Journal of Oleo Science
Online ISSN : 1347-3352
Print ISSN : 1345-8957
ISSN-L : 1345-8957
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Gold-Colored Organic Crystals Formed from an Azobenzene Derivative
Akiko MatsumotoMaho KawaharazukaYutaka TakahashiNorio YoshinoTakeshi KawaiYukishige Kondo
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2010 Volume 59 Issue 3 Pages 151-156

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Abstract

The azobenzene derivative 4,4’-bis{1-[2-(N,N-dimethylamino)]ethoxy}azobenzene has been found to form gold-colored plate-like crystals. The thin film obtained by accumulating the crystals has a maximum specular reflectance of ca. 15% for visible light. To investigate the structure of the gold-colored crystals, UV-vis, X-ray diffraction (XRD), and IR analyses were performed. UV-vis measurements show that the molecules in the crystal produce J-aggregates. Furthermore, XRD measurements estimated the long-range d-spacing for the crystal as 1.51 nm. These results indicate that the azobenzene moieties are oriented diagonally against the crystal surfaces. When the crystals are placed in a desiccator (humidity 40%) for 1 d, their color changes from gold to yellow. IR measurements show that the gold-colored crystals contain crystallized water, while there are no water molecules in the yellow crystals, in which the structure of the J-aggregates is disrupted. These results show that the crystallized water molecules are essential for the formation of the J-aggregates and the resultant gold luster.

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© 2010 by Japan Oil Chemists' Society
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