N-oxide Molecules Research Articles

Interplay of hydrogen bonding and π–π interactions in the molecular complex of 2,6-lutidine N-oxide and water

The crystal and molecular structure of 2,6-lutidine N-oxide monohydrate ( 1) has been determined by X-ray diffraction analysis. Each water molecule is acting as bridging ligand between the N→O moieties of two 2,6-lutidine N-oxide molecules through moderate strong intermolecular hydrogen bonding (O–H⋯O, O⋯O distances are 2.787(2) and 2.832 (2) Å) giving rise to a one-dimensional (1D) polymeric helical chain. A two-dimensional (2D) layered network is then formed by self-assembly of 1D helical chains via strong π–π interactions of the aromatic rings (interplanar distances 3.385 Å). The molecular structure of 1 is compared with that for the already reported molecular structures of 2-acetylamino-6-methylpyridine N-oxide monohydrate and pyridine trihydrate. Finally, on the basis of the present studies a possible explanation for the formation of the molecular complexes is proposed and discussed.

Gas-Phase Infrared and ab Initio Study of the Unstable CF3CNO Molecule and Its Stable Furoxan Ring Dimer

The unstable trifluoroacetonitrile N-oxide molecule, CF3CNO, has been generated in high yield in the gas phase from CF3BrC=NOH and studied for the first time by gas-phase mid-infrared spectroscopy. Cold trapping of this molecule followed by slow warming forms the stable ring dimer, bis(trifluoromethyl)furoxan, also investigated by gas-phase infrared spectroscopy. The spectroscopy provides an investigation into the vibrational character of the two molecules, the assignments supported by calculations of the harmonic vibrational frequencies using in the case of CF3CNO both ab initio (CCSD(T)) and density functional theory (B3LYP) and B3LYP for the ring dimer. The ground-state structures of both molecules were investigated at the B3LYP level of theory, with CF3CNO further investigated using coupled-cluster. The CCSD(T) method suggests a slightly bent (C(s)) structure for CF3CNO, while the B3LYP method (with basis sets ranging from 6-311G(d) to cc-pVTZ) suggests a close-to-linear or linear CCNO chain. The CCN bending potential in CF3CNO was explored at the CCSD(T)(fc)/cc-pVTZ level, with the results suggesting that CF3CNO exhibits strong quasi-symmetric top behavior with a barrier to linearity of 174 cm(-1). Since both isomerization and dimerization are feasible loss processes for this unstable molecule, the relative stability of CF3CNO with respect to the known cyanate (CF3OCN), isocyanate (CF3NCO), and fulminate (CF3ONC) isomers and the mechanism of the dimerization process to the ring furoxan and other isomers were studied with density functional theory.

Crystal structure of bis(2,3,5-trimethylpyridine N-oxide) 2,4,6-trinitrophenolate: Cation complex tied by the extremely strong OHO hydrogen bonding

The salt of bis(2,3,5-trimethylpyridine N-oxide) 2,4,6-trinitrophenolate, C22H25N5O9, crystallizes in monoclinic space group C2/c with a=12.411(2)A, b=15.326(3)A, c=13.559(3)A, β=113.13(1)°, V=2371.8(8)A3, Z=4, Dc=1.410 mg/m3, F(000)=1056. The molecule of 2,3,5-trimethylpyridine N-oxide is protonated. Two pyridine N-oxide molecules are linked by extremely strong OHO hydrogen bonding (2.378(4)A) to form a cation complex. CHO hydrogen bonding and π–π interactions also play important role in stablizing the structure of the salt.

Synthesis and characterization of La methanesulfonate coordination compounds with pyridine- N-oxide and 2-, 3-, and 4-picoline- N-oxide

Synthesis, characterization and thermal (TG, DSC, GC–MS) study of the coordination compounds La(MS) 3·(pyNO) 2, La(MS) 3·(2-picNO) 2, La(MS) 3·(3-picNO) 2 and La(MS) 3·(4-picNO) 1.5·H 2O are reported. The observed thermal stability trend is 2-picNO<pyNO<3-picNO<4-picNO. Under heating, the rupture of the La– N-oxide bond is promoted, together with fragmentation of the N-oxide molecule.

