Benzothiadiazole vs. iso-Benzothiadiazole: Synthesis, Electrochemical and Optical Properties of D–A–D Conjugated Molecules Based on Them

Abstract

This paper presents an improved synthesis of 4,7-dibromobenzo[d][1,2,3]thiadiazole from commercially available reagents. According to quantum-mechanical calculations, benzo[d][1,2,3]thiadiazole (isoВТD) has higher values of ELUMO and energy band gap (Eg), which indicates high electron conductivity, occurring due to the high stability of the molecule in the excited state. We studied the cross-coupling reactions of this dibromide and found that the highest yields of π-spacer–acceptor–π-spacer type compounds were obtained by means of the Stille reaction. Therefore, 6 new structures of this type have been synthesized. A detailed study of the optical and electrochemical properties of the obtained π-spacer–acceptor–π-spacer type compounds in comparison with isomeric structures based on benzo[c][1,2,5]thiadiazole (BTD) showed a red shift of absorption maxima with lower absorptive and luminescent capacity. However, the addition of the 2,2′-bithiophene fragment as a π-spacer resulted in an unexpected increase of the extinction coefficient in the UV/vis spectra along with a blue shift of both absorption maxima for the isoBTD-based compound as compared to the BTD-based compound. Thus, a thorough selection of components in the designing of appropriate compounds with benzo[d][1,2,3]thiadiazole as an internal acceptor can lead to promising photovoltaic materials.

Novel D-A-π-A1 Type Organic Sensitizers from 4,7-Dibromobenzo[d][1,2,3]thiadiazole and Indoline Donors for Dye-Sensitized Solar Cells

“…For all four dyes, π/π* transition absorption peaks were observed in a narrow wavelength range, i.e., 394-401 nm, which characterizes close values of the energy level gap. The long-wavelength absorption maxima obeyed the previously established regularity [27]: the asymmetric nature of benzo…”

“…Surprisingly, its isomer, benzo [d][1,2,3]thiadiazole (isoBT), has not been explored in DSSCs. It was previously found that the most suitable precursor, 4,7-dibromobenzo [d][1,2,3]thiadiazole, can be easily prepared in a two-step synthesis process from the commercially available 2-aminobenzothiol [26,27]. A study of its chemical properties showed that the nucleophilic substitution of 4,7-dibromobenzo [d][1,2,3]thiadiazole with morpholine gave selectively mono-4-substituted 4- (7-bromobenzo[d][1,2,3]thiadiazol-4yl)morpholine [28].…”

“…A study of its chemical properties showed that the nucleophilic substitution of 4,7-dibromobenzo [d][1,2,3]thiadiazole with morpholine gave selectively mono-4-substituted 4- (7-bromobenzo[d][1,2,3]thiadiazol-4yl)morpholine [28]. In addition to the cross-coupling reactions of this dibromide, 4,7-di(hetaryl) derivatives can be easily prepared in moderate yields by Stille reaction [27], and some 4,7-di(hetaryl)benzo [d][1, 2,3]thiadiazoles can lead to compounds with promising photovoltaic properties. Therefore, in this work, we aimed to obtain new organic dyes based on the benzo [d][1,2,3]thiadiazole (isoBT) unit.…”

Efficient Synthesis of 4,8-Dibromo Derivative of Strong Electron-Deficient Benzo[1,2-d:4,5-d’]bis([1,2,3]thiadiazole) and Its SNAr and Cross-Coupling Reactions

“…Meanwhile, it has been shown that the replacement of the 1,2,5-thiadiazole ring in 2,1,3-benzothiadiazole (BTD) by the 1,2,3-thiadiazole ring leads to benzo[ d ][1,2,3]thiadiazole (isoBTD) compounds with properties similar to those of BTD, but with higher values of E LUMO and the band gap (Eg), which indicates a high electronic conductivity due to the high stability of the molecule in the excited state. The careful selection of components in the design of appropriate compounds with benzo[ d ][1,2,3]thiadiazole as an internal acceptor can lead to promising photovoltaic materials [ 23 ]. In this regard, it becomes relevant to study the BBT isomer, benzo[1,2- d :4,5- d ’]bis([1,2,3]thiadiazole) (isoBTD), which differs in the order of atoms in two five-membered heterocyclic rings.…”

Pd-G3 XantPhos Mediated Approach to Bis-arylsulfenyl-benzo-2,1,3-thiadiazoles under Microwave Irradiation in DMF: Synthesis and Fluorescent Properties

“…Other bis-arylsulfenyl-2,1,3-benzothiadiazole derivatives with a similar profile for the UV/Vis absorption spectrum have also been reported. 19b,21,23 According to Gudim et al (2021), 24 intramolecular charge transfer between the donor and acceptor parts of molecules is confirmed by the presence of an  MaxAbs at wavelengths between 400 and 500 nm. Considering compound 3a as a reference, which differs from most other compounds by the bond to the aromatic ring of bis-arylsulfenyl-2,1,3-benzothiadiazole,  MaxAbs are observed at 303 and 412 nm.…”