Dendrimers as ligands. Formation of a 2:1 luminescent complex between a dendrimer with a 1,4,8,11-tetraazacyclotetradecane (cyclam) core and Zn2+.
Details
Serval ID
serval:BIB_2A09B186534C
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Dendrimers as ligands. Formation of a 2:1 luminescent complex between a dendrimer with a 1,4,8,11-tetraazacyclotetradecane (cyclam) core and Zn2+.
Journal
Journal of the American Chemical Society
ISSN
0002-7863
Publication state
Published
Issued date
2003
Peer-reviewed
Oui
Volume
125
Number
15
Pages
4424-4425
Language
english
Abstract
We have investigated the formation of metal complexes between Zn2+ and two derivatives, 1 and 2, of the well-known 1,4,8,11-tetraazacyclotetradecane (cyclam) ligand. Compound 1 is 1,4,8,11-tetrakis(naphthylmethyl) cyclam, and compound 2 is a dendrimer consisting of a cyclam core with appended 12 dimethoxybenzene and 16 naphthyl units. Compound 1 exhibits an emission band with a maximum around 480 nm, assigned to the formation of exciplexes between amine and excited naphthyl units. Dendrimer 2 exhibits three types of weak emission bands, assigned to naphthyl localized excited states (lambdamax = 337 nm), naphthyl excimers (lambdamax ca. 390 nm), and naphthyl-amine exciplexes (lambdamax = 480 nm). In CH3CN-CH2Cl2 1:1 v/v, titration of ligand 1 with Zn2+ causes the disappearance of the exciplex emission and the appearance of a strong naphthyl localized fluorescence; the titration plot is linear and reaches a plateau for a 1:1 stoichiometry, showing that a highly stable [Zn(1)]2+ complex is formed. In the case of 2, titration with Zn2+ causes the disappearance of the exciplex band, with a concomitant increase in the excimer and naphthyl localized emissions; the titration plot is again linear, but in this case it reaches a plateau for a 2:1 stoichiometric ratio, showing the unexpected formation of a [Zn(2)2]2+ complex. Such an unexpected stoichiometry for the complex of the dendritic ligand has been fully confirmed by 1H NMR titrations. The results obtained show that the dendrimer branches not only do not hinder, but in fact favor coordination of cyclam to Zn2+.
Pubmed
Web of science
Create date
19/05/2008 11:00
Last modification date
20/08/2019 13:09