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A photochromism molecule, (E)-4-phenyl-1-(pyridine-2-ylmethylene)semicarbazide (1), was reported. Photochromism of 1 in solution was shown to result from the trans–cis photoisomerization of its CN double bond, by using absorption, 1H NMR (including 2D NOESY) and directly the crystal structure of 1 obtained from solutions before and after UV irradiation. Photochromism of 1 in the solid state was found to take place, too, but via changes in the molecular geometry and packing upon UV irradiation.
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Lin et al. (2012) studied this question.
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