Self-assembly of novel discrete binuclear molecular box structure from a novel bis-N,O-bidentate Schiff-base ligand and ZnII, CoII salts

In our efforts to design discrete polynuclear metal complexes with tailored structures, a novel bis-N,O-bidentate Schiff-base ligand, 2,5-bis(N-salicylidene-3-aminophenyl)-1,3,4-oxadiazole (L), have been synthesized. The reaction of L with Zn(OAc)2 · 2H2O or Co(OAc)2 · 4H2O in a CH3OH/CHCl3 medium yielded two new complexes, [Zn2L2](CHCl3)1/2 (1) and [Co2L2](CHCl3)1/2 (2), which exhibit novel discrete dinuclear structure in which the metal centers take pseudo-tetrahedral coordination mode. In each of the two complexes, the L ligands adopt two different conformations (Cisoid-I (close) and Cisoid-II (open)), respectively, to incorporate with the metal centers into box structure. π–π stacking interactions were found to play important roles in the self-assembly processes.