Rhodamine spirolactam

Cyanamide has been introduced into a rhodamine spirolactam framework to give a colourless non-fluorescent compound that exhibits reversible ring opening/ring closure in response to the solution pH and exhibits an ON/OFF switching in its fluorescence (Scheme 68). ... 

A rare example of a Pt " selective fluorescent probe 25 was reported by Tae and co-workers in which it was hypothesised that Pt " coordination would induce ring opening of the rhodamine spirolactam. Excellent selectivity for the detection of Pt " over a wide range of other metal ions was observed by fluorescence emission. 

Scheme 2 Ring opening of rhodamine spirolactam 25 in the presence of Pt ...

Imaging/Labeling Applications Amantadine aminoglycosides anti-digoxin baclofen bacteria peptide chloromethyl ketones gabapentin herbicides histamine H1/H2 receptor antagonists 4 5 memantine metal ions (Fe(III)) nanoparticles nucleic acids/ nucleotides " phosphatidylethanolamine " proteins/ peptides " risedronate amino functionalized rhodamine spirolactams ... 

Cu2+ and Hg2+ are perhaps the most obvious targets for reaction-based signaling systems. However, this approach has also been realized for monovalent Ag+. Here, again a rhodamine derivative (rhodamine B spirolactam 48, Fig. 18) allows the highly selective detection of Ag+ with a detection limit of 14 ppb in water containing 20% ethanol. Silver nanoparticles, a topical analyte today, can also be detected, after oxidation of the particles with H2O2/H3PO4 [141]. The selectivity was tested with Ca2+, Ba2+, Mg2+, Cr2+, Mn2+, Fe3+, Co2+, Ni2+, Cu+, Cu2+, Zn2+, Pd2+, Cd2+, Hg+, and Hg2+ and no interference was found. 

The Cu-sensing mechanism is based on structural changes of the rhodamine derivative, i.e. spirolactam (OFF) to open ring (ON) form, upon ion coordination (Fig. 19). 

Fig. 19 Ft film-immobilised rhodamine system for Cu -induced ring-opening of spirolactam. Reprinted with permission from [65]...

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