Double lactonization in triarylamine-conjugated dimethyl diethynylfumarate: formation of intensely colored and luminescent quadrupolar molecules including a missing structural isomer of Pechmann dyes.

Acid-induced double lactonization in triarylamine-conjugated dimethyl diethynylfumarate E-1 opens up a new synthetic route to Pechmann dyes. This one-pot reaction affords three donor–acceptor–donor quadrupolar molecules (P55-1, P66-1, and P56-1); P56-1 comprises a missing structural isomer of Pechmann dyes. They are intensely colored and brightly luminescent. An organic field-effect transistor device fabricated with P66-1 functions as a p-type semiconductor.