Studies of the solvent effect on the chemical shifts in n.m.r. spectroscopy. II. Solutions of succinic anhydride, maleic anhydride, and the N-substituted imides

1967 ◽  
Vol 45 (16) ◽  
pp. 1829-1835 ◽  
Author(s):  
Taku Matsuo
Keyword(s):  
Maleic Anhydride ◽  
Succinic Anhydride ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Specific Interaction ◽  
Lone Pair ◽  
Polar Solvents ◽  
Low Field ◽  
Solvent Molecules ◽  
Lone Pair Electrons

Proton magnetic resonance spectra of succinic anhydride, maleic anhydride, and the N-ethyl- or N-(p-chlorophenyl)-imides have been investigated in various media. In benzene solution, a specific interaction between the π-electron cloud of the solvent and the moiety of the protons alpha to the carbonyl groups is suggested. The strength of the interaction is considered to be in the order of (i) maleic anhydride, (ii) succinic anhydride, and (iii) the N-substituted imides. The interaction may be due to both the large electron affinity and the polarization of the carbonyl group. The low-field shifts in strongly polar solvents, such as acetone or dimethyl sulfoxide, are ascribed to the preferential associations of the lone-pair electrons of polar solvents to the electron-deficient sites of solute molecules. In some cases, however, the solvent effects on the chemical shifts are opposite to those expected from the donor properties of the solvents. An explanation may be available from the anisotropic magnetic susceptibilities of the polar groups of the solvent molecules.

Solvation and redox properties of [Co(en)3]3+-[Co(en)3]2+ system

1980 ◽  
Vol 45 (2) ◽  
pp. 335-338 ◽  
Author(s):  
Adéla Kotočová ◽  
Ulrich Mayer
Keyword(s):  
Hydrogen Bond ◽  
Lewis Acid ◽  
Specific Interaction ◽  
Redox Properties ◽  
Solvation Effect ◽  
Interacting Particles ◽  
Acid Base ◽  
Polar Solvents ◽  
Oxidation Reduction ◽  
Solvent Molecules

The solvation effect of a number of nonaqueous polar solvents was studied on the oxidation-reduction properties of the [Co(en)3]3+-[Co(en)3]2+ system. Interactions of these ions with the solvent molecules are discussed in terms of their coordination, which is accompanied by a specific interaction of the Lewis acid-base type, namely formation of a hydrogen bond between the interacting particles. This is the main controlling factor of the redox properties of the studied system.

Temperature dependence of proton magnetic resonance solvent shifts. 3,5-Dichlorosalicylaldehyde in carbon tetrachloride and benzene

1968 ◽  
Vol 46 (19) ◽  
pp. 3110-3112 ◽  
Author(s):  
G. Kotowycz ◽  
T. Schaefer
Keyword(s):  
Carbon Tetrachloride ◽  
Temperature Dependence ◽  
Proton Magnetic Resonance ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Relative Temperature ◽  
Proton Shift ◽  
Solvent Shifts ◽  
Solvent Molecules ◽  
Proton Chemical Shifts

The ring proton chemical shifts of 3,5-dichlorosalicylaldehyde as a function of temperature in carbon tetrachloride and benzene solutions indicate that if there is association with solvent molecules in benzene solution, then there is also association with carbon tetrachloride solvent molecules. The aldehydic proton shift shows a much smaller (relative) temperature dependence in the carbon tetrachloride solution.

N.M.R. spectra and stereochemistry of the bipyridyls. III. 2,2'-Bipyridyl and dimethyl derivatives, 3,3'- bipyridyl, and 4,4' - bipyridyl

1967 ◽  
Vol 20 (6) ◽  
pp. 1227 ◽  
Author(s):  
TM Spotswood ◽  
CI Tanzer
Keyword(s):  
Hydrogen Bonding ◽  
Electrostatic Field ◽  
Field Effect ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Diamagnetic Anisotropy ◽  
Equal Importance ◽  
Nitrogen Lone Pair ◽  
Lone Pair Electrons ◽  
Derivatives Of

The analysis of the n.m.r, spectra of 2,2?-, 3,3?-, and 4,4?-bipyridyl and three dimethyl-2,2?-bipyridyls is reported and the factors determining the relative chemical shifts of the ring protons and methyl groups in several solvents are discussed. The diamagnetic anisotropy of the neighbouring ring and electrostatic field effect of the nitrogen lone pair electrons are shown to be of roughly equal importance for derivatives of 2,2?-bipyridyl except in hydrogen bonding solvents. Attenuation of the electrostatic field effect in polar, and particularly in hydrogen bonding solvents, is established for 4- picoline, and for the bipyridyls, and this effect is responsible for striking changes in the spectrum of 2,2?-bipyridyl in hydrogen bonding solvents. An approximate interplanar angle of 58� is derived for 3,3?- dimethyl-2,2?-bipyridyl, and 2,2?-bipyridyl and its 4,4?- and 5,5?- dimethyl derivatives appear to be trans coplanar in all solvents. 3,3?- Bipyridyl and 4,4?-bipyridyl are probably highly twisted in all solvents, or alternatively, behave as essentially free rotors. The predicted conformations are in good agreement with the electronic spectral data.

