Linked Life Data

15052369

Source:http://linkedlifedata.com/resource/pubmed/id/15052369

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
2004-3-30
pubmed:abstractText
The photoisomerization kinetics of a squaraine dye has been the object both of experimental investigation and of interpretation in the framework of a qualitative theoretical model formulated by the aid of simple HMO calculations and orbital symmetry considerations. Such a model has first confirmed that the electronic structure and the spectroscopic properties of symmetrical squaraines are related to those of the parent cyanines, with ketocyanines as intermediate systems. Extension of the approach to structures twisted by 90[degree] about a polymethine bond has then provided insight into the electronic aspects and the mechanism of the photoisomerization of the squaraine under study. The reaction, previously indirectly investigated by fluorescence analysis, has been directly monitored by laser flash photolysis. These experiments indicate that, while photoisomerization is likely the main radiationless decay route from the spectroscopic minimum of the lowest excited singlet state (S(1)), the cis photoisomer is produced with only a 1% yield, likely because of an unfavourable cis/trans branching ratio from the perpendicular minimum of the S(1)-state potential energy surface. In contrast with what found for symmetrical cyanines, an increase in the solvent polarity was found to accelerate both the direct, excited-state reaction and, to a much larger extent, the ground-state back-isomerization. Such observations are consistent with predictions of the theoretical model and provide a clue for the identification of the isomerization coordinate.
pubmed:language
eng
pubmed:journal
pubmed:status
PubMed-not-MEDLINE
pubmed:month
Apr
pubmed:issn
1474-905X
pubmed:author
pubmed:issnType
Print
pubmed:volume
3
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
396-402
pubmed:year
2004
pubmed:articleTitle
Electronic structure and photochemistry of squaraine dyes: basic theoretical analysis and direct detection of the photoisomer of a symmetrical squarylium cyanine.
pubmed:affiliation
Dipartimento di Chimica, Universita di Modena e Reggio Emilia, via Campi 183, 41100 Modena, Italy.
pubmed:publicationType
Journal Article