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.

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.

Hydrogen Bonding to Thiocyanate Anions: Statistical and Quantum-Chemical Analyses

1998 ◽  
Vol 54 (3) ◽  
pp. 316-319 ◽  
Author(s):  
J. P. M. Lommerse ◽  
J. C. Cole
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Statistical Analysis ◽  
Lone Pair ◽  
Unexpected Result ◽  
Acta Cryst ◽  
Energy Calculations ◽  
Acceptor Atom ◽  
Detailed Statistical Analysis ◽  
Nitrogen Lone Pair

A statistical analysis of entries from the CSD (Cambridge Structural Database) showed that the average hydrogen-bond geometry to the nitrogen acceptor atom of the thiocyanate anion was not collinear with respect to the molecular axis of the anion and so not collinear with the nitrogen lone pair [Tchertanov & Pascard (1996). Acta Cryst. B52, 685–690]. This somewhat unexpected result has been investigated further using theoretical energy calculations applying Intermolecular Perturbation Theory in combination with a more detailed statistical analysis of an appropriate CSD dataset. The energy calculations pointed to the formation of the strongest hydrogen bonds in the nitrogen lone-pair direction. The statistical analysis showed that this directionality occurs in cases where the N atom accepts one hydrogen bond only. The non-linear average hydrogen-bond geometry observed in the earlier study can be attributed to multiple hydrogen bonding to the N atom. In such cases, there is a shift away from the optimum orientation.

Liaison hydrogène des arylamines : compétition des sites π et N

2004 ◽  
Vol 82 (9) ◽  
pp. 1413-1422 ◽  
Author(s):  
Eric Marquis ◽  
Jérôme Graton ◽  
Michel Berthelot ◽  
Aurélien Planchat ◽  
Christian Laurence
Keyword(s):  
Hydrogen Bonding ◽  
Lone Pair ◽  
Molecular Electrostatic Potentials ◽  
Hydrogen Bond Donor ◽  
Complexation Constant ◽  
Steric Factors ◽  
Troger's Base ◽  
Nitrogen Lone Pair ◽  
Ir Study ◽  
Hydrogen Bonded

An IR study, in the region of OH stretching, of a reference hydrogen-bond donor, 4-fluorophenol, hydrogen bonded to primary, secondary, and tertiary arylamines differently substituted on the ring and on the nitrogen, shows the formation of two kinds of 1:1 complexes in CCl4 solution: an OH···π and an OH···N hydrogen-bonded complex. The IR method gives only access to a global complexation constant Kt. A method is proposed for separating Kt into a Kπ component for hydrogen bonding to the π system and a KN component for hydrogen bonding to the nitrogen atom. This method is validated by comparing the estimated Kπ and KN values to theoretically calculated descriptors of basicity: the nitrogen lone pair orientation towards the aromatic ring, the molecular electrostatic potentials around the nitrogen and the π cloud, and the enthalpy of hydrogen bonding of hydrogen fluoride with the π system of selected arylamines. The main electronic and steric factors governing the competition between π and N sites are analysed. The strongest π and N bases among the arylamines are julolidine and Tröger's base, respectively. Triphenylamine and diphenylamine, which are nitrogen Brønsted bases, become π bases in hydrogen bonding. Moreover, there is no correlation between the pKHB and the pKBH+ scales of basicity of arylamines. The use of the pKBH+ scale is therefore not recommended in hydrogen-bonding studies.Key words: hydrogen bonding, arylamines, pKHB scale, competition of π and N hydrogen-bonded sites.

scholarly journals Supramolecular Architecture in a Ni(II) Complex with a Weakly Bonded N,N′-(1,4-phenylenedi- carbonyl)Diglycinate Counter-Anion: Crystal Structure Investigation and Hirshfeld Surface Analysis

Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 615
Author(s):  
Niels-Patrick Pook
Keyword(s):  
Hydrogen Bonding ◽  
Surface Analysis ◽  
Electrostatic Interactions ◽  
Noncovalent Interactions ◽  
Lone Pair ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Water Molecules ◽  
Counter Anion ◽  
Cationic Complex

In this work, we describe the structural investigation of a Ni(II) complex, [Ni(C12H8N2)2(H2O)2]2·(C12H10N2O6)·(NO3)2·10H2O, with phenanthroline ligands, a deprotonated aromatic dicarboxylic acid, N,N′-(1,4-phenylenedicarbonyl)diglycine, and a nitrate as counter-anions, as well as water molecules. Noncovalent interactions, such as π–π stacking, lone-pair···π, and C–H···π between the phenanthrolines of the cationic complex, [Ni(C12H8N2)2(H2O)2]2+, and counter-anions are observed. Moreover, the solvated and noncoordinating counter-anion, N,N′-(1,4-phenylenedicarbonyl)diglycinate, is embedded in classical and nonclassical hydrogen-bonding interactions with water molecules and phenanthrolines. The two water molecules coordinated by the NiII atom and hydrogen bonded to the carboxylate of the N,N′-(1,4-phenylenedicarbonyl)diglycinate show attractive secondary electrostatic interactions, and a DD/AA hydrogen bonding pattern is formed. The noncovalent interactions of the cationic complex and the solvated N,N′-(1,4-phenylenedicarbonyl)diglycinate counter anion were explored with a Hirshfeld surface analysis, and related contributions to crystal cohesion were determined. The results of the N,N′-(1,4-phenylenedicarbonyl)diglycinate counter anion were compared to those of a solvated N,N′-(1,4-phenylenedicarbonyl)diglycine molecule of a previously described copper(II) complex.

