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A new rhodamine 6G-based chemosensor (L3) was synthesized and characterized by 1H, 13C, IR and mass spectroscopy studies. It exhibited an excellent selective and sensitive CHEF-based recognition of trivalent metal ions M3+ (M = Fe, Al and Cr) over mono and di-valent and other trivalent metal ions with prominent enhancement in the absorption and fluorescence intensity for Fe3+ (669-fold), Al3+ (653-fold) and Cr3+ (667-fold) upon the addition of 2.6 equivalent of these metal ions in the probe in H2O/CH3CN (7 : 3, v/v, pH 7.2). The corresponding Kd values were evaluated to be 1.94 × 10−5 (Fe3+), 3.15 × 10−5 (Al3+) and 2.26 × 10−5 M (Cr3+). The quantum yields of L3, [L3–Fe3+], [L3–Al3+] and [L3–Cr3+] complexes in H2O/CH3CN (7 : 3, v/v, pH 7.2) were found to be 0.0005, 0.335, 0.327 and 0.333, respectively, using rhodamine-6G as the standard. The LODs for Fe3+, Al3+ and Cr3+ were determined by 3σ methods and found to be 2.57, 0.78 and 0.47 μM, respectively. The cyanide ion snatched Fe3+ from the [Fe3+–L3] complex and quenched its fluorescence via its ring-closed spirolactam form. Advanced level molecular logic devices using different inputs (2 and 4 input) and a memory device were constructed. [ABSTRACT FROM AUTHOR]

A new rhodamine 6G-benzylamine-based sensor (L1), having only hydrocarbon skeletons in the extended part, was synthesized and characterized by single-crystal X-ray crystallographic study. It exhibited excellent selective and sensitive recognition of trivalent metal ions M3+ (M = Fe, Al and Cr) over mono- and di-valent and other trivalent metal ions. A large enhancement of the fluorescence intensity for Fe3+ (41-fold), Al3+ (31-fold) and Cr3+ (26-fold) was observed upon the addition of 3.0 equivalent of these metal ions into the probe in H2O/CH3CN (4 : 1, v/v, pH 7.2) with naked eye detection. The corresponding Kf values were evaluated to be 9.4 × 103 M−1 (Fe3+), 1.34 × 104 M−1 (Al3+) and 8.7 × 103 M−1 (Cr3+). Quantum yields of the L1, [L1–Fe3+], [L1–Al3+] and [L1–Cr3+] complexes in H2O/CH3CN (4 : 1, v/v, pH 7.2) were found to be 0.012, 0.489, 0.376 and 0.310, respectively, using rhodamine-6G as standard. LODs for Fe3+, Al3+ and Cr3+ were determined by 3σ methods and found to be 1.28, 1.34 and 2.28 μM, respectively. Cyanide ion scavenged Fe3+ from the [Fe3+–L1] complex and quenched its fluorescence via its ring-closed spirolactam form. Advanced level molecular logic devices using different inputs (2 and 4 inputs) as advanced level logic gates and memory devices were constructed. The large enhancement in fluorescence emission of L1 upon complexation with M3+ metal ions makes the probe suitable for the bio-imaging of M3+ (M = Fe, Al and Cr) in living cells. [ABSTRACT FROM AUTHOR]