scholarly journals Solvent Effect in NMR Spectroscopy. II. A Repulsive Interaction between the Benzene Solvent Molecule and the Nitrogen Lone-Pair, and the Effects Induced by the Addition of Protic Substances

1968 ◽  
Vol 41 (10) ◽  
pp. 2297-2305 ◽  
Author(s):  
Teijiro Yonezawa ◽  
Isao Morishima ◽  
Kazuhiko Fukuta
Keyword(s):  
Nmr Spectroscopy ◽  
Solvent Effect ◽  
Solvent Molecule ◽  
Lone Pair ◽  
Repulsive Interaction ◽  
Nitrogen Lone Pair

Electronic spectrum of bibenzimidazole homologue: effects of solvents and acid concentration

1989 ◽  
Vol 67 (7) ◽  
pp. 1200-1205 ◽  
Author(s):  
Awadesh Kumar ◽  
Hemant K. Sinha ◽  
Sneh K. Dogra
Keyword(s):  
Spectral Characteristics ◽  
Solvent Molecule ◽  
Lone Pair ◽  
Direct Interaction ◽  
Blue Shift ◽  
Intramolecular Hydrogen Bonding ◽  
Wavelength Absorption ◽  
Nitrogen Lone Pair ◽  
Intramolecular Hydrogen ◽  
Different Characteristics

The absorption and fluorescence spectra of bibenzimidazole (BBI), N, N′-dimethylbibenzimidazole (MBBI), and methylene, 2,2′-bibenzimidazole (MtBBI) have been recorded in six solvents of different characteristics and at various acid concentrations. This study indicates the presence of intramolecular hydrogen bonding in BBI in both S0 and S1 states, leading to large conjugation of two benzimidazole (BI) rings. The geometry of BBI is the same in the S0 and S1 states. The spectral characteristics of BBI are insensitive to the solvents. The interaction of solvent molecule attached to the nitrogen lone pair and methyl group rotates the benzimidazolyl ring in MBBI around the single bond. This leads to a blue shift in the long wavelength absorption band maximum and a decrease in the intensity of this band. The two MBI rings are coplanar in the S1 state. Presence of methylene group inhibits the direct interaction between the BI groups and these rings behave almost independently, i.e., the spectral characteristics of this molecule nearly resemble those of benzimidazole. Keywords: absorption spectrum, fluorescence spectrum, pKa, bibenzimidazoles, excited state pKa.

Structure and bonding in cyclic phosphoramidates as determined by carbon-13 magnetic resonance

1979 ◽  
Vol 57 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Frederick G. Morin
Keyword(s):  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Electron Pair ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Ring Conformation ◽  
Delocalized Electron ◽  
Nitrogen Lone Pair ◽  
Structure And Bonding

13C chemical shifts and 13C–31P couplings are reported for 11 cyclic phosphoramidates of ring sizes from four to nine. Vicinal couplings are compared with those of carbocyclic analogs and provide insight regarding the degree of nitrogen lone pair derealization into the N—P bond. For six-membered and larger rings, there appears to be nearly complete lone pair delocalization, i.e., a trigonal planar nitrogen atom. In azetidine derivatives the nitrogen lone pair remains localized, giving rise to a highly puckered ring conformation. Pyrrolidine derivatives are viewed as having a nitrogen with a partially delocalized electron pair.

Characterization and Catalytic Activity of Poly(4-Vinylpyridine-Co-Divinylbenzene)-Co2+ Complex

2005 ◽  
Vol 494 ◽  
pp. 363-368 ◽  
Author(s):  
D. Lončarević ◽  
Ž. Čupić
Keyword(s):  
Catalytic Activity ◽  
Molecular Level ◽  
Supported Catalysts ◽  
Lone Pair ◽  
Polymer Support ◽  
Polymeric Complex ◽  
Reaction Conditions ◽  
Pyridine Nitrogen ◽  
Nitrogen Lone Pair ◽  
Thermal Stability Of

