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)}(2)Co(H2O)].2CH(3)CN (1) and [{Co(L)(-OAc)Co(MeOH)(2)}(2)].2CH(3)COCH(3) (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 interactions in 1. Interestingly, an infinite 2-D-layer plane structure is formed by the self-assembling array of 2 linked by C-H interactions. 1 and 2 exhibit blue emissions with the maximum emission wavelengths (max)=403 and 395nm when excited at 330nm.