A Six‐Armed Phenhomazine Ligand with a Potential "Turn‐Off" Copper(II) Sensing Capability through Terbium(III) Luminescence Quenching. Issue 55 (11th September 2020) - Trupp, Leandro
Abstract: Herein, the design, synthesis, and characterization of a phenhomazine ligand are described. The ligand has six pendant acetate arms designed for the combined coordination of copper(II) and lanthanide(III) ions, with the perspective of developing a "turn‐off" copper sensor. The key step for the ligand preparation was the one‐step endomethylene bridge fission of a diamino Tröger's base with a concomitant alkylation. Fluorescence and absorption spectroscopies as well as nuclear magnetic resonance (NMR) experiments were performed to analyze and understand the coordination properties of the ligand. Transition metal coordination was driven by the synergistic effect of the free nitrogen atoms of the diazocinic core and the two central acetate arms attached to those nitrogen atoms, whereas lanthanide coordination is performed by the external acetate arms, presumably forming a self‐assembled 2:2 metallosupramolecular structure. The terbium complex shows the typical green emission with narrow bands and long luminescence lifetimes. The luminescence quenching produced by the presence of copper(II) ions was analyzed. This work sets, therefore, a starting point for the development of a phenhomazine‐based "turn‐off" copper(II) sensor. Abstract : Copper sensing : The first use of a phenhomazine ligand in the preparation of luminescent lanthanide(III) complexes is presented, and its potential for "turn‐off" copper(II) sensing through quenching of terbium(III) luminescence is explored. The ligand was designed to present two different coordination sites, one for copper(II) and one for lanthanide(III) ions, and was synthesized with a key step of endomethylene bridge fission of a Tröger's base.