Syntheses, Crystal Structures, and Antibacterial Activities of Four Schiff Base Complexes of Copper and Zinc

Abstract

AbstractFour Schiff base complexes, [Cu2(L1)2(μ‐NCS)2] (1), [Cu2(L2)2(μ‐N3)2] (2), Cu[Cu(CH3COO)(L3)]2 (3), and [Zn{Zn(C3H4N2)(L3)}2(NO3)](NO3) (4) (where L1 = 2‐[(pyridin‐2‐ylmethylimino)methyl]phenol, L2 = 1‐[(pyridin‐2‐ylmethylimino)methyl]naphthalen‐2‐ol, and L3 = bis(salicylidene)‐1, 3‐propanediamine), were synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X‐ray determinations. Both 1 and 2 are structurally similar di‐nuclear complexes, which are located at crystallographic inversion centers (with the center of the central Cu2N2 ring). In 1, each copper atom has a slightly distorted square pyramidal configuration, coordinated by two nitrogen atoms and one oxygen atom from L1 and another two terminal nitrogen atoms from two bridging thiocyanate anions. The Cu···Cu separation is 3.466(3) Å. The structure of 2 is similar to that of 1, with Cu···Cu separation of 3.368(2) Å. Both 3 and 4 are linear tri‐nuclear complexes. In 3, the central Cu2+ ion is located on an inversion centre and has a distorted octahedral coordination involving four bridging O atoms from two Schiff base ligands (L3) in the equatorial plane and one O atom from each bridging acetate group in the axial positions. The coordination around the terminal Cu2+ ions is irregular‐square pyramidal, with two O and two N atoms of L3 in the basal plane and one O atom from an acetate group in the apical position. The acetate bridges linking the central and terminal Cu2+ ions are mutually trans. The Cu···Cu separation is 3.009(3) Å. In 4, the coordination configuration of the central and the terminal zinc atoms are similar to that of the 3, with Zn···Zn separation of 3.153(4) Å. The three Schiff bases and the corresponding three copper complexes exhibit good antibacterial properties, while the zinc complex 4 has nearly no.