25 Photoresponsive Molecular Crystals …
437
Fig. 25.11 Series of snapshots and sketches of the five kinematic effects of UV-excited crystals of
[Co(NH 3 ) 5 (NO 2 )]Cl(NO 3 ). Adapted with permission from Ref. [45]. Copyright 2013 Wiley-VCH
Verlag GmbH & Co. KGaA, Weinheim
of diarylethene molecules are used, the crystal shape is not restored thermally and
reversibly changes by irradiation with UV light and visible light. Further, the righthanded or left-handed spiral formation can be controlled according to the crystal
plane to which UV light is irradiated. It has been clarified that the spiral formation is
because the induction period exists before the crystal deformation occurs in addition
to the diagonal contraction of the crystal. It was also confirmed that when dimethyl-2(3-anthracen-9-yl)arylidene) malonate nanowire crystals were irradiated with light,
the crystals were irreversibly deformed into a coil shape [39]. In this crystal, not an
intermolecular [4 + 4] dimerization reaction of anthracene, but an E ↔ Z isomerization reaction in the molecule proceeds, whereby the crystal/amorphous mixed-phase
generated in the crystal causes internal strain, causing a dramatic shape change.
437
Fig. 25.11 Series of snapshots and sketches of the five kinematic effects of UV-excited crystals of
[Co(NH 3 ) 5 (NO 2 )]Cl(NO 3 ). Adapted with permission from Ref. [45]. Copyright 2013 Wiley-VCH
Verlag GmbH & Co. KGaA, Weinheim
of diarylethene molecules are used, the crystal shape is not restored thermally and
reversibly changes by irradiation with UV light and visible light. Further, the righthanded or left-handed spiral formation can be controlled according to the crystal
plane to which UV light is irradiated. It has been clarified that the spiral formation is
because the induction period exists before the crystal deformation occurs in addition
to the diagonal contraction of the crystal. It was also confirmed that when dimethyl-2(3-anthracen-9-yl)arylidene) malonate nanowire crystals were irradiated with light,
the crystals were irreversibly deformed into a coil shape [39]. In this crystal, not an
intermolecular [4 + 4] dimerization reaction of anthracene, but an E ↔ Z isomerization reaction in the molecule proceeds, whereby the crystal/amorphous mixed-phase
generated in the crystal causes internal strain, causing a dramatic shape change.