Elektronendichte und chemische Verschiebung der Styryldiazin- und Diazaphenanthrenprotonen / Electrondensity and Proton Chemical Shift of Styryldiazines and Diazaphenanthrenes

1972 ◽  
Vol 27 (2) ◽  
pp. 310-319
Author(s):  
H.-H. Perkampus ◽  
Th. Bluhm ◽  
J. Knop
Keyword(s):  
Ring Current ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Current Effect ◽  
Electron Densities ◽  
Paramagnetic Effect ◽  
Nitrogen Lone Pair ◽  
Chemische Verschiebung ◽  
Lone Pair Electrons ◽  
Proton Chemical Shifts

AbstractProton chemical shifts in styryldiazines and diazaphenanthrenes linearly correlate with SCF-π-electron densities of the attached carbon atom and with the electron densities of the hydrogen atom (calculated by the CNDO/2 method). The observed deviations from linearity are discussed in terms of ring current effect, steric effects and the paramagnetic effect of the nitrogen lone pair electrons. An appreciable weakening of ring current is found for diazaphenanthrenes with two adjacent N-atoms. Under the same condition the paramagnetic effect on ortho-hydrogens is increased.

Untersuchungen der kernmagnetischen Resonanz von Phosphorverbindungen XXIV

1971 ◽  
Vol 26 (4) ◽  
pp. 282-291 ◽  
Author(s):  
Gernot Heckmann ◽  
Ekkehard Fluck
Keyword(s):  
Stark Effect ◽  
Chemical Shifts ◽  
White Phosphorus ◽  
Dispersion Interactions ◽  
Polar Solvents ◽  
Dissolved Phosphorus ◽  
Diamagnetic Anisotropy ◽  
Order Of Magnitude ◽  
Solvent Molecules ◽  
The One

Solvent effects of 31P nuclear magnetic resonance of white phosphorus in n-paraffins, substituted and cyclic paraffins, as well as in benzene, and some amines are discussed. The largest chemical shifts were caused on the one hand by dispersion interactions of dissolved phosphorus and solvent molecules and on the other hand by interaction of different phosphorus molecules; the latter influence may shift the resonance signal of white phosphorus about 35 ppm towards higher field relative to solid white phosphorus. Specific interactions between dissolved phosphorus and halogen atoms increased in the series Cl, Br, I. Phosphorus acted as an electron donor. Electron acceptor properties in amines as solvents were not found. Shifts towards lower field in the order of magnitude of 1 ppm were caused by highly polar solvents (Stark effect). By comparing dilute solutions of phosphorus in 1,3-cyclohexadiene and benzene, respectively, the influence of the diamagnetic anisotropy on the resonance of phosphorus could be estimated to result in a shift of about 1 ppm towards higher field, whereby the different dispersion interactions, were taken into account.

Concerning lone-pair stereospecificity of intramolecular OH hydrogen bonds to oxygen and sulfur in solution

1987 ◽  
Vol 65 (5) ◽  
pp. 908-914 ◽  
Author(s):  
Ted Schaefer ◽  
David M. McKinnon ◽  
Rudy Sebastian ◽  
James Peeling ◽  
Glenn H. Penner ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Coupling Constants ◽  
Boat Conformation ◽  
Lone Pairs ◽  
Saturated Ring ◽  
Hydroxyl Protons ◽  
Lone Pair Electrons

The 1H nuclear magnetic resonance spectra for CCl4 solutions are analyzed for 2-(thioethyl)phenol, 2,3-dimethoxyphenol, and 8-hydroxythiochroman. The chemical shifts of the hydroxyl protons in these compounds, in 2,3-dihydroxyanisole, and 2-hydroxybenzyl methyl ether are discussed in terms of stereospecific intramolecular OH hydrogen bonds to lone-pair electrons on oxygen and sulfur. The O—H … O hydrogen bonds can be adequately discussed in terms of equivalent lone pairs on oxygen. There is very little difference between the hydrogen bond energies for 2,3-dihydroxyanisole and 2,3-dimethoxyphenol. In the latter the central hydrogen bonded methoxy group lies nearly perpendicular to the ring plane. The O—H … S hydrogen bonds are best described in terms of nonequivalent, 3s and 3p, lone pairs on sulfur. It is estimated that an O—H … H 3s hydrogen bond is at least 8 kJ/mol weaker than an O—H … 3p hydrogen bond. The former is predominant in the thiochroman derivative and the latter in the thioethylphenol, in which the thioethyl group prefers a plane perpendicular to the benzene ring. The long-range benzylic coupling constants in the thiochroman derivative indicate inversion of the saturated ring between distorted half-chair conformations. The boat conformation can be ruled out.

