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IJC-B Vol.46B(11) [November 2007] >


Title: Wavelength dependent regioselective E→Z isomerization of 9-anthryldiene derivatives
Authors: Reddy, Majjigapu Janaki Ram
Kumar, Perepogu Arun
Srinivas, Uppalanchi
Reddy, Vummadi Venkat
Reddy, Maruthi Janaki Ram
Rao, G Venugopal
Rao, Vaidya Jayathirtha
Keywords: Anthryldienes
Photoisomerization
Wavelength dependence
Regioselectivity
Charge transfer
Fluorescence
Issue Date: Nov-2007
Publisher: CSIR
Abstract: 9-Anthryldiene derivatives 1-5 are synthesized to study E→Z photoisomerization. Photoisomer composition upon direct excitation, and triplet-sensitized isomerization are determined. Quantum yield of isomerization, quantum yield of fluorescence and fluorescence life times are determined for these compounds. Interestingly, upon direct excitation the anthryldiene derivatives 1-3 carrying electron withdrawing end groups (EWG) displayed wavelength dependent regioselective E→Z isomerization from the singlet excited state. Triplet sensitization studies revealed that these anthryldiene derivatives undergo Z→E isomerization and not E→Z isomerization. The dual fluorescence observed for 1, 2, 3 and 2E, 4Z-1, indicates the involvement of two different emissive states. The fluorescence solvatochromism displayed by 1, 2, 3 and 2E, 4Z-1 is a clear indication of the involvement of a highly polarized/charge transfer singlet-excited state and the same is involved in the isomerization process. Fluorescence lifetimes measured for these compounds displayed bi-exponential behavior supporting the presence of two emissive states. A mechanism for photoisomerization is suggested.
Page(s): 1833-1847
ISSN: 0376-4699
Source:IJC-B Vol.46B(11) [November 2007]

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