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

Abstract

2,1,3-Benzothiadiazole (BT) is a widely used electron-accepting unit in organic electronics including organic solar cells (OSCs). As modifications of BT skeleton, two types of azolefused BT units were designed and synthesized; thiazole-fused BT with an electronwithdrawing C=N bond and imidazole-fused BT with an electron-donating nitrogen atom as well as an electron-withdrawing C=N bond. Electrochemical measurements and theoretical calculations suggest that thiazole-fusion enhances the electron-accepting ability, whereas imidazole-fusion endows the BT skeleton with electron-donating ability while maintaining its electron-accepting ability. Moreover, in thiazole-fused BT units, the electronic structure could be further modulated by varying the oxidation state of the sulfur atom in methylthio group at the fused thiazole ring.

Azoles for Renewable Energy Development and Wood Treatment

“…These are thiazole-fused BT containing electron-withdrawing C=N bond and imidazole-fused BT containing electron-donating nitrogen atom as well as an electron-withdrawing C=N bond. Theoretical calculations and measurements by electrochemical means suggest that thiazole-fusion enhances electron-accepting ability [39]. In contrast, imidazole-fusion bestows the benzothiadiazole skeleton with electron-donating capacity while sustaining its electron-accepting ability.…”

“…In contrast, imidazole-fusion bestows the benzothiadiazole skeleton with electron-donating capacity while sustaining its electron-accepting ability. Besides, in thiazole-fused BT units, the electronic configuration could be additionally controlled by tuning the oxidation number of the sulfur atom in methylthio group at the fused thiazole ring [39]. Thus, the electron withdrawing ability of BT can be further increased by replacing one carbon atom with sp 2 -hybridized N atom (Figure 8).…”

Recent Advances in Organic Photovoltaic Materials Based on Thiazole‐Containing Heterocycles

“…The chemical structures and molecular orbitals distribution of thiazole‐containing heterocycles reported in the lectures. [ 23 ] …”

“…The chemical structures and molecular orbitals distribution of thiazole-containing heterocycles reported in the lectures. [23] quinoxaline (Qx), [2d,9] dithieno[3',2':3,4;2'',3'':5,6]benzo[1,2c][1,2,5]thiadiazole (DTBT), [2a] benzo[1,2-c:4,5-c´]dithiophene-4,8-dione (BDD), [10] benzo[1,2-b: 4,5-c´]dithiophene-4,8-dione (TTDO), [11] thieno[3,4-c]pyrrole-4,6-dione (TPD), [12] phthalimide (PhI), [11,13] 4,8-di(thiophen-2-yl)-[1,2,3]triazolo[4,5-f]isoindole-5,7-(2H,6H)-dione (TzBI), [14] naphthalenothiophene imide (NTI), [15] isoindigo (IID), [16] etc. The design and synthesis of photovotaic polymers based on these A units largely promoted the rapid progress of OSCs.…”