Novel bithienyl-benzimidazoles: one-pot synthesis and optical and solvatochromic studies

Benzimidazoles are a group of heterocyclic compounds which have been applied in numerous aspects of science and technology. As a result of their interesting electronic and optical properties when incorporated in push-pull systems, benzimidazole derivatives found application as solvatochromic and fluorescent probes, chemosensors, organic light emitting diodes (OLEDs) and non-linear optical (NLO) chromophores.^[1]

In the last decade our research group has reported experimental and theoretical results regarding the auxiliary donor/acceptor effect of electron deficient benz-X-azole derivatives in push-pull systems.^{[1b-c, 1e, 1g-i]} In this work we describe the synthesis, UV-visible absorption, fluorescence and solvatochromic studies of a series of heterocyclic chromophores of the benzimidazole type. These new bithienyl-benzimidazoles were synthesised in good to excellent yields, by metal-free one-step reaction of o-nitroanilines in the presence of formyl-bithiophenes, via a reductive cyclization, and their optical and solvatochromic properties were evaluated in solvents of different character.

References:

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Acknowledgements

Thanks are due to Fundação para a Ciência e Tecnologia (Portugal) for financial support through project FEDER-COMPETE for financial support through the CQ/UM PEst-C/QUI/UI0686/2013 (FCOMP-01-0124-FEDER-037302) and a post-doctoral grant to R.M.F. Batista (SFRH/BPD/79333/2011). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network, and was purchased with funds from POCI2010 (FEDER) and FCT.