Thiazole-fused Benzothiadiazole as a Key Skeleton for T-Shaped Electron-accepting Building Blocks

Abstract

A series of thiazole-fused benzothiadiazoles were designed and synthesized, and their structural, electrochemical, and photophysical properties were analyzed. The observed high solubility, in combination with desirably high levels of electron-accepting ability and planarity in the solid state, promises great potential for the application of these compounds as π-electron-accepting building blocks in organic electronic materials. In addition, the two-dimensional expansion of π conjugation through the fused thiazole moiety renders these compounds ideal candidates for use as T-shaped π-conjugation junctions.

Synthesis of Azole-fused Benzothiadiazoles as Key Units for Functional π-Conjugated Compounds

“…We have previously reported the construction of thiazole-fused BT skeleton by thermal [11] or oxidative [12] cyclization of thioamide. In those cases, aryl groups have to be introduced at 4,7-position of BT before the cyclization.…”

“…1c, d). We anticipated that thiazole-fusion enables the further lowering of LUMO energy level by the existence of the electron-withdrawing imine moiety [11,12] (Fig. 2).…”

Donor–acceptor polymers containing thiazole-fused benzothiadiazole acceptor units for organic solar cells

“…30,31 We have recently developed a thiazole-fused BT skeleton (TzBT) as a new type of electron acceptor unit with further enhancement of the electron-accepting ability of BT skeleton. [32][33][34] Additional tuning of the electron-accepting character is realized by changing the alkylthio group to alkylsulfonyl ( Fig. 1a).…”

Near-infrared Emissive Donor–Acceptor-type Molecules Containing Thiazole-fused Benzothiadiazole as an Electron-acceptor Moiety

“…In the compounds containing this unit, the solubility and electronic structure can be fine-tuned by introducing substituents at the 2-position of the fused thiazole ring, while the π-conjugation is extended two-dimensionally via the fused thiazole moiety. 9 Herein, we report a new and more effective synthetic method for the construction of the thiazole-fused BT skeleton. The combination of this unit with common D units such as diphenylaminothiophene or triphenylamine-substituted thiophene afforded DAD-type molecules that exhibited emission in the NIR region ( Figure 1a).…”

“…Previously, we reported the synthesis of thiazole-fused benzothiadiazole 3a with the 2-ethylhexyl group by the thermal radical cyclization of thioamide 5a at 140°C under microwave irradiation (Scheme 1). 9 While 3a, containing thiazole side groups, could be synthesized in 52% yield, its thiophene analog 3b was obtained only in 24% yield due to the lower reactivity of the thioamide-containing BT moiety. When the reaction temperature was increased to 160°C, the formation of the fused pyridine ring occurred predominantly to afford 6 in 70%, while the desired thiazole-fused product 3b was obtained only in 17% yield.…”