Reactivity of Tetrabutylammonium Iodide with a Heteronuclear 6Copper(II)–4Na(I) Complex: Selective Recognition of Iodide Ion

Abstract

A complex of type [Cu6Na4(μ-O)4(NTA)2(bpy)6(H2O)4(NO3)2]·3H2O 1 was allowed to react separately with tetrabutylammonium salts (TBAX), X = F–, Cl–, Br–, I–, AcO–, NO3–, and H2PO4–. The color of complex 1 changed immediately on the addition of TBAI (tetrabutylammonium iodide) only. However, keeping the corresponding solution for 2 months at room temperature, four complexes of compositions [Cu6(μ-OH)4(NTA)2(bpy)6]2I–·5H2O 2, [Cu2(bpy)2(OH)2(I)]2(NO3)2(H2O) 3, [Cu(bpy)2I]I3– 4, and [Cu(bpy)2I]I·TBAI 5 (bpy = 2,2′-bipyridyl, H3NTA = nitrilotriacetic acid) together with some residues of TBAI and complex 1 were isolated in one-pot synthesis. These complexes were characterized using elemental analysis, spectroscopic (IR, UV–vis) and single crystal X-ray diffraction techniques. Colorimetric response of complex 1 with iodide anions was further supported by the changes in its UV–vis spectra recorded in methanol. The results indicated that 1 exhibits a strong affinity for iodide anions.