Switching-On Fluorescence by Copper (II) and Basic Anions: A Case Study with a Pyrene-Functionalized Squaramide
Giacomo Picci, Jessica Milia, M. Carla Aragoni, Massimiliano Arca, Simon J. Coles, Alessandra Garau, Vito Lippolis, Riccardo Montis, James B. Orton, Claudia Caltagirone
Abstract
The new symmetric acyclic N,N’-bis(1-pyrenyl) squaramide (H2L) functionalized with the pyrene moiety as a fluorogenic fragment has been designed and its ability to selectively detect specific anions and metals investigated. H2L selectively binds Cl− both in solution (DMSO 0.5% H2O and MeCN) and in the solid state, and allows to selectively detect Cu2+ in MeCN with the formation of a 2:1 metal-receptor complex, with a green intense emission appreciable by naked eye under the UV lamp. The H2L copper complex preserves its emission properties in the presence of Cl−. The addition of basic anions (OH−, CN−, and F−) up to 10 equivalents caused the deprotonation of the squaramide NHs and a dramatic change of the emission properties of the H2L copper complex.