Two Supramolecular Cobalt(II) Complexes: Syntheses, Crystal Structures, Spectroscopic Behaviors, and Counter Anion Effects

Two new Co(II) complexes, [{Co(L)}2{Co(Pic)2(CH3OH)2}] (1) and [{CoL(μ-OAc)}2Co] (2), where H2L = 2,2′-[Ethylenedioxybis(nitrilomethylidyne)]dinaphthol, were designed, synthesized and characterized by elemental analysis, FT-IR spectra, UV-Vis spectra, and X-ray crystallography. Complex 1 consists of two [CoL] and one [Co(Pic)2(CH3OH)2] (Pic = picrate) units and in the [CoL] unit, the Co(II) atom is tetra-coordinated with a slightly distorted square-planar geometry. In the [Co(Pic)2(CH3OH)2] unit, the Co(II) atom is hexa-coordinated with a slightly distorted octahedral geometry. Meanwhile in complex 2, two acetate ions coordinate to three Co(II) atoms through Co-O-C-O-Co bridges and four μ-naphthoxo oxygen atoms from two [CoL] units also coordinated to the central Co(II) atom. Thus, complex 2 has two distorted square pyramidal coordination geometries around the terminal Co(II) atom and an octahedral geometry around the central Co(II) atom. The supramolecular structures of complex 1 is a 3D-network supramolecular structure linked by C-H···O hydrogen bonds and π···π stacking interaction, but complex 2 possesses a self-assembled 2D-layer supramolecular structure linked by C-H···π and π···π stacking interactions. The structure determinations show that the coordination anions are important factors influencing the crystalline array.