1,4,7,10‐Tetraisoalkyltetracenes: Tuning of Solid‐State Optical Properties and Fluorescence Quantum Yields by Peripheral Modulation

We have synthesized 1,4,7,10‐tetraisoalkyltetracenes from a 2,6‐naphthodiyne precursor and 2,5‐diisoalkylfurans 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 optical properties of these compounds in solution. The isopropyl derivative exhibited the highest fluorescence quantum yield in the solid state of 0.90 in the series of alkylated tetracenes. X‐ray analysis revealed that there were significant structural differences in alkyl conformation and crystal packing. The crystallochromy effects are derived from the unique crystal‐packing patterns. The fluorescence quantum yields in the solid state probably depend on the relative positional relationship of the nearest neighboring molecules in one column as well as the crystal rigidity.