Journal of Structural Chemistry

Tarakanova, E.; Yukhnevich, G.

doi: 10.1007/s10947-009-0150-8pmid: N/A

The applicability of the equation $$ e^{ - ((r_1 - r_0 )/b)^{5/3} } + e^{ - ((r_2 - r_0 )/b)^{5/3} } = 1 $$ has been studied. The equation defines the relationship between the experimental values of the covalent (r 1) and hydrogen (r 2) bond lengths in O-H...O bridges for describing the relation between the experimental interatomic distances in N-H...N bridges and the parameters of X-H...X fragments (X = O, N, F, Cl) calculated by the density functional method (B3LYP/6-31++G(d,p)) for neutral, positive, and negative molecular complexes. Here r 0 is the mean value of the X-H bond length in free molecules; r sym is the X...H distance in the symmetrical bridge; and b is the coefficient defined by the equation b = (r sym − r 0)/(ln2)3/5. This equation allows us to adequately describe the relationships between bond lengths in nearly linear hydrogen bridges formed by oxygen, nitrogen, fluorine, and chlorine atoms. It is thus universal and can be used in studies of a wide range of substances.

Zhuravlev, Yu.; Korabelnikov, D.

doi: 10.1007/s10947-009-0151-7pmid: N/A

The densities of states, atomic charges, and partial components were calculated by the B3LYP method for lithium, sodium, and potassium nitrites, nitrates, chlorates, perchlorates, sulfites, and sulfates using a localized basis of atomic orbitals and CRYSTAL06 software. The calculated densities of states N(E) are in good agreement with the experimental photoelectron spectrum (UPS). The crystallographically nonequivalent metal and oxygen atoms are in different charged states, which leads to a splitting of the N(E) bands.

Litinskii, G.; Krikunova, V.

doi: 10.1007/s10947-009-0152-6pmid: N/A

A simple generalization of the free electron model is suggested for describing the heteroatomic conjugate molecules and obtaining analytical equations for the energy levels of these systems. The δ-like potential is used as a potential of a heteroatom in this model, and the energy levels are obtained as corrections for first order perturbation theory.

Antina, E.; Belova, N.; Berezin, M.; Girichev, G.; Giricheva, N.; Zakharov, A.; Petrova, A.; Shlykov, S.

doi: 10.1007/s10947-009-0153-5pmid: N/A

The molecular structure of zinc acetylacetonate was studied in a simultaneous electron diffraction and mass spectrometric experiment at 376(7) K and by quantum-chemical calculations. The Zn(acac)2 molecule has a structure of D 2d symmetry with the chelate rings lying in mutually perpendicular planes. The main geometrical parameters of the molecule are r h1(Zn-O) = 1.942(4) Å, r h1(C-O) = 1.279(3) Å, r h1(C-Cr) = 1.398(3) Å, r h1(C-C m ) = 1.504(5) Å, ∠(O-Zn-O) = 93.2(7)°, ∠(Zn-O-C) = 125.9(7)°, ∠(C-Cr-C) = 125.8(14)°, ∠(O-C-C m ) = 115.2(9)°. The effective rotation angle of methyl groups is close to 30°, which is indicative of the free rotation of these groups. The vibration frequencies were obtained by quantumchemical calculations, and the IR spectrum of the Zn(acac)2 molecule was interpreted.

Peng, S.; Li, X.; Zhang, Y.; Zhao, S.

doi: 10.1007/s10947-009-0154-4pmid: N/A

A series of exohedrally functionalized derivatives of the D 6-symmetrical C24 fullerene, with attached -CH2OH, -CONH2, -COOH, and -COH chemical groups, have been investigated by using density-functional theory approach at the UB3LYP/6-31G(d) level. According to the calculated results, the C24(COOH) is the most stable structure, with −73.58 kcal mol−1 value for the functionalization reaction energy and 3.16 eV for the dissociation energy, while C24(CONH2) displays the largest dipole moment (3.09 D). It was also found that the HOMO-LUMO energy gaps, the vertical ionization potentials (VIP), and vertical electron affinities (VEA) of these functionalized derivatives are similar to those of the more stable C24 fullerene. Moreover, their corresponding HOMO and LUMO orbitals are mainly associated with the surface of the cage. Also, the vibrational frequencies of these derivatives are discussed. It was concluded that it would be possible to produce novel species for bio-medical applications by attaching selected chemical groups.

