Making benzotrithiophene a stronger electron donor.

A new member of the benzotrithiophene family, benzo[2,1-b:-3,4-b':5,6-c″]trithiophene (3a), and its alkyl substituted derivatives (3b-e) were synthesized and characterized. Their photophyscial, electrochemical, crystallographic, and self-assembly properties were described. Thin film structures varied widely with the exact nature of the alkyl substitution pattern, with decreasing self-assembly propensity with increasing alkyl chain length. The high HOMO levels and the coplanarity of these molecules show their potential as organic semiconductors and as donor components in donor-acceptor copolymers.