A review on Rhodamine-based Schiff base derivatives: synthesis and fluorescent chemo-sensors behaviour for detection of Fe3+ and Cu2+ ions

Rhodamine Schiff bases as fluorescent chemo-sensors, fluorogenic cation sensors, is scientifically exigent work. Rhodamine Schiff base derivatives have gained attention due to their structural variability. The combination of donor and acceptor groups with delocalized π-orbital results in excellent fluorescent properties due to intramolecular charge transfer (ICT) and opening of spirolactam ring of Rhodamine moiety. In this review, we summarize information about Rhodamine Schiff bases sensors reported over the past two decades (2002–2022). We focused on the design, synthesis, and sensing mechanism (ON/OFF, OFF/ON, and ON-OFF-OFF) of these sensors for Fe3+ and Cu2+ metal ions, as well as their practical applications. We also examined how the photophysical properties of these sensors change when they coordinate with the metal ions, resulting in changes in the typical sensing behaviour, such as a hypochromic/hyperchromic or hypsochromic/bathochromic shift. We anticipate that this review will provide a fundamental framework for researchers to further investigate Rhodamine Schiff-based sensors.