Mercury(II)–methylene blue interactions: Complexation and metallate formation

Reactions of HgX2 (X = Cl, Br, I) with methylene blue (MB) chloride dihydrate and the reaction of HgCl2 with MB nitrate dihydrate have been undertaken in an attempt to prepare metal derivatives of MB. The products were characterized by elemental analysis, UV–Vis, IR, 1H NMR spectroscopy and X-ray crystallography. The reaction of HgCl2 with MB chloride dihydrate and subsequent crystallization in a DMF/H2O mixture yielded the products (1 and 2) with different crystal morphologies. The structure of complex 1 represents the first structural report of a complex of MB with any metal ion. The efficacy of MB to act as a ligand in spite of its cationic nature is thus demonstrated. The structure of 1 comprises a distorted tetrahedral geometry around Hg(II); the coordination valencies being provided by three chloride ions and a MB cation. The structure of 2 is a salt consisting of an View the MathML sourceHgCl42- anion and two MB cations. The reaction of HgI2 and HgBr2 with MB chloride dihydrate yielded salts 3 and 4 with View the MathML sourceHg2X62- (X = Br or I) anions and MB cations. A mixed salt 5, whose anions comprise mercury(II), chloride and nitrate species resulted from the reaction between HgCl2 with MB nitrate dihydrate. The reaction of Hg2F2 with MB chloride dihydrate and the crystallization of the resulting product 6 in aqueous DMF yielded crystals of (MB)2HgCl4 · H2O.