Dendrimers as ligands: an investigation into the stability and kinetics of Zn2+ complexation by dendrimers with 1,4,8,11-tetraazacyclotetradecane (cyclam) cores.

Détails

ID Serval
serval:BIB_90A88D3B28FD
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
Dendrimers as ligands: an investigation into the stability and kinetics of Zn2+ complexation by dendrimers with 1,4,8,11-tetraazacyclotetradecane (cyclam) cores.
Périodique
Chemistry
Auteur(s)
Saudan C., Balzani V., Gorka M., Lee S.K., Van Heyst J., Maestri M., Ceroni P., Vicinelli V., Vögtle F.
ISSN
0947-6539
Statut éditorial
Publié
Date de publication
2004
Peer-reviewed
Oui
Volume
10
Numéro
4
Pages
899-905
Langue
anglais
Résumé
We have investigated the complexation of Zn(2+) with 1,4,8,11-tetrakis(naphthylmethyl) cyclam (1; cyclam=1,4,8,11-tetraazacyclotetradecane) and with two dendrimers consisting of a cyclam core with four dimethoxybenzene and eight naphthyl appendages (2), and twelve dimethoxybenzene and sixteen naphthyl appendages (3). An important, common feature of model compound 1 and dendrimers 2 and 3 is that their potentially fluorescent naphthyl units are quenched by exciplex formation with the cyclam nitrogen atoms. Complexation with Zn(2+), however, prevents exciplex formation and results in the appearance of an intense naphthyl fluorescence signal that can be used for monitoring the complexation process. Luminescence titration, together with competition experiments and (1)H NMR titration, have shown that 1:1 and 1:2 (metal/ligand) complexes are formed in the cases of 2 and 3, whereas model compound 1 gives only a 1:1 complex. We have also investigated the 1:1 complexation kinetics by the stopped-flow technique. In the case of 1, a second-order process (k(1)=44x10(5) M(-1) s(-1)) is followed by two consecutive first-order steps (k(2)=0.53 s(-1) and k(3)=0.10 s(-1)). For 2, a slower second-order process (k(1)=4.9x10(5) M(-1) s(-1)) is followed by a slow first-order step (k(2)=0.40 s(-1)). In the case of 3, only a very slow second-order process was observed (k(1)=1.2x10(5) M(-1) s(-1)). The different metal-ion incorporation rates for model compound 1 and dendrimers 2 and 3 have been discussed in terms of conformational changes of the dendron subunits affecting the chelating properties of the cyclam core. This work reports the first kinetic study on metal-ion coordination by dendrimers with a well-defined coordination site.
Pubmed
Web of science
Création de la notice
19/05/2008 12:00
Dernière modification de la notice
03/03/2018 19:26
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