The molecular structure of copper phthalocyanine was determined by synchronous gas-phase electron diffraction(GED) and mass spectrometric experiment and quantumchemical calculations. The DFT calculations with employing different basis sets give a molecular structure with D 4h symmetry that agreed satisfactorily the one found in experiment at 497 ± 5°C. The most important structural parameters are (GED): r h1 (Cu-N) = 1.949(5) Å , r h1 (N1-C1) = 1.381(5) Å , r h1 (C1-N2) = 1.325(5) Å , r h1 (C1-C2) = 1.459(5) Å , r h1 (C2-C3) = 1.399(4) Å , r h1 (C3-C4) = 1.397(4) Å , \CuN1C1 = 125.9(2)°, \N1C1N2 = 128.2(5)°, \C8N3C9 = 121.9(7)°, \N1C1C2 = 109.5(5)°, \C2C7C6 = 121.3(2)°.
Gold(III) complexes with different ligands can provide researchers with a measure against pathogenic microorganisms with antibiotic resistance. We reported in our previous paper that the UV-Vis spectra of different protonated species of complexes formed by gold(III) and five hydrazones derived from pyridoxal 5′-phosphate are similar to each other and to the spectra of free protonated hydrazones. The present paper focuses on the reasons of the noted similarity in electron absorption spectra. The geometry of different protonated species of complexes of gold(III) and hydrazones (15 structures in total) was optimized using the density functional theory (DFT). The coordination polyhedron of gold(III) bond critical points were further studied to identify the symmetry of the gold coordination sphere and the type of interactions that hold the complex together. The UV-Vis spectra were calculated using TD DFT methods. The molecular orbitals were analyzed to interpret the calculated spectra.
We have designed and constructed a combined experimental setup for synchronous measurements of electron diffraction patterns and mass-spectra of gas samples. Test measurements have been performed for acetic acid at two temperatures, 296 K and 457 K. Electron diffraction data have been analyzed taking into account mass spectra measured in the same experiments. From the diffraction intensities, molecular structures and mole fractions of the acetic acid monomer and dimer have been refined. The obtained results demonstrate the importance of measuring mass spectra in gas electron diffraction experiments. In particular, it is possible to detect the sample decomposition, which can be used for the optimization of experimental conditions and for the data interpretation. The length of the hydrogen bond in the acetic acid dimer determined in this work, re(O⋯H) = 1.657(9) Å, is in good agreement with modern theoretical predictions. We recommend measuring the diffraction patterns of acetic acid for the calibration of the sample pressure in the diffraction volume.
Modification of porphyrins by a replacement of N atom(s) with a heteroatom(s) resulted in the so called heteroporphyrins which exhibit interesting physicochemical properties. In this work, the spectral properties of ions and neutral forms of 5,10,15,20-tetraphenyl-21,23-dithia porphyrin (S 2 PP) and 5,10,15,20-tetraphenyl-21-thia-porphyrin (HSPP) have been investigated. According to the spectrophotometric analysis in acetonitrile -perchloric acid solution, the dication H 2 S 2 PP 2 + reveals an ability to coordinate two ClO 4 À anions, which was not found for H 3 SPP 2 + . This fact, as observed in the UV-Vis absorption spectra, indicates the possibility of exhibiting chemosensory properties of S 2 PP molecules. The geometries of the neutral and ionized forms were derived from B3LYP/cc-pVTZ calculations. The perimeters of the cavities increase in the series: H 2 PP!HSPP!S 2 PP. This trend is kept in case of the ionized forms; the protonation expands the cavity perimeter. Electron density distributions were analyzed in terms of quantum theory of atoms in molecules (QTAIM). The UV-vis spectra simulated on the base of the TD-DFT calculations match the experimental results.
The molecular structure of 4-nitropyridine N-oxide, 4-NO 2 -PyO, has been determined by gas-phase electron diffraction monitored by mass spectrometry (GED/MS) and by quantum chemical calculations (DFT and MP2). Comparison of these results with those for non-substituted pyridine N-oxide and 4methylpyridine N-oxide CH 3 -PyO, demonstrate strong substitution effects on structural parameters and electron density distribution. The presence of the electron-withdrawing eNO 2 group in para-position of 4-NO 2 -PyO results in an increase of the ipso-angle and a decrease of the semipolar bond length r(N/O) in comparison to the non-substituted PyO. The presence of the electron-donating eCH 3 group in 4-CH 3 -PyO leads to opposite structural changes. Electron density distribution in pyridine-N-oxide and its two substituted compounds are discussed in terms of natural bond orbitals (NBO) and quantum theory atoms in molecule (QTAIM).
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