Intuitive Understanding of sigma Delocalization in Loose and sigma Localization in Tight Helical Conformations of an Oligosilane Chain

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388963%3A_____%2F17%3A00476131" target="_blank" >RIV/61388963:_____/17:00476131 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.1002/asia.201700226" target="_blank" >http://dx.doi.org/10.1002/asia.201700226</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1002/asia.201700226" target="_blank" >10.1002/asia.201700226</a>

Result language

angličtina

Original language name

Intuitive Understanding of sigma Delocalization in Loose and sigma Localization in Tight Helical Conformations of an Oligosilane Chain

Original language description

Conformational effects on the sigma-electron delocalization in oligosilanes are addressed by Hartree-Fock and time-dependent density functional theory calculations (B3LYP, 6-311G**) at MP2 optimized geometries of permethylated uniformly helical linear oligosilanes (all--SinR2n+2) up to n=16 and for backbone dihedral angles =55-180 degrees. The extent of sigma delocalization is judged by the partition ratio of the highest occupied molecular orbital and is reflected in the dependence of its shape and energy and of UV absorption spectra on n. The results agree with known spectra of all-transoid loose-helix conformers (all-[+/- 165]-SinMe2n+2) and reveal a transition at approximate to 90 degrees from the sigma-delocalized limit at =180 degrees toward and close to the physically non-realizable sigma-localized tight-helix limit =0 with entirely different properties. The distinction is also obtained in the Huckel Ladder H and C models of sigma delocalization. An easy intuitive way to understand the origin of the two contrasting limits is to first view the linear chain as two subchains with alternating primary and vicinal interactions (sigma hyperconjugation), one consisting of the odd and the other of the even sigma(SiSi) bonds, and then allow the two subchains to interact by geminal interactions (sigma conjugation).

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10401 - Organic chemistry

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2017

Confidentiality

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

Name of the periodical

Chemistry-An Asian Journal

ISSN

1861-4728

e-ISSN

—

Volume of the periodical

12

Issue of the periodical within the volume

11

Country of publishing house

DE - GERMANY

Number of pages

14

Pages from-to

1250-1263

UT code for WoS article

000402930000015

EID of the result in the Scopus database

2-s2.0-85019744566