Chiral Fluorescent Probes for Determination of Both Concentration and Enantiomeric Composition of Amino Acids

A novel 1,1'-bi-2-naphthol (BINOL)-based fluorescent probe (R)-(E)-2,2'-dihydroxy-3'-((quinolin-7-ylimino)methyl)-[1,1'- binaphthalene]-3-carbaldehyde [(R)- 2] and its isomer (R)-(E)-2,2'-dihydroxy- 3'-((quinolin-6-ylimino)methyl)-[1,1'-binaphthalene]-3-carbaldehyde [(R)-3] were designed and synthesized. The quinoline imine groups at 3'-position of the probes were involved in the molecular recognition of amino acids through complexation between N atom and Zn(II), which synergically enhanced the enantioselectivity of BINOL-aldehyde to amino acids. The probe molecule exhibited chiral independent fluorescence enhancement for various amino acids at 438 nm, while exhibiting excellent enantioselective fluorescence response at 513 nm. The dependence function of the intensities of the above two emission peaks on arginine concentrations and enantiomeric excess (ee) was studied, and the concentrations and ee values of several arginine samples were measured by the fitted function equation. The interaction mechanism between (R)-2 and D-/L-arginine in the presence of Zn2+ was investigated by H-1 NMR and HRMS. The thermodynamic stability of the arginine enantiomer/probe/Zn(II) complexes was calculated by Gaussian 16 program to elucidate the origin of the enantioselectivity. This work affords a platform for the determination of the concentration and enantiomeric composition of 7 amino acids (Glu, Arg, Gln, Ser, Thr, Met, Ala) through a single probe.