Four novel trinuclear copper(II)/nickel(II) complexes with four trianionic pentadentate ligands,
N-(3-
t-butylbenzoyl)-5-nitrosalicylhydrazide (H
33-
t-bbznshz),
N-(3,5-dimethylbenzoyl)salicylhydrazide (H
33,5-dmbzshz),
N-(phenylacetyl)-5-bromosalicylhydrazide (H
3pabshz) and
N-(3-
t-butylbenzoyl)salicylhydrazide (H
33-
t-bbzshz) have been synthesized and characterized by X-ray crystallography. These trinuclear compounds all have an M–N–N–M–N–N–M core formed by three metal ions and two ligands. The geometries of three Cu(II) ions in compound Cu
3(3-
t-bbznshz)
2(H
2O)(DMF)(py)
2 · DMF (
1) alternate between distorted square pyramidal and square planar, while in compound Cu
3(3,5-dmbzshz)
2(py)
2 (
2), they are all square planar. Three Ni(II) ions in compound Ni
3(pabshz)
2(DMF)
2(py)
2 (
3) and Ni
3(3-
t-bbzshz)
2(py)
4 · 2H
2O (
4) follow square-planar/octahedral/square-planar coordination geometry. Compounds
1,
2 and
4 are bent trinuclear, with the bend angles of 156.4°, 141.49° and 127.1°, respectively, while the three nickel ions in compound
3 are strictly linear, with an angle of 180°. Studies on the trinuclear Ni(II) complexes show that the β-branched
N-acylsalicylhydrazide ligands with sterically flexible C
methylene groups are easier to yield linear trinuclear Ni(II) complexes, while
-branched
N-acylsalicylhydrazides ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data indicate that the trinuclear Cu(II) compound
2 is more active than
1 and mononuclear Cu(II) compound, bent trinuclear Ni(II) compound
4 is more active than linear compound
3 and less active than tetranuclear nickel compound in the previous study.