molecules Review The Role of Zinc(II) Ion in Fluorescence Tuning of Tridentate Pincers: A Review Rosita Diana and Barbara Panunzi * Department of Agriculture, University of Napoli Federico II, via Università 100, 80055 Portici NA, Italy;
[email protected] * Correspondence:
[email protected] Academic Editors: Jorge Bañuelos Prieto and Ugo Caruso Received: 6 October 2020; Accepted: 25 October 2020; Published: 28 October 2020 Abstract: Tridentate ligands are simple low-cost pincers, easy to synthetize, and able to guarantee stability to the derived complexes. On the other hand, due to its unique mix of structural and optical properties, zinc(II) ion is an excellent candidate to modulate the emission pattern as desired. The present work is an overview of selected articles about zinc(II) complexes showing a tuned fluorescence response with respect to their tridentate ligands. A classification of the tridentate pincers was carried out according to the binding donor atom groups, specifically nitrogen, oxygen, and sulfur donor atoms, and depending on the structure obtained upon coordination. Fluorescence properties of the ligands and the related complexes were compared and discussed both in solution and in the solid state, keeping an eye on possible applications. Keywords: zinc ion; fluorescence; tridentate ligand 1. Introduction Over the past 20 years, fluorescence-responsive compounds are increasingly required for many technological applications, from lighting and switch devices to bio-imaging and analytical probes. Materials based on transition metal complexes were advantageously utilized. In this area, interest is growing in the abundant, less expensive, and environmentally “green” zinc(II) metal cation. Today, science is in great demand to address the challenge of sustainability.