Characterization of CF Bonds with Multiple‐Bond Character: Bond Lengths, Stretching Force Constants, and Bond Dissociation Energies

Kraka, Elfi

doi:10.1002/cphc.200800699

Cited by 107 publications

(88 citation statements)

References 74 publications

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“…This result was contrasted by an investigation of Ohno and coworkers (entry 61), who could derive a simplified Badger-type equation by using effective bond lengths in the study of 74 CX bonds (X¼C, Si, Ge, N, P, As, O, S, Se, F, Cl, Br) contained in polyatomic molecules. Kraka and Cremer [67] made a similar observation when investigating some 46 isoelectronic CO and CF þ bonds. For the purpose of resolving these contradictory claims on the applicability of the Badger-Herschbach-Laurie equations between bond length and bond stretching force constant, there is the need to reinvestigate the physical basis of Badger-type relationships and to obtain a reliable assessment of their predictive value.…”

Section: Introductionmentioning

confidence: 67%

“…Instead, there is the need for local mode information that provides bond stretching frequencies or force constants, which are no longer contaminated by contributions from other vibrational modes. For the purpose of clarifying the relationship between delocalized normal and local internal coordinate modes, we present here the theory of the adiabatic internal coordinate modes (AICoMs), recently used to set up bond length-bond stretching force constant relationships by Kraka and Cremer [67]. The standard method for calculating the vibrational spectra of polyatomic molecules with K atoms is based on two major approximations [73,74].…”

Section: Dissection Of a Polyatomic Molecule Into A Collection Of Quamentioning

confidence: 99%

“…For example, the standard procedure to calculate the geometry of a molecule is based on an initial guess of the energy Hessian derived with the help of the Badger rule [42,55]. It is due to these three reasons that there is ongoing research exploring the relationships between bond length r, bond stretching [56][57][58][59][60][61][62][63][64][65][66][67]). Investigations focusing on relationships between bond properties such as r, k, v, N, and D are summarized in Table 4.1.…”

Section: Introductionmentioning

confidence: 99%

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Generalization of the Badger Rule Based on the Use of Adiabatic Vibrational Modes

Kraka

Larsson

Cremer

2010

Computational Spectroscopy

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115

150

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Empirical relationships relating bond lengths to the corresponding bond stretching frequencies or bond stretching force constants were first derived in 1920s (see Table 4.1 for a summary) and have ever since been a topic of research on the nature of the chemical bond . It is remarkable that in a time of easily accessible quantum chemical results, there remains a need for empirically based estimates of either bond lengths or stretching frequencies. There are three primary reasons why such empirical rules and relationships are still valuable tools for modern research:(1) Established relationships between bond properties add to our understanding of the chemical bond, especially if they can be rationalized on a quantum mechanical basis because bonding between atoms is a quantum mechanical phenomenon.(2) There are experimental situations in which it is relatively easy to measure one bond property but difficult to obtain other bond properties. For example, it is easier to measure the vibrational spectra of a compound than to carry out a structural analysis. This is especially true for solid materials that do not crystallize, molecules on a surface, or molecules in some form of aggregation. If quantum chemical calculations are feasible only for model systems rather than the actual targets of chemical research, then vibrational spectroscopy may be the only tool for obtaining information that provides an insight into bond properties. (3) In the realm of computational chemistry, there is also a need for empirical relationships. They may be used to determine suitable bonding force fields for molecular mechanics utilizing force constant -bond length relationships. For quantum chemical geometry optimization, there is the need to set up a guess matrix of energy second derivatives (the Hessian matrix corresponding to the force constant matrix of a molecule), which is best done with the help of available geometry information and a suitable force constant -bond length relationship. For example, the standard procedure to calculate the geometry of a molecule is based on an initial guess of the energy Hessian derived with the help of the Badger rule [42,55]. It is due to these three reasons that there is ongoing research exploring the relationships between bond length r, bond stretching Computational Spectroscopy: Methods, Experiments and Applications. Edited by J€ org Grunenberg

