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Issue 5, 2015
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Synthesis of a double-stranded spiroborate helicate bearing stilbene units and its photoresponsive behaviour

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Abstract

A novel spiroborate-based double-stranded helicate bearing photoresponsive cis-stilbene units in the middle (cis-3) was successfully synthesised from the corresponding cis-stilbene-bound tetraphenol strand in the presence of NaBH4, whereas the tetraphenol strands with a trans-stilbene or trans-azobenzene unit did not form such a double-stranded helicate. The 1H NMR and NOESY experiments revealed that cis-3 adopted contracted (cis-3C) and extended (cis-3E) forms under equilibrium in CD3CN at 25 °C. The contracted cis-3C that accommodated a Na+ ion in the center showed almost reversible extension and contraction motions by removal and addition of a Na+ ion. The cis-to-trans photoisomerisation of the extended cis-3E with UV light (295 nm) further induced an extension of the helicate, producing a mixture of cis,trans-3E and trans-3E helicates in the photostationary state. However, trans-to-cis photoisomerisation of the trans-mixtures using UV light (360 nm) was irreversible in this system and produced the photooxidated aldehyde species (trans-4), resulting from the photo-cleavage of the trans-stilbene moieties of trans-3E.

Graphical abstract: Synthesis of a double-stranded spiroborate helicate bearing stilbene units and its photoresponsive behaviour

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Publication details

The article was received on 27 Sep 2014, accepted on 07 Nov 2014 and first published on 07 Nov 2014


Article type: Paper
DOI: 10.1039/C4NJ01669F
Citation: New J. Chem., 2015,39, 3259-3269
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    Synthesis of a double-stranded spiroborate helicate bearing stilbene units and its photoresponsive behaviour

    D. Taura, H. Min, C. Katan and E. Yashima, New J. Chem., 2015, 39, 3259
    DOI: 10.1039/C4NJ01669F

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