Phenolate Ligand Synthesis And The Identification Of The Zinc Ions In Near-physiological Conditions

A new multidentate phenol-containing fluorescent ligand2,6-bis{[(2-hydroxybenzyl)(2-hydroxyethyl)amino]methyl}-4-methylphenol (L) as a probe for zinc ion was synthesized and characterized by FTIR,ESIMS and ¹H NMR. UV-Vis and fluorescence spectra were used tostudy the response of L towards Zn²⁺.1) Synthesis of ligand LLigand L was synthesized by 2, 6-bis(hydroxymethyl)-p-cresol and2-[(2-hydroxyethyl-amino)-methyl]-phenol, then purified by solventextraction and column chromatography. Compounds were characterizedby FTIR, ESIMS and ¹H NMR.2) The influence of temperature and pH towards UV-Vis andfluorescence spectra of L and L-Zn²⁺ complex had been studied.Upon addition of Zn²⁺ into the L solution, there was a gradualdecrease of absorbance, and the maximum absorbance wavelengthred-shifted. There was hardly absorbance spectra change of L when thepH changed from 2 to 12, but the maximum absorbance wavelength ofL-Zn²⁺ complex red-shifted when the solution became alkalescent. Theabsorbance spectra of L and L-Zn²⁺ complex maked no difference whenthe temperature of solution changed.L showed Zn²⁺ chelation-enhanced fluorescence property in aqueousmethanol solution under pseudobiological conditions. The fluorescenceintensity of L was increased by about 250％upon the addition of amicromolar rage of Zn²⁺. A stoichiometry of 1:2 for the formed complexof L and Zn²⁺ was determined by Job's method from the obtainedspectroscopic data. Temperature and pH were of influence to thefluorescence spectra of the L-Zn²⁺ complex.3) The fluorescent response of L toward Zn²⁺ was more sensitive inpolar protic solvent than in polar aprotic solvent.4) A high selectivity for Zn²⁺ over other tested metal ions wasobserved by fluorescence spectra.