Poly(4-vinylpyridine-co-divinylbenzene)-Co2+ was characterized using infrared spectroscopy (IR), thermogravimetric analysis (TG-DTA), N2-physisorption and polarography. Thermal analysis suggests sufficient thermal stability of the polymer support, under reaction conditions. From polarography measurements, the Co2+ content on polymer-supported catalysts is estimated and it was proved that no significant leaching occurred during the activity tests. At the molecular level, FTIR of P4VP-DVB-Co2+ reveals that the pyridine nitrogen lone pair coordinates to the metal center in the polymeric complex. The obtained P4VP-DVB-Co2+ catalysts performed interesting catalytic activity in reaction of the cyclohexane oxidation with air, indicating that increasing Co2+ content lowers the initiation temperature and raises the decomposition of cyclohexylhydroperoxide.

scholarly journals The N-atom in [N(PR3)2]+ cations (R = Ph, Me) can act as electron donor for (pseudo) anti-electrostatic interactions

CrystEngComm ◽  
2015 ◽  
Vol 17 (20) ◽  
pp. 3768-3771 ◽  
Author(s):  
Antonio Bauzá ◽  
Antonio Frontera ◽  
Tiddo J. Mooibroek ◽  
Jan Reedijk
Keyword(s):  
Hydrogen Bonding ◽  
Electron Donor ◽  
Molecular Hydrogen ◽  
Electrostatic Interactions ◽  
Lone Pair ◽  
Dft Study ◽  
Nitrogen Lone Pair

A CSD analysis and DFT study reveal that the nitrogen lone-pair in [N(PPh3)2]+ is partially intact and involved in intramolecular hydrogen bonding.

A Discussion on photoelectron spectroscopy - Orderings of π and σ ionization potentials in carbocyclic and heterocyclic aromatic compounds

1970 ◽  
Vol 268 (1184) ◽  
pp. 131-140 ◽  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Aromatic Compounds ◽  
Lone Pair ◽  
Ionization Potentials ◽  
Photoelectron Spectra ◽  
Light Sources ◽  
Orbital Energies ◽  
Substituted Pyridines ◽  
Nitrogen Lone Pair ◽  
Electron Correlation Effects

Data on calculated orbital energies and experimentally measured ionization potentials of carbocyclic and heterocyclic aromatic compounds are compared and contrasted. The ordering or orbital energies and ionization potentials do not always seem to parallel one another, probably owing to either electron correlation effects, or to deviations from Koopman’s theorem. The effects on photoelectron spectra of using different light sources and analysers are discussed in relation to their bearing on the orbital orderings of aromatic compounds. The high resolution He 584 A. photoelectron spectrum of pyridine is shown to be open to two interpretations regarding the ordering of the ionization potentials of the π orbitals and the ‘nitrogen lone pair’ (n). One of the interpretations involves the three lowest pyridine ionization potentials being π (9.2 eV), π L (9.5 eV) and n (10.5 eV) whilst the other has the first three ionization potentials being the order π , n, π . The photoelectron spectra of substituted pyridines and diazines are discussed in the light of the two possible explanations for the pyridine spectrum.

scholarly journals Structure of a dinuclear cadmium complex with 2,2′-bipyridine, monodentate nitrate and 3-carboxy-6-methylpyridine-2-carboxylate ligands: intramolecular carbonyl(lone pair)...π(ring) and nitrate(π)...π(ring) interactions

2015 ◽  
Vol 71 (8) ◽  
pp. 890-894
Author(s):  
Juan Granifo ◽  
Sebastián Suarez ◽  
Ricardo Baggio
Keyword(s):  
Complex Molecule ◽  
Solvent Molecule ◽  
Lone Pair ◽  
Dinuclear Complex ◽  
Cadmium Complex ◽  
Nitrate Anion ◽  
Coordination Geometry ◽  
Complex Molecules ◽  
Carboxylate Ligands ◽  
Solvent Molecules

