Template synthesis of macrocyclic dinuclear Cu^II complexes and conversion into mononuclear complexes by site-selective copper elimination

The acyclic dinucleating ligand, N,N′-dimethyl-N,N′-trimethylenedi-(3-formyl-2-hydroxy-5- methylbenzylamine) (H₂L), has been prepared. It combines two Cu^II ions with its N(amine)₂O₂ and O₄ metal-binding sites to form a dinuclear complex [Cu₂(L)](ClO₄)₂. The [1:1] condensation of [Cu₂(L)](ClO₄)₂ with an aliphatic or aromatic diamine has provided macrocyclic dinuclear Cu^II complexes [Cu₂(Lⁱ)](ClO₄)₂ (Lⁱ = L¹ for the diamine = ethylenediamine, L² for trimethylenediamine, L³ for tetramethylenediamine, L⁴ for o-phenylenediamine and L⁵ for 1,8-diaminonaphthalene). X-ray crystallographic studies for [Cu₂(L¹)(H₂O)](ClO₄) ₂MeCN and [Cu₂(L⁵)](ClO₄)₂2MeOH demonstrate a macrocyclic dinuclear core structure with the two Cu^II ions in the N(amine)₂O₂ and N(imine)₂O₂ sites, in the Cu-Cu separation of ca. 3.0 Å. The dinuclear complexes are studied in magnetic, electronic spectral and electrochemical properties. The treatment of the dinuclear complexes with Na₂S in acetonitrile resulted in the elimination of one Cu to afford the mononuclear complexes [Cu(Lⁱ)]xNaClO₄. The X-ray crystallography for [Cu(L²)], [Cu(L³)NaClO₄ and [Cu(L⁴)] has demonstrated that the Cu in the N(amine)₂O₂ site is selectively eliminated. In the latter complex, the Na¹ion is accommodated in the aminic site.