Syntheses and structures of two new bis-N,O-bidentate Schiff base ligands and their respective copper(II) complexes with dinuclear double-helical configuration

Two flexible Schiff base ligands bis-[(N,N′-3,5-di-tert-butylsalicylidene)-4,4′-diaminodiphenyl] ether (H2L1) and bis-[(N,N′-3-tert-butyl-5-methylsalicylidene)-4,4′-diaminodiphenyl] ether (H2L2) were prepared in high yields and their structures were determined by X-ray single-crystal diffraction. Different packing modes were observed in H2L1 and H2L2 due to the different spacial hindrance of substituted groups bonded to the phenol rings. Reaction of ligands H2L1 and H2L2 with Cu(ClO4)2 · 6H2O in hot methanol yielded neutral double-helical dinuclear complexes [Cu2L21]·2H2O (1) and [Cu2L22]·2H2O (2) where each Cu(II) center has a pseudo-tetrahedral coordination sphere with two-wrapped ligands.