Photochemical E (trans)→Z (cis) isomerization in substituted 1-naphthylacrylates

Mani Bushan, K. ; Venugopal Rao, G. ; Soujanya, T. ; Jayathirtha Rao, V. ; Saha, S. ; Samanta, A. (2001) Photochemical E (trans)→Z (cis) isomerization in substituted 1-naphthylacrylates Journal of Organic Chemistry, 66 (3). pp. 681-688. ISSN 0022-3263

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jo000819v

Related URL: http://dx.doi.org/10.1021/jo000819v

Abstract

Substituted naphthylacrylates, 1-3, not showing rotamerism have been synthesized with a view to study photochemical E (trans)→Z (cis) isomerization. Photostationary state composition of the isomers upon direct excitation, triplet sensitized isomerization, quantum yield of isomerization, and steady state and time-resolved fluorescence behavior have been studied for these naphthylacrylates. The direct excitations of the compounds yield high Z (~80%) isomer composition, whereas the triplet sensitization results in less Z (~20%) isomer composition. This indicates that the singlet pathway is very efficient in converting the E isomer to the Z isomer. The naphthylacrylates 1 and 2 exhibit structured fluorescence at room temperature in hexane and upon changing the solvent to CH3CN; the structure of the fluorescence is lost, indicating that the singlet excited-state develops a polar character in a polar environment. The polar nature of the singlet excited state becomes more clear in the case of 3 from its fluorescence solvatochromism. The naphthylacrylates did not exhibit excitation wavelength-dependent fluorescence at room temperature suggesting that the ground state conformers (rotamers) are not involved. Fluorescence lifetimes measured for these compounds displayed biexponential behavior, which is explained using a two-state model.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:51623
Deposited On:29 Jul 2011 04:02
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