Synthesis, Optical Properties, and Crystal Structure of 1,4‐Dipropyltetracene

We synthesized 1,4‐dipropyltetracene on a 200‐mg scale, the key step of which involved a Diels–Alder reaction between alkyl‐substituted o ‐quinodimethane, generated in situ, and 1,4‐naphthoquinone. The product was obtained as an orange solid, which was soluble in organic solvents including hexane. The optical properties of the product in solution showed no marked differences from those of other 1,4,7,10‐tetraalkyltetracenes. Solid‐state absorption and fluorescence spectra exhibited 20–30 nm blueshifts compared with those of 1,4,7,10‐tetrapropyltetracene. X‐ray analysis revealed that two propyl groups were coplanar with the tetracene ring, that there was no π overlap along the stacking direction, and that the molecules formed a herringbone structure. The peripheral alkyl chains were found to be important for controlling the molecular packing and optical properties in the solid state.