Salamo-type trinuclear and tetranuclear cobalt(II) complexes based on a new asymmetry Salamo-type ligand: syntheses,crystal structures,and fluorescence properties

Two multinuclear Co(II) complexes, {Co(L)(i-PrOH)}₂Co(H₂O)]?2CH₃CN (1) and {Co(L)(μ-OAc)Co(MeOH)₂}₂]?2CH₃COCH₃ (2), have been synthesized with a new asymmetric Salamo-type ligand (H₃L = 6-hydroxy-6′-ethoxy-2,2′-ethylenediyldioxybis(nitrilomethylidyne)]diphenol). The Co(II) complexes were obtained by different solvents, and the structures are completely different. In the Co(II) complex 1, the ratio of the ligand H₃L to Co(II) atom is 2 : 3 and the Co(II) ions are all five-coordinate with trigonal bipyramidal geometries. In the Co(II) complex 2, the ratio of the ligand H₃L to Co(II) atom is 2 : 4. Two central Co(II) ions are six coordinate with distorted octahedral geometries and two terminal Co(II) ions are five coordinate with distorted trigonal bipyramidal geometries. Self-assembling of an infinite 1-D supramolecular chain is formed by C–H?π interactions in 1. Interestingly, an infinite 2-D-layer plane structure is formed by the self-assembling array of 2 linked by C–H?π interactions. 1 and 2 exhibit blue emissions with the maximum emission wavelengths λ_max? = 403 and 395 nm when excited at 330 nm.