The synthesis, characterization, X-ray structure and magnetism of dinuclear-based bis[mu-(1,1,3,3-tetracyano-2-ethoxypropenido-kappa N-2,N) (1,1,3,3-tetracyano-2-ethoxypropenido-kappa N)(2,2-bipyridine)copper(II)] organized in alternating chains via semi-coordinating Cu-N distances