Ivshina, N.; Bartashevich, E.; Potemkin, V.; Grishina, M.; Ishmetova, R.; Rusinov, G.; Latosh, N.; Slepukhin, P.; Charushin, V.

doi: 10.1007/s10947-009-0155-3pmid: N/A

The complexation of 3,6-substituted 1,2,4,5-tetrazines with benzotriazole was studied theoretically based on the vibrational spectra. For model complexes, the energy was minimized by the geometrical parameters, and the spectral characteristics were calculated by the PM3 method. The shift of the bond vibration frequencies of the atoms involved in complexation after the formation of different various intermolecular contacts was determined. This made it possible to determine the type of intermolecular interaction and suggest the structures of the complexes.

Chernobay, G.; Chesalov, Yu.; Boldyreva, E.

doi: 10.1007/s10947-009-0156-2pmid: N/A

The IR spectra of L-serylglycine (H 3 + N-CH(CH2-OH)-CO-NH-CH2-COO−), recorded at 413–93 K, have been studied, and the observed frequencies were assigned. Based on the results, we concluded that the stability of hydrogen bonds in the structure changed as a result of variation of temperature. The conclusions were compared with the results of IR spectroscopic studies of the crystals of α-glycylglycine, DL-serine, and glycine under the similar conditions.

Il’yasov, S.; Lobanova, A.; Bagryanskaya, I.; Rybalova, T.; Gatilov, Yu.

doi: 10.1007/s10947-009-0157-1pmid: N/A

The properties and behavior of dinitrourea and its potassium and dipotassium salts in different solvents have been studied by IR and UV spectroscopy. In different media, dinitrourea can exist in several tautomeric forms. An XRD study of the potassium and dipotassium salts of dinitrourea revealed a tendency toward equalization of the bond lengths of the C-N−-NO2 fragments compared with those of C-NH-NO2, which agrees with the results of quantum-chemical calculations.

Shundrin, L.; Melnikov, P.; Polenov, E.

doi: 10.1007/s10947-009-0158-0pmid: N/A

The temperature dependences of the EPR spectrum of the 2-trifluoromethylnitrobenzene radical anion in DMF:H2O mixtures, caused by the dynamic modulation of the fluorine isotropic hyperfine interaction by the hindered internal rotation of the CF3 group, have been measured and reconstructed numerically. The activation energy of rotation (E F) and the dynamic mode depended on the water content in the mixture. For mixtures with a molar fraction of water χ = 0, 0.186, 0.315, 0.409, 0.534, 0.650, 0.810, and 0.910, E F = 34.70 kJ/mol, 41.31 kJ/mol, 42.30 kJ/mol, 38.41 kJ/mol, 37.01 kJ/mol, 34.51 kJ/mol, 24.10 kJ/mol, and 21.78 kJ/mol, respectively. For χ = 0.186 in the temperature ranges accessible for measurements, the dynamic exchange is slow; for χ = 0.315, 0.409, 0.534, and 0.650, transitions from slow to intermediate and fast exchange take place; for χ = 0.810 and 0.910 in the temperature ranges under study T ∈ [252, 309]; [254, 297] (K), the exchange is fast. In the range 0.6 < χ < 0.9, E F decreased drastically, and the activation energy of rotational diffusion (E r) of the radical anion became maximum, which corresponds to the range of the compositions of DMF:H2O with maximum deviations from the ideal state.

Moroz, È.; Kriventsov, V.; Kochubei, D.

doi: 10.1007/s10947-009-0159-zpmid: N/A

The supported Pt/SiO2 (EuroPt-1) catalyst has been studied by the radial distribution of electron density (RDED) and EXAFS techniques. The starting sample of the catalyst was stored in air, not subjected to any further treatment, and contained metal platinum Pt0 and platinum oxide PtO in a ∼1:2 ratio. An analysis of the EXAFS data was based on three possible structural models of platinum particles. Model 1 suggested that there was one Pt-Pt short contact, which was the same in the bulk of the particles and on the surface. Model 2 considered two different Pt-Pt distances for the particle volume and surface. For model 3, we additionally assumed that the corresponding Debye-Waller factors differed. For the oxidized sample, model 2 was most reliable, and the Pt-Pt distance between the surface atoms was shortened by ∼0.14 Å. For the reduced samples, the structural data obtained are consistent with model 3.