L'échelle pKHB de basicité de liaison hydrogène des amines tertiaires aliphatiques

2002 ◽  
Vol 80 (10) ◽  
pp. 1375-1385 ◽  
Author(s):  
Jérôme Graton ◽  
François Besseau ◽  
Michel Berthelot ◽  
Ewa D Raczynska ◽  
Christian Laurence
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Amino Nitrogen ◽  
Lone Pair ◽  
Steric Effects ◽  
Tertiary Amines ◽  
Complexation Constant ◽  
Hydrogen Bond Acceptor ◽  
Nitrogen Lone Pair ◽  
Hydrogen Bond Basicity

The hydrogen bond acceptor strength of 40 tertiary amines has been measured by Fourier transform – infrared (FTIR) spectrometry from their 1:1 complexation constant towards 4-fluorophenol in CCl4 at 25°C (the pKHB scale). Also measured was the frequency shift, Δν(OH), of the ν(OH) band of methanol hydrogen-bonded to these amines. The comparison of the thermodynamic hydrogen bond basicity scale, pKHB, with the spectroscopic one, Δν(OH), and with the Brønsted pKa scale, points to the great sensitivity of pKHB to steric effects. The pKHB scale of tertiary amines extends from 2.71 for quinuclidine to –0.34 for N,N-diisopropyl-3-pentylamine. The main factors governing this important variation (17 kJ·mol–1 on the Gibbs energy scale) are the electron-withdrawing inductive effect and various kinds of steric effects (e.g., opening of the CNC angles and hindrance to OH fixation on the nitrogen lone pair). Infrared (IR) spectra show the attachment of 4-fluorophenol to the nitrile nitrogen of Me2NCH2C[Formula: see text]N and Me2NCH2CH2C[Formula: see text]N, to the oxygen of N-methylmorpholine, and to the π electrons of (HC[Formula: see text]CCH2)3N and (PhCH2)3N, in addition to the attachment to the amino nitrogen. In (PhCH2)3N, the electron-withdrawing effect of the three benzyl substituents and, mainly, the very important congestion of the nitrogen lone pair reduce the nitrogen hydrogen-bond basicity almost to nothing, so that tribenzylamine, a nitrogen Brønsted base, turns to a π base in hydrogen bonding. From this example, the large differences between the pKHB and pKa scales of organic bases are emphasized.Key words: basicity, hydrogen bonding, tertiary amines, pKHB scale.

scholarly journals Theoretical Study of the Structures of 4-(2,3,5,6-Tetrafluoropyridyl)Diphenylphosphine Oxide and Tris(Pentafluorophenyl)Phosphine Oxide: Why Does the Crystal Structure of (Tetrafluoropyridyl)Diphenylphosphine Oxide Have Two Different P=O Bond Lengths?

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2778
Author(s):  
Joseph R. Lane ◽  
Graham C. Saunders
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Phosphine Oxide ◽  
Density Functional ◽  
Lone Pair ◽  
Diphenylphosphine Oxide ◽  
Functional Theory ◽  
Weak Hydrogen Bonding ◽  
Independent Molecules ◽  
The Difference

The crystal structure of 4-(2,3,5,6-tetrafluoropyridyl)diphenylphosphine oxide (1) contains two independent molecules in the asymmetric unit. Although the molecules are virtually identical in all other aspects, the P=O bond distances differ by ca. 0.02 Å. In contrast, although tris(pentafluorophenyl)phosphine oxide (2) has a similar crystal structure, the P=O bond distances of the two independent molecules are identical. To investigate the reason for the difference, a density functional theory study was undertaken. Both structures comprise chains of molecules. The attraction between molecules of 1, which comprises lone pair–π, weak hydrogen bonding and C–H∙∙∙arene interactions, has energies of 70 and 71 kJ mol−1. The attraction between molecules of 2 comprises two lone pair–π interactions, and has energies of 99 and 100 kJ mol−1. There is weak hydrogen bonding between molecules of adjacent chains involving the oxygen atom of 1. For one molecule, this interaction is with a symmetry independent molecule, whereas for the other, it also occurs with a symmetry related molecule. This provides a reason for the difference in P=O distance. This interaction is not possible for 2, and so there is no difference between the P=O distances of 2.

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.

Interaction between an Amide Nitrogen Lone Pair and a Noncontiguous Carbonyl Carbon and its Effect on Amide Rotation

Nature ◽  
1971 ◽  
Vol 230 (5294) ◽  
pp. 457-459 ◽  
Author(s):  
P. S. PORTOGHESE ◽  
J. G. TURCOTTE
Keyword(s):  
Lone Pair ◽  
Amide Nitrogen ◽  
Carbonyl Carbon ◽  
Nitrogen Lone Pair ◽  
Amide Rotation

Influence of Electrostatic Interactions and Hydrogen Bonding on the Activity of Cyclodextrin-based Superoxide Dismutase Models

2001 ◽  
Vol 13 (5) ◽  
pp. 619-625 ◽  
Author(s):  
Alex Fragoso ◽  
Roberto Cao ◽  
Alicia Díz ◽  
Ileana Sånchez ◽  
Leticia Sånchez
Keyword(s):  
Superoxide Dismutase ◽  
Hydrogen Bonding ◽  
Electrostatic Interactions
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