Linked Life Data

19300815

Source:http://linkedlifedata.com/resource/pubmed/id/19300815

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
7
pubmed:dateCreated
2009-3-20
pubmed:abstractText
The efficient methodology of the cycloaddition between electron-rich alkynes and tetracyanoethylene (TCNE) or 7,7,8,8-tetracyanoquinodimethane (TCNQ), followed by retro-electrocyclisation, is extended to dicyanovinyl derivatives to produce new donor-acceptor push-pull 1,1-dicyanobutadienyl chromophores in excellent to quantitative yield (63-98%) that express strong charge-transfer (CT) absorptions from 300 to 600 nm. The scope of this reaction is established by both varying the nucleophilic and electrophilic components. Electrochemical studies show that the CT properties of these systems are readily tunable by substitution on the electrophile, which has the largest effect on the lowest unoccupied molecular orbital (LUMO). Non-reversible reduction potentials range from ca. -1.2 to -1.9 V in CH(2)Cl(2), against the ferricinium/ferrocene couple (Fc(+)/Fc) according to cyclovoltammetry (CV) and rotating disk voltammetry (RDV). The chromophores show a significant non-planarity between the N,N-dimethylanilino donor and the 1,1-dicyanovinyl acceptor moieties, with torsional angles around 40 degrees from X-ray analysis, but retain strong quinoidal character. The mechanism of this reaction has been studied computational using density functional methods in the gas-phase and using the polarizable continuum model (PCM) for addressing solvent effects. The complete reaction free-energy profile has been determined for the reaction of 1,1-dicyanoethene and 4-ethynyl-N,N-dimethylaniline. The process proceeds through formal [2+2] cycloaddition followed by retro-electrocyclisation. The formation of a zwitterionic intermediate in the cycloaddition step is shown.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
1477-0539
pubmed:author
pubmed:issnType
Electronic
pubmed:day
7
pubmed:volume
7
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1312-22
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
New donor-acceptor chromophores by formal [2+2] cycloaddition of donor-substituted alkynes to dicyanovinyl derivatives.
pubmed:affiliation
Laboratorium für Organische Chemie, Eidgenössische Technische Hochschule, Hönggerberg, HCI, CH-8093 Zürich, Switzerland.
pubmed:publicationType
Journal Article