Development of a Polyfunctional Dipodal Schiff Base: An Efficient Chelator and a Potential Zinc Sensor

A novel polyfunctional dipodal ligand, L = N,N'-bis[۲-[(۲-hydroxy-۱-naphthyl)methyleneamino]ethyl]propanediamide (DOTA۲HNAP) was developed and characterized through elemental and spectral analyses. The complexation behavior of the ligand was investigated with Co۲+, Cu۲+, and Zn۲+ metal ions by potentiometric and spectrophotometric methods in the H۲O-DMSO mixture (۹۹:۱) at µ = ۰.۱M KCl and ۲۵ ± ۱ °C. Four protonation constants for –OH of naphtholate groups and –N of imine were determined for the ligand. The ligand forms monomeric complexes of ML type with the metal ions, where coordination occurs through N-imine and O-naphtholate donors (N۲O۲). In the case of a complex of copper, an additional species, MLH-۲, was formed due to ionization of the amide groups in a higher pH. The minimum energy structures of the metal complexes in solution have been obtained through molecular modeling studies by using the semi-empirical/ PM۳ method. The photophysical properties of DOTA۲HNAP were investigated in the presence of a wide range of biologically relevant metal ions. The fluorescence emission of the ligand at ۴۵۰ nm (λex = ۳۶۱ nm) exhibited a remarkable enhancement with Zn۲+ ions (۱ equivalent) at physiological pH amongst all metal ions. Such behavior enables the ligand to be considered as a suitable model for the detection of Zn۲+ towards environmental applications.

کلیدواژه ها:

Fluorescence spectroscopy ، Dipodal chelator ، Zn۲+ Sensor ، Potentiometric ، Spectrophotometry ، Transition metals