Solvent Controlled Colorimetric and Fluorometric Detection of Fe2+ and Cu2+ Ions by Naphthaldimine-Glucofuranose Conjugate.

The sensing properties of naphthaldimine-glucofuranose conjugates 1 and 2 towards metal ions were investigated by 1H NMR titration, Fourier-transform infrared spectroscopy (FTIR), absorbance, and fluorescence spectroscopic methods. The absorbance and fluorescence studies indicated that compound 1 formed coordination with Fe2+ and Cu2+ ions in dimethyl sulfoxide (DMSO) through color changes yellow to brown and colorless, respectively. The Job's plots using absorbance data showed metal-ligand binding ratio is 1:1 for both cases. The formation of 1-Fe2+ and 1-Cu2+ complexes have been analyzed by absorption and emission spectroscopy, high-resolution mass spectrometry (HRMS) data, FTIR, 1H NMR titration experiment, and density functional theory (DFT) calculations. The detection limits of naphthaldimine sugar conjugate 1 towards Fe2+/Cu2+ were calculated from UV-vis and fluorescence data according to the standard method. The sugar-naphthaldimine conjugate 2 has been used to establish the binding mode of 1 with Fe2+ or Cu2+ ions in DMSO.