Synthesis, characterisation and anticancer activity screening of lanthanide(III) acetate complexes with benzohydrazone and nicotinohydrazone ligands

Abstract

Centrosymmetric, acetato-bridged dinuclear coordination compounds with the formulae [La2(Hphen)2(OAc)4(H2O)2]·DMF·H2O (1), [Ln2(HNic)2(OAc)4(H2O)2]·DMF·H2O (Ln = La (2) and Nd (3)) and [Ln2(HNic)2(OAc)4(H2O)2]·DMF (Ln = Er (4) and Yb (5)) (H2phen = (E)-N'-(2-hydroxybenzylidene)benzohydrazide and H2Nic = (E)-N'-(2-hydroxybenzylidene)nicotinohydrazide) were isolated from the reactions of lanthanide acetates and hydrazones, and characterised by elemental analyses, IR spectroscopy, UV–Vis spectroscopy, X-ray diffraction studies and SHAPE 2.1. The nine-coordinate distorted spherical capped square antiprism complexes 1–3 crystallise in the triclinic space group P-1, while the eight-coordinate triangular dodecahedron (D2d) Er(III) and Yb(III) complexes belong to the monoclinic system (space group P21/c). Geometry optimisation of the monoanionic forms of the hydrazone ligands (Hphen– and HNic–) were performed at the DFT/B3LYP/aug-cc-pVTZ level of theory. Natural population analysis (NPA) and molecular electrostatic potential (MEP) maps indicated that the most preferred sites for electrophilic attack in the anionic ligands were the phenolate and carbonyl oxygen atoms, and the azomethine nitrogen atoms. Cytotoxic studies of the compounds on breast cancer (MCF-7), endometrial carcinoma (HEC-1A) and human monocytic (THP-1) cell lines using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) assay revealed that the hydrazone ligands and complexes 1–4 are partially cytotoxic against MCF-7 cells, while the Schiff bases and complexes 3–5 significantly inhibit cell growth in HEC-1A cells.