Fluorescence pH-dependent sensing of Zn(II)by a tripodal ligand. A comparative X-ray and DFT study

A new complex was obtained starting from a pyridyl/phenolic/benzothiazole functionalized ligand (BPAP)with zinc acetate. The structural and photoluminescence properties of the complex were investigated by X-ray diffraction and confirmed by DFT calculations. By comparing the results with previous studies, we found that the mode of binding of the sensor was influenced by the pH of the medium, changing the zinc coordination sphere. In a basic aqueous solution, the metal coordinates two neutral nitrogen atoms and two negative sites, the phenate oxygen and the deprotonate amide nitrogen and a water molecule. In this condition, the ligand was found to behave as a more sensitive naked eye fluorescence chemosensor towards Zn2+, showing blue photoluminescence with a lower detection limit of 375 nM.