End-to-end thiocyanato-bridged zig-zag polymers of CuII, CoII and NiII with a hydrazone ligand: EPR, magnetic susceptibility and biological study

Abstract

The reactions of a tridentate hydrazone ligand, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (LH), derived from condensation of 2-acetylpyridine with acetic hydrazide, with M(NO3)2·nH2O [M=Cu, Co and Ni] in the presence of thiocyanate afford three end-to-end zig-zag coordination polymers, [CuLH(NO3)(μ1,3-NCS)]n·nH2O (1), [CoLH(NCS)(μ1,3-NCS)]n (2) and [NiLH(NCS)(μ1,3-NCS)]n (3) (where LH=CH3C(O)–N–NCCH3C5H4N). Single-crystal X-ray structural determination studies reveal that in all the complexes, the hydrazone ligand in the neutral keto form (LH) coordinates a MII ion that is bridged to two neighboring metal centers by SCN− anions, generating a 1-D helical coordination chain. In 1, the CuII atom adopts a distorted tetragonal bipyramid geometry whereas in 2 and 3, the central CoII or NiII atom possesses into a distorted octahedral environment. All the aforementioned compounds have been fully characterized by elemental analysis, IR, UV–Vis and EPR spectra. Variable temperature magnetic susceptibility measurement of 1 accounts the weak antiferromagnetic interactions whereas 2 shows single-ion anisotropy. Compound 3 is well described as a 3-D ferromagnetic. The inhibitory effects of all the complexes on the cell population growth of human lung carcinoma cells (A549 cells), human colorectal carcinoma cells (COLO 205 cells and HT-29 cells), and human hepatocellular carcinoma cells (PLC5 cells) were determined by MTT assays.