A polynuclear helical and two dinuclear copper(II) complexes of a monocondensed N,N,O donor Schiff base with pseudohalides as co-ligand

Three copper(II) complexes, [Cu2L2(μ1,1-NCO)(NCO)] (1), [Cu2L2(μ1,3-NCS)(NCS)] (2) and [CuL(μ1,5-dca)]n·nH2O (3), where HL = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol, have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy, single crystal X-ray diffraction studies and by cyclic voltammetry. Complexes 1 and 3 crystallize in monoclinic space group P21/n and complex 2 in monoclinic P21/c. In complex 1, OCN− shows μ1,1 bridging mode; in complex 2, SCN− shows μ1,3 bridging mode whereas in complex 3, N ( CN ) 2 - shows μ1,5 bridging mode. The tridentate Schiff base ligand reacts with copper(II) to occupy its three equatorial positions. The coordination polyhedra around one of the copper center in compounds 1 and 2 are best described as an elongated (4 + 1) square pyramid, whereas the coordination polyhedra around other copper center is square planer. The copper atom in compound 3 has a slightly distorted square pyramidal environment. Significant C–H/π interactions are observed in both complexes 1 and 2. Complex 3 is an example of MOFs containing penta-cordinated Cu(II) ions linked together by N ( CN ) 2 - to yield 1D infinite P and M-helical chains.