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Synthesis and characterization of four novel 1,3-azole based push-pull heterocyclic systems
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1  Universidade do Minho


Benz[X]azole derivatives are interesting compounds due to their diverse biological activities1 and interesting optical properties.2  The benzothiazole, benzimidazole, and benzoxazole heterocycles are heteroaromatic electron deficient moieties that act as both acceptor groups and pi-conjugated spacers with auxiliary electron withdrawing ability.2,3 Moreover, benzimidazole derivatives offers the possibility of substitution on the nitrogen atom for further tuning of their optical and electronic properties.

Recently we have reported the synthesis and evaluation of the electronic, thermal and optical properties of a large number of series of benz[X]azole derivatives functionalized with different π-spacers having in mind their application as optical chemosensors, nonlinear optical and photochromic materials, and emissive organic components for OLEDs.2

In continuation of the work developed by our research group, we report in this communication the synthesis, the characterization and the evaluation of the optical properties of four novel 1-(4-thiophene-2-yl)phenyl)-1H-pyrrole derivatives functionalized with different benz[X]azole moieties (benzothiazole, benzimidazole, and benzoxazole). The results showed that the optical properties could be readily tuned by changing the electronic nature of the azole ring, or even by the introduction of a strong acceptor group.


Acknowledgements: Thank are due to Fundação para a Ciência e Tecnologia (Portugal) and FEDER-COMPETE for financial support through Centro de Química (UID/QUI/00686/2013 and UID/ QUI/0686/2016), and a PhD grant to S. S. M. Fernandes (SFRH/BD/87786/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased within the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT.



  1. (a) Boiani, M.; Gonzalez, M., Imidazole and benzimidazole derivatives as chemotherapeutic agents. Mini-Rev. Med. Chem. 2005, 5 (4), 409-424; (b) Keri, R. S.; Patil, M. R.; Patil, S. A.; Budagumpi, S., A comprehensive review in current developments of benzothiazole-based molecules in medicinal chemistry. Eur. J. Med. Chem. 2015, 89 (Supplement C), 207-251.
  2. (a) Costa, S. P. G.; Batista, R. M. F.; Cardoso, P.; Belsley, M.; Raposo, M. M. M., 2-Arylthienyl-substituted 1,3-benzothiazoles as new nonlinear optical chromophores. Eur. J. Org. Chem. 2006, 3938-3946; (b) Batista, R. M. F.; Costa, S. P. G.; Belsley, M.; Raposo, M. M. M., Synthesis and second-order nonlinear optical properties of new chromophores containing benzimidazole, thiophene, and pyrrole heterocycles. Tetrahedron 2007, 63 (39), 9842-9849; (c) Batista, R. M. F.; Costa, S. P. G.; Malheiro, E. L.; Belsley, M.; Raposo, M. M. M., Synthesis and characterization of new thienylpyrrolyl-benzothiazoles as efficient and thermally stable nonlinear optical chromophores. Tetrahedron 2007, 63 (20), 4258-4265; (d) Batista, R. M. F.; Ferreira, R. C. M.; Raposo, M. M. M.; Costa, S. P. G., Novel optical chemosensors for anions and cations based on an amino acid core functionalized with benzimidazoles. Tetrahedron 2012, 68 (36), 7322-7330; (e) Pina, J.; Seixas de Melo J. S.; Batista, R. M. F.; Costa, S. P. G.; Raposo, M. M. M. Triphenylamine-benzimidazole derivatives: synthesis, excited-state characterization, and DFT studies. J. Org. Chem.201378 (22), 11389-11395; e) Castro, M. C. R.; Belsley, M.; Raposo, M. M. M., Push–pull second harmonic generation chromophores bearing pyrrole and thiazole heterocycles functionalized with several acceptor moieties: syntheses and characterization. Dyes Pigments 2016, 128, 89-95; f) Garcia-Amorós, J.; Castro, M. C. R.; Coelho, P.; Raposo, M. M. M.; Velasco, D. Fastest non-ionic azo dyes and transfer of their thermal isomerization kinetics into liquid-crystalline materials. Chem. Commun. 2016, 52 (29), 5132-5135.
  3. Revuelta, J.; Machetti, F.; Cicchi, S., Five-membered heterocycles: 1,3-azoles. In Modern Heterocyclic Chemistry, Wiley-VCH Verlag GmbH & Co. KGaA: 2011; pp 809-923.
Keywords: benzothiazole, benzimidazole, benzoxazole, push-pull heterocyclic systems