Monatshefte für Chemie - Chemical Monthly

, Volume 141, Issue 3, pp 357–372

Photochromism of dihydroindolizines. Part XV: Synthesis and photophysical properties of dihydroindolizine photoswitches bearing a conjugated aryleneethynylene tripodal linker system

Original Paper

DOI: 10.1007/s00706-010-0267-7

Cite this article as:
Ahmed, S.A. & Al-Raqa, S.Y. Monatsh Chem (2010) 141: 357. doi:10.1007/s00706-010-0267-7


Different photochromic dihydroindolizines (DHIs) bearing conjugated aryleneethynylene tripodal linker systems were synthesized using several Sonogashira coupling reactions. The spirocyclopropene precursors incorporating different acetylenic bridge moieties at the 2-position of the fluorene moiety were synthesized via chemical and photochemical routes. Multiaddressable photochromic properties of the DHI derivatives substituted in the fluorene (region A) and pyridazine (region C) parts were studied. Optimization of the formation of the DHIs was also done by applying different palladium-mediated Sonogashira coupling reactions. Irradiation of the photochromic DHIs with polychromatic light led to colored betaines which undergo thermal 1,5-electrocyclization. The kinetics of the thermal 1,5-electrocyclization were studied by using a multichannel FT–UV–Vis spectrophotometer. A pronounced effect on the kinetic behavior of the 1,5-electrocyclization process of the betaines was observed by changing substitution from non-substituted to dimethyl-substituted pyridazines. Photodegradation experiments and the bleaching and fading cycles revealed high photostability of the betaines under investigation. These properties of betaines of tripodal linker conjugates will help these materials to find applications.

Graphical abstract


Photochromism Dihydroindolizines Sonogashira coupling Aryleneethynylenes Tripodal linker Photostability 

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Chemistry Department, Faculty of ScienceTaibah UniversityAl-Madena Al-MounawaraSaudi Arabia
  2. 2.Chemistry Department, Faculty of ScienceAssiut UniversityAssiutEgypt

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