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Langmuir. 2005 Mar 29;21(7):2754-60.

Photoinduced gelation by stilbene oxalyl amide compounds.

Author information

  • 1Laboratory of Analytical Chemistry, Faculty of Science, University of Zagreb, Strossmayerov trg 14, 10000 Zagreb, Croatia. miljanic@rudjer.irb.hr

Abstract

Oxalyl amide derivatives bearing 4-dodecyloxy-stilbene as a cis-trans photoisomerizing unit were synthesized. The trans derivative acted as a versatile gelator of various organic solvents, whereas the corresponding cis derivative showed a poor gelation ability or none at all. In diluted solution (c = 2.0 x10(-5) mol dm(-3), ethanol), the cis isomer was photochemically converted into the trans isomer within 4 min. Depending on the radiation wavelength, the trans isomer was stable or liable to photodecomposition. When exposed to irradiation, a concentrated solution of the cis isomer (c = 2.0 x 10(-2) mol dm(-3), ethanol) turned into a gel. The FT-Raman, FT-IR, and 1H NMR spectra demonstrated that the gelation process occurred because of a rapid cis --> trans photoisomerization followed by a self-assembly of the trans molecules. Apart from the formation of hydrogen bonding between the oxalyl amide parts of the molecules, confirmed by FT-IR spectroscopy, it was assumed that the pi-pi stacking between the trans-stilbene units of the molecule and a lipophilic interaction between long alkyl chains were the interactions responsible for gelation.

PMID:
15779945
[PubMed]
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