Reactivity of nitrilotriacetic acid with polypyridyl protected as well as naked copper(II) nitrate

Abstract

Six complexes of types [Cu(NTA)Na(H2O)]n 1, [Cu(H2NTA)2]H2O 2, [Cu3(C2O4)2(bpy)3(H2O)2](NO3)2 3, [Cu6Na4(NTA)2(μ-O)2(bpy)6(H2O)4(NO3)2]·3H2O 4, [Cu2(C2O4)(phen)2(NO3)2] 5, and [Cu(phen)2(Cl)](NO3)2(H2O) 6 (bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline, H3NTA = nitrilotriacetic acid and C2O42− = oxalate) were synthesized and characterized using elemental analysis, spectroscopic (IR, UV–Vis and ESR), single crystal X-ray diffraction, cyclic voltammetry and differential pulse voltammetric techniques. The crystal packing of complexes 1, 2 and 3 using secondary interactions provided star like, cross linked single stranded helical and 1D zig-zag structures, respectively. Complex 4 comprised of six Cu(II) centers and four Na centers. Its assembly using secondary interactions along c axis displayed a wavy chain structure where as 5 assembled along b axis in a ladder-structure. The complex 6 is a mononuclear Cu(II) complex bearing two 1,10-phenanthroline groups, showed π–π interactions between their aromatic rings. DFT calculations suggested that copper activates the H3NTA towards formation of coordinated oxalate groups in complexes 3 and 5.