Copper(II) Inverse‐[9‐Metallacrown‐3] Compounds Accommodating ­Nitrato or Diclofenac Ligands: Structure, Magnetism, and Biological Activity

Abstract

AbstractInteraction of Cu(NO3)2 with phenyl 2‐pyridyl ketoxime (PhPyCNOH) in the presence or absence of sodium diclofenac (Nadicl) leads to the formation of mono‐ or double‐decker trinuclear clusters, respectively, characterized as inverse‐9‐metallacrown‐3 accommodating dicl– or NO3– anions. The structures of [Cu3(PhPyCNO)3(µ3‐O)(NO3)]2 (1) and [Cu3(PhPyCNO)3(µ3‐OH)(dicl)2]·MeOH·0.5H2O (2·MeOH·0.5H2O) were determined by X‐ray crystallography. Magnetic studies show a large antiferromagnetic interaction, whereas a discrepancy appears between the low‐temperature magnetic data and that predicted from an isotropic Hamiltonian model, indicating the influence of antisymmetric interactions. By using a different magnetic model with antisymmetric terms, the low‐temperature susceptibility and magnetization data were fitted. The EPR data support the observation that 2 has isosceles or lower magnetic symmetry, whereas the antisymmetric exchange mechanism is used to identify the reported g values of the spectra. EPR studies also revealed that complex 2 keeps its structure in solution. The complexes interact with calf‐thymus DNA by intercalation. The complexes, as well as [Cu2(dicl)4(H2O)2] (3), bind to albumins with relatively high binding constants. The highest cytotoxicity of the diclofenac compounds was observed after 24 h of incubation, whereas HL‐60 cells recovered after 72 h of incubation in the presence of each compound. Moreover, complex 3 was the most cytotoxic among the compounds, and complex 2 was as cytotoxic as Nadicl.