The NMR spectra of some fluorinated pyridine derivatives

The ¹H and ¹⁹F spectra of a variety of mono- and di- fluorinated pyridines are examined, and compared with the corresponding spectra of the pyridinium ions. The magnitudes and signs of the ¹H? ¹⁹F coupling constants are in general in accord with those observed for the corresponding ¹H? ¹H couplings, with an exaggerated range. Large changes in the NMR parameters are observed on protonation of the nitrogen, ³J(H? F) changing sign in some of the α-fluoropyridine derivatives.     

Ultraviolet absorption spectra of some pyridine and nicotine derivatives

Summary Comparison of the ultraviolet spectra of nicotine, N-methylanabasine, and their N-oxides shows that though the characters of the absorption of compounds containing the N-oxide group in the aromatic part of the molecule, on the one hand, and in the hydrogenated part, do not differ considerably, they are nevertheless sufficiently specific for a clear distinction to be drawn.For Communication 3 see [1].     

Molecular spectra and molecular structure of heterocyclic compounds. Infrared and near ultraviolet absorption spectra of pyridine N-oxide derivatives

The infrared and ultraviolet spectra of many pyridine N-oxide derivatives have been studied. Ultraviolet spectra show a strong solvent effect in going from aprotic to hydroxylic solvents due to strong hydrogen bonding. Values of δ H° for several systems CH₃OH/XPyNO in tetra-chloroethylene solution were evaluated by infrared techniques and a linear correlation δ H° vs. δ v OH has been found. Features of the infrared and ultraviolet characteristic absorption bands were also investigated.     

Infrared absorption spectra of pyridine N-oxide and benzoic acid complexes

The infrared absorption spectra in the 4000–1600cm⁻¹ region of some benzoic acid pyridine N-oxide derivative complexes are described.     

Electronic structures of pyridine N-oxide and 4-nitrosopyridine N-oxide

The -electron structure of pyridine N-oxide was calculated by the Pariser-Parr-Pople method, the effect of -polarization of the NO bond upon the valence state ionization potentials and electron affinities being taken into account. By the aid of these results, the -electron structure of 4-nitrosopyridine N-oxide was studied by the composite system method. The calculated transition energies and oscillator strengths can satisfactorly explain the observed electronic absorption spectrum. The 372 m band was ascribed to the charge-transfer transition from the oxygen atom of the NO group to the nitroso group via the pyridine nucleus.     

Synthesis and molecular structures of complexes of TlBrI2 with pyridine N-oxide and some substituted pyridine N-oxides

The following compounds, TlBrI₂(PyO)₂, TlBrI₂(2-PicO)₂, TlBrI₂(3-PicO)₂, TlBrI₂(4-PicO)₂, TlBrI₂(4-Cl-PyO)₂, TlBrI₂(4-CN-PyO)₂, TlBrI₂(4-NO₂-PyO)₂ and TlBrI₂(4-CH₃O-PyO)₂, have been prepared and characterized by elemental analysis. The solids behave as non-electrolytes in acetonitrile solution and are monomers in benzene. Vibrational (IR and Raman) spectra suggest that the most probable structure is that of a trigonal bipyramid with the halogen atoms in equatorial positions and the two ligands in axial positions.     

Electronic spectra and structure of methyl derivatives of 4-nitropyridine N-oxide

The UV spectra of seven methyl derivatives of 4-nitropyridine N-oxide in ethanol have been examined. The electronic spectra were calculated by a modified INDO method. Transition energies, intensities and assignments were compared with UV spectra. Spectroscopic manifestations of intramolecular interaction indicate that methyl groups modify the electronic interaction between the N-oxide and NO₂ groups mainly through a steric strain.Department of Organic Chemistry, University of Economics, Pl-53342 Wroclaw, Poland. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 786–793, June, 2000.     

Absorption spectra and structure of benzimidazoquinozalinone derivatives

Infrared and electronic spectroscopy and X-ray fluorescent analysis were used to study the structures of 5,6-dihydrobenzo[4,5]imidazo[1,2-c]quinazolin-6-one and its 5-ethyl and carboxy and sulfo derivatives. The latter compounds we obtained for the first time. The ketone and its monocarboxy derivative exist as lactam tautomers, and the sulfo derivative, in the zwitter ion form. Electronic and energy characteristics of the compounds were calculated by the Pariser-Parr-Pople method.     

Reductive dimerization of pyridine N-oxide

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 133–134, January, 1988.     

Absorption and fluorescence spectra of 7-aminocoumarin derivatives

The absorption and fluorescence spectra of twelve 7-aminocoumarin derivatives have been studied with methanol and chloroform as solvents. Electronic transitions to nπ^* states have been traced. The effect of different substituents on the nitrogen was easily observed in the fluorescence spectra. Fluorescence quantum yields and oscillator strengths were evaluated. The role of hydrogen bonding on emission maxima, quantum yields and photolytic dissociation were discussed.     

The 13C NMR spectra of 1,2,3-triazolo[1,5-a]pyridine and some monodeuteriated derivatives

The ¹³C signals of 1,2,3-triazolo[1,5-a]pyridine (1) are assigned, using the corresponding 3-, 6- and 7-deuterio-heterocycles; coupling constants are also given for compound 1.     

Mass spectra of pyridine monoamidoximes and their O-trimethylsilyl ether derivatives

The mass spectra of pyridine-2-, -3-, and -4-amidoxime and their O-trimethylsilyl derivatives have been investigated. Also included in this study were the deuterated derivates. Main pathways of fragmentation of these compounds have been proposed. A comparison with the mass spectra of the corresponding pyridine aldoximes has been made.     

Synthesis and anticancer activity of some new pyridine derivatives

Different substituents were introduced in positions 2 and 6 of 2,6 diaminopyridine in order to obtain new heterocyclic compounds. A new series of aza pyridine, imidazopyridine, benzodiazepine, indole, pyrimidine, and benzimidazole heterocyclic derivatives were synthesized in good yields. The anticancer activities of some of the new compounds were evaluated against liver cancer cell line HEPG2. Compounds 3, 4, 10, 11, 12, and 17 showed the highest activity when compared to 5-flurouracil (5-FU) and doxorubicin (DOX) chemotherapy.