Tricyclic-fused bithiophenes and related analogues: Important building blocks for conjugated materials

Tunable Regioselectivity in C−H‐Activated Direct Arylation Reactions of Dithieno[3,2‐b:2’,3’‐d]pyrroles

“…DTPs represent highly interesting and frequently used multifunctional and electron‐rich building block in organic semiconducting materials for application in organic electronic devices [24–31] or in polymeric form as electrode material in rechargeable batteries [32,33] . DTPs are typically synthesized by Pd‐catalyzed Buchwald–Hartwig amination/cyclization of 3,3’‐dibromo‐2,2’‐bithiophene precursors and alkyl or aryl amines to form the central pyrrole ring [34] . We recently extended the scope of N‐substituted DTPs by Pd‐ or Cu‐catalyzed coupling of H ‐DTP 1 with well available aryl, acene, and heterocyclic halides resulting in a series of N‐arylated and N‐heteroarylated DTPs, which were subsequently implemented into functional materials for single material organic solar cells [35] or as hole transport material for perovskite solar cells, [36] respectively.…”

Molecular Tuning in Diaryl-Capped Pyrrolo[2,3-d:5,4-d′]bisthiazoles: Effects of Terminal Aryl Unit and Comparison to Dithieno[3,2-b:2′,3′-d]pyrrole Analogues

“…One successful synthetic strategy for molecular tuning has been the annulation of aromatic rings to generate various fused-ring species, with a popular approach involving the insertion of a bridging unit between the adjacent thiophene rings of 2,2′-bithiophene [ 9 ]. The most commonly applied examples of such species include cyclopenta[2,1- b :3,4- b ′]dithiophene (CPDT, E = C) [ 8 , 9 , 10 , 11 ], silolo[3,2- b :4,5- b ′]dithiophene (SiDT, E = Si) [ 8 , 9 , 10 , 11 , 12 , 13 ], and dithieno[3,2- b :2′,3′- d ]pyrrole (DTP, E = N) [ 8 , 9 , 11 , 12 , 14 ], but a large number of such monomeric units have been generated as illustrated in Figure 1 [ 9 ]. The fused-ring nature of these units enhances the planar nature of the ground state, thus facilitating more efficient electron delocalization and a corresponding reduction in band gap [ 9 , 12 , 13 , 14 ].…”

“…The most commonly applied examples of such species include cyclopenta[2,1- b :3,4- b ′]dithiophene (CPDT, E = C) [ 8 , 9 , 10 , 11 ], silolo[3,2- b :4,5- b ′]dithiophene (SiDT, E = Si) [ 8 , 9 , 10 , 11 , 12 , 13 ], and dithieno[3,2- b :2′,3′- d ]pyrrole (DTP, E = N) [ 8 , 9 , 11 , 12 , 14 ], but a large number of such monomeric units have been generated as illustrated in Figure 1 [ 9 ]. The fused-ring nature of these units enhances the planar nature of the ground state, thus facilitating more efficient electron delocalization and a corresponding reduction in band gap [ 9 , 12 , 13 , 14 ]. In addition, this ring fusion reduces contributions of interannular torsional vibrations, which can decrease vibrational relaxation of the excited state and lead to increased emission [ 9 , 11 ].…”

“…The fused-ring nature of these units enhances the planar nature of the ground state, thus facilitating more efficient electron delocalization and a corresponding reduction in band gap [ 9 , 12 , 13 , 14 ]. In addition, this ring fusion reduces contributions of interannular torsional vibrations, which can decrease vibrational relaxation of the excited state and lead to increased emission [ 9 , 11 ]. Lastly, the bridging unit can modulate the electronics via inductive effects to tune the energies of the frontier orbitals, while the central placement of the side chains reduces potential issues of regioirregularity in the resulting polymers, while also allowing the use of relatively bulky groups without deleterious steric interactions that can result in reduced backbone planarity [ 11 , 14 ].…”