Abstract :
[en] Organopalladium complexes with the general formula [PdX(PPh3)2Ar] are well-known and widely used as efficient catalysts for numerous organic reactions. Nowadays, palladium complexes are also studied for their biological activities.[1] In this contribution, we present a novel one-pot water-compatible synthesis of trans square-planar [PdX(PPh3)2Ar] complexes and their radical scavenging activity. [PdI(PPh3)2(4-RC6H4)] with R = H, MeO, AcO, were readily obtained by oxidative addition of p-RC6H4I on Pd(PPh3)4. By contrast, bromo- and chloropalladium analogues were synthesized by a novel one-pot procedure by reacting overnight Pd(PPh3)4, p-RC6H4I and KBr or KCl in toluene/water suspension. This method avoids degradation of the complexes during decantation under air and the use of toxic benzyltriethylammonium bromide or chloride.[2] Investigation of the antioxidant properties showed that these complexes exhibit a strong radical scavenging activity against DPPH (1,1-diphenyl-2-picrylhydrazyl) radical, in a dose-dependent manner. Complexes [PdI(PPh3)2(4-MeOC6H4)] and [PdCl(PPh3)2(4-MeOC6H4)] showed the highest activity with IC50 equal to 1.14 and 1.9 μM, respectively. These results were confirmed in ABTS (2, 2-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid)) radical scavenging tests, and compared favorably with those obtained with cis-platine and quercetine. The enzymatic model used to evaluate their antiradical scavenging activity was based on their interaction with the HRP (horseradish peroxidase) -H2O2/L012 (8-amino-5-chloro-7-phenylpyrido[2,4-d]pyridazine-1,4(2H,3H)dione) system.
