Description of Molecular Distortions: IV. Relationships Between the Distortion and the Hydrogen Bond Strength for Some Compounds Containing HSO4 Ions

Several methods are known for describing the distortions of tetrahedral molecules. In the present paper, some correlations between the hydrogen bond strength and the different measures for the distortions of HS04~ ions are evaluated. In terms of the distortion indices the rasults reflect similar trends to those calculated for phosphates1. It is found that weaker hydrogen bonding as accompanied by larger distortions of the HS04 tetrahedra

The Motion of the Benzene Molecules in the Host Lattices of M(NH3)2M’(CN)4·2C6H6 Clathrates

In our previous report1 we discussed host-guest interactions in a series of Hofmann-type clathrates of the general formula: M(NH3)2M’(CN)4-2C6H6, where M is Ni, Fe, Co, Zn, Mn and Cd and M’ is Ni. It was found that the splitting of the band due to CH out-of-plane vibration in benzene, at liquid nitrogen temperature, (at around 985 cm-1), increases as the volume of the tetragonal unit cell decreases. A similar behaviour we recorded in a series of benzene clathrate compounds (isostructural with Hofmann-type clathrates) in which the M’ metal was replaced by Pt or Pd, and it was interpreted as a consequence of a »free« rotation in the benzene molecules at room temperature but hindered at low temperatures. The magnitude of the splitting of this band, at liquid nitrogen temperatures, for all the clathrates studied was correlated with the volume of the tetragonal unit cell and with the effective ionic radii of the octahedrally coordinated metal M and the square- planar coordinated metal M’. The slope of Ai< vs, V(Unitcell) is =-100 cm"1 nm-3

Correlations Between Effective Crystal Radii and Unit Cell Volume in Tutton Salts

The unit cell volumes of 29 Tutton salts (the general formula of which is M2IMn(XY4)2 • 6H2O) were retrieved from the literature. Assuming that the unit cell volume may be represented by a function of the type: V = a + b R(M+) + c J?(M2 +) + d RQt-Y) + e Ey (R(M+) where R(M2+) are the effective crystal radii of the uni- and divalent cations, respectively, J?(X-Y) is the X-Y distance in the tetrahedral anion and Ey is the Pauling electronegativity of the Y atoms, the multiple linear regression analysis was applied. The agreement between the observed and the predicted values of V is rather good (adjusted r2 = 0.966), thus allowing to predict the values for effective crystal radii of ions that have not been published so far. In line with this, the Ru-Tutton salts are predicted to be low-spin Ru2+ hexaaquacomplexes. Some points concerning the possibility of the existence of particular iso- morphs are also discussed

Structure and Vibrational Spectra of Pyridine Solvated Solid Bis(Pyridine)silver(I) Perchlorate, [Agpy₂ClO₄]·0.5py

A hemipyridine solvate of bis(pyridine)silver(I) perchlorate, [Agpy2ClO4]·0.5py (compound 1) was prepared and characterized by single crystal X-ray analysis and vibrational spectroscopy (R and low-temperature Raman). Compound 1 was prepared via the trituration of [Agpy2ClO4] and 4[Agpy2ClO4]·[Agpy4]ClO4 (as the source of the solvate pyridine) in a mixed solvent of acetone:benzene =1:1 (v = v) at room temperature. The monoclinic crystals of compound 1 were found to be isomorphic with the analogous permanganate complex (a = 19.1093(16) Å, b = 7.7016(8) Å, c = 20.6915(19) Å, β = 105.515(7)°; space group: C2/c). Two [Agpy2]+ cations formed a dimeric unit [Agpy2ClO4]2, and each silver ion was connected to two ClO4− anions via oxygen atoms. The Ag∙∙∙Ag distance was 3.3873(5) Å, the perchlorate ions were coordinated to silver ions, and the Ag∙∙∙O distances were 2.840(2) Å and 2.8749(16) Å in the centrosymmetric rectangle of Ag-O-Ag-O. The stoichiometric ratio of the monomer [Agpy2ClO4] and the solvent pyridine was 1:0.5. The guest pyridine occupied 527.2 Å3, which was 18.0% of the volume of the unit cell. There was no additional residual solvent-accessible void in the crystal lattice. The solvate pyridine was connected via its a-CH to one of the O atoms of the perchlorate anion. Correlation analysis, as well as IR and low-temperature Raman studies, were performed to assign all perchlorate and pyridine vibrational modes. The solvate and coordinated pyridine bands in the IR and Raman spectra were not distinguishable. A perchlorate contribution via Ag-O coordination to low-frequency Raman bands was also assigned

Optical and Electron Spectrometry of Molecules of Biological Interest

Optical absorption and emission spectroscopy together with low energy electron interaction (elastic scattering, excitation, ionization, resonances) with biologically relevant molecules (nitrogen, oxygen, water, alcohols, tetrahydrofuran, tetrahydrofurfuril alcohol, 3-hydroxytetrahydrofuran, pyrimidine, glycine, alanine) are studied in order to understand radiation damage and to investigate the presence of pollutants in the atmosphere. Versatile high resolution electron spectrometers are used in the present study of electron-molecule interactions. Energy loss spectra were recorded for these molecules in order to identify electronic transitions from ground state to both allowed and optically forbidden states. Optical emission spectra have been recorded from gas discharge processes by low resolution optical spectrometer (Ocean Optics 2000). Also, electronic spectra were compared with high resolution synchrotron photoabsorption spectra where these spectra had been available. Experimental methods of absorption-based laser spectroscopy were reviewed being of the most widely used analytical tools for detection of a specific molecule and quantitative measurements, based on the Beer-Lambert absorption law

Optical and Electron Spectrometry of Molecules of Biological Interest

Optical absorption and emission spectroscopy together with low energy electron interaction (elastic scattering, excitation, ionization, resonances) with biologically relevant molecules (nitrogen, oxygen, water, alcohols, tetrahydrofuran, tetrahydrofurfuril alcohol, 3-hydroxytetrahydrofuran, pyrimidine, glycine, alanine) are studied in order to understand radiation damage and to investigate the presence of pollutants in the atmosphere. Versatile high resolution electron spectrometers are used in the present study of electron-molecule interactions. Energy loss spectra were recorded for these molecules in order to identify electronic transitions from ground state to both allowed and optically forbidden states. Optical emission spectra have been recorded from gas discharge processes by low resolution optical spectrometer (Ocean Optics 2000). Also, electronic spectra were compared with high resolution synchrotron photoabsorption spectra where these spectra had been available. Experimental methods of absorption-based laser spectroscopy were reviewed being of the most widely used analytical tools for detection of a specific molecule and quantitative measurements, based on the Beer-Lambert absorption law