Recent advances in small-molecule fluorescent probes bearing a triaminoguanidinium unit and their sensing, bio-imaging and multifunctional applications

Since their discovery, triaminoguanidinium-salicylidene-based Schiff bases have emerged as a significant class of compounds known for their solvent-dependent fluorescence emission, which varies depending on the substituents in their aromatic frameworks. These compounds are easy to synthesize, stable, cost-effective, and highly suitable for diverse applications, including chemosensing, biological studies, and multifunctional uses. This comprehensive review summarizes recent advancements in AIE-active triaminoguanidinium-salicylidene-based threefold symmetric Schiff molecules, particularly their role as chemosensors for detecting various analytes. It explores different chemosensing strategies for identifying metal ions (Zn²⁺, Cd²⁺, Cu²⁺, Fe³⁺, and Co²⁺) and anions (EDTA, I⁻ PPi⁻, and S²⁻), focusing on the progress of triaminoguanidinium-salicylidene-based threefold symmetric Schiff bases over the past five years, particularly their systems for supramolecular host–guest interactions, AIEgen-ESIPT activity, COFs, bioimaging, etc. We hope this review provides a comprehensive overview of the current research landscape and encourages further exploration of novel triaminoguanidinium-salicylidene-based threefold symmetric Schiff base compounds with expanded applications.