Control of the helical chirality of enantiopure sulfinyl (Z)-azobenzene-based photoswitches.
A new class of enantiopure ortho,ortho-disubstituted azobenzene photoswitches has been synthesized from (S)-2-(p-tolylsulfinyl)benzoquinone and arylhydrazines. The sulfoxide acts as a unidirectional controller of the helical chirality that arises in the Z isomer after photoisomerization. Highly congested E-azobenzenes 5 c showed two atropisomeric diastereoconformers in the solid state that converged upon irradiation into a unique Z isomer with defined helicity (M), as evident in the X-ray structure. The chiroptical properties of this three-state enantiopure switch can be externally tuned both photochemically and/or thermally. Theoretical CD spectra calculated by using time-dependent DFT methods support the existence of two atropoisomeric E isomers and only one Z isomer with (M) helicity. Complementary to the classical azobenzene-based switches, the photoswiching event is promoted under green/blue light and do not occur under UV irradiation.
Departamento de Química Orgánica (Módulo-01), Universidad Autónoma de Madrid, Cantoblanco, 28049-Madrid, Spain.
Irene
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Núñez
Estíbaliz
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Merino
Mercedes
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Lecea
Silvia
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Pieraccini
Gian Piero
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Rosini
Giuseppe
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Mazzeo
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Ribagorda
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