The centrosymmetric dinuclear complex bis(μ-3-carboxy-6-methylpyridine-2-carboxylato)-κ3N,O2:O2;κ3O2:N,O2-bis[(2,2′-bipyridine-κ2N,N′)(nitrato-κO)cadmium] methanol monosolvate, [Cd2(C8H6NO4)2(NO3)2(C10H8N2)2]·CH3OH, was isolated as colourless crystals from the reaction of Cd(NO3)2·4H2O, 6-methylpyridine-2,3-dicarboxylic acid (mepydcH2) and 2,2′-bipyridine in methanol. The asymmetric unit consists of a CdIIcation bound to a μ-κ3N,O2:O2-mepydcH−anion, anN,N′-bidentate 2,2′-bipyridine group and anO-monodentate nitrate anion, and is completed with a methanol solvent molecule at half-occupancy. The Cd complex unit is linked to its centrosymmetric image through a bridging mepydcH−carboxylate O atom to complete the dinuclear complex molecule. Despite a significant variation in the coordination angles, indicating a considerable departure from octahedral coordination geometry about the CdIIatom, the Cd—O and Cd—N distances in this complex are surprisingly similar. The crystal structure consists of O—H...O hydrogen-bonded chains parallel toa, further bound by C—H...O contacts alongbto form planar two-dimensional arrays parallel to (001). The juxtaposed planes form interstitial columnar voids that are filled by the methanol solvent molecules. These in turn interact with the complex molecules to further stabilize the structure. A search in the literature showed that complexes with the mepydcH−ligand are rare and complexes reported previously with this ligand do not adopt the μ-κ3coordination mode found in the title compound.

scholarly journals Crystal structure of poly[[[μ4-5-(9H-carbazol-9-yl)isophthalato][μ3-5-(9H-carbazol-9-yl)isophthalato]bis(dimethylformamide)(methanol)dizinc] dimethylformamide monosolvate]

2015 ◽  
Vol 71 (8) ◽  
pp. m152-m153 ◽  
Author(s):  
Liubov M. Lifshits ◽  
Charles Campana ◽  
Jeremy K. Klosterman
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Title Compound ◽  
Solvent Molecule ◽  
Lone Pair ◽  
Π Interactions ◽  
Carboxylate Groups ◽  
Medium Strength ◽  
Secondary Building Units ◽  
Coordination Spheres

The structure of the polymeric title compound, {[Zn2(C20H11NO4)2(C3H7NO)2(CH3OH)]·C3H7NO}n, comprises carbazolylisophthalate moieties connecting dimetallic tetracarboxylate zinc secondary building units (SBUs) parallel to [100] and [010], leading to a layer-like arrangement parallel to (001). Each SBU consists of two Zn atoms in slightly distorted tetrahedral and octahedral coordination environments [Zn...Zn = 3.5953 (6) Å]. Three carboxylate groups bridge the two Zn atoms in a μ2-O:O′ mode, whereas the fourth coordinates through a single carboxylate O atom (μ1-O). The O atoms of two dimethylformamide (DMF) and one methanol molecule complete the Zn coordination spheres. The methanol ligand interacts with the noncoordinating DMF moleculeviaan O—H...O hydrogen bond of medium strength. Carbazoles between the layers interdigitate through weak C—H....π interactions to form a laminar solid stacked along [010]. Two kinds of C—H...π interactions are present, both with a distance of 2.64 Å, between the H atoms and the centroids, and a third C—H...π interaction, where the aromatic H atom is located above the carbazole N-atom lone pair (H...N = 2.89 Å). Several C—H...O interactions occur between the coordinating DMF molecule, the DMF solvent molecule, and ligating carboxylate O atoms.

ChemInform Abstract: STUDIES ON NITROGEN LONE - PAIR ORIENTATION AND NONBONDED N-PI INTERACTION IN N-HETEROCYCLIC COMPOUNDS

1975 ◽  
Vol 6 (22) ◽  
pp. no-no
Author(s):  
I. MORISHIMA ◽  
K. YOSHIKAWA ◽  
K. TOYODA ◽  
K. BEKKI ◽  
S. SAKATA ◽  
...  
Keyword(s):  
Heterocyclic Compounds ◽  
Lone Pair ◽  
Nitrogen Lone Pair
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