Mercury selective hydrogelation of a pyridinyl substituted terpyridine ligand

Abstract

We report the addition of aqueous solution of different divalent transition metal ions M2+ (M = Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg) to a dilute acidic solution of 4′-(pyridin-2-yl)-2,2′:6′,2″-terpyridine (L). An irreversible, translucent, and thixotropic hydrogel was selectively produced in the case of Hg(II). FESEM and HR-TEM images of Hg(II)-hydrogel showed non-uniform, fibrous, and cross-linked gel morphology. Further, the hydrogel was treated with sodium salts of different anions (F−, I−, Br−, Cl−, SO42−, NO3−, HCO3−, SO32−) in water. The iodide ion showed unusual behavior by forming a yellow precipitate of the hydrogel with a plate-like structure, as observed from FESEM images. DFT study has also been conducted to understand the aggregation behavior in Hg(II) based hydrogel. We also synthesized the mercury complex HgCl2L and characterized it by 1H NMR, elemental analysis, and mass spectrometry.