The isomerization kinetics of three indobenzimidazolo polymethine cyanines have been investigated and compared with the corresponding properties of the parent symmetric dyes. A significant alternation of the pi bond orders in the polymethine chain was found in the ground states (S-0) of the asymmetric dyes. A similarly alternant behaviour was exhibited by the calculated S-0 potential energy barriers for twisting around the polymethine chain bonds of the asymmetric carbocyanine, whereas uniform barriers were found for the symmetric parent compounds. The experimentally observed sequence of back-isomerization activation energies was interpreted on the basis of these theoretical results. It was suggested by some spectral and kinetic fluorescence properties, and it was confirmed by the calculated polymethine-chain pi bond orders of the lowest singlet excited slates (S-1) that the electronic asymmetry induced by the different terminal heterocycles was strongly reduced upon excitation of these dyes to their S-1 states. In spite of this, the trans-cis photoisomerization of asymmetric cyanines occurred invariably around those bonds having the highest pi bond orders in the ground state. A tentative theoretical explanation of this systematic behaviour is reported.
|Data di pubblicazione:||1995|
|Titolo:||PHOTOISOMERIZATION OF ASYMMETRIC INDOBENZIMIDAZOLO CYANINE DYES|
|Autore/i:||Tatikolov, As; Derevyanko, Na; Ishchenko, Aa; Baraldi, Ivan; Caselli, Monica; Momicchioli, Fabio; Ponterini, Glauco|
|Codice identificativo ISI:||WOS:A1995RB32200011|
|Codice identificativo Scopus:||2-s2.0-84939790540|
|Citazione:||PHOTOISOMERIZATION OF ASYMMETRIC INDOBENZIMIDAZOLO CYANINE DYES / Tatikolov, As; Derevyanko, Na; Ishchenko, Aa; Baraldi, Ivan; Caselli, Monica; Momicchioli, Fabio; Ponterini, Glauco. - In: ZEITSCHRIFT FÜR PHYSIKALISCHE CHEMIE. - ISSN 0942-9352. - STAMPA. - 99(1995), pp. 763-769.|
|Tipologia||Articolo su rivista|
File in questo prodotto:
I documenti presenti in Iris Unimore sono rilasciati con licenza Creative Commons Attribuzione - Non commerciale - Non opere derivate 3.0 Italia, salvo diversa indicazione.
In caso di violazione di copyright, contattare Supporto Iris