Issue 21, 2000

Effect of protons and metal ions on the fluorescence properties of a polylysin dendrimer containing twenty four dansyl units

Abstract

The interaction of protons, Co2+, Ni2+ and Zn2+ ions (as nitrate salts) with a polylysin dendrimer, D, functionalized in the periphery with 24 5-dimethylamino-1-naphthalenesulfonamido (dansyl) units has been investigated in acetonitrile–dichloromethane solution. The dendrimer consists of a benzene core branched in the 1, 3, and 5 positions. Each branch starts with a (dialkyl)carboxamide-type moiety and carries (i) six aliphatic amide groups and (ii) eight fluorescent dansyl units. For comparison purposes, the behaviour of a monodansyl reference compound (I) has also been investigated. The absorption spectrum and the fluorescence properties of the dendrimer are those expected for a species containing 24 non-interacting dansyl units. Both for the model compound and for the dendrimer, protonation causes a shift of the absorption and fluorescence bands towards higher energies; for the dendrimer, however, the changes in fluorescence intensity during the acid titration reveal the occurrence of intradendrimer quenching processes, with signal amplification. Addition of Co2+ or Ni2+ ions to a basic solution of the model compound I does not cause any effect in the absorption and emission properties, whereas in the case of dendrimer D a strong fluorescence quenching is observed. At low metal ion concentration each metal ion quenches about 9 dansyl units; the fluorescence quenching takes place by a static mechanism involving co-ordination of metal ions in the interior of the dendrimer. Addition of Zn2+ to a basic solution of the dendrimer causes only a very small decrease in the fluorescence intensity. The co-ordinated Co2+ and Ni2+ ions are fully displaced by addition of Zn2+ or H+ with revival of the dansyl fluorescence. The results obtained show that a dendrimer can exhibit an unusual co-ordinating ability and sensory signal amplification.

Article information

Article type
Paper
Submitted
20 Apr 2000
Accepted
20 Jun 2000
First published
09 Oct 2000

J. Chem. Soc., Dalton Trans., 2000, 3765-3771

Effect of protons and metal ions on the fluorescence properties of a polylysin dendrimer containing twenty four dansyl units

V. Balzani, P. Ceroni, S. Gestermann, M. Gorka, C. Kauffmann and F. Vögtle, J. Chem. Soc., Dalton Trans., 2000, 3765 DOI: 10.1039/B003214J

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements