Crystal structure, vibrational and optic properties of 2-N-methylamino-3-methylpyridine N-oxide - Its X-ray and spectroscopic studies as well as DFT quantum chemical calculations

The crystal and molecular structure and physicochemical properties of 2-N-methylamino-3-methylpyridine N-oxide (MA3MPO) have been studied. MA3MPO was synthesized from 2-amino-3-methylpyridine by several steps to form colorless crystals suitable for crystallographic analysis. The data reveal that MA3MPO crystallizes in the monoclinic space group P2₁/n. The studied compound contains a nearly flat triply substituted pyridine skeleton whose structure is stabilized by an intramolecular N–H⋅⋅⋅O hydrogen bond. The N-oxide molecules are connected together by weak C–H⋯O hydrogen bonds, an acceptor of which is the oxygen atom from the N-oxide group. This leads to creation of two-dimensional network of hydrogen bonds. Its IR, Raman, UV–Vis and luminescence spectra have been measured and analyzed on the basis of DFT and NBO quantum chemical calculations in which the B3LYP/6-311++G(d,p) approach was applied. The distribution of the electron levels in the studied compound has been analyzed in terms of the possibility of its participation in the ligand-to-lanthanide ion energy transfer.

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The 2-N-methylamino-3-methylpyridine N-oxide (MA3MPO) was synthesized and characterized.

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The studied compound structure is stabilized by an intramolecular N–H⋯O hydrogen bond.

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The molecules are connected together by weak C–H⋯O hydrogen bonds.

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The amino group plays the role of effective hydrogen-bond donor but the N-oxide group is a hydrogen-bond acceptor.

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X-ray, IR, Raman and DFT methods recognized the existence of the intramolecular N–H⋯O hydrogen bond in the studied compound.

Conformation of the azo bond and its influence on the molecular and crystal structures, IR and Raman spectra, and electron properties of 6-methyl-3,5-dinitro-2-[(E)-phenyldiazenyl]pyridine - Quantum chemical DFT calculations

The crystal and molecular structures of 6-methyl-3,5-dinitro-2-[(E)-phenyldiazenyl]pyridine have been determined by X-ray diffraction and quantum chemical DFT calculations. The crystal is monoclinic, space group Cc (No. 9) with Z=4 with the unit cell parameters: a=12.083(7), b=12.881(6), c=8.134(3) Å and β=97.09(5)°. The azo-bridge appears in the trans conformation in which C2-N2-N2'-C1' torsion angle takes a value -178.6(3)°, whereas the dihedral angle between the planes of the phenyl and pyridine rings is 3.5(2)°. The IR and Raman spectra measured in the temperature range 80-350K and quantum chemical calculations with the use of B3LYP/6-311G(2d,2p) approach confirmed the trans configuration of the azo-bridge as the most stable energetically and allowed determination of the energy other virtual structures. The observed effects were used in the discussion of vibrational dynamics of the studied compound. The energy gap between cis and trans conformers equals to 1.054eV (0.03873 Hartree). The electron absorption and emission spectra have been measured and analyzed on the basis of DFT calculations. The life time of the excited state is 12μs and the Stokes shift is close to 5470cm^-1.

The hydrazo-bond in 4,4'-dimethyl-3,3'-dinitro-2,2'-hydrazobipyridine - crystal structure, conformation and vibrational characteristics

The crystal and molecular structure of 4,4'-dimethyl-3,3'-dinitro-2,2'-hydrazobipyridine have been determined by X-ray diffraction and quantum chemical DFT analysis. The title compound crystallizes in P1¯ space group, with one-half molecule in the asymmetric unit. The molecular structure is stabilized by intramolecular NH···O hydrogen bonds. The molecules are linked by a combination of weak intermolecular CH⋯O interactions and also aromatic π-π stacking. The molecular structure of the studied compound has been determined using the DFT B3LYP/6-311G(2d,2p) approach and compared to that derived from X-ray studies. The IR and Raman wavenumbers have been calculated for the optimized geometry of a possible monomer structural model. The structural and vibrational properties of the intramolecular NH···O interaction are described.

