencies for the monomer, five dimers and tetramer have been calculated and discussed as to the changes in the most sensitive to the complexation vibrations and as to the strengths of the O⋯Hue5f8O and N⋯Hue5f8O hydrogen bondings. Vibrational analysis at B3LYP/6-31G* level confirmed the suggestion for a cooperativity in the cyclic H-bonded complexes. Natural population analysis was performed to predict electrostatic interactions in the cyclic H-bonded complexes. The π-delocalization was estimated on the basis of the calculated AIM ellipticity.

IR and Raman study of Pt(II) and Pd(II) complexes of amino substituted phosphine oxides: Normal coordinate analysis

Abstract IR and Raman spectra of Pt(dapo) 2 Cl 2 and Pd(dapo) 2 Cl 2 (dapo=dimethyl(aminomethyl)phosphine oxide) have been measured in the 200–4000 cm −1 frequency range. Both the IR and Raman spectra show that dimethyl(aminomethyl)phosphine oxide ligands are monodentate coordinate. The results from the normal coordinate analysis calculations confirm the monodentate coordination of the ligands in agreement with some literature data. For Pd(dapo) 2 Cl 2 complex the possibility for bidentate coordination of one dapo ligand is also considered.

Conformational stability and vibrational spectrum of glyoxilic acid oxime predicted from ab initio study

Abstract The conformational stability of glyoxilic acid oxime (HOOC–CH–NOH) (GAO) and its anions has been studied by ab initio calculations at different levels of the theory, HF/6-311G ∗∗ , MP2/6-311G ∗∗ and B3LYP/6-311G ∗∗ . Geometry optimization was performed for 16 conformations of GAO and five anions in C s symmetry. The interconversion pathways for the four lowest energy conformers as well as the corresponding transition states have been investigated using QST3 and IRC techniques. The minima and the transition states obtained were estimated by calculations of the vibrational frequencies. The energy barriers of three interconversions, ectt–ecct, ectt–ettt and ectt–zccc, have been estimated. Vibrational spectra and IR intensities of the lowest energy conformers, zccc, ectt, ettt and ecct, have been calculated and discussed at HF/6-311G ∗∗ optimized geometries.

Schwingungsspektren und Normalkoordinatenanalysen sterisch überladener Silane: Tetrakis(trimethylsilyl)silan und Hexakis(trimethylsilyl)disilan

Zusammenfassung The infrared and Raman vibrational spectra of (Me3Si)4Si and (Me3Si)3SiSi(SiMe3)3 as well as of their perdeuterated derivatives have been measured and assigned with the aid of normal coordinate analyses. SiSi force constants were calculated for these strained molecules. They are considerably smaller than force constants of disilanes or trisilanes. Zusammenfassung Die Infrarot- und Ramanspektren von (Me3Si)4Si und (Me3Si)3SiSi(SiMe3)3 sowie ihrer perdeuterierten Derivate wurden aufgenommen und mit Hilfe von Normalkoordinatenanalysen zugeordnet. Die fur diese gespannten Molekule errechneten SiSi-Valenzkraftkonstanten sind deutlich kleiner als jene von Disilanen oder Trisilanen.

Synthesis and Spectroscopic Study of a New Lanthanum(III) Complex of 3,3¿-Benzylidenedi-4-hydroxycoumarin

Abstract The coordination ability of 3,3′‐benzylidenedi‐4‐hydroxycoumarin (H2bhc) has been proved in a complexation reaction with lanthanum(III) ion. The new lanthanum(III) complex of bhc2− was studied by elemental analyses, mass spectra, 1H, 13C NMR, and IR spectroscopy. The data obtained are in agreement with the metal:ligand ratio of 1:l, and the formula La(bhc)(OH)(H2O), where bhc2− = C25H14O6 2−. The calculated condensed Fukui functions for bhc2− predicted that both hydroxyl and carbonyl oxygen atoms are probable reactive sites for coordination to the metal. The vibrational analysis of the lanthanum(III) complex, free H2bhc, bhc2−, and 4‐hydroxycoumarin showed that in the La(III) complex the ligand coordinates to the metal ion through both deprotonated hydroxyl groups. The participation of both carbonyl groups in coordination to the metal ion was confirmed by the significant shift of ν(C˭O) to lower wave number.

Vibrational study of new Pt(II) and Pd(II) complexes with functionalized nitrogen-containing tertiary phosphine oxides. Ab initio study of ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline

Vibrational study of new Pt(II) and Pd(II) complexes of functionalized nitrogen-containing tertiary phosphine oxides, namely ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline (o-, m- and p-dpmoa), (CH3)2P(O)CH2OC6H4NH2, have been presented. Geometry optimization of the ligands was performed at HF/6-31G* and B3LYP/6-31G* levels of the theory. Harmonic frequencies were calculated at HF/6-31G* optimized geometries. Relative gas-phase and solution-phase (H2O and CH3CN) basicities of o-, m- and p-dpmoa ligands have been determined by ab initio calculations at STO-3G level with the Onsager reaction field model. On the basis of the vibrational study, physical and analytical data it was suggested that the ligands in the complexes studied coordinate through the amino group and form square-planar platinum and palladium complexes of the general formula ML2Cl2 (M = Pt, Pd, L = o-, m- and p-dpmoa).

Synthesis and vibrational study of platinum(II) and palladium(II) complexes of glyoxilic acid oxime

Abstract New platinum(II) and palladium(II) complexes of glyoxilic acid oxime (gao) have been prepared and characterised by infrared (4000–150 cm−1) and Raman (4000–200 cm−1) spectra. The gao acts as bidentate ligand bonding through the oxime nitrogen and carboxyl oxygen atoms to form neutral bis-chelate square-planar complexes. The lowest energy conformer of the gao ligand (ectt) was selected among 16 theoretically possible conformers on the basis of ab initio calculations at HF/3-21G*, HF/6-31G* and HF/6-311** levels of the theory from which structural parameters and conformational stabilities have been obtained. A complete vibrational assignment of the gao was performed for the lowest energy ectt conformer on the basis of ab initio optimised parameters and normal coordinate analysis calculations (PED). NCA calculations of the complexes studied were also performed.

Novel platinum (II) complexes with (pyridyloxymethylene)dimethylphosphine oxides-synthesis, IR and Raman study.: Normal coordinate analysis

The synthesis and spectroscopic properties of novel platinum (II) halide complexes with (4-pyridyloxymethylene)dimethylphosphine oxide (p-tpo) and (3-pyridyloxymethylene)dimethylphosphine oxide (m-tpo) are reported. The vibrational (IR and Raman) and physical data are in agreement with suggested stoicheiometry ML2Cl2 (Lp-tpo and m-tpo) and cis-square planar PtN2Cl2 configuration. Both p-tpo and m-tpo act as monodentate ligands and coordinate through the pyridyloxymethylene ring nitrogen to the metal ion. IR and Raman spectra exhibit no shift to lower frequencies of the n(PO) and thus provide unambiguous evidence for a free PO oxygen. Normal coordinate analysis (NCA) calculations of both ligands confirm the monodentate coordination of the ligands.