A ratiometric chemosensor for Al3+ based on naphthalene-quinoline conjugate with the resultant complex as secondary sensor for F−: Interpretation of molecular logic gates

• A Schiff-base compound, 1-((quinolin-3-ylimino)methyl)naphthalen-2-ol (HL) has been developed as highly selective and sensitive ratiometric fluorescent chemosensor for Al3+ ion.
• HL forms 1:1 complex with Al3+ (complex 1).
• Complex 1 behaves as a fluoride sensor by snatching Al3+ from complex 1 thereby releasing HL.
• Molecular logic gates have constructed and interpreted.

1-((quinolin-3-ylimino)methyl)naphthalen-2-ol (HL) has been synthesized by one step Schiff-base condensation reaction between 2-hydroxy-naphthaldehyde and 3-aminoquinoline in 1:1 ratio in acetonitrile and characterized by elemental analysis and different spectroscopic techniques. Emission spectrum of HL shows peak at 412 nm with high intensity in methanol when it is excited at 350 nm. In the presence of Al3+ ion, emission intensity of the Schiff-base at 412 nm decreases and a new peak at 464 nm emerges indicating HL as a ratiometric chemosensor for the Al3+ ion. Other metal ions are not able to change the fluorescence intensity or peak position significantly. Job’s plot analysis indicates 1:1 binding with the formation of complex (complex 1) which is supported by mass spectral measurement. Emission intensity of complex 1 at 464 nm (excitation at 350 nm) decreases with the gradual addition of F− ion with the concomitant development of a peak at 412 nm with fast increasing intensity. Small LOD value of HL suggests it is sensitive towards Al3+. Based on change in fluorescence intensity of HL in the presence of Al3+ and F− ions at 412 and 464 nm, INHIBIT and IMPLICATION molecular logic gates have been constructed and interpreted.

This is an example of naphthalene based Schiff-base molecule (HL) acting as a ratiometric fluorescence chemosensor for Al3+ and the resultant Al-HL complex for F−.Figure optionsDownload as PowerPoint slide