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Section: Introductionmentioning

confidence: 67%

Section: Dissection Of a Polyatomic Molecule Into A Collection Of Quamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Generalization of the Badger Rule Based on the Use of Adiabatic Vibrational Modes

Kraka

Larsson

Cremer

2010

Computational Spectroscopy

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115

150

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“…The force constant k a of an AB stretching mode (A and B being bonded) is a reliable measure for the AB bond strength [132][133][134][135]. This does not hold for the local frequency ω a which depends also on the masses of atoms A and B thus disguising the electronic origin of the bond strength.…”

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confidence: 98%

Strength of the Pnicogen Bond in Complexes Involving Group Va Elements N, P, and As

2014

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A set of 36 pnicogen homo- and heterodimers, R3E···ER3 and R3E···E′R′3, involving differently substituted group Va elements E = N, P, and As has been investigated at the ωB97X-D/aug-cc-pVTZ level of theory to determine the strength of the pnicogen bond with the help of the local E···E′ stretching force constants k(a). The latter are directly related to the amount of charge transferred from an E donor lone pair orbital to an E′ acceptor σ* orbital, in the sense of a through-space anomeric effect. This leads to a buildup of electron density in the intermonomer region and a distinct pnicogen bond strength order quantitatively assessed via k(a). However, the complex binding energy ΔE depends only partly on the pnicogen bond strength as H,E-attractions, H-bonding, dipole-dipole, or multipole-multipole attractions also contribute to the stability of pnicogen bonded dimers. A variation from through-space anomeric to second order hyperonjugative, and skewed π,π interactions is observed. Charge transfer into a π* substituent orbital of the acceptor increases the absolute value of ΔE by electrostatic effects but has a smaller impact on the pnicogen bond strength. A set of 10 dimers obtains its stability from covalent pnicogen bonding whereas all other dimers are stabilized by electrostatic interactions. The latter are quantified by the magnitude of the local intermonomer bending force constants XE···E′. Analysis of the frontier orbitals of monomer and dimer in connection with the investigation of electron difference densities, and atomic charges lead to a simple rationalization of the various facets of pnicogen bonding. The temperature at which a given dimer is observable under experimental conditions is provided.

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“…One of the most useful applications is the analysis of bond dissociation energy. In fact, bond dissociation energy has been analyzed to understand the bond strength, bond character, and reactivity [126,127,128,129,130,131,132,133,134,135]. It was found that the C–F bond is relatively stronger than C–H.…”

Section: Chemical Degradation Mechanism Studied By Theoretical Metmentioning

confidence: 99%

A Review of Molecular-Level Mechanism of Membrane Degradation in the Polymer Electrolyte Fuel Cell

Ishimoto

Koyama

2012

Membranes

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Chemical degradation of perfluorosulfonic acid (PFSA) membrane is one of the most serious problems for stable and long-term operations of the polymer electrolyte fuel cell (PEFC). The chemical degradation is caused by the chemical reaction between the PFSA membrane and chemical species such as free radicals. Although chemical degradation of the PFSA membrane has been studied by various experimental techniques, the mechanism of chemical degradation relies much on speculations from ex-situ observations. Recent activities applying theoretical methods such as density functional theory, in situ experimental observation, and mechanistic study by using simplified model compound systems have led to gradual clarification of the atomistic details of the chemical degradation mechanism. In this review paper, we summarize recent reports on the chemical degradation mechanism of the PFSA membrane from an atomistic point of view.

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Characterization of CF Bonds with Multiple‐Bond Character: Bond Lengths, Stretching Force Constants, and Bond Dissociation Energies

Cited by 107 publications

References 74 publications

Generalization of the Badger Rule Based on the Use of Adiabatic Vibrational Modes

Generalization of the Badger Rule Based on the Use of Adiabatic Vibrational Modes

Strength of the Pnicogen Bond in Complexes Involving Group Va Elements N, P, and As

A Review of Molecular-Level Mechanism of Membrane Degradation in the Polymer Electrolyte Fuel Cell

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