Topology of Quantum Mechanical Current Density Vector Fields Induced in a Molecule by Static Magnetic Perturbations

Lazzeretti, Paolo

doi:10.1007/978-3-319-29022-5_7

Cited by 4 publications

(3 citation statements)

References 111 publications

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“…Electric dipole polarizabilities [313,316] of nuclear magnetic shielding and nuclear spin-spin coupling have the required property of being odd under P, and have been proposed for direct chiral discrimination by Buckingham [66,317] and Buckingham and Fischer [312]. Definitions and computational recipes are arrived at by RSPT and by theoretical procedures explicitly considering the quantum mechanical current densities induced in the electrons of a molecule by the external magnetic field and the intramolecular magnetic dipoles at the nuclei [123,221,318,319].…”

Section: Electric Polarizabilities Of Nuclear Magnetic Shielding and ...mentioning

confidence: 99%

Chiral discrimination in nuclear magnetic resonance spectroscopy

Lazzeretti

2017

J. Phys.: Condens. Matter

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Chirality is a fundamental property of molecules whose spatial symmetry is characterized by the absence of improper rotations, making them not superimposable to their mirror image. Chiral molecules constitute the elementary building blocks of living species and one enantiomer is favoured in general (e.g. L-aminoacids and D-sugars pervade terrestrial homochiral biochemistry) because most chemical reactions producing natural substances are enantioselective. Since the effect of chiral chemicals and drugs on living beings can be markedly different between enantiomers, the quest for practical spectroscopical methods to scrutinize chirality is an issue of great importance and interest. Nuclear magnetic resonance (NMR) is a topmost analytical technique, but spectrometers currently used are 'blind' to chirality, i.e. unable to discriminate the two mirror-image forms of a chiral molecule, because, in the absence of a chiral solvent, the spectral parameters, chemical shifts and spin-spin coupling constants are identical for enantiomers. Therefore, the development of new procedures for routine chiral recognition would offer basic support to scientists. However, in the presence of magnetic fields, a distinction between true and false chirality is mandatory. The former epitomizes natural optical activity, which is rationalized by a time-even pseudoscalar, i.e. the trace of a second-rank tensor, the mixed electric dipole/magnetic dipole polarizability. The Faraday effect, magnetic circular dichroism and magnetic optical activity are instead related to a time-odd axial vector. The present review summarizes recent theoretical and experimental efforts to discriminate enantiomers via NMR spectroscopy, with the focus on the deep connection between chirality and symmetry properties under the combined set of fundamental discrete operations, namely charge conjugation, parity (space inversion) and time (motion) reversal.

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Section: Electric Polarizabilities Of Nuclear Magnetic Shielding and ...mentioning

confidence: 99%

Chiral discrimination in nuclear magnetic resonance spectroscopy

Lazzeretti

2017

J. Phys.: Condens. Matter

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“…These surfaces are known as separatrix surfaces. Topological characterizations of the induced molecular current density field are fairly abundant in the literature 6,8–26 and analogies between the QTAIM analysis and the SG graph analysis have been discussed. 3 Unlike for bond paths in QTAIM, there are no established empirical rules or simple models of interpretation for the topology of the magnetically induced current density, yet.…”

Section: Introductionmentioning

confidence: 99%

A natural scheme for the quantitative analysis of the magnetically induced molecular current density using an oriented flux-weighted stagnation graph. I. A minimal example for LiH

Berger

Dimitrova

2022

Phys. Chem. Chem. Phys.

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“…[29,30,33,49] A more general definition of current susceptibility vector has been proposed. [65] The relationships (1), (8), and (10) hold in the limit of the one-loop polygonal model based on classical BSL. [46,47] They are not supposed to work with satisfactory accuracy for PAHs supporting delocalized currents flowing in many loops, which may have different centers and areas and are placed at different heights from the plane of the molecule.…”

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confidence: 99%

Polygonal current models for polycyclic aromatic hydrocarbons and graphene sheets of various shapes

Pelloni

Lazzeretti

2017

J Comput Chem

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Assuming that graphene is an "infinite alternant" polycyclic aromatic hydrocarbon resulting from tessellation of a surface by only six-membered carbon rings, planar fragments of various size and shape (hexagon, triangle, rectangle, and rhombus) have been considered to investigate their response to a magnetic field applied perpendicularly. Allowing for simple polygonal current models, the diatropicity of a series of polycyclic textures has been reliably determined by comparing quantitative indicators, the p-electron contribution to I B , the magnetic field-induced current susceptibility of the peripheral circuit, to n k and to r k ðCMÞ52NICS k ðCMÞ, respectively the out-of-plane components of the magnetizability tensor and of the magnetic shielding tensor at the center of mass. Extended numerical tests and the analysis based on the polygonal model demonstrate that (i) n k and r k ðCMÞ yield inadequate and sometimes erroneous measures of diatropicity, as they are heavily flawed by spurious geometrical factors, (ii) I B values computed by simple polygonal models are valid quantitative indicators of aromaticity on the magnetic criterion, preferable to others presently available, whenever current susceptibility cannot be calculated ab initio as a flux integral, (iii) the hexagonal shape is the most effective to maximize the strength of p-electron currents over the molecular perimeter, (iv) the edge current strength of triangular and rhombic graphene fragments is usually much smaller than that of hexagonal ones, (v) doping by boron and nitrogen nuclei can regulate and even inhibit peripheral ring currents, (vi) only for very large rectangular fragments can substantial current strengths be expected.

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Topology of Quantum Mechanical Current Density Vector Fields Induced in a Molecule by Static Magnetic Perturbations

Cited by 4 publications

References 111 publications

Chiral discrimination in nuclear magnetic resonance spectroscopy

Chiral discrimination in nuclear magnetic resonance spectroscopy

A natural scheme for the quantitative analysis of the magnetically induced molecular current density using an oriented flux-weighted stagnation graph. I. A minimal example for LiH

Polygonal current models for polycyclic aromatic hydrocarbons and graphene sheets of various shapes

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