Table of Contents
International Journal of Inorganic Chemistry
Volume 2016, Article ID 3415690, 10 pages
http://dx.doi.org/10.1155/2016/3415690
Research Article

Synthesis and Study in Solution of a New Dansyl-Modified Azacryptand

Department of Chemistry, University of Pavia, Via Taramelli 12, 27100 Pavia, Italy

Received 15 July 2016; Accepted 22 August 2016

Academic Editor: Alfonso Castiñeiras

Copyright © 2016 Greta Bergamaschi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We report the synthesis of a new asymmetric azacryptand (L1), characterized by three p-xylyl spacers, one of which carries a dansyl side arm. The fluorescent sensor has been studied by potentiometric, UV-Vis, and emission studies in MeOH : water 3 : 2 mixture (0.07 M NaNO3), determining, in particular, the protonation constants of the free ligand and metal ion complexation equilibria. Interestingly, the obtained results revealed that the new receptor is fluorescent at neutral pH with a typical emission band of the dansyl group. Metal addition induced a partial quenching of the dansyl emission band; this behavior is more pronounced with Cu(II) that reduces the receptor’s emission by 60%. With all the studied cations, quenching follows the formation of a dimetallic complex. Similar studies on the model compound L2 confirmed that fluorescence quenching is mainly driven by a static mechanism, attributable to the formation of the inclusion dicopper complex [L1Cu2]4+. In order to test the stability of copper complexes under physiological conditions, spectrofluorimetric titrations with Cu(II) were performed in water buffered at pH = 8 (HEPES 0.07 M) and the values of binding constants, K11 and K12, were determined.