Chloro-fac-tricarbonylrhenium(I) complexes of asymmetric azines derived from 6-acetyl-1,3,7-trimethylpteridine-2,4(1H,3H)-dione with hydrazine and aromatic aldehydes: Preparation, structural characterization and biological activity against several human tumor cell lines

A number of new asymmetric azines derived from hydrazine and 6-acetyl-1,3,7-trimethyllumazine (lumazine = pteridine-2,4(1H,3H)-dione) and its derivatives with several aromatic aldehydes have been prepared and characterized by usual procedures (XRD, IR, ¹H and ¹³C NMR). These were reacted with ReCl(CO)₅] to give the corresponding mononuclear chloro-fac-tricarbonylrhenium(I) ReCl(CO)₃L] compounds. The complexes were characterized by elemental analysis, thermogravimetry (TG) and differential scanning calorimetry (DSC), IR, ¹H and ¹³C NMR. Furthermore, single-crystal X-ray diffraction studies have also allowed to report two different coordination modes of the ligands, which are strongly influenced by the basicity of the heteroatoms on the aromatic aldehyde; thus, the hydrazones derived from hydrazine and hydroxyaldehydes are linked to Re(I) through N5 atom from the pyrazine ring and the N61 one from the hydrazino group, whereas with the ligand derived from pyridin-2-carbaldehyde, the N62 atom of the hydrazino group and the N1 from the pyridine moiety are preferred ligand-to-metal binding sites. The study of the effects of the compounds on the growth of four human tumor cell lines (neuroblastoma NB69, glioma U373, and breast cancer MCF-7 and EVSA-T) suggests a modulator behaviour, according to the concentration, of cell growth due to their estrogen-like characteristics.