Molybdenum(II) complexes with p-substituted BIAN ligands: synthesis, characterization, biological activity and computational study
New complexes [Mo(η3-C3H5)X(CO)2(4-Y-BIAN)] complexes (4-Y-BIAN = bis(4-Y-phenyl)-acenaphthenequinonediimine), with X=Br and Y=H, Me, OMe, COOH and X=Cl, Y=OMe, as well as the cation with X=NCMe and Y=OMe were synthesized, expanding the scope of this family of complexes. Two single crystal X-ray structures (X=Br, Y=Me, OMe) display the less symmetric arrangement (axial isomer), where one N donor atom is trans to the allyl and the second to one CO. DFT studies showed similar energies for the two possible isomers of the complexes, with a very small preference for the observed axial isomer. The HOMO of the complexes is localized in the metal and the HOMO-1 of the oxidized species has contribution of the BIAN ligand, while the LUMO is fully localized in BIAN. Electrochemistry studies showed one process corresponding to the oxidation of Mo(II) to Mo(III) for complexes with X=Br, Y=H, Me, and two oxidations for those with X=Br, Y=Cl, OMe, while the COOH derivative exhibited no oxidation wave. The antitumor effect of the complexes with X=Br was tested in cancer lines, and the H and OMe complexes were particularly active, with EC50 values below 8 µM in HeLa cell lines. The DNA binding constants determined by titration experiments were comparable with those of doxorubicin and ethidium bromide, suggesting a mechanism of action based on intercalation in DNA.