Synthesis and structures of Cu^I,II complexes with a 2,2´-bipyridine derivative bearing a (+)-3-carene moiety

The complex salt {[CuL₂][Cu₄I₆]•MeCN}_n (1) and the compound [Cu₄L₃I₄]•3 MeCN (2) (L is a chiral ligand bearing a natural monoterpene (+)-3-carene moiety) were synthesized. The crystal structures of compounds 1 and 2 were determined by X-ray diffraction. The structure of compound 1 consists of complex cations [CuL₂]²⁺ (N₃O₂ polyhedron is a trigonal bipyramid) and Cu^I coordination polymers (CuI₄ polyhedron is a tetrahedron) as anions. The experimental magnetic moment μ_eff at 300 K is 1.90 μ_B, which is consistent with the X-ray diffraction data and the assumption that compound 1 is mixed-valence. The structure of compound 2 comprises a tetranuclear Cu^I complex, in which three Cu atoms are coordinated by two N atoms of the ligand L and two I atoms, and the fourth Cu atom is coordinated by four I atoms (coordination polyhedra are distorted tetrahedra). Compounds L and 2 were found to influence the viability of human laryngeal carcinoma cells (Hep2). The IC₅₀ value for complex 2 (13.0±1.7 μM) is substantially smaller than IC₅₀ for compound L (30.5±0.5 μM).