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1 March 2000 On the Photochromism of Spiro[cyclohexadiene-dihydroacridines]
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Abstract

The recently synthesized spiro[cyclohexadiene-dihydroacridines] consisting of perpendicularly arranged aroylcyclohexadiene and N-methyl-dihydroacridine moieties were found to have photochromic properties. The reversible photoisomerization from the spiro compound toward a colored merocyanine caused by C–C bond cleavage in the cyclohexadiene was studied by stationary and time-resolved measurements of their optical spectra. The course of the absorption under UV and visible irradiation, respectively, and HPLC analysis of the photoproducts result in the determination of excitation energy-dependent quantum yields for the merocyanine formation and, in reverse, the ring closure, as well as degradation. Whereas the thermal back reaction completely recovers the spiro compound (k ≈ 6.8 × 10−4 s−1, T = 22°C), degradation of the merocyanine under irradiation at 480 nm has a probability of about 6%. Picosecond-resolved measurements of the fluorescence and the transient absorption show that photoisomerization occurs via the first excited singlet state within 100 ps depending on the activation barrier.

T. Häupl, T. Zimmermann, R. Hermann, and O. Brede "On the Photochromism of Spiro[cyclohexadiene-dihydroacridines]," Photochemistry and Photobiology 71(3), 294-299, (1 March 2000). https://doi.org/10.1562/0031-8655(2000)071<0294:OTPOSC>2.0.CO;2
Received: 4 August 1999; Accepted: 1 December 1999; Published: 1 March 2000
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