A theoretical approach to experimental nitration of phenyl and benzyl substituted pyridine- N-oxide derivatives

Quantum chemical calculations of 2-, 3-, and 4-phenyl substituted pyridine- N-oxide derivatives revealed that 2- and 3-phenyl derivatives nitrate via free base mechanism. For 4-phenylpyridine- N-oxide, however, calculations imply conjugated acid mechanism for nitration. For 2- and 4-benzylpyridine- N-oxide molecules a conjugated acid mechanism were suggested in nitration process. Attempts to search a correlation between the experimental acidity constants, p K a, and computed acidity constants were successful.

Linear and nonlinear optical properties of pyridine N-oxide molecule

This paper presents an investigation of the structure, dipole moment, dipole polarizability, first hyperpolarizability and second hyperpolarizability properties of pyridine N-oxide molecule. These properties were calculated at the static regime with fully C 2 v optimized geometries by using Hartree–Fock theory, second order perturbation Møller–Plesset MP2 methods, BLYP and B3LYP hybrid approaches within the density functional theory (DFT) framework, and CCSD methods, with the 6-31+G(d,p), 6-311++G(3d,3p) and Sadlej basis sets, and the gaussian 98 suite of programs. Similar calculations were also performed for pyridine molecule, and comparison between their properties was made.

Gas-Phase Spectroscopy of the Unstable Acetonitrile N-Oxide Molecule, CH3CNO

The unstable acetonitrile N-oxide molecule, CH3CNO, has been thermolytically generated in very high yield in the gas phase from its stable ring dimer, dimethylfuroxan, and studied by ultraviolet photoelectron spectroscopy, photoionization mass spectroscopy, and mid-infrared spectroscopy. The individual spectroscopies provide a detailed investigation into the vibrational and electronic character of the molecule, and are supported by both conventional ab initio calculations and density functional theory. The ground-state structure is also investigated by theory at the B3-LYP, MPn (n = 2−4), QCISD, and QCISD(T) levels with medium to large basis sets, and illustrates the need for a precise description of electron correlation. Given that both isomerization and dimerization are feasible loss processes for this unstable molecule, the relative stability of CH3CNO with respect to the known cyanate (CH3OCN), isocyanate (CH3NCO), and fulminate (CH3ONC) isomers and the mechanism of the dimerization processes were stu...

A host-guest complex of diaquabis[1-hydroxy-2(1H)-pyridinethionato-O,S]magnesium(II ) and 2,2'-dithiobis(pyridine N-oxide).

The title compound, [Mg(C5H4NOS)2(H2O)2]·C10H8N2O2S2, is a two-component host–guest material. The 2,2′-di­thio­bis(pyridine N-oxide) molecule has crystallographic twofold symmetry. The metal complex lies on an inversion centre and associates via C—H⋯S interactions into chains which thread the 2,2′-di­thio­bis­(pyridine N-oxide) lattice in perpendicular directions. Hydro­gen bonds exist between the water mol­ecules of the di­aqua­magnesium units and the N—O groups of the host lattice.

A host–guest complex of diaquabis[1-hydroxy-2(1H)-pyridinethionato-O,S]magnesium(II) and 2,2′-dithiobis(pyridine N-oxide)

The title compound, [Mg(C5H4NOS)2(H2O)2]·C10H8N2O2S2, is a two-component host–guest material. The 2,2′-di­thio­bis(pyridine N-oxide) molecule has crystallographic twofold symmetry. The metal complex lies on an inversion centre and associates via C—H⋯S interactions into chains which thread the 2,2′-di­thio­bis­(pyridine N-oxide) lattice in perpendicular directions. Hydro­gen bonds exist between the water mol­ecules of the di­aqua­magnesium units and the N—O groups of the host lattice.

