as the starting materials (isoalkyl: isopropyl, isobutyl, and isopentyl). The tetracene molecules exhibited crystallochromy: The solid-state colors of the isopropyl, isobutyl, and isopentyl derivatives were yellow, red, and orange-yellow, respectively. In contrast, there were no marked differences in the opticalproperties of these compounds in solution. The isopropyl derivative exhibited the highest