Synthesis of π-Conjugated Polymers Containing Benzodipyrrole Moieties in the Main Chain through Cleavage of C–H Bonds in 1,4-Bis(acetylamino)benzene

Abstract

Rhodium-catalyzed copolymerization between 1,4-bis(acetylamino)benzene and diynes through C−H bond cleavage afforded π-conjugated polymers containing benzodipyrrole moieties. The polymers with substituted benzene units exhibited nearly the same absorption peaks and HOMO levels. Fluorenone and benzothiadiazole moieties can be also introduced as electron-acceptor units to the main chain by polymerization in tert-amyl alcohol and tetrahydropyran as mixed solvent, leading to absorption at longer wavelength.π-Conjugated polymers showed attractive absorption, luminescence, and semiconducting properties, which can be applied to organic photovoltaic cells, light-emitting diodes, or field-effect transistors. 1 To tune their power conversion of efficiency, color or mobility from the synthetic point of view, many π-conjugated polymers with various (hetero)arylene moieties in the main chains were proposed and synthesized. 2 Among them, N-hetero arenes are useful to modify the frontier orbital energies correlated to the optical and electronic properties. 3 While aromatics containing amide or imine moieties lower the LUMO levels and tend to accept electrons, pyrrole-type aromatics elevate the HOMO levels and elevate hole affinity.One of the most conventional methods to prepare soluble π-conjugated polymers is transition metal-catalyzed crosscoupling polymerization through cleavage of carbon−halogen (C−X) bond and carbon−metal bond. 4 This approach bases on successive formation of a single bond between two aromatic units. Although the cross-coupling polymerization usually achieved high molecular weight and reliable regioselectivity, preparation of the halogenated, and metalated monomers sometimes required many synthetic steps to introduce functional groups at desired positions and generate a lot of byproducts and impurities. In recent years, transition metalcatalyzed direct C−H arylations have been applied to polymerization to reduce the cost and waste. 5 In direct C−H arylation polymerization through C−H and C−X cleavage, monomers with acidic protons or directing groups gave soluble π-conjugated polymers in good yield and regioselectivity. Moreover, some results supported that purity or performance of polymers by C−H direct arylation was better than those by conventional cross-coupling method. 6 Nowadays, transition metal-catalyzed C−H activation followed by alkyne insertion is useful method for synthesis of fused aromatic rings. 7 Fagnou and co-workers developed facile synthesis of indoles by rhodium-catalyzed C−H bond cleavage of acetanilide and alkyne insertion. 8 The reaction proceeded under mild condition and gave indoles in good yield and high regioselectivity. Herein, we applied the C−H functionalization leading to indoles to synthesis of π-conjugated polymers containing N-heteroarenes in the main chain. The synthetic efficiency of the polymerization described here is highlighted by simultaneous formation of N-heterocycles with extension of the main chain and also by no need to prepare halogenated monomers or organometa...

Functional isocoumarin-containing polymers synthesized by rhodium-catalyzed oxidative polycoupling of aryl diacid and internal diyne

“…1 As a group of new advanced materials, polymers with fused-heterocyclic units in the main chains have attracted considerable attention. In the past few decades, a series of fused-heterocyclic polymers, for example, polymers containing benzodipyrrole, 2 benzofuran, 3 benzothiophene, 4 benzothiadiazole, 5 benzylcarb-azole, 6 and naphthopyran, 7 have been developed and investigated. Owing to their structural advantages of both the high conjugation of fused rings and the distinctive electrical and photophysical properties of heterocyclic moieties, they have found a variety of applications as external stimuli-responsive materials, 8 fluorescent sensors 9 and photoelectronic devices, such as polymer solar cells, 10 polymer field-effect transistors, 11 polymer light-emitting diodes, 6 etc.…”

Synthesis of Linearly Fused Benzodipyrrole Based Organic Materials

“…Tokoro et al developed a transition metal-catalyzed C-H activation to convert N,N′ -(1,4-phenylene)diacetamide 168 and an arylalkyne 169 into substituted pyrrolo[2,3- f ]indole 170 (Scheme 45). The reaction works well with simple aryls (8%–63%) as well with electron deficient systems (benzothiadiazole (76%), fluorenone (80%)) and electron rich systems (carbazole (64%)) [95].…”

“…The absorption spectrum of the polymer with a benzene moiety in the backbone showed a maximum at 365 nm (in DCM solution). When electron withdrawing systems like benzothiadiazole 239 or fluorenonyl 240 were used instead of benzene, the absorption peak shifted to 442–453 nm [95].…”

Donor‐acceptor copolymers from cyclopentannulation polymerizations with dicyclopenta[cd,jk]pyrene and dicyclopenta[cd,lm] perylene acceptors

“…The annulation polymerization approach has only more recently been utilized to grow polymeric materials. [16][17][18][19][20][21][22][23] Our preliminary work involved only the cyclopenta[h,i]aceanthrylene acceptor unit. To develop a larger library of donor-acceptor copolymers, we have designed and synthesized a series of new donoracceptor copolymers with new acceptor units based on dicyclopenta[cd,jk]pyrenes and dicyclopenta[cd,lm] perylenes.…”

“…This strategy is reminiscent of C‐H activation polymerization chemistry that is an atom economical process. The annulation polymerization approach has only more recently been utilized to grow polymeric materials 16–23 . Our preliminary work involved only the cyclopenta[ h , i ]aceanthrylene acceptor unit.…”