Journal ArticleDOI
Low barrier hydrogen bonds in sterically modified Schiff bases
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TLDR
In this paper, the steric repulsion of the substituted methyl group results in an unusual strengthening of the hydrogen bonds, decreasing the barrier for the proton movement within the hydrogen bridge, which leads to a delocalization of the position.Abstract:
Five derivatives of an ortho-hydroxy Schiff base (2-(N-alkyl-α-iminoethyl)phenols) with very short intramolecular hydrogen bonds (dO(H)⋯N
≤ 2.500 A) were synthesised. The crystal structures were determined. The steric repulsion of the substituted methyl group results in an unusual strengthening of the hydrogen bonds, decreasing the barrier for the proton movement within the hydrogen bridge, which leads to a delocalization of the proton position. The very strong influence of the character of the substituent in the phenol ring as well as the character of the N-alkyl chain on the proton distribution is demonstrated for these hydrogen bonds from the so-called inversion range.read more
Citations
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Interrelation between H-bond and Pi-electron delocalization.
TL;DR: H-bond plays a double role in biological systems: on one hand, as a relatively strong directional interaction, it leads to relatively stable supramolecular structures, and on the other hand, because of dynamic features of the proton, it is an active site for initiation of chemical reactions.
Journal ArticleDOI
Heterobimetallic Zn(II)-Ln(III) phenylene-bridged schiff base complexes, computational studies, and evidence for singlet energy transfer as the main pathway in the sensitization of near-infrared Nd3+ luminescence.
Wing Kit Lo,Wai-Kwok Wong,Wai-Yeung Wong,Jianping Guo,Kai Tai Yeung,Yuen Kit Cheng,Xiaoping Yang,Richard A. Jones +7 more
TL;DR: NIR sensitization studies of [Zn(mu-L')Nd(NO3)3(H2O)n] (L' = L1-L4) complexes showed that Nd3+ sensitization took place via the 3LC and 1LC states when the spacer between the imine groups of the Schiff base ligand was an ethylene and a phenylene unit.
Journal ArticleDOI
Theoretical studies of strong hydrogen bonds
TL;DR: In this article, strong hydrogen bonds are analyzed and their specific characteristics are given, and the decomposition scheme of the interaction energy and the Bader theory of atoms in molecules are discussed.
Journal ArticleDOI
Variable-Temperature X-ray Crystallographic and DFT Computational Study of the NH···O/N···HO Tautomeric Competition in 1-(Arylazo)-2-naphthols. Outline of a Transiton-State Hydrogen-Bond Theory
TL;DR: In this article, a series of 1-arylazo-2-naphthols (AANs) with tautomeric and dynamically disordered NH···O ⇌ N···HO bonds according to the electronic properties of their substituents were studied by X-ray crystallography.
Journal ArticleDOI
Do coupling constants and chemical shifts provide evidence for the existence of resonance-assisted hydrogen bonds?
TL;DR: In this article, the magnetic properties of the two-bond spin-spin coupling constants and the chemical shifts of the hydrogenbonded protons provided evidence for the existence of resonance-assisted hydrogen bonds (RAHBs).
References
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Journal ArticleDOI
Density‐functional thermochemistry. III. The role of exact exchange
TL;DR: In this article, a semi-empirical exchange correlation functional with local spin density, gradient, and exact exchange terms was proposed. But this functional performed significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.
Journal ArticleDOI
Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
TL;DR: Numerical calculations on a number of atoms, positive ions, and molecules, of both open- and closed-shell type, show that density-functional formulas for the correlation energy and correlation potential give correlation energies within a few percent.
Journal ArticleDOI
Phase annealing in SHELX-90: direct methods for larger structures
TL;DR: In this article, a phase annealing method, related to the simulated-annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution.
Journal ArticleDOI
Self—Consistent Molecular Orbital Methods. XII. Further Extensions of Gaussian—Type Basis Sets for Use in Molecular Orbital Studies of Organic Molecules
TL;DR: In this article, two extended basis sets (termed 5-31G and 6 -31G) consisting of atomic orbitals expressed as fixed linear combinations of Gaussian functions are presented for the first row atoms carbon to fluorine.
Journal ArticleDOI
The hydrogen bond in the solid state.
TL;DR: The hydrogen bond is the most important of all directional intermolecular interactions, operative in determining molecular conformation, molecular aggregation, and the function of a vast number of chemical systems ranging from inorganic to biological.
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