Two angular-shaped 4,9-didodecyl α-aNDT and 4,9-didodecyl β-aNDT isomeric structures have been regiospecifi cally designed and synthesized. The distannylated α-aNDT and β-aNDT monomers are copolymerized with the Br-DTNT monomer by the Stille coupling to furnish two isomeric copolymers, PαNDTDTNT and PβNDTDTNT, respectively. The geometric shape and coplanarity of the isomeric α-aNDT and β-aNDT segments in the polymers play a decisive role in determining their macroscopic device performance. Theoretical calculations show that PαNDTDTNT possesses more linear polymeric backbone and higher coplanarity than PβNDTDTNT. The less curved conjugated main chain facilitates stronger intermolecular π-π interactions, resulting in more redshifted absorption spectra of PαNDTDTNT in both solution and thin fi lm compared to the PβNDTDTNT counterpart.

2,7-Diiodo-3,6-dibromofluorene and 2,7-dichloro-3,6-dibromofluorene have been successfully synthesized. The two key intermediates enable us to implement a regioselective Sonogashira reaction followed by intramolecular thiolate/acetylene cyclization, forming two regiospecific pentacyclic dithieno[2,3-b:7,6-b']fluorene (2,7-DTF) and dithieno[3,2-b:6,7-b']fluorene (3,6-DTF) isomeric molecules, respectively. By using a similar strategy, selenophene-based diselenopheno[2,3-b:7,6-b']fluorene (2,7-DSF) as well as diselenopheno[3,2-b:6,7-b']fluorene (3,6-DSF) were also prepared. The isomeric and sulfur/selenium effects determine the optical, electrochemical, and orbital properties. X-ray crystallography revealed that 2,7-DTF and 3,6-DTF molecules assemble into supramolecular helical structures.

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