Fig. 1

Molecular structure and the synthetic route of acceptors. a Synthetic route of DOC6-IC, DOC8-IC, DOC2C6-IC, DC6-IC, and DOC2C6-2F. b Chemical structures of PBDB-T and acceptors with and without intramolecular S···O interactions in the core. Reagents and conditions: (i) n-BuLi, THF, 0 °C; (ii) Pd(PPh3)4, toluene, 120 °C; (iii) n-BuLi, THF, −78 °C; DMF, −78 °C to r.t.; (vi) for 6a, chloroform, reflux; for 6b, chloroform, r.t.