On the coordination behaviour of diorganoselenium ligands based on amino and azole functionalities: silver(I) complexes with relevance for biological applications

A series of novel silver(I) complexes of type [Ag(OTf)L] (L = RR'Se), namely [Ag(OTf)Se{C6H4(CH2NMe2)-2}(CH(2)Phtz)] (1), [Ag(OTf)Se{C6H4(CH2NEt2)-2}(CH(2)Phtz)] (2), [Ag(OTf)Se{C6H4[CH2N(CH2CH2)(2)O]-2}(CH(2)Phtz)] (3), [Ag(OTf)Se{C6H4(CH2NMe2)-2}(CH(2)CH(2)pz)] (4), [Ag(OTf)Se{C6H4(CH2NEt2)-2}(CH(2)CH(2)pz)] (5), [Ag(OTf)Se{C6H4[CH2N(CH2CH2)(2)O]-2}(CH(2)CH(2)pz)] (6), and [Ag(OTf)Se(CH(2)Phtz)(2)] (7), were obtained by reacting the diorganoselenides L1-L7 with AgOTf in a 1 : 1 molar ratio. The new ligand L7 and the Ag(I) complexes were characterized by multinuclear NMR spectroscopy (H-1, C-13{H-1}, F-19{H-1}, and Se-77{H-1}), ESI+ mass spectrometry, elemental analysis, IR spectroscopy and molar conductivity. The molecular structures of complexes 2, 3, 7 and the hydrolysis product [Ag(OTf)(2)Se{C6H4[CH2N(H)(CH2CH2)(2)O]-2}(CH(2)CH(2)pz)](2) (6a) were determined by single-crystal X-ray diffraction. The metal complexes behave as 1 : 1 electrolytes in solution, but in the solid state the OTf group is coordinated to silver. The diorganoselenides show different coordination patterns, i.e. a kappa N-2,N'-kappa Se coordination mode in the monomeric species 2 and 3, while in the dimeric species 7 and 6a the ligands are coordinated in a mu-(1 kappa N:2 kappa N')-1,2 kappa Se-2 and a mu-(1 kappa Se:2 kappa N) fashion, respectively. The in vitro antiproliferative activity of selected compounds was investigated and the results show that the silver(I) complexes have promising activity against the murine melanoma B16.F10 cells.