Light-induced adiabatic structural relaxation and electronic energy deactivation in Pyridinium bications

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 132; no. 1; pp. 59 - 66
• Main Authors: Knyazhansky, Michael I., Metelitsa, Anatoly V., Makarova, Nadezhda I., Feygelman, Vladimir M., Tymyansky, Jacob R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20.03.2000
• Subjects: Intramolecular energy transfer; Photocyclization; Pyridinium bications; Intramolecular energy transfer; Pyridinium bications; Photocyclization
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/S1010-6030(99)00242-7

The comparative detailed investigation of the Bication pyridinium systems (BCP) and corresponding model pyridinium cations (CP) has been carried out by the spectral luminescent methods. BCP consist of the two identical moieties bound by the various space bridges ensuring their very weak interaction in the ground state. The Adiabatic Structural Relaxation (ASR) followed by the photocyclization reaction is realized only in one of BCP fragments in accordance with the general scheme typical for CP. The ASR is not realized in another BCP fragment owing to the S 1 state deactivation by the extremely fast Interfragmental Intramolecular S-S Energy Transfer from the unchanged fragment to the cyclized one. The ASR mechanism, luminescent properties and photoproduct structures depend strongly on the solvent temperature (viscosity) and on the steric interactions typical for the BCP. The additional information concerning the N phenyl role in the fluorescence and photo-chemical properties’ formation in CP has been obtained by the study of the BCP.