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Issue 4, 2012
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Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions

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Two new tetranuclear cationic metalla-bowls 4 and 5 were self-assembled from a bis-pyridine amide ligand (H2L) (1) and arene-ruthenium acceptors, [(Ru2(μ-η4-C2O4)(η6-p-cymene)2](O3SCF3)2 (2) and [Ru2(dhnd)(η6-p-cymene)2](O3SCF3)2 (dhnd = 6,11-dihydroxy-5,12-naphthacenedionato) (3), respectively. The metalla-bowls were characterized by multinuclear NMR, ESI-MS, UV-Vis spectroscopy, and single crystal X-ray diffraction study of 4. The crystal structure of 4 reveals unambiguous proof for the molecular shape of the metalla-bowl and the encapsulation of one triflate anion in the cavity through hydrogen bonding. The metalla-bowl 5 has been evaluated for anion binding studies by use of amide ligand as a hydrogen bond donor and arene-Ru acceptor as a signalling unit. UV-Vis titration studies showed that 5 selectively binds with multi-carboxylate anions such as oxalate, tartrate and citrate in a 1 : 1 fashion with high binding constants of 4.0–5.5 × 104 M−1. Furthermore, the addition of multi-carboxylate anions into a solution of 5 gave rise to a large enhancement of fluorescence intensity attributable to the blocking of a photo-induced electron transfer process from the arene-ruthenium moiety to the amidic donor in 5. However, the fluorescence intensity almost remains unchanged upon addition of other anions including F, Cl, PF6, MeCOO, NO3 and PhCOO, as identically seen in the UV-Vis titration experiments, pointing to the high selectivity of 5 for the sensing of multi-carboxylate anions.

Graphical abstract: Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions

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Supplementary files

Article information

26 Aug 2011
13 Oct 2011
First published
25 Nov 2011

Dalton Trans., 2012,41, 1195-1201
Article type

Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions

A. Mishra, V. Vajpayee, H. Kim, M. H. Lee, H. Jung, M. Wang, P. J. Stang and K. Chi, Dalton Trans., 2012, 41, 1195
DOI: 10.1039/C1DT11612F

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