Tetracoordinate cobalt(II) complexes with neocuproine: single-molecule magnets with potential biological activity

Interaction of two mononuclear tetracoordinate complexes [Co( dmphen )Br 2 ] and [Co( dmphen )I 2 ] ( dmphen = 2,9-dimethyl-1,10-phenanthroline), which have been recently reported to behave as single-molecule magnets (SMMs) in an applied external field, with calf thymus (CT) DNA in solution was studied by spectral methods (UV–Vis, fluorescence, and circular dichroism). Results indicate that both complexes along with their chlorido analogue [Co( dmphen )Cl 2 ] are able to bind with the CT DNA via intercalation, with the values of Stern–Volmer constants obtained from the linear quenching plot in range of 1.86 × 10 4 –2.11 × 10 4 M −1 . Furthermore, Topoisomerase I inhibition studies suggest that all three complexes exhibit inhibition activity at concentrations of 45 μM.