Steric clash in real space: biphenyl revisited

Laplaza, Rubén; Boto, Roberto A.; Contreras‐García, Julia; Montero‐Campillo, M. Merced

doi:10.1039/d0cp03359f

Cited by 19 publications

(44 citation statements)

References 24 publications

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“…The graphical representation of the reduced density gradient,

s (r) = |\nabla ρ ((), r)| / ρ {(r)}^{4 / 3}

, for the BP moiety in the crystal is shown in Figure 4(c); it does not provide any indication of steric strain involving the H⋅⋅⋅H contact but the non‐covalent nature of this interaction. A similar result has been recently reported for the planar isolated BP molecule [28] …”

Section: Resultssupporting

confidence: 91%

Non‐Covalent Interactions in the Biphenyl Crystal: Is the Planar Conformer a Transition State?

Landeros‐Rivera

Jancik

Moreno‐Esparza

et al. 2021

Chemistry A European J

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A combined experimental and theoretical study of the biphenyl (BP) crystal is presented. The X‐ray diffraction data collected at 100 K were subjected to Hirshfeld atom and multipole refinements of the electron density, ρ(r). A theoretical exploration of the potential energy surface (PES) of the crystal was also carried out. This investigation challenges the common assumption that the planar structure of BP in the phase I crystal is an average of two twisted configurations in a double‐well potential. The theoretical computations provide compelling evidence that this structure corresponds to a minimum on the PES hence to a stable molecular arrangement. Consistently, the experiment showed no evidence of positional or dynamic disorder. The intramolecular hydrogen‐hydrogen bonds detected are not repulsive. The topological analysis of the experimental and theoretical ρ(r) reveals that both the intra‐ and intermolecular H⋅⋅⋅H and the C−H⋅⋅⋅π contacts stabilize the BP crystal.

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“…The graphical representation of the reduced density gradient,

s (r) = |\nabla ρ ((), r)| / ρ {(r)}^{4 / 3}

Section: Resultssupporting

confidence: 91%

Non‐Covalent Interactions in the Biphenyl Crystal: Is the Planar Conformer a Transition State?

Landeros‐Rivera

Jancik

Moreno‐Esparza

et al. 2021

Chemistry A European J

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“…A particularly controversial example is that of close H,H contacts in the planar conformer of biphenyl (Bph), which has been the subject of a raging debate for the last few decades. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] The H,H contacts serve as a good case study of the difficulty in reconciling atomistic chemistry with holistic quantum approaches. In a recent study [23] on a purely MO-based description of the H,H contact in Bph, we have shown that (a) MO isosurfaces provide very little information on the contact or any other bond in the molecule, (b) each MO contributes in a vastly different nature to every diatomic interaction, and (c) only through the combination of all MOs in a molecule can an interaction be characterized in any meaningful manner.…”

Section: Introductionmentioning

confidence: 99%

The CH···HC interaction in biphenyl is a delocalized, molecular‐wide and entirely non‐classical interaction: Results from FALDI analysis

2021

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In this study we aim to determine the origin of the electron density describing a CHÁÁÁHC interaction in planar and twisted conformers of biphenyl. In order to achieve this, the fragment, atomic, localized, delocalized, intra-and inter-atomic (FALDI) decomposition scheme was utilized to decompose the density in the inter-nuclear region between the ortho-hydrogens in both conformers. Importantly, the structural integrity, hence also topological properties, were fully preserved as no 'artificial' partitioning of molecules was implemented. FALDI-based qualitative and quantitative analysis revealed that the majority of electron density arises from two, non-classical and non-local effects: strong overlap of ortho C H σ-bonds, and long-range electron delocalization between the phenyl rings and ortho carbons and hydrogens. These effects resulted in a delocalized electron channel, that is, a density bridge or a bond path in a QTAIM terminology, linking the H-atoms in the planar conformer. The same effects and phenomena are present in both conformers of biphenyl. We show that the CHÁÁÁHC interaction is a molecular-wide event due to large and long-range electron delocalization, and caution against approaches that investigate CHÁÁÁHC interactions without fully taking into account the remainder of the molecule.

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“…Furthermore, we found that the region where the protobranches seems to appear in the alkanes studied here is above s(r)=0.60. Finally, we stablish that the classical steric clash situation in the studied compound comes from the interplay of attractive and repulsive NCI, as outlined in the reference [7] …”

Section: Discussionmentioning

confidence: 88%

“…As mentioned before, the main outcome in the analysis of the steric factors is the lack of rigorous definition. To date, different approaches and energy partition schemes have been proposed to quantify it, but there is no consensus about which is the best method [7,20–26] . Therefore, it is important to examine steric phenomena using methodologies which do not depend on the energy partition approximation.…”

Section: Introductionmentioning

confidence: 99%

NCI Study of the Influence of Steric Hindrance on the Conformational Isomers of Propane, Butane, and Ethane Derivatives

2022

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The role of the steric clash in the rotational energy barrier in CX 3 CX 3 (X=H, CH 3 , F), propane, and butane compounds was studied using the NCI method and QTAIM approach. We found that the values of the repulsive density integral of NCI agrees with the traditional chemical steric model, as it increases with the size of the substituent. However, not in every case studied here, was the steric clash identified as the origin of the energy barrier. In the ethane case we note the absence of repulsive and attractive NCI across the full spectrum of the dihedral angles studied, whereas only in the propane and butane cases are the results consistent with the classical picture of the steric clash being the origin of the energy barrier. The energy profile for 2,2,3,3-tetramethylbutane shows two energy barriers of 8.7 kcal/mol and 0.96 kcal/mol, their origin was analysed in terms of the alkyl-alkyl interactions.

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Steric clash in real space: biphenyl revisited

Abstract: A textbook case of twisted structure due to hydrogen-hydrogen steric clash, the biphenyl molecule, has been studied in real space from a new perspective. Long-term discrepancies regarding the origin of...

Cited by 19 publications

References 24 publications

Non‐Covalent Interactions in the Biphenyl Crystal: Is the Planar Conformer a Transition State?

Non‐Covalent Interactions in the Biphenyl Crystal: Is the Planar Conformer a Transition State?

The CH···HC interaction in biphenyl is a delocalized, molecular‐wide and entirely non‐classical interaction: Results from FALDI analysis

NCI Study of the Influence of Steric Hindrance on the Conformational Isomers of Propane, Butane, and Ethane Derivatives

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