Intramolecular Dipole Reorientation of Amino Compounds and their Interaction with Solvent Molecules. I

1972 ◽  
Vol 27 (11) ◽  
pp. 1652-1662
Author(s):  
Jaakko Eloranta
Keyword(s):  
Phenyl Ring ◽  
Relaxation Times ◽  
Lone Pair ◽  
Far Infrared ◽  
Amino Group ◽  
Substituted Anilines ◽  
Dielectric Absorption ◽  
Amino Compounds ◽  
Solvent Molecules ◽  
Lone Pair Electrons

Abstract The dielectric absorption of dilute solutions of aniline, methyl substituted anilines, chlorine substituted anilines, N,N,N',N'-tetramethyl-p-phenylene diamine and 4-aminobiphenyl in various sol-vents has been measured between 0.3 and 135 GHz. The measurements have been carried out at 20 °C and for some mesitylene solutions also at -30 °C and 60 °C. The absorption curves have been resolved into multiple absorption regions. A far infrared (FIR) term had to be included in each analysis. Its contribution to the total dipole reorientation depends on the solvent and on the mobility of the substituted groups in the phenyl ring. The obtained group relaxation times are longer than those reported previously and also their weight factors are smaller. Differences in the mobility of the amino group are observed in methyl substituted anilines. Methyl substituents in the amino group itself strongly reduce the mobility. The decrease in the group mobility parallels the increasing mesomeric interaction between the lone pair electrons in the nitrogen and the Π-electrons of the phenyl ring. In addition to the reorientation of the amino group of 4-aminobiphenyl another internal reorientation process is found which is attributed to a mesomeric charge shift. In-dications are obtained for weak association between some amino compounds and mesitylene.

Effect of delocalization of nonbonding electron density on the stability of the M–Ccarbene bond in main group metal-imidazol-2-ylidene complexes: a computational and structural database study

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Samuel Tetteh ◽  
Albert Ofori
Keyword(s):  
Electron Density ◽  
Lone Pair ◽  
Main Group ◽  
Binding Energies ◽  
Electrostatic Model ◽  
Group Metal ◽  
Main Group Metal ◽  
Structural Database ◽  
The Stability ◽  
Lone Pair Electrons

Abstract The M–Ccarbene bond in metal (M) complexes involving the imidazol-2-ylidene (Im) ligand has largely been described using the σ-donor only model with donation of σ electrons from the sp-hybridized orbital of the carbene carbon into vacant orbitals on the metal centre. Analyses of the M–Ccarbene bond in a series of group IA, IIA and IIIA main group metal complexes show that the M-Im interactions are mostly electrostatic with the M–Ccarbene bond distances greater than the sum of the respective covalent radii. Estimation of the binding energies of a series of metal hydride/fluoride/chloride imidazol-2-ylidene complexes revealed that the stability of the M–Ccarbene bond in these complexes is not always commensurate with the σ-only electrostatic model. Further natural bond orbital (NBO) analyses at the DFT/B3LYP level of theory revealed substantial covalency in the M–Ccarbene bond with minor delocalization of electron density from the lone pair electrons on the halide ligands into antibonding molecular orbitals on the Im ligand. Calculation of the thermodynamic stability of the M–Ccarbene bond showed that these interactions are mostly endothermic in the gas phase with reduced entropies giving an overall ΔG > 0.

scholarly journals Long-term stability in γ-CsPbI3 perovskite via an ultraviolet-curable polymer network

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Nam-Kwang Cho ◽  
Hyun-Jae Na ◽  
Jeeyoung Yoo ◽  
Youn Sang Kim
Keyword(s):  
Polymer Network ◽  
Lone Pair ◽  
Ambient Conditions ◽  
Absorption Properties ◽  
Term Stability ◽  
Long Term Stability ◽  
Ultraviolet Curable ◽  
Oxygen Lone Pair ◽  
Lone Pair Electrons

AbstractBlack-colored (α, γ-phase) CsPbI3 perovskites have a small bandgap and excellent absorption properties in the visible light regime, making them attractive for solar cells. However, their long-term stability in ambient conditions is limited. Here, we demonstrate a strategy to improve structural and electrical long-term stability in γ-CsPbI3 by the use of an ultraviolet-curable polyethylene glycol dimethacrylate (PEGDMA) polymer network. Oxygen lone pair electrons from the PEGDMA are found to capture Cs+ and Pb2+ cations, improving crystal growth of γ-CsPbI3 around PEGDMA. In addition, the PEGDMA polymer network strongly contributes to maintaining the black phase of γ-CsPbI3 for more than 35 days in air, and an optimized perovskite film retained ~90% of its initial electrical properties under red, green, and blue light irradiation.

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