Development of 8-hydroxy-9-iminyljulolidine derivatives as fluorescent sensors

Abstract

The development of fluorescent sensor which is specify toward metal ion become important. In this work, the fluorescent sensor containing julolidine derivative as a fluorophore linked with the control part using of dipicolylamine derivative substituted on aniline ring at ortho- (J2P), meta- (J3P) and para- (J4P) position, respectively, were successfully developed and synthesized via Schiff base reaction. According to the experimental results under the mixed solvent condition of H2O/methanol (1:9, v/v), the maximum absorption bands of compounds J2P, J3P and J4P were observed at 380, 415 and 420 nm, respectively. Moreover, in the presence of aluminum ion (Al3+), the fluorescent signals of compound J2P significantly enhanced. The maximum emission intensity appeared at 490 nm along with the fluorescence quantum yield as 0.156. The association constant (Ka) was calculated as 2.25 x 105 M-1. Furthermore, when the solvent condition was changed to H2O/DMSO (5:95, v/v), compound J2P provided significant response toward only magnesium ion (Mg2+). The strongest fluorescent signal was observed at 470 nm with the fluorescence quantum yield as 0.096. The Ka value of the coordination between J2P and Mg2+ is 4.00 x 104 M-1. The stoichiometric complexation between J2P ligand and both metal ion supported the formation of 1:1 and the detection limits (LOD) for Al3+ and Mg2+ detection under above conditions were 0.17 µM and 1.32 µM, respectively. In addition, the fluorescence enhancing phenomenon was extrapolated to occur through the Chelation-enhanced fluorescence (CHEF) mechanism.