Mononuclear coordination compounds containing a pyrazole-based ligand: Syntheses, magnetism and acetylcholinesterase inhibition assays

Abstract

A series of three pseudo-octahedral coordination compounds with general formula cis-[M(L)2(OH2)4], where M stands for FeII (1), CoII (2) or NiII (3), and HL is 5-amino-1-(benzo[d]thiazol-2-yl)-1H-pyrazole-4-carboxylic acid proligand was synthesized by slow diffusion methodology and thoroughly characterized by spectroscopic techniques, magnetic measurements and ab initio calculations. Single crystal X-ray diffraction data obtained for 1 and 2 revealed that the crystal packing is stabilized by a hydrogen bond network while X-ray powder pattern, Raman and IR spectra indicated that compounds 1 and 3 are isomorphic. Mössbauer spectra recorded at 3 and 300 K for 1 showed that the FeII ion is in its high spin state. Magnetic studies carried out for complexes 1–2 showed the key role played by the zero-field splitting and the experimental fit data were correlated and supported by CASSCF calculations. The activity of acetylcholinesterase enzyme was investigated towards L and 1–3 by using Elman’s methodology, affording inhibition rates of 20%, 56%, 35% and 36%, respectively.