The effect of phosphate on the nuclease activity of vanadium compounds
Résumé
The nuclease activity of VO(acac)2 (1, acac = acetylacetone) and its derivatives VO(hd)2 (2, hd = 3,5-
heptanedione), VO(Cl-acac)2 (3, Cl-acac = 3-chloro-2,4-pentanedione), VO(Et-acac)2 (4, Et-acac = 3-ethyl-2,4-
pentanedione) and VO(Me-acac)2 (5, Me-acac = 3-methyl-2,4-pentanedione), is studied by agarose gel electropho-
resis, UV–visible spectroscopy, cyclic and square wave voltammetry and 51V NMR. The mechanism is shown to be
oxidative and associated with the formation of reactive oxygen species (ROS). Hydrolytic cleavage of the phospho-
diester bond is also promoted by 1, but at much slower rate which cannot compete with the oxidative mechanism.
The generation of ROS is much higher in the presence of phosphate buffer when compared with organic buffers and
this was attributed to the formation of a mixed-ligand complex containing phosphate, (VIVO)(VVO)(acac)2(HnPO4n-3),
presenting a quasi-reversible voltammetric behavior. The formation of this species was further observed by
Electrospray Ionization Mass Spectrometry (ESI-MS). Phosphate being an essential species in most biological
media, the importance of the formation of mixed-ligand species in other vanadium systems is emphasized.