Specific recognitions of multivalent cyclotriphosphazene derivatives in sensing, imaging, theranostics, and biomimetic catalysis

Abstract

Owing to its easy functionalization, many structurally and functionally diverse and versatile multi-valent derivatives of hexachlorocyclotriphosphazene (Cl6Cpz) have been prepared with the same or different substituents. These derivatives possess unique properties such as biochemically specific cooperativity and multiple functions/activities and have broad applications in many areas, including chemical and biological recognitions, sensing, imaging, flame retardation, catalysis, and biocompatible materials. For applications in sensing and bioimaging, Cl6Cpz has been frequently modified with various fluorophores and moieties with specific recognition sites for fluorescent sensing. Owing to such potential applications in many disciplines, this review focuses on the design and development of Cl6Cpz-based derivatives for a) fluorescent sensing of various targets and recognition of small molecules and metal ions, b) applications in analytical, biological, medicinal, theranostic, and environmental domains, c) metal-mediated biomimetic recognition and catalysis, and d) some potential future applications. Some experimental designs, metal and molecular recognitions/interactions, and coordination chemistry of metal ions are critically assessed and future perspectives discussed which are expected to guide and foster potential applications of Cpz-based derivatives for sensing/detection of specific molecules, metal ions, and other ions, carrying and delivering of drugs and bioactive products, metal-mediated recognition and catalysis, and energy sustainability and environmental conservation and protection.