On the error in the nucleus-centered multipolar expansion of molecular electron density and its topology: A direct-space computational study

Michael, J. Robert; Koritsánszky, T.

doi:10.1063/1.4983633

Cited by 6 publications

(6 citation statements)

References 43 publications

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“…ðÞ .H owever, as with any other model, care must be taken not to interpret the model beyondi ts limits [106] and not to ask for information absent in the experimental data. [107] An example of as uitable researchq uestion is measuring the correct covalentb ond distance from X-ray diffraction in bonds involving hydrogen atoms.…”

Section: Chargedensity From X-ray Diffractionmentioning

confidence: 99%

Quantum Crystallography: Current Developments and Future Perspectives

Genoni

Bučinský

Claiser

et al. 2018

Chemistry A European J

127

114

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Crystallography and quantum mechanics have always been tightly connected because reliable quantum mechanical models are needed to determine crystal structures. Due to this natural synergy, nowadays accurate distributions of electrons in space can be obtained from diffraction and scattering experiments. In the original definition of quantum crystallography (QCr) given by Massa, Karle and Huang, direct extraction of wavefunctions or density matrices from measured intensities of reflections or, conversely, ad hoc quantum mechanical calculations to enhance the accuracy of the crystallographic refinement are implicated. Nevertheless, many other active and emerging research areas involving quantum mechanics and scattering experiments are not covered by the original definition although they enable to observe and explain quantum phenomena as accurately and successfully as the original strategies. Therefore, we give an overview over current research that is related to a broader notion of QCr, and discuss options how QCr can evolve to become a complete and independent domain of natural sciences. The goal of this paper is to initiate discussions around QCr, but not to find a final definition of the field.

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Section: Chargedensity From X-ray Diffractionmentioning

confidence: 99%

Quantum Crystallography: Current Developments and Future Perspectives

Genoni

Bučinský

Claiser

et al. 2018

Chemistry A European J

127

114

View full text Add to dashboard Cite

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“…The results presented below are based on the combination of the vector fields experimentally obtained for the crystals and on the ones theoretically computed for the optimized molecules and associates. The latter systems are devoid of the shortcomings of multipole modeling , and experimental errors, − and a more accurate description and better approximations are also available for them. Such a consideration should make it possible to exclude the possibility that the regularities described in the previous paragraphs are artifacts of the multipole model and to provide justifications for the sufficient accuracy of the inner-crystal force fields obtained experimentally.…”

Section: Introductionmentioning

confidence: 99%

Electronic and Crystal Packing Effects in Terms of Static and Kinetic Force Field Features: Picolinic Acid N-Oxide and Methimazole

Kartashov

Shteingolts

Stash

et al. 2023

Crystal Growth & Design

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Herein, we experimentally obtained and studied the inner-crystal scalar potential fields and the associated vector force fields of static and kinetic nature in picolinic acid N-oxide (PANO) and methimazole. The “through-bond” and “through-space” electronic effects were defined and distinguished via the vector fields and concurred with the penetration of the electron contributor’s electrostatic and kinetic force field pseudoatoms (φes- and φ k -basins) into the occupier’s chemical atom (ρ-basin). A special focus was given to the dipolar N+–O– bond as well as to the thioamide N–CS and carboxylic OC–OH fragments. An unusual way of interatomic charge transfer was revealed between two nonbonded hydrogen atoms [COO−]H···H[−C] in the PANO crystal. The experimental electric and kinetic force fields in the molecular crystals were compared to the theoretical ones for the free molecules and hydrogen-bonded associates, which helped figure out the natural consequences of the crystal packing effect. As expected, the appearance of neighboring attractors in a dense crystal packing requires zero-flux surfaces (ZFSs) emerging in the vector fields and the compression of the outer force field pseudoatoms of a molecule. We proposed to consider a ZFS in the kinetic force field to be a turning surface for electrons in the sense that an electron passed through the boundary is immediately affected by the redirected force attributed to another attractor. The strengthening and noticeable increase observed in the covalency of the intramolecular hydrogen bond O–H···O in the PANO crystal is a direct consequence of such compression of the hydrogen atom and pseudoatoms by the inner-crystal environment. The Pauli and fermionic scalar and vector fields were applied to locate electron lone pairs and describe their involvement in noncovalent interactions within the donor–acceptor mechanism.

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“…It is somewhat expected that the results obtained from the theoretical calculations might differ substantially from the experimental data. Differences between the quantum-chemical calculations and the experimental multipole data can be explained, on the one hand, by the dependence of theoretical methods on a functional/basis set or, on the other hand, by the accuracy of the multipole model approximations. − Based on the topological characteristics of BCPs, both hydrogen bonds still belong to closed-shell interactions. Hydrogen bond H(3a)···S(1b) persisted to be noticeably stronger than the H(3b)···S(1a) bond.…”

Section: Resultsmentioning

confidence: 99%

X-ray Charge Density Study of the Drug Methimazole with Z′ = 2: Differences in the Electronic Structure of the Thiourea Core due to Crystal Packing Effects

Shteingolts

Fayzullin

2020

Crystal Growth & Design

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Herein we present a detailed experimental charge-density study for the low-temperature polymorph of the antithyroid drug methimazole crystallized with two crystallographically independent molecules lacking conformational freedom. Quantum-topological analysis of experimental electron density allowed us to detect the distinctive differences in the electron distribution within their thiourea groups, arising primarily from crystal packing effects. The sulfur atom S(1a) features two separate regions of positive deformation density, while the other atom S(1b) is found to be more diffuse with positive density taking a toroidal form. In contrast to S(1a), the couple of the lone pairs of S(1b) derived by nonbonding charge concentrations takes a more significant turn relative to the molecular plane and proves to be distorted. We also report an ambiguous electronic structure of the heteroatoms, i.e., the appearance of "false" Laplacian critical points (CPs) (3, +3) or splitting of true ones, which is caused by neglecting or excessive use of Gram−Charlier coefficients. Further, the turn of lone pairs, behavior of source function within the thiourea fragment, and atomic charges indicate decreased bond order of the formally double CS bond and increased contribution of the [CH 3 −]N (+) C−S (−) canonical structure into π-conjugation. Moreover, intermolecular hydrogen bonds N−H•••S and head-to-head interactions CS•••SC are described.

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On the error in the nucleus-centered multipolar expansion of molecular electron density and its topology: A direct-space computational study

Cited by 6 publications

References 43 publications

Quantum Crystallography: Current Developments and Future Perspectives

Quantum Crystallography: Current Developments and Future Perspectives

Electronic and Crystal Packing Effects in Terms of Static and Kinetic Force Field Features: Picolinic Acid N-Oxide and Methimazole

X-ray Charge Density Study of the Drug Methimazole with Z′ = 2: Differences in the Electronic Structure of the Thiourea Core due to Crystal Packing Effects

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