C–H Arylation of Unsubstituted Furan and Thiophene with Acceptor Bromides: Access to Donor–Acceptor–Donor-Type Building Blocks for Organic Electronics

Abstract

Pd-catalyzed direct arylation (DA) reaction conditions have been established for unsubstituted furan (Fu) and thiophene (Th) with three popular acceptor building blocks to be used in materials for organic electronics, namely 4,7-dibromo-2,1,3-benzothiadiazole (BTBr2), N,N′-dialkylated 2,6-dibromonaphthalene-1,4,5,8-bis(dicarboximide) (NDIBr2), and 1,4-dibromotetrafluorobenzene (F4Br2). Reactions with BTBr2, F4Br2, and NDIBr2 require different solvents to obtain high yields. The use of dimethylacetamide (DMAc) is essential for the successful coupling of BTBr2 and F4Br2, but detrimental for NDIBr2, as the electron-deficient NDI core is prone to nucleophilic core substitution in DMAc as solvent but not in toluene. NDIFu2 is much more planar compared to NDITh2, resulting in an enhanced charge-transfer character, which makes it an interesting building block for conjugated systems designed for organic electronics. This study highlights direct arylation as a simple and inexpensive method to construct a series of important donor–acceptor–donor building blocks to be further used for the preparation of a variety of conjugated materials.

Defect-free Naphthalene Diimide Bithiophene Copolymers with Controlled Molar Mass and High Performance via Direct Arylation Polycondensation

“…32 Obviously, this poses ideal conditions under which polycondensation can be conducted efficiently, and thus we investigated the stoichiometric reaction between NDIBr 2 and T2 and the resulting products PNDIT2 in detail (Scheme 1).…”

“…It is interesting to note that the herein used catalytic system without a phosphine ligand is very efficient but fails for the DA of an excess of thiophene and 3,7-dibromobenzothiadiazole, where Pd black precipitates. 32 To further test the catalytic efficacy and the robustness of the system, we performed the reaction at lower Pd loadings. For amounts of Pd 2 dba 3 down to 0.1 mol %, the quantitative yield was maintained albeit M n was lower ( Figure 1b, Table 1, entries 22 and 23).…”

Effects of PNDIT2 end groups on aggregation, thin film structure, alignment and electron transport in field-effect transistors

“…Importantly, the polarity of the solvents seems to play a major role. 13,24 While this side reaction is prevalent in polar solvents such as DMAc 24 and THF preventing build-up of long chains, its extent in aromatic solvents is much reduced and only seen for low monomer concentrations when polycondensation is slow. 13 With the initial aim to find a greener solvent for the synthesis of PNDIT2 and eventually for other conjugated polymers, we replaced THF with MeTHF.…”

Phthalimide-based π-conjugated small molecules with tailored electronic energy levels for use as acceptors in organic solar cells

“…For each DHA reaction, catalyst loadings of 5 mol% Pd with 20 mol% pivalic acid and potassium carbonate as the base were used. 44 All products were purified in the same manner, by first separating the heterogeneous catalyst from the reaction mixture using a filtration apparatus, followed by column chromatography on silica-gel with a pentane-CH 2 Cl 2 gradient to elute the products. Branched alkyl chains such as this can provide increased solubility compared to their linear counterparts while minimizing the amount of non-conjugated moieties in the molecule.…”

“…[8][9][10] In addition, the majority of D-A compounds are easily synthesized though standard organic chemistry techniques using widely available starting materials. 44 All products were purified in the same manner, by first separating the heterogeneous catalyst from the reaction mixture using a filtration apparatus, followed by column chromatography on silica-gel with a pentane-CH 2 Cl 2 gradient to elute the products. 11-13 Donor materials making use of the D-A design strategy are well studied and thousands of materials with different physical properties have been presented in the literature, allowing for versatility when selecting the donor component for use in OSCs.…”