Chloro- and Fluoro-Substituted Phosphites, Phosphates, and Phosphoranes Exhibiting Sulfur and Oxygen Coordination(1).

New cyclic phosphoranes, O(2)S[Me(t-Bu)C(6)H(2)O](2)PCl(3) (1), O(2)S[Me(t-Bu)C(6)H(2)O](2)P(OC(6)H(4)-m-CF(3))(3) (2), and O(2)S[(t-Bu)(2)C(6)H(2)O](2)PCl(3) (3), containing sulfone donor groups and halogen substituents were synthesized by oxidative addition reactions of a diol with a tricoordinated phosphorus precursor. Cyclic phosphates, O(2)S[(t-Bu)(2)C(6)H(2)O](2)P(O)Cl (4) and O(2)S[Me(t-Bu)C(6)H(2)O](2)P(O)(OC(6)H(4)-m-CF(3)) (5), resulted from hydrolysis reactions of 3 and 2, respectively. Phosphate O(2)S[Me(t-Bu)C(6)H(2)O](2)P(O)(OC(6)F(5)) (6) was prepared from a known phosphorane precursor and independently from the reaction of an N-oxide molecule with a parent phosphite, O(2)S[Me(t-Bu)C(6)H(2)O](2)P(OC(6)F(5)). Two additional compounds containing a sulfur atom in place of the sulfone group, a cyclic phosphite, S[Me(2)C(6)H(2)O](2)P(OC(6)F(5)) (7), and a cyclic phosphate, S[Me(2)C(6)H(2)O](2)P(O)Cl (8), were synthesized. X-ray analysis and NMR data were obtained on all of these compounds to establish the role of electronegative ligands in promoting donor interaction. Compounds 1-3 were hexacoordinate as a consequence of oxygen atom coordination while 7 and 8 were trigonal bipyramidal due to sulfur atom coordination. The chlorine atom and the pentafluorophenoxy group promote similar degrees of coordination in these compounds. The results support the conclusion that the sulfur atom and oxygen atom of the sulfone group show similar coordination abilities in donor action with phosphoranes containing strongly electronegative ligands while in the presence of less electronegative ligands sulfur is the stronger coordinating agent. With phosphates and phosphites the sulfur atom exerts the stronger donor action independent of the electronegativity of the attached ligands.

Urea–picoline N-oxide (4:2) cocrystal: an unusual channel inclusion compound

The crystal structure of urea–picoline N-oxide cocrystal reveals urea channel formation in which two independent picoline N-oxide molecules are stacked with their charge-transfer axes aligned approximately at 60° toward the crystallographic b-axis.

Preparation of Smectite/Dodecyldimethylamine N-oxide Intercalation Compounds

The adsorption of dodecyldimethylamine N-oxide into the interlayer space ofNa-saponite was investigated. The Na-saponite/dodecyldimethylamine N-oxide intercalation compounds were prepared as supported and unsupported films. Intercalation compounds with two different arrangements of the intercalated dodecyldimethylamine N-oxide were obtained, depending on the adsorbed amounts. When the adsorbed amount was greater than 400 mmol/100 g of clay, the intercalated dodecyldimethylamine N-oxide took a paraffin type bilayer. On the other hand, the intercalated dodecyldimethylamine N-oxide molecules are thought to arrange as a bimolecular coverage with their alkyl chains parallel to the silicate sheet when the added amount of dodecyldimethylamine N-oxide was 100 mmol/100 g of clay. The coadsorption of tris(2,2'-bipyridine)ruthenium(II) with dodecyldimethylamine N-oxide was achieved. The luminescence characteristics of tris(2,2'-bipyridine)ruthenium(II) revealed that there are certain interactions between the adsorbed tris(2,2'-bipyridine)ruthenium(II) and dodecyldimethylamine N-oxide in the interlayer space of saponite. Since the products have been obtained as highly transparent supported and self-standing films, the intercalation ofdodecyldimethylamine N-oxide is a way to control the adsorbed states of cationic dyes on the surface of smectites.