The role of hydrogen bonds in the crystals of 2-amino-4-methyl-5-nitropyridinium trifluoroacetate monohydrate and 4-hydroxybenzenesulfonate - X-ray and spectroscopic studies

Two new organic-organic salts, 2-amino-4-methyl-5-nitropyridinium trifluoroacetate monohydrate (AMNP-TFA), and 2-amino-4-methyl-5-nitropyridinium 4-hydroxybenzenesulfonate (AMNP-HBS), were obtained and characterized by means of FT-IR, FT-Raman and single crystal X-ray crystallography. In the former crystal, the cations, anions and water molecules are linked into layers by three types of hydrogen bonds, NPH⋯O, NAH⋯O and OH⋯O. These layers are connected by weaker CH⋯O hydrogen bonds. In the latter crystal, the cations and anions form one-dimensional structure through a number of hydrogen-bonding interactions involving the OH, NH(+) and NH2 groups as donors. In this case the NPH⋯O and NAH⋯O hydrogen bonds are formed. The combination of interactions between cations and anions results in the formation of columns. Additionally, there are π-π stacking interactions between the columns. The obtained X-ray structural data are related to the vibrational spectra of the studied crystals.

Comprehensive physicochemical studies of a new hybrid material: 2-amino-4-methyl-3-nitropyridinium hydrogen oxalate

A new organic-organic salt, 2-amino-4-methyl-3-nitropyridinium hydrogen oxalate (AMNPO), and its deuterium analogue have been synthesized and characterized by means of FT-IR, FT-Raman, DSC and single crystal X-ray studies. The DSC measurements and temperature dependence of the IR and Raman spectra in the range 4-295 K show that it undergoes a reversible phase transition at ~240 K. At room temperature it crystallizes in noncentrosymmetric space group P21. The unit-cell is built of the 2-amino-4-methyl-3-nitropyridinium cations and oxalate monoanions which are connected via the N-H···O and O-H···O hydrogen bonds. The geometrical and hydrogen bond parameters are similar for non-deuterated (at 120 and 293 K) and deuterated compounds (at 90K). The phase transition is probably a consequence of order-disorder transition inside of hydrogen network. The 6-311G(2d,2p) basis set with B3LYP functional have been used to discuss the structure and vibrational spectra of the studied compound.

Vibrational spectra, crystal structure, DFT quantum chemical calculations and conformation of the hydrazo-bond in 6-methyl-3-nitro-2-(2-phenylhydrazinyl)pyridine

The crystal and molecular structures of 6-methyl-3-nitro-2-(2-phenylhydrazinyl)pyridine (6-methyl-3-nitro-2-phenylhydrazopyridine) have been determined by X-ray diffraction and quantum chemical DFT analysis. The crystal is monoclinic, space group C2/c, with Z=8 formula units in the elementary unit cell of dimensions a=16.791(4), b=6.635(2), c=21.704(7)Å, β=100.54(3)°. The molecule consists of two nearly planar pyridine subunits. A conformation of the linking hydrazo-bridge CNHNHC is bend and the dihedral angle between the planes of the phenyl and pyridine rings is 88.2(5)°. The hydrogen bonding of the type NH···N and possibly also CH···O favors a dimer formation in the crystal structure. The dimers are further linked by a NH···O hydrogen bond, so forming a layer parallel to the ab plane. The molecular structure of the studied compound has been determined using the DFT B3LYP/6-311G(2d,2p) approach and compared to that derived from X-ray studies. The IR and Raman wavenumbers have been calculated for the optimized geometry of a possible monomer structural model but the possibility of the dimer formation through the NH···N hydrogen bond has also been considered. The structural and vibrational properties of the intra-molecular NH···O interaction are described.

Molecular and crystal structures, vibrational studies and quantum chemical calculations of 3 and 5-nitroderivatives of 2-amino-4-methylpyridine

The crystal structures of 2-amino-4-methyl-3-nitropyridine (I), 2-amino-4-methyl-3,5-dinitropyridine (II) and 2-amino-4-methyl-5-nitropyridine (III) have been determined. The compounds crystallize in the monoclinic P2(1)/n, triclinic P-1 and monoclinic C2/c space groups, respectively. These structures are stabilized by a combination of N-H···N and N-H···O hydrogen bonds and exhibit layered arrangement with a dimeric N-H···N motif in which the molecular units are related by inversion centre. The molecular structures of the studied compounds have been determined using the DFT B3LYP/6-311G(2d,2p) approach and compared to those derived from X-ray studies. The IR and Raman wavenumbers have been calculated from the optimized geometry of monomers and dimers formed in the unit cell and compared to the experimental values obtained from the spectra.