Research article summary (published 8 Aug 2009):

Polyamine receptors containing dipyridine or phenanthroline units: clues for the design of fluorescent chemosensors for metal ions.

Full Abstract

The synthesis of the macrocyclic receptor L1, which contains a tetraamine chain linking the 6,6'-positions of a 2,2'-dipyridine moiety, is reported. Its basicity properties and complexation features toward Cu(II), Zn(II), Cd(II) and Pb(II) have been studied in aqueous solutions by means of potentiometric, UV/Vis spectroscopy and fluorescence emission measurements and compared with those of ligand L2, in which a 1,10-phenanthroline moiety replaces the dipyridine unit of L1. In metal coordination, L1 shows a marked selectivity toward Cd(II) over Zn(II) and Pb(II). The crystal structures of its metal complexes shows that L1 possesses a preferential tetradentate binding site for metal cations, composed of the dipyridine unit and the two adjacent benzylic amine groups. This binding site has the proper dimension and conformation to selectively coordinate the Cd(II) ion, as confirmed by DFT calculations carried out on the complexes. This coordinative zone is lost in L2. The rigidity of phenanthroline does not allow the simultaneous binding of both the benzylic amine groups to Zn(II) and Cd(II) and, in fact, one benzylic amine is not coordinated to these metal cations. The fluorescence emission properties of the L1 and L2 complexes are strongly pH dependent. Only the Zn(II) and Cd(II) complexes with L1 display fluorescence emission at neutral pH. This feature is related to the formation in solution at pH 7 of emissive protonated complexes of the type [M(H(x)L)]((2+x)+) (x=1-3), in which all the nitrogen donors are involved in metal or proton binding. The emissive characteristics of these protonated complexes are confirmed by the fluorescence emission spectra collected on the [Zn(HL1)Br][ClO(4)](2) and [Cd(HL1)Br][ClO(4)](2) solid compounds dissolved in CH(3)CN. Conversely, the Zn(II) and Cd(II) complexes with L2 are not emissive; in fact, they contain a benzylic amine group not involved in metal or proton binding that can quench the fluorescence emission of the fluorophore, thanks to a photoinduced electron-transfer process.

Author information

Author/s: Bazzicalupi, Carla (C); Bencini, Andrea (A); Biagini, Silvia (S); Bianchi, Antonio (A); Faggi, Enrico (E); Giorgi, Claudia (C); Marchetta, Melania (M); Totti, Federico (F); Valtancoli, Barbara (B);

Affiliation: Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Chemistry (Weinheim an der Bergstrasse, Germany) (Chemistry), published in Germany. (Language: eng)

Reference: 2009-Aug; vol 15 (issue 32) : pp 8049-63

Dates: Created 2009/08/11; Completed 2009/09/11;

PMID: 19504514, status: MEDLINE (last retrieval date: 9/11/2009, IMS Date: )

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

2,2'-Dipyridyl - analogs & derivatives; chemistry Cadmium - chemistry Copper - chemistry Fluorescence Fluorescent Dyes - chemical synthesis; chemistry

Lead - chemistry Molecular Structure Phenanthrolines - chemistry Polyamines - chemistry Zinc - chemistry

Associated Chemicals: Fluorescent Dyes (0) ; Phenanthrolines (0) ; Polyamines (0) ; 2,2'-Dipyridyl (366-18-7) ; Lead (7439-92-1) ; Cadmium (7440-43-9) ; Copper (7440-50-8) ; Zinc (7440-66-6)

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