Electrochemical assembling/disassembling of helicates with hysteresis

A series of eight tetradentate, ditopic, bisimino bisheterocyclic ligands (1−8), and their complexes with CuI and CuII, have been studied in CH3CN solution, by means of 1H NMR, mass, and UV/vis spectroscopy, while the crystal and molecular structure of the CuII complexes [Cu(3)](CF3SO3)2 and [Cu(4)](CF3SO3)2 and of the CuI complexes [Cu2(4)2](ClO4)2 and [Cu2(5)2](ClO4)2 have been determined by X-ray diffraction methods. The CuII complexes are monomeric, almost square-planar structures, both in solution and in the solid state, while the CuI complexes are two-metal, two-ligand dimers which can be both helical and “box-like” in the solid, while they adopt a simple helical configuration in acetonitrile solution. The systems made of ligands 1−8 and copper are bistable, as under the same conditions either the CuI helical dimers or the CuII monomers can be obtained and are stable. The electrochemical behavior of the 16 copper complexes has been studied in acetonitrile solutions by cyclic voltammetry.