A Critical Look at Linus Pauling’s Influence on the Understanding of Chemical Bonding

Pan, Sudip; Frenking, Gernot

doi:10.3390/molecules26154695

Cited by 11 publications

(11 citation statements)

References 119 publications

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“…The complex stabilization energy (correlated with the A – D bond dissociation energy ( D e )) and the strength of the A – D bond can characterize the stability of the complex. However, as discussed below, these properties do not always directly correlate 9 , 13 , 26 .…”

Section: Introductionmentioning

confidence: 98%

The stability of covalent dative bond significantly increases with increasing solvent polarity

Manna

Lamanec

et al. 2022

Nat Commun

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It is generally expected that a solvent has only marginal effect on the stability of a covalent bond. In this work, we present a combined computational and experimental study showing a surprising stabilization of the covalent/dative bond in Me3NBH3 complex with increasing solvent polarity. The results show that for a given complex, its stability correlates with the strength of the bond. Notably, the trends in calculated changes of binding (free) energies, observed with increasing solvent polarity, match the differences in the solvation energies (ΔEsolv) of the complex and isolated fragments. Furthermore, the studies performed on the set of the dative complexes, with different atoms involved in the bond, show a linear correlation between the changes of binding free energies and ΔEsolv. The observed data indicate that the ionic part of the combined ionic-covalent character of the bond is responsible for the stabilizing effects of solvents.

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Section: Introductionmentioning

confidence: 98%

The stability of covalent dative bond significantly increases with increasing solvent polarity

Manna

Lamanec

et al. 2022

Nat Commun

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“…Comprehensive computational studies on transition metal carbonyl complexes, for example, performed by Frenking and co‐workers 65–70 and other groups 71–77 have applied the DC model to explore the stabilizing role of CO ligands for both mono and poly‐nuclear metal‐carbonyl complexes. Some limitation of the DC and other Lewis type bonding model were recently pointed out 78–80 . Two other popular strategies to describe M‐L bond strengths are based on (1) M‐L bond dissociation energies (BDE)s 76,81–84 and (2) M‐L bond lengths.…”

Section: Introductionmentioning

confidence: 99%

“…Some limitation of the DC and other Lewis type bonding model were recently pointed out. [78][79][80] Two other popular strategies to describe M-L bond strengths are based on (1) M-L bond dissociation energies (BDE)s 76,[81][82][83][84] and (2) M-L bond lengths. While all these attempts have certainly contributed to the chemical understanding of metal complexes, one has to realize that BDE values or bond lengths provide little insight into the intrinsic strength of the M-L bond.…”

Section: Introductionmentioning

confidence: 99%

CO bonding in hexa‐ and pentacoordinate carboxy‐neuroglobin: A quantum mechanics/molecular mechanics and local vibrational mode study

2022

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We present a comprehensive investigation on the different role of CO in carboxyneuroglobin (1) as ligand of the heme group in the active site forming a bond with the heme iron and (2) dissociated from the heme group but still trapped inside the active site, focusing on two specific orientations, one with CO perpendicular to the plane defined by the distal histidine of the enzyme (form A) and one with CO located parallel to that plane (form B). Our study includes wild type carboxy-neuroglobin and nine known protein mutations. Considering that the distal histidine interacting with the heme group can adapt two different tautomeric forms and the two possible orientations of the dissociated CO, a total of 36 protein systems were analyzed in this study. Fully optimized geometries and vibrational frequencies were calculated at the QM/MM level, followed by the local mode analysis, to decode CO bond properties.The intrinsic bond strengths derived from the local mode analysis, complemented with NBO and QTAIM data, reveal that the strength of the CO bond, in the hexacoordinate (where CO is a ligand of the heme group) and pentacoordinate (where CO is dissociated from the heme group) scenarios, is dominated by through bond and through space charge transfer between CO and Fe, fine-tuned by electrostatic and dispersion interactions with the side chain amino acids in the distal heme pocket.Suggestions are made as to advise on how protein modifications can influence the molecular properties of the coordinated or dissociated CO, which could serve the fine-tuning of existing and the design of new neuroglobin models with specific FeC and CO bond strengths.

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“… 96 − 99 Recent studies based on the Pauling valence bond theory lead to formulation of the charge-shift bond, a new type of bonding besides the covalent and ionic bonds. 96 , 100 − 104 The total bond energy of the 2c3e charge-shift bond is obtained from the resonance of the charge shift between the valence bond structures. Here none of the valence bond structures themselves have any bonding, and in each valence bond, the three electrons maintain Pauli repulsion.…”

Section: Introductionmentioning

confidence: 99%

Unusual Water Oxidation Mechanism via a Redox-Active Copper Polypyridyl Complex

et al. 2023

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To improve Cu-based water oxidation (WO) catalysts, a proper mechanistic understanding of these systems is required. In contrast to other metals, high-oxidation-state metal–oxo species are unlikely intermediates in Cu-catalyzed WO because π donation from the oxo ligand to the Cu center is difficult due to the high number of d electrons of CuII and CuIII. As a consequence, an alternative WO mechanism must take place instead of the typical water nucleophilic attack and the inter- or intramolecular radical–oxo coupling pathways, which were previously proposed for Ru-based catalysts. [CuII(HL)(OTf)2] [HL = Hbbpya = N,N-bis(2,2′-bipyrid-6-yl)amine)] was investigated as a WO catalyst bearing the redox-active HL ligand. The Cu catalyst was found to be active as a WO catalyst at pH 11.5, at which the deprotonated complex [CuII(L –)(H2O)]+ is the predominant species in solution. The overall WO mechanism was found to be initiated by two proton-coupled electron-transfer steps. Kinetically, a first-order dependence in the catalyst, a zeroth-order dependence in the phosphate buffer, a kinetic isotope effect of 1.0, a ΔH ⧧ value of 4.49 kcal·mol–1, a ΔS ⧧ value of −42.6 cal·mol–1·K–1, and a ΔG ⧧ value of 17.2 kcal·mol–1 were found. A computational study supported the formation of a Cu–oxyl intermediate, [CuII(L •)(O•)(H2O)]+. From this intermediate onward, formation of the O–O bond proceeds via a single-electron transfer from an approaching hydroxide ion to the ligand. Throughout the mechanism, the CuII center is proposed to be redox-inactive.

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A Critical Look at Linus Pauling’s Influence on the Understanding of Chemical Bonding

Cited by 11 publications

References 119 publications

The stability of covalent dative bond significantly increases with increasing solvent polarity

The stability of covalent dative bond significantly increases with increasing solvent polarity

CO bonding in hexa‐ and pentacoordinate carboxy‐neuroglobin: A quantum mechanics/molecular mechanics and local vibrational mode study

Unusual Water Oxidation Mechanism via a Redox-Active Copper Polypyridyl Complex

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