Conjugated solution-processable polymeric semiconductors have been widely explored as materials for lightweight, inexpensive, flexible plastic electronics and potential application in large area devices.1 A promising strategy to enhance the performance of the optical devices to include fused aromatic heterocycles into the conjugated copolymer backbone.2 Aromatic heterocycles are versatile building blocks in the construction of π-conjugated polymers for electronic and optical devices. Generally for the synthesis of π-conjugated polymers transition M[0]-catalyzed Stille/Suzuki-coupling reactions were employed.3 Transition-metal catalyst systems are often expensive and poisonous (Sn-derivatives), and they required air-sensitive and costly phosphine ligand. For the environmental and economical consideration, development of a transition-metal-free system for the synthesis of π-conjugated polymers is an attractive route. Since the introduction of i-PrMgCl.LiCl (turbo-Grignard reagent) by Prof. Knochel in 2004, it has been made an incredible contribution towards preparative organic synthesis.4 Turbo-Grignard reagent shows higher functional group tolerance and greater selectivity under milder reaction condition. i-PrMgCl.LiCl also used in Grignard metathesis (GRIM) polymerization reactions using Ni[II] catalysts.5 In this contribution, we report the synthesis of pyrrolo[3,2-d:4,5-d’]bisthiazole (PBTz)6 homo-polymers using the i-PrMgCl.LiCl complex to afford polymers with good molecular weights. No transition metal catalyst was required for the polymerization. The PBTz-based homo polymers showed broad absorption from 450 to 850 nm in the thin film and excellent photochemical and thermal stability.

Novel transition-metal-free homo-polymerization of Pyrrolo[3,2-d:4,5-d’]Bisthiazole (PBTz) using turbo-Grignard for organic electronics

253rd National Meeting (2017)

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