3,3′‐ and 4,4′‐Dimethoxy‐2,2′‐bipyrroles: Highly Electron‐Rich Model Compounds for Polypyrrole Formation.

Abstract

3,3'-Dimethoxy-2,2'-bipyrrole (1) and 4,4'-dimethoxy-2,2'-bipyrrole (2) were obtained in short sequences and good yields from N-benzyl-3-hydroxypyrrole-2,4-dicarboxylic acid. The key intermediate leading to 1 is an N-benzyl-3-methoxypyrrole, which is dimerized by lithiation and oxidation with NiCl(2). The formation of 2 is achieved by a classical Ullmann coupling of diethyl 1-benzyl-2-bromo-4-methoxypyrrole-3,5-dicarboxylate. The N-benzyl protection groups of 1 and 2 are cleaved under reducing conditions with sodium in liquid ammonia. Both isomeric bipyrroles are extremely sensitive toward air. Compound 1 has a very low oxidation potential of 0.09 V against AgCl but film formation hardly occurs. On the other hand, compound 2 with a potential of 0.35 V readily forms stable polypyrrole films with anodic waves at -0.51 and -0.35 V and a cathodic wave at -0.77 V, the lowest potential ever observed for a p-doped polymer.

Bis-EDOT end capped by n-hexyl or n-hexylsulfanyl groups: the effect of the substituents on the stability of the oxidized states

“…In oligothiophene series, -dimers have never been isolated but different systems with analogous chemical properties have been isolated. 28,29 In the continuation of our current interest in conjugated systems based on EDOT moieties, we report here on the effect of the n-hexyl and n-hexylsulfanyl groups on the electronic properties of bis-EDOT derivatives EEa-c (Chart 1) and we show the impact of the sulphur atom on the stability of the oxidized species. …”

Conjugated 4‐Methoxybipyrrole Thiophene Azomethines: Synthesis, Opto‐Electronic Properties, and Crystallographic Characterization

“…For example, poly(3,4-dimethoxypyrrole) has higher conductivity and is easier to synthesize than its unsubstituted and alkyl-substituted counterparts. [14,15] In this light, bipyrroles represent interesting starting points for constructing conducting polymers; however, to the best of our knowledge, only symmetric bipyrroles [9,16] have been studied, likely due to a dearth of methods for preparing unsymmetrical bipyrroles. [17][18][19][20] Functional materials with multiple color states and a large palette of colors are required to meet the requirements for new electrochromic devices.…”

Facile preparation and fluorescence properties of a soluble oligopyrrole derivative

“…Numerous methods have been developed for the synthesis of oligopyrroles with various structures, such as Vilsmeier condensation, Paal-Knorr cyclization, dipolar cycloaddition, Ullmann coupling and other metal-mediated coupling reactions [8][9][10][11]. Generally, these methods involve drastic reaction conditions and tedious procedures more or less.…”