Template Synthesis of Macrocyclic Dinuclear CuII Complexes and Conversion into Mononuclear Complexes by Site-Selective Copper Elimination

Abstract

Abstract The acyclic dinucleating ligand, N,N′-dