2002 Volume 75 Issue 11 Pages 2359-2370
The derivatives of 1-phenyl-2-(2-thienyl)-5-[5-(tricyanoethenyl)-2-thienyl]pyrrole (1a) formed crystals with gold-like or bronze-like metallic luster. When a small substituent is located at the para position of the 1-phenyl group, gold-like lustrous crystals were formed. In contrast, the derivatives of 1 having a longer alkyl chain at the para position of the 1-phenyl group gave bronze-like crystals. The gold-like lustrous crystals have a sheet structure. In the sheet, the molecules of 1 are close to each other via the intermolecular interaction of cyano nitrogen with the hydrogen of the nearest thiophene or pyrrole ring, which enables the side-by-side interaction of the cyano group with the nearest thiophene and pyrrole rings. The bronze-like crystals have a lamella structure of the long alkyl chains that is sandwiched by two π-electron walls. In the wall, the 2-(2-thienyl)-5-[5-(tricyanoethenyl)-2-thienyl]pyrrole moieties are arranged in a ribbon structure to interact to each other. The relationship of the arrangement of the 2-(2-thienyl)-5-[5-(tricyanoethenyl)-2-thienyl]pyrrole moieties with the metallic color of the crystals is discussed.
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