π-Bindungsordnung-bindungslängenbeziehung für ungesättigte kohlenwasserstoffe

Häfelinger, Günter

doi:10.1016/s0040-4020(01)92822-4

Cited by 16 publications

(2 citation statements)

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“…Like already mentioned, the branching effect of delocalized π-electron systems generally changes both the bond length alternation (BLA) and the bond order alternation (BOA), which are only zero in the aromatic benzene cycle as well as in ideal polymethine chains. To give an example, in Scheme 3, the x-ray bond lengths of the triphenylmethane dye 17 containing a branched nonamethine chain are given (in picometers), whereas the aromatic naphthalene 18 represents the HMO bond lengths determined by the empirical bond lengths-HMO bond orders relationship [62,63]. The bond lengths of both entities are governed by the Gebhard-Pauling rule, which states that the bond strength emanating from an atom is nearly constant [40].…”

Section: Polymethine Interpretation Of Characteristic Examples Of Vis...mentioning

confidence: 99%

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The polymethine nature of Vis/NIR chromophores

Dähne,

Yesudas,

Dekhtyar

2023

J Chinese Chemical Soc

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The polymethine concept is known to rationalize a plethora of spectroscopic issues, thus finding wide applications in modern color theory. This approach was questioned by the arguments in the relevant “dye” literature. Based on the critical analysis of these arguments, the errors are clarified and the superiority of the polymethine concept above other attempts to qualitatively explain color and constitution relationships is exemplified at relevant dye molecules absorbing in the visible and near‐infrared spectral region. The classical chromophore theory, topological approaches, different‐level semiempirical techniques, and DFT/ab initio methods are comparatively analyzed to interpret the optical effects of structural modifications in conjugated compounds regarded as polymethine derivatives.

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Section: Polymethine Interpretation Of Characteristic Examples Of Vis...mentioning

confidence: 99%

“…Therefore, the elongation of the bond length of S C H E M E 3 X-ray-derived and empirically calculated bondlengths of aromatic compounds. Empirical bond lengths [62,63] were calculated from HMO bond orders p rs as CC rs [pm] = 158.5 -29.5 p rs .…”

Section: Polymethine Interpretation Of Characteristic Examples Of Vis...mentioning

confidence: 99%

The polymethine nature of Vis/NIR chromophores

Dähne,

Yesudas,

Dekhtyar

2023

J Chinese Chemical Soc

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Free‐Energy Relationships in Strongly Conjugated Substituents: The Polymethine Approach

Dähne

Hoffmann

1991

Progress in Physical Organic Chemistry

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MO‐π‐Bindungsordnung‐Bindungslängen‐Beziehungen für Hetero‐π‐Systeme, I. π‐Systeme mit CN‐Bindungen

Häfelinger

1970

Chem. Ber.

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rn Mit Hilfe einer fur ungesattigte Kohlenwasserstoffe erhaltenen HMO-n-Bindungsordnung-Bindungslangen-Beziehung werden fur CN-Hetero-r-Bindungssysteme die emprrischen Resonanzintegral-Heteroparameter / L -i i und ~C -N zu 1.10 bzw. 1 .OO bestimmt. Die mit diesen Parametern berechneten HMO-n-Bindungsordnungen ergeben mit experimentellen Bindungsabstanden, die mit einer Standardabweichung von hochstens 0.01 5 8, bestimmt wurden, eine lineare Beziehung, deren Gleichung nach der Methode der kleinsten Fehlerquadrate zu R z M O [A] 1.474 0.225 prs mit einer Standardabweichung van 0.019 A und einem Korrelationskoeffizienten von 0 865 fur 114 Punkte bestjmmt wurde. Fur PPP-SCF-n-Bindungsordnungen betragt die Ausgleichsgerade mit einer Standardabweichung von 0.022 A und einem Korrelat~onskoeffizienten von 0.801 fur 168 Werte. RP,PP [A] = 1 443 0.167 prs MO-x-Bond Order-Bond Lengths Relations for Hetero-rr-Systems, 1 x-Systems with CN-Bonds A HMO-n-bond order-bond lengths relation obtained for unsaturated hydrocarbons allows the empirical determination of the HMO resonance integral parameters for CN-n-bonds as kC=N = 1 , l O and kC-N = 1,OO. HMO-x-Bond orders calculated with these parameters give a linear relation with bond lengths determined experimentally with a standard deviation of less than 0,015 A. The equation determined by linear least squares methods is R Z M O [A] ~~ 1,474 -0,225 p n with a standard deviation of 0,019 A and a correlation coefficient of 0,865 for 114 points. For PPP-SCF-x-bond orders the least squares equation yields RgpP [A] = 1,443 --0,167 prs with a standard deviation of 0,022 A and a correlation coefficient of 0,801 for 168 points.Zwischen der MO-x-Bindungsordnung 1) und dem entsprechenden Bindungsabstand in ungesattigten Verbindungen besteht ein Zusammenhang, der theoretisch begriindet HafeelingerJdhrg. 103

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π-Bindungsordnung-bindungslängenbeziehung für ungesättigte kohlenwasserstoffe

Cited by 16 publications

References 29 publications

The polymethine nature of Vis/NIR chromophores

The polymethine nature of Vis/NIR chromophores

Free‐Energy Relationships in Strongly Conjugated Substituents: The Polymethine Approach

MO‐π‐Bindungsordnung‐Bindungslängen‐Beziehungen für Hetero‐π‐Systeme, I. π‐Systeme mit CN‐Bindungen

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