Sensing Zn<sup>2+</sup> in Aqueous Solution with a Fluorescent Scorpiand Macrocyclic Ligand Decorated with an Anthracene Bearing Tail
Matteo Savastano,
Matteo Fiaschi,
Giovanni Ferraro,
Paola Gratteri,
Palma Mariani,
Antonio Bianchi,
Carla Bazzicalupi
Affiliations
Matteo Savastano
Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3-13, 50019 Sesto Fiorentino, Italy
Matteo Fiaschi
Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3-13, 50019 Sesto Fiorentino, Italy
Giovanni Ferraro
Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3-13, 50019 Sesto Fiorentino, Italy
Paola Gratteri
Department of NEUROFARBA-Pharmaceutical and Nutraceutical section, and Laboratory of Molecular Modeling Cheminformatics & QSAR, University of Florence, Via Ugo Schiff 6, 50019 Sesto Fiorentino, Italy
Palma Mariani
Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3-13, 50019 Sesto Fiorentino, Italy
Antonio Bianchi
Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3-13, 50019 Sesto Fiorentino, Italy
Carla Bazzicalupi
Department of Chemistry “Ugo Schiff”, University of Florence, Via della Lastruccia, 3-13, 50019 Sesto Fiorentino, Italy
Synthesis of the new scorpiand ligand L composed of a [9]aneN3 macrocyclic ring bearing a CH2CH2NHCH2-anthracene tail is reported. L forms both cation (Zn2+) and anion (phosphate, benzoate) complexes. In addition, the zinc complexes of L bind these anions. The equilibrium constants for ligand protonation and complex formation were determined in 0.1 M NaCl aqueous solution at 298.1 ± 0.1 K by means of potentiometric (pH-metric) titrations. pH Controlled coordination/detachment of the ligand tail to Zn2+ switch on and off the fluorescence emission from the anthracene fluorophore. Accordingly, L is able to sense Zn2+ in the pH range 6–10 down to nM concentrations of the metal ion. L can efficiently sense Zn2+ even in the presence of large excess of coordinating anions, such as cyanide, sulphide, phosphate and benzoate, despite their ability to bind the metal ion.
