Novel 1D chain Fe(III)-salen-like complexes involving anionic heterocyclic N-donor ligands. Synthesis, X-ray structure, magnetic, (57)Fe Mössbauer, and biological activity studies.

The iron(III) salen-type complexes Fe(salen)(L) (1-6) involving heterocyclic N-donor ligands HL {HL = 1H-imidazole (Himz), 1H-tetrazol-5-amine (Hatz), 5-methyl-1H-tetrazole (Hmtz), 1H-benzimidazole (Hbimz), 1H-1,2,4-triazole (Htriz) and 1H-benzotriazole (Hbtriz)} have been prepared and characterised by elemental analysis, FT IR, CI mass and (57)Fe Mössbauer spectroscopies, and variable temperature magnetic measurements. Single crystal X-ray analysis of Fe(salen)(btriz) (6) revealed a 1D chain-polymeric structure of the complex with the btriz anion as a bridging ligand. Magnetic data for all complexes were fitted using Fisher's model (for S = 5/2) and also using a heptanuclear closed ring model showing a weak antiferromagnetic interaction (J approximately -1 to -2 cm(-1)), and moreover, molecule-based magnet properties have been observed in the case of Fe(salen)(atz) (2). The exponential correlation between the magnetic properties (the isotropic exchange parameter J) and the basicity of the free ligands (K(b)) has been found. The antiferromagnetic ordering as well as a moderate structural dissimilarity in the vicinity of iron atoms has been proved by the (57)Fe Mössbauer low-temperature (2 K) in-field (7 T) experiments in the case of (2), in which two sextets with the line intensities (3/4/1/3/4/1) have been observed. The compounds have been tested for their SOD-like activity, DNA cleavage activity, and in vitro cytotoxicity against two human cancer cell lines: chronic myelogenous erythroleukemia (K562) and breast adenocarcinoma (MCF7). The best result regarding the cytotoxicity has been achieved for the complex of Fe(salen)(atz) (2), where IC(50) = 6.4 microM against K562.