2:1 Complex of 3-PicolineN-Oxide and Hydroquinone

The title system, 2C 6 H 7 NO.C 6 H 6 O 2 , belongs to a series of molecular complexes formed from 3-picoline N-oxide and diverse hydrogen-bond donors. The molecular complex owes its formation to a hydrogen bond between the O atom of the N-oxide group of each 3-picoline N-oxide molecule and the O atom of an OH group of the hydroquinone molecule. The complex has a dihedral angle of 48.16 (5)° between the aromatic rings and exhibits overlap between the hydroquinone and 3-picoline N-oxide molecules in the [001] direction. The structural characteristics of the title complex are compared with those of similar systems.

1:1 Complex Formed by 2-Picoline N-Oxide and 4-Nitrophenol

The 2-picoline N-oxide and 4-nitrophenol moieties in the title complex, C6H7NO.C6H5NO3, are held together by an intermolecular O-H⋯CN hydrogen bond. This crystal structure exhibits partial overlap between the rings of the molecules, in the [110] direction. The complex formed may be described by two planes which contain the 2-picoline N-oxide and 4-nitrophenol molecules, respectively.

Structure and FTIR spectra of 3 : 2 complexes of trimethylamine N-oxide and 4-dimethylamine-2,6-dimethylpyridine N-oxide with perchloric acid

Trimethylamine N-oxide and 4-dimethylamine-2,6-dimethylpyridine N-oxide form three types of crystalline complexes with perchloric acid, with the base-to-acid ratio 1 : 1, 2 : 1 and 3 : 2, which are easily distinguished by their IR absorption. The asymmetric unit of the P1̄ unit cell contains two (Me 3NO) 3·(HClO 4) 2 formula units. Each of the formula units assembles into a (Me 3NO) 32H + dication and two independent ClO − 4 anions which show to H-bond interactions with the cationic components. The oxygen atom of a central trimethylamine N-oxide molecule accepts hydrogen bonds from two protonated trimethylamine N-oxide cations with O … O distances in the range 2.537(5) – 2.562(7) Å. The O … HO bonds are linear and formed along direction of the two electron lone-pairs on the oxygen atom. In acetonitrile solutions the 3 : 2 complexes exist as mixtures of the 1 : 1 and 2 : 1 complexes.

Structure and FTIR spectra of 3:2 complexes of trimethylamine N-oxide and 4-dimethylamine-2,6-dimethylpyridine N-oxide with perchloric acid

Trimethylamine N-oxide and 4-dimethylamine-2,6-dimethylpyridine N-oxide form three types of crystalline complexes with perchloric acid, with the base-to-acid ratio 1:1, 2:1 and 3:2, which are easily distinguished by their IR absorption. The asymmetric unit of the P 1 unit cell contains two (Me 3NO) 3·(HClO 4) 2 formula units. Each of the formula units assembles into a (Me 3NO) 32H + dication and two independent ClO − 4 anions which show no H-bond interactions with the cationic components. The oxygen atom of a central trimethylamine N-oxide molecule accepts hydrogen bonds from two protonated trimethylamine N-oxide cations with O...O distances in the range 2.537(5) – 2.562(7) Å. The O...HO bonds are linear and formed along direction of the two electron lone-pairs on the oxygen atom. In acetonitrile solutions the 3:2 complexes exist as mixtures of the 1:1 and 2:1 complexes.

Ground, Excited, and Ionic States of the NCCNO Molecule: A HeI Photoelectron, Infrared, Ultraviolet, and ab Initio Investigation

