Alkanes versus Oligosilanes: Conformational Effects on σ-Electron Delocalization

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388963%3A_____%2F22%3A00551652" target="_blank" >RIV/61388963:_____/22:00551652 - isvavai.cz</a>

Výsledek na webu

<a href="https://doi.org/10.1021/jacs.1c10616" target="_blank" >https://doi.org/10.1021/jacs.1c10616</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1021/jacs.1c10616" target="_blank" >10.1021/jacs.1c10616</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Alkanes versus Oligosilanes: Conformational Effects on σ-Electron Delocalization

Popis výsledku v původním jazyce

Observations and computations both suggest that the extent and the conformational dependence of σ-electron delocalization in frontier molecular orbitals are quite different in alkanes CnH2n+2 and oligosilanes SinH2n+2, the isosteric and isoelectronic saturated chains built from carbon or silicon atoms, respectively. We find that the different conformational effects can be understood in simple intuitive terms. There are two modes of σ-electron delocalization, strongly conformation-sensitive skeletal delocalization through backbone X–X bonds (σ-conjugation and σ-hyperconjugation) and only weakly conformation-sensitive lateral delocalization through lateral X–H bonds (σ-hyperconjugation and σ-homoconjugation). In alkanes, both modes are active and complement each other, leading to delocalization in all conformations. In oligosilanes, only skeletal delocalization of holes is important in frontier orbitals, and the even simpler ladder C model provides an adequate intuitive description of the strong conformational dependence of σ-electron delocalization. Ultimately, the difference is primarily due to the similar electronegativity of carbon and hydrogen as opposed to the lower electronegativity of silicon, which causes a polarization of Si–H bonds. This understanding has been derived from an analysis of approximate algebraic solutions of a simple Hückel-level extended ladder H model for an infinite regular helical chain, using the effective mass of a hole as a measure of delocalization. This model is derived from the classical Sandorfy H model, and is parametrized by fitting to results of density functional or Hartree–Fock theory.

Název v anglickém jazyce

Alkanes versus Oligosilanes: Conformational Effects on σ-Electron Delocalization

Popis výsledku anglicky

Observations and computations both suggest that the extent and the conformational dependence of σ-electron delocalization in frontier molecular orbitals are quite different in alkanes CnH2n+2 and oligosilanes SinH2n+2, the isosteric and isoelectronic saturated chains built from carbon or silicon atoms, respectively. We find that the different conformational effects can be understood in simple intuitive terms. There are two modes of σ-electron delocalization, strongly conformation-sensitive skeletal delocalization through backbone X–X bonds (σ-conjugation and σ-hyperconjugation) and only weakly conformation-sensitive lateral delocalization through lateral X–H bonds (σ-hyperconjugation and σ-homoconjugation). In alkanes, both modes are active and complement each other, leading to delocalization in all conformations. In oligosilanes, only skeletal delocalization of holes is important in frontier orbitals, and the even simpler ladder C model provides an adequate intuitive description of the strong conformational dependence of σ-electron delocalization. Ultimately, the difference is primarily due to the similar electronegativity of carbon and hydrogen as opposed to the lower electronegativity of silicon, which causes a polarization of Si–H bonds. This understanding has been derived from an analysis of approximate algebraic solutions of a simple Hückel-level extended ladder H model for an infinite regular helical chain, using the effective mass of a hole as a measure of delocalization. This model is derived from the classical Sandorfy H model, and is parametrized by fitting to results of density functional or Hartree–Fock theory.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10401 - Organic chemistry

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2022

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Journal of the American Chemical Society

ISSN

0002-7863

e-ISSN

1520-5126

Svazek periodika

144

Číslo periodika v rámci svazku

1

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

15

Strana od-do

463-477

Kód UT WoS článku

000739358000001

EID výsledku v databázi Scopus

2-s2.0-85122701754