Designing of receptors capable of anion binding by hydrogen bonds continues to be an area of active research. In contrast to many possible hydrogen bond donors, the pyrrole ring does not contain a built-in hydrogen bond acceptor and this unique feature makes the pyrrole moiety an attractive motif in anion recognition [1]. The conjugation with benzene ring leads to increased acidity of the pyrrole N-H, hence enhanced anion binding ability. For this reason the incorporation of a benzopyrrole subunit into the anion receptors has become recently a subject of intensive exploration [2]. In this communication we would like to present results of the examination of the indolamine-based receptors.

We prepared aromatic bisamides from indol-7-amine and phenylamine and compared their anion binding properties. The incorporation of the indole moiety into hosts can lead to over five times stronger interaction with anions. The structural analysis of the indole-containing receptors revealed the correlation between their conformational preferences and their affinity towards anions.

[1] J. L. Sessler, S. Camiolo, P. A. Gale, Coord. Chem. Rev. 2003, 240, 17.
[2] a) P. Piatek, V. M. Lynch, J. L. Sessler, J. Am. Chem. Soc. 2004, 126, 16073. b) M. J. Chmielewski, M. Charon, J. Jurczak, Org. Lett. 2004, 6, 3501. c) D. Curiel, A. Cowley, P. D. Beer, Chem. Commun. 2005, 236. d) K. J. Chang, D. Moon, M. S. Lah, K. S. Jeong, Angew. Chem. Int. Edit. 2005, 44, 7926. e) X. M. He, S. Z. Hu, K. Liu, Y. Guo, J. Xu, S. Shao, J. Org. Lett. 2006, 8, 333.

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