Hydrogen bond-rigidified planar squaraine dye and its electronic and organic semiconductor properties.

The one-step reaction of a dicyanovinyl-functionalized squaric acid with Fischer bases afforded C2v symmetric squaraine dyes with rigid planar structures due to intramolecular N-HO hydrogen bonds. Dense molecular packing, decrease of HOMO level, and sufficient thermal stability for sublimation enabled vacuum-processed OTFTs with hole mobility up to 0.32 cm2 V-1 s-1 and current on/off ratio of 106.