The cyanogen N-oxide molecule NCCNO was recently identified for the first time in the gas phase. In the present work, NCCNO, generated from its stable ring dimer dicyanofuroxan by low-pressure thermolysis, is characterized by HeI photoelectron, photoionization mass, ultraviolet, and infrared spectroscopies. From stop-flow and revaporization experiments the molecule may be categorized as semistable, having a lifetime of a few hours in the dilute gas phase. The ground state molecular geometry and vibrational frequencies are explored with ab initio calculations at the MP3, QCISD, and QCISD(T) levels for comparison with experiment. The standard correlated methods have some difficulty with the structure; density functional theory gives results closer to recent microwave data and suggests that bigger basis sets are necessary. The molecule is predicted to have a large amplitude deformation, suggesting possible quasi-linear behavior. For the ionic states, the semiempirical HAM/3 method gives very good agreement with the measured ionization energies. The low lying singlet excited states, optimized at the CIS level of theory, assist with the interpretation of the ultraviolet spectrum. Taken together, the ab initio calculations and the spectroscopic data suggest that both the ground state molecule and the ion have linear structures, but the lowest π* ← π electronic transition leads to a molecule strongly bent in the lowest excited singlet state.

The molecular dipole moment of the non-linear optical 3-methyl 4-nitropyridine N-oxide molecule: X-ray diffraction and semi-empirical studies

The 3-methyl 4-nitropyridine N-oxide molecule (POM) is characterised by its weak dipole moment. The low polarity of this molecule results mainly from the electronic competition of the two electron-accepting groups, N-oxide and nitro. An accurate electron density distribution and the electrostatic potential around the molecule have been calculated from a high-resolution X-ray diffraction study. The data were collected at 123 K using graphite-monochromated Mo-Kα radiation to sin(θ)/λ= 1.24 Å–1. Crystal data: C6H6O3N2, orthorhombic, space group P212121, a= 20.890, b= 6.094, c= 5.123 Å, µ= 0.2 mm–1, λ= 0.71 Å. The integrated intensities of 8000 reflections were measured and reduced to 2296 independent reflections with I 3σ(I). The experimental dipole moment is in a reasonable agreement with the semi-empirical calculations of the isolated molecule. The calculated net charges, the dipole moment and the electrostatic potential around the molecule deduced from this study reveal the nature of the intramolecular charge transfer due to the electron-accepting nitro and N-oxide groups.

Investigation of alkaloid N-oxides by secondary-ion mass spectrometry

An advantage of theSIMS method for investigating alkaloid N-oxides has been shown. In the case of N-oxides of steroid, diterpene, tropane, and pyrrolizidine alkaloids, fragments including the oxygen of the N-oxide group are revealed. The protonation of N-oxide molecules in a glycerol matrix takes place mainly through the negatively polarized oxygen atom of the N-oxide function. On fragmentation, theMH+ ions of N-oxides of monoester tropane and pyrrolizidine alkaloids tend to form fragmentary ions of the protonated forms of the aminoalcohols (A+). The energies of the metastable transitionsMH+ → A+ have been calculated for the Noxides of the pyrrolizidine alkaloids viridif lorine, trachelanthamine, and echinatine.

Preparation, spectral and crystal structure study of polymeric 1:1 and dimeric 1:2 complexes of copper(II) azide with pyridine- N-oxide and 3-acetylpyridine, [Cu(Pyridine- N-oxide)(N 3) 2] n and [Cu(3-acetylpyridine) 2(N 3) 2] 2

The synthesis and characterization of two new complexes of copper(II) azide, 1:1 with pyridine- N-oxide ( 1) and 1:2 with 3-acetylpyridine ( 2) are described. The structure of complex 1 features five-coordinated copper in a distorted tetragonal pyramidal environment with N(11), N(11a), N(21) and N(21b) of the two μ(1,1) bridging azido ligands in basal sites [CuN from 2.003(3) to 2.026(3) Å] and O(1) of the pyridine- N-oxide molecule occupying the apical position [ Cu O = 2.185(3) A ̊ ]. The chains of polyhedra are directed along the a axis of the unit cell. The dimeric molecule of 2, which possesses a crystallographic inversion centre, contains both terminal and μ(1, 1) bridging azido groups. Each copper(II) atom is further coordinated by two nitrogen atoms from 3-acetylpyridine molecules to give a distorted square pyramid. The IR and electronic spectra of the solid complexes are given and discussed.