Photoinduced Pyridine Cleavage-Closure in Viscous Polymer Solutions

Evgenia Vaganova, Cornelia Damm, Gunter Israel, Shlomo Yitzchaik*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


We have found that photoinduced pyridine ring cleavage-closure occurs in polymeric viscous solution, because in certain polymer solutions, pyridine can serve as a photo-modulated crosslinker. We suggest this reaction as a way to control a polymer's optical properties. Irradiation of the system: poly(4-vinyl pyridine)/pyridine/water with 250-nm wavelength range leads to the appearance of a new absorption band centered at 360 nm, new red-shifted emission, and HOMO-LUMO band gap changes. The subsequent irradiation with 360 nm (the new absorption band maximum) leads to reversion almost to the initial stage. A main active product of the photoreaction is aldehyde enamine, which has two active groups: primary amine and aldehyde, which can associate with the polymer molecules to form a physical crosslinked supramolecular structure. We evaluated the activation energy of the pyridine ring cleavage and back reaction depending on the polymer/pyridine/water ratio and by changing the polymer structure. The activation energy of pyridine's ring cleavage in viscous polymeric solutions is in the range of 0.6-3.2 Kcal/mol. The activation energy of the back reaction is significantly lower and is in the range of 0.05-0.15Kcal/mole.

Original languageAmerican English
Pages (from-to)219-224
Number of pages6
JournalJournal of Fluorescence
Issue number2
StatePublished - Jun 2002

Bibliographical note

Funding Information:
E. V. gratefully acknowledges financial support from the Israel Ministry for Immigrant Absorption. We thank Prof. V. Khodorkovsky for illuminating discussions.


  • Dewar pyridine
  • Photochemistry
  • Physical crosslinking
  • Poly(4-vinyl pyridine)
  • Pyridine


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