Infrared spectroscopic study of hydrogen-bonded complexes of triphenylcarbinol and triphenylsilanol with ethers

Hydrogen bonding between triphenylcarbinol and triphenylsilanol with eight ethers of different types was investigated. Shifts of OH frequencies of the formed complexes were recorded in dilute CCl₄ solutions of the components. The observed shifts were correlated with the nucleophilicity parameters of the ethers, with their polarity and polarizability factors, their pK_a values and association constants of the ether-‘ol’ complexes. The silanol-ether interaction is perceptibly stronger than the ether-carbinol one. The acid-base mechanism in the interactions dominates, but polar and steric factors play a significant role in some cases.     

Infrared spectroscopic studies of transition metal complexes and polarizability effect

The literature data on substituent influence on the CS, CN, NC, NN, and NO stretching frequencies (ν) in the IR spectra and in specific cases on their respective stretching force constants (k) have been analyzed for 28 series of the transition metal complexes. The ν and k values were first established to depend not only on the inductive and resonance effects but on the polarizability of substituents as well. The contribution of the polarizability effect varies from 0 to 57% with the type of series.     

Density functional studies on hydrogen-bonded complexes

Results of density functional calculations will be reported on a variety of hydrogen-bonded complexes, ranging from weak to strong hydrogen bonds. The charged bimolecular NH₃? NH complex and the dimers of water and methanol were investigated using a local approximation of the exchange-correlation potential and two different nonlocal potentials with gradient corrections. In the case of the water dimers, the dependence of the results on the extension of the atomic basis set has also been investigated. The equilibrium structures of all complexes have been determined. Dipole moments, hydrogen-bond lengths, and hydrogen-bonding energies, calculated with corrections for the basis-set superposition error using the counterpoise method, have been found to agree well with the corresponding experimental results. © 1994 John Wiley & Sons, Inc.     

Resonance Raman spectroscopic studies of hydroperoxo-myoglobin at cryogenic temperatures

In agreement with previous reports (Gasyna, Z. FEBS Lett. 1979, 106, 213-218 and Leibl, W.; Nitschke, W.; Huettermann, J. Biochim. Biophys. Acta 1986, 870, 20-30) radiolytically reduced samples of oxygenated myoglobin at cryogenic temperatures have been shown by optical absorption and EPR studies to produce directly the peroxo-bound myoglobin at 77 K. Annealing to temperatures near 185 K induces proton transfer, resulting in the formation of the hydroperoxo heme derivative. Resonance Raman studies of the annealed samples has permitted, for the first time, the direct observation of the key nu(Fe-O) stretching mode of the physiologically important Fe-OOH fragment of this ubiquitous intermediate. The assignment of this mode to a feature appearing at 617 cm(-1) is strongly supported by documentation of a 25 cm(-1) shift to lower energy upon substitution with (18)O(2) and by a 5 cm(-1) shift to lower energy for samples prepared in solutions of deuterated solvent.     

Infrared spectroscopic studies of substituted 1,2-diphenylcyclopropenes

For the investigation of the character of a substituent at position 3 of the ring and the double bond, i.r. spectra of substituted 1,2-diphenilcyclopropenes were studied. Frequencies and integral intensities of the double bond stretching vibration band were determined. It was proved that changes of the band's parameters caused by intermolecular interactions are substantially smaller than effects observed by changing the substituent. On the basis of correlation between changes of intensities of the ν_CC band and resonance constants of substituents and the character of the frequency dependence, a conclusion was reached on the resonance interactions of the substituent with σ_Walsh —MO of the cycle.     

Infrared and Raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions

Infrared (IR), far-infrared (far-IR) and Raman spectra have been recorded of the hydrated lanthanide(III) trifluoromethanesulfonates, [Ln(OH2)9](CF3SO3)3, (Ln=La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), and also for the deuterated [La(OD2)9](CF3SO3)3 compound. This has enabled complete assignments of all seven metal-oxygen stretching modes for the first time. Force constant calculations have been performed for an LnO9(3+) moiety, with a tricapped trigonal prismatic oxygen atom arrangement in D3h point group symmetry. The lanthanide contraction in reflected in continuously increasing trends for the averaged LnO stretching frequencies and force constants with increasing inverse of ionic radii. The stretching force constants increased from 0.81 to 1.16 Ncm-1 for the LnO6 prism in the series from La to Lu, while those for the capping LnO3 bonds increased from 0.49 to 0.65 Ncm-1. The LnO stretching force constants showed a smooth correlation with the LnO bond distances to the prism oxygen atoms, while the correlation to the LnO capping oxygen atoms has a different shape, reflecting the increased ligand-ligand repulsion with decreasing lanthanide ion size.     

