Synthesis of conjugated polymers possessing diketopyrrolopyrrole units bearing phenyl, pyridyl, and thiazolyl groups by direct arylation polycondensation: Effects of aromatic groups in DPP on physical properties

Abstract

Conjugated polymers containing phenyl-, pyridyl-, and thiazolyl-flanked diketopyrrolopyrrole (DPP) were synthesized by direct arylation polycondensation of 3,4-ethylenedioxythiophene derivatives and dibrominated DPP-based monomers, in order to probe the effects of the aromatic groups in the DPP units on the absorption property, energy level, and crystallinity. A polymer possessing thiazolyl-flanked DPP units was found to display long-wavelength absorption properties and higher crystallinity than the polymers bearing phenyl-and pyridyl-flanked DPP units. These features of the thiazolyl-based polymer were afforded by its coplanar structure of the main chain. The synthesized polymers showed semiconducting properties in organic field effect transistors and organic photovoltaics. Direct arylation polycondensation is an efficient synthetic method that affords a series of DPP-based polymers in a simple fashion and, thus, helping in a comprehensive understanding on the relationship between the aromatic groups in DPP units and their physical properties.

An Electron-Transporting Thiazole-Based Polymer Synthesized Through Direct (Hetero)Arylation Polymerization

“…However, in order to avoid β-branching on the 3- and 4-positions of the thiophene unit, we protected them with small methyl groups [ 24 , 25 ]. One can notice that a similar polymer was recently synthesized by DHAP and published by Kuwabara et al [ 26 ]. As we did in the present study, they protected the β-position, but by using an electron-rich 3,4-ethylylenedioxythiophene (EDOT) unit instead of a simple thiophene; but surprisingly, they used the dibrominated derivative of the thiazole-based DPP.…”

Sustainable protocols for direct C–H bond arylation of (hetero)arenes

“…395 In 2016, the same group reported the synthesis of π-conjugated polymers by microwave-assisted direct C-H bond arylation co-polymerization of EDOT with dibrominated phenyl-, pyridyl-and thiazolyl-flanked DPPs. 396 Reactions were carried out using Pd(OAc) 2 (1 mol%) as the catalyst and potassium pivalate as the base in DMA under microwave irradiation at 100 °C for 1 h, affording the target polymers in 37-94% yields. As for most investigations related to the synthesis of π-conjugated systems, also in these works the authors were not mainly focused on the development of sustainable protocols: reactions were typically carried out with homogeneous Pd(OAc) 2 (although often under ligand-less conditions) and in poorly sustainable solvents, therefore their overall interest in the framework of Green Chemistry appears in our opinion quite low.…”

Direct arylation polycondensation for synthesis of optoelectronic materials

“…The highly active catalytic system allows the preparation of the corresponding polymer with a high molecular weight (Mn = 31800) in 3 h. 34 In addition to bithiophene derivatives, this reaction system is available for the polycondensation of bithiazole, thienothiophene, monothiohene derivatives, and naphthalenediimide-based monomers (Scheme 3). [35][36][37][38][39][40][41][42][43] This simple catalytic system has been used for the preparation of a variety of conjugated polymers by other groups, [44][45][46][47] presumably because of its high reactivity and ease of use. It is important to note that this highly reactive system sometimes induces side reactions causing structural defects; a direct arylation reaction can occur at undesired C-H bonds.…”