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Selective photoisomerization of methyl substituted nitro diphenylbutadienes

Authors
Journal
Journal of Photochemistry and Photobiology A Chemistry
1010-6030
Publisher
Elsevier
Publication Date
Volume
293
Identifiers
DOI: 10.1016/j.jphotochem.2014.07.019
Keywords
  • Regioselective Photoisomerization
  • Intramolecular Charge Transfer
  • Solvatochromism
Disciplines
  • Chemistry
  • Physics

Abstract

Abstract A series of p-nitro substituted trans-diphenylbutadienes is synthesized and their photophysical and photochemical properties are investigated. All the dienes have a very low quantum yield of fluorescence but exhibit remarkable solvatochromic emission shifts attributed to twisted intramolecular charge transfer. Photochemical irradiation of simple p-nitro substituted diphenylbutadienes reveals inefficient or no detectable photoisomerization. However, substituting a methyl group on the butadiene chain of p-nitro substituted diphenylbutadiene or replacing the nitro group with cyano group yields the corresponding trans–cis isomers. In the case of simple nitrodienes, strong intramolecular charge transfer character in the excited state aids dissipation of absorbed energy through non-photochemical and non-radiative channels. The steric effect caused by the presence of methyl group lowers the isomerization barrier in methyl substituted dienes leading to a regioselective isomerization.

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