Silver(I) Complexes Based on Oxadiazole-Functionalized α -Aminophosphonate: Synthesis, Structural Study, and Biological Activities.

Two silver(I) complexes, bis{diethyl[(5-phenyl-1,3,4-oxadiazol-2-yl-κ N 3 :κ N 4 -amino) (4-trifluoromethylphenyl)methyl]phosphonate-(tetrafluoroborato-κ F )}-di-silver(I) and tetrakis-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-yl-κ N 3 -amino)(4-trifluoromethylphenyl)methyl]phosphonate} silver(I) tetrafluoroborate, were prepared starting from the diethyl[(5-phenyl-1,3,4-oxadiazol-2-yl-amino)(4-trifluoromethylphenyl)methyl]phosphonate ( 1 ) ligand and AgBF 4 salt in Ag/ligand ratios of 1/1 and 1/4, respectively. The structure, stoichiometry, and geometry of the silver complexes were fully characterized by elemental analyses, infrared, single-crystal X-ray diffraction studies, multinuclear NMR, and mass spectroscopies. The binuclear complex ([Ag 2 ( 1 ) 2 (BF 4 ) 2 ]; 2 ) crystallizes in the monoclinic asymmetric space group P 2 1 /c and contains two silver atoms adopting a {AgN 2 F} planar trigonal geometry, which are simultaneously bridged by two oxadiazole rings of two ligands, while the mononuclear complex ([Ag( 1 ) 4 ]BF 4 ; 3 ) crystallizes in the non-usual cubic space group Fd-3 c in which the silver atom binds to four distinct electronically enriched nitrogen atoms of the oxadiazole ring, in a slightly distorted {AgN 4 } tetrahedral geometry. The α -aminophosphonate and the monomeric silver complex were evaluated in vitro against MCF-7 and PANC-1 cell lines. The silver complex is promising as a drug candidate for breast cancer and the pancreatic duct with half-maximal inhibitory concentration (IC 50 ) values of 8.3 ± 1.0 and 14.4 ± 0.6 μM, respectively. Additionally, the interactions of the ligand and the mononuclear complex with Vascular Endothelial Growth Factor Receptor-2 and DNA were evaluated by molecular docking methods.