Effects of the tetravanadate [V 4 O 12 ] 4- anion on the structural, magnetic, and biological properties of copper/phenanthroline complexes.

The aim to access linked tetravanadate [V 4 O 12 ] 4- anion with mixed copper(II) complexes, using α-amino acids and phenanthroline-derived ligands, resulted in the formation of four copper(II) complexes [Cu(dmb)(Gly)(OH 2 )] 2 [Cu(dmb)(Gly)] 2 [V 4 O 12 ]·9H 2 O (1) [Cu(dmb)(Lys)] 2 [V 4 O 12 ]·8H 2 O (2), [Cu(dmp) 2 ][V 4 O 12 ]·C 2 H 5 OH·11H 2 O (3), and [Cu(dmp)(Gly)Cl]·2H 2 O (4), where dmb = 4,4'-dimethioxy-2,2'-bipyridine; Gly = glycine; Lys = lysine; and dmp = 2,9-dimethyl-1,10-phenanthroline. The [V 4 O 12 ] 4- anion is functionalized with mixed copper(II) units in 1 and 2; while in 3, it acts as a counterion of two [Cu(dmp)] 2+ units. Compound 4 crystallized as a unit that did not incorporate the vanadium cluster. All compounds present magnetic couplings arising from Cu⋯O/Cu⋯Cu bridges. Stability studies of water-soluble 3 and 4 by UV-Vis spectroscopy in cell culture medium confirmed the robustness of 3, while 4 appears to undergo ligand scrambling over time, resulting partially in the stable species [Cu(dmp) 2 ] + that was also identified by electrospray ionization mass spectrometry at m/z = 479. The in vitro cytotoxicity activity of 3 and 4 was determined in six cancer cell lines; the healthy cell line COS-7 was also included for comparative purposes. MCF-7 cells were more sensitive to compound 3 with an IC 50 value of 12 ± 1.2 nmol. The tested compounds did not show lipid peroxidation in the TBARS assay, ruling out a mechanism of action via reactive oxygen species formation. Both compounds inhibited cell migration at 5 µM in wound-healing assays using MCF-7, PC-3, and SKLU-1 cell lines, opening a new window to study the anti-metastatic effect of mixed vanadium-copper(II) systems.