Rhodamine 6G-based efficient chemosensor for trivalent metal ions (Al 3+ , Cr 3+ and Fe 3+ ) upon single excitation with applications in combinational logic circuits and memory devices.

A new rhodamine 6G-based chemosensor (L3) was synthesized and characterized by 1 H, 13 C, IR and mass spectroscopy studies. It exhibited an excellent selective and sensitive CHEF-based recognition of trivalent metal ions M 3+ (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 Fe 3+ (669-fold), Al 3+ (653-fold) and Cr 3+ (667-fold) upon the addition of 2.6 equivalent of these metal ions in the probe in H 2 O/CH 3 CN (7 : 3, v/v, pH 7.2). The corresponding K d values were evaluated to be 1.94 × 10 -5 (Fe 3+ ), 3.15 × 10 -5 (Al 3+ ) and 2.26 × 10 -5 M (Cr 3+ ). The quantum yields of L3, [L3-Fe 3+ ], [L3-Al 3+ ] and [L3-Cr 3+ ] complexes in H 2 O/CH 3 CN (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 Fe 3+ , Al 3+ and Cr 3+ were determined by 3 σ methods and found to be 2.57, 0.78 and 0.47 μM, respectively. The cyanide ion snatched Fe 3+ from the [Fe 3+ -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.