Ethynylene‐Linked Oligomers Based on Benzodithiophene: Synthesis and Photoelectric Properties

Abstract

Two conjugated ethynyl-linked oligomers, oligo(benzodithiophene-ethynylene-benzothiadiazole) (O1) and oligo(benzodithiophene-ethynylene-carbazole) (O2), were synthesized by Sonogashira coupling reaction. Their degrees of polymerization were 7 and 10, respectively. Their photophysical and electrochemical properties were investigated. O1 exhibitd two strong absorption bands at 404 nm and 483 nm, and O2 at 401 nm and 429 nm. The results of UV-Vis, cyclic voltammetry (CV) and theoretical calculations showed that O1 has a narrower band gap than O2. The conductivities of O1 and O2 were 1.05×10 −15 and 6.98×10 −16 S/cm, respectively, and would increase to 1.23×10 −10 and 1.05×10 −10 S/cm after doping with iodine.

Synthesis and Reactivity of Dithienopyrazines**

“…The yield increased to 60 % for the NBS‐bromination of 4,8‐dihexylbenzo[1,2 ‐b : 4,5 ‐b ′]dithiophene [43] . If the stronger electrophile elemental bromine is used, 4,8‐dioctyloxybenzo[1,2‐ b : 4,5‐ b′ ]dithiophene is brominated in the 2,6‐positions in 99 % yield [44] . NBS‐bromination of isomeric syn ‐benzo[1,2‐ b : 5,4‐ b′ ]dithiophene 2 led to an inseparable mixture of differently brominated products [25] …”

“…[43] If the stronger electrophile elemental bromine is used, 4,8-dioctyloxybenzo[1,2-b : 4,5-b']dithiophene is brominated in the 2,6-positions in 99 % yield. [44] NBS-bromination of isomeric syn-benzo[1,2-b : 5,4b']dithiophene 2 led to an inseparable mixture of differently brominated products. [25] Structurally related to our dithienopyrazines, thieno[2,3b]pyridine, thieno[3,2-b]pyridine, and thieno [2,3-b]pyrazine are throughout halogenated with elemental bromine or chlorine at the fused thiophene β-position in moderate to good yields.…”

Synthesis and Reactivity of Dithienopyrazines

“…[43] If elemental bromine as stronger electrophile is used, 4,8-dioctyloxybenzo[1,2-b:4,5-b']dithiophene is brominated in the 2,6-positions in 99% yield. [44] NBS-bromination of isomeric syn-benzo[1,2-b:5,4b']dithiophene 2 led to an inseparable mixture of differently brominated products. [25] Structurally related to our dithienopyrazines, thieno [2,3-b]pyridine, thieno [3,2-b]pyridine, or thieno [2,3-b]pyrazine are throughout halogenated with elemental bromine or chlorine at the fused thiophene -position in moderate to good yields.…”