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A novel fluorescent chemosensor based on a rhodamine derivative (L) was designed, synthesized, and used as a selective Al+3 ion sensor. Upon addition of Al3+ to an aqueous-acetonitrile solution of L, the development of a strong fluorescence signal by a chelation-enhanced fluorescence (CHEF) process was observed with an attractive glowing orange emission. This sensor shows high selectivity towards Al3+ ions in the presence of other competing metal ions. The fluorescence quantum yield of L–Al3+ (Φf = 0.30) was found to be very high compared to the bare ligand. The limit of detection (LOD) of Al3+ ions was calculated to be 2 × 10−8 M by fluorescence titration. The 1 : 1 binding stoichiometry of the metal complex was established by combined UV-vis, fluorescence and TOF-MS spectroscopy. [ABSTRACT FROM AUTHOR]

5-methoxy isatin-appended rhodamine dye, (E)-3'-(diethylamino)-6'-(ethyl(methyl)amino)-2-((5-methoxy-2-oxoindolin-3-ylidene)amino)spiro[isoindoline-1,9'-xanthen]-3-one (L) has been designed, synthesized, and characterized by different spectroscopic techniques. The chemosensor L shows high sensitivity towards Al3+ ions without interference from other biologically important cations in DMSO/H2O (1/9, v/v) media. The Al3+-ion promoted ring opening of the rhodamine spirolactam ring in chemosensor L evokes a fluorescence turn-on response via chelation-enhanced fluorescence (CHEF) process. Its lowest detection limit for Al3+ is 2.2x10-8 M, and displays a significant color change from almost colorless to deep pink in the presence of Al3+. The titration results show a 1:1 complex formation between chemosensor L and Al3+. [ABSTRACT FROM AUTHOR]

Abstract: A novel rhodamine-based chemosensor, 3′,6′-bis(diethylamino)-2-((2,7-dimethoxy-9H-fluoren-9-ylidene)amino)spiro[isoindoline-1,9′-xanthen]-3-one (1) for aluminum ion, was designed and synthesized. Compound 1 is an orange colored, weak fluorescent compound which was synthesized via one-step facile reaction of rhodamine B hydrazide with 2,7-dimethoxy-9H-fluoren-9-one in MeOH. When Al3+ salt was added in methanol:water (30:70, v/v) solution then spirolactum ring of 1 was opened. The absorbance and fluorescence of the mixed solution were increased dramatically because of the opening of the lactum ring. Thus, signal transduction occurred via reversible CHEF (chelation-enhanced fluorescence) mechanism in the range 580–584nm. [Copyright &y& Elsevier]