Infrared studies of cryogenic transitions in poly(ethylene terephthalate)

Measurements of infrared absorbance as a function of temperature down to 77°K have been made on poly(ethylene terephthalate). Transitions observed by other techniques such as torsion pendulum measurements are reflected in the infrared measurements by an abrupt change in the slope of the absorbance versus temperature. The infrared measurements are made on bands of known structural origin so the structures contributing to each transition can be determined. The β transition is shown by infrared to be a composite of two peaks with the lower-temperature portion arising from the amorphous regions and the higher-temperature portion from the crystalline regions.     

Infrared spectroscopic and photochemical study of water-ozone complexes in solid argon

Infrared spectroscopy has been coupled with the matrix isolation technique, firstly for a study of the molecular complexes between ozone and water, secondly to investigate the mechanism of the water photooxidation by ozone at 15 K by UV light. The 1:1, 1:2 and 2:1 complexes are isolated and mainly characterized by a shift in the infrared absorption of the H₂O (D₂O) submolecule. Force field calculations involving anharmonicity corrections allows us to conclude into the non-equivalence of the two OH oscillators within the 1:1 complex. This result suggests the formation of a very weak hydrogen bond of the type HOH...OO₂. By photolysis of the water-ozone mixture in solid argon (λ < 310 nm), formation of H₂O₂ with very small amounts of O₂H and OH is observed. This process occurs through the reaction between the O(¹D) atom generated by photodissociation of O₃ belonging to the one H₂O: O₃ pair and the water molecule of the same pair, without diffusion of the oxygen atom.     

IR-laser induced interconversions of hydrogen-bonded dimers in cryogenic matrices

IR-laser induced interconversions of hydrogen-bonded alcohol dimers have been studied in cryogenic matrices by means of FTIR spectroscopy and a tunable F-center laser as photolysis source. Four different conformational forms of the open chain methanol dimer have been identified in solid nitrogen matrices. These conformations have been interconverted by selective vibrational excitation into the OH stretching absorption bands.     

Infrared spectroscopic studies of free-base tetraphenylporphine and its dication

We present here the infrared absorption spectra of free-base tetraphenylporphine and its dication. Most of the allowed IR bands of porphyrin skeletal are observed in pairs due to two-fold symmetry of the free-base tetraphenylporphine. Observation of some new bands, disappearance of few bands in the IR spectrum of dication are interpreted on the basis of point group symmetry S4. Intensity change in the observed bands due to vibrational motion of the phenyl rings for dication is also explained on the basis of symmetry of dication. Sharing of electrons of the B(1u) orbitals by the two added protons are responsible for the shifts in the position of certain IR bands for dication.     

纳米尺寸氧化铝的红外光谱研究

用改进的溶胶-凝胶法制备了均一粒径的纳米尺寸Al~2O~3样品,在相同仪器条件下测得红外光谱。研究了烧结温度、反应物前驱体的pH值和分散介质对IR谱的影响。结果表明,纳米氧化铝IR谱的峰值、强度和带宽有规律变化与制备因素、颗粒尺寸及结构有关。当粒径变小处于表面的原子数增多时,与Al~2O~3纵向声子跃迁有关的谱带强度有增强趋势。     

Infrared spectroscopic studies of dihydrogen adsorbed on oxide surfaces

The complex structure of the IR spectra of dihydrogen adsorbed at 60–77 K on several oxide adsorbents, in the 4300–4000 cm^–1 region, is supposed to be due to the combination of ^v H-H with a low-frequency vibration of the H₂ molecule with respect to the surface.

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4300–4000 ^–1 - H₂, 60–77 . , ^v H-H .

     

IR spectroscopic studies of some uranyl tetrachloride complexes

The IR spectra of dipotassium, dirubidium and diammonium uranyl tetrachloride hydrates (K₂UO₂Cl₄·3H₂O, Rb₂UO₂Cl₄·H₂O, (NH₄)₂UO₂Cl₄·4H₂O) have been measured in the region from 4000 down to 30 cm⁻¹. A normal coordinate analysis of the (UO₂Cl₄)²⁻ ion apart from the K⁺, Rb⁺ and NH₄⁺ ions has been made using Wilson's FG matrix method. The force constants associated with the UO and UCl bonds have been obtained on the basis of both the force models of modified Urey-Bradley and valence force fields. An effort has been directed towards the understanding of the uranyl bond weakening with coordination of the ligands. It has been suggested that this bond weakening is caused by charge transfer from the ligands to the uranium atom.     

Synthesis and spectroscopic studies of europium chelate complexes

The synthesis of the mixed complexes of the europium ion with 2-pyridylcarbinol-N-oxide, and 2,2′-dipyridyl and 1,10-phenanthroline were prepared. The compounds, were characterized by means of chemical analyses, vibrational spectra, molar conductivities, and electronic spectra. The emission of the [EuL₃, phen] complex at 10 K is very intense and an assignment of the point symmetry of the Eu(III) ion has been made.     

Infrared spectroscopic studies on interactions in trifluoroacetic acid-sulfur dioxide systems

The method of frustrated multiple internal reflection (FMIR) infrared spectroscopy was used to study the nature of intermediates that formed upon oxidation of sulfur dioxide in trifluoroacetic acid (TFA) of various concentrations at 30°C. It was established that sulfur dioxide bound to a complex with TFA is oxidized by dissolved oxygen in systems that contain 99.9 and 55.5% trifluoroacetic acid.     

Infrared and raman spectroscopic investigations of cadmium tetracyanonickelate complexes of aminopyridines

The infrared and Raman spectra of three new complexes of the formula CdL₂Ni(CN)₄ {L = 2-aminopyridine or 2-amino-4-methylpyridine} and Cd(L) (NH₃)-Ni(CN)₄ {L = 2-amino-3-methylpyridine} are reported. It is concluded that the ring nitrogen and not the amino nitrogen is involved in complex formation. Vibrational assignments for all the bands observed are proposed. The complexes are shown to have a structure consisting of two dimensional polymeric layers formed with Ni(CN)₄ ions bridged by CdL₂ {L = 2-aminopy or 2-amino-4-methylpy} or Cd(NH₃)(L) {L = 2-amino-3-methylpy} cations. Several modes of coordinated aminopyridines have upward wavenumber shifts in comparison to those of the free molecules. These are thought to be due to the coupling of the internal modes of aminopyridines with the MN vibrations.     

Infrared and MÖSSBAUER spectroscopic studies on complexes of Hal2SnIV moieties with tridentate ligands

Novel complexes hal₂Sntrid, where hal ? Cl, Br, and trid^2? are dianions of ?planar”? tridentate ligands with ONO and SNO donor basic atoms, were synthesized and structurally investigated in the solid state mainly by far infrared and MÖSSBAUER spectroscopy. Possible configurations were advanced and discussed, and it was concluded that the most probable is a monomeric trigonal bipyramidal structure for all compounds, although polymers, or dimers with O or Cl bridges, were not a priori excluded, in a special way for Br₂Sntrid.     

Enthalpies of hydrogen-bonded butylamine-chloroform complexes

Enthalpies of mixing of isomeric butylamine with chloroform were determined at 30°C by a Calvet-type microcalorimeter. The system showed highly exothermic behaviour due to hydrogen-bonded complex formation on mixing. The enthalpies of complex formation were calculated by means of a thermo-chemical cycle and the values vary from 1-aminobutane to 2-amino-2-propane complexes. NCL Communication No. 4255     

Are matrix isolated species really isolated? Infrared spectroscopic and theoretical studies of noble gas-transition metal oxide complexes

In this review, we summarize our recent results on matrix isolation infrared spectroscopic studies and theoretical investigations of noble gas-transition metal oxide complexes. The results show that some transition metal oxide species trapped in solid noble gas matrices are chemically coordinated by one or multiple noble gas atoms forming noble gas complexes and, hence, cannot be regarded as isolated species. Noble gas coordination alters the vibrational frequencies as well as the geometric and electronic s...