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

Abstract

A series of novel silver(I) complexes of type [Ag(OTf)L] (L = RR′Se), namely [Ag(OTf)Se{C₆H₄(CH₂NMe₂)-2}(CH₂Phtz)] (1), [Ag(OTf)Se{C₆H₄(CH₂NEt₂)-2}(CH₂Phtz)] (2), [Ag(OTf)Se{C₆H₄[CH₂N(CH₂CH₂)₂O]-2}(CH₂Phtz)] (3), [Ag(OTf)Se{C₆H₄(CH₂NMe₂)-2}(CH₂CH₂pz)] (4), [Ag(OTf)Se{C₆H₄(CH₂NEt₂)-2}(CH₂CH₂pz)] (5), [Ag(OTf)Se{C₆H₄[CH₂N(CH₂CH₂)₂O]-2}(CH₂CH₂pz)] (6), and [Ag(OTf)Se(CH₂Phtz)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 (¹H, ¹³C{¹H}, ¹⁹F{¹H}, and ⁷⁷Se{¹H}), ESI+ mass spectrometry, elemental analysis, IR spectroscopy and molar conductivity. The molecular structures of complexes 2, 3, 7 and the hydrolysis product [Ag(OTf)₂Se{C₆H₄[CH₂N(H)(CH₂CH₂)₂O]-2}(CH₂CH₂pz)]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 κ²N,N′-κSe coordination mode in the monomeric species 2 and 3, while in the dimeric species 7 and 6a the ligands are coordinated in a μ-(1κN:2κN′)-1,2κ²Se and a μ-(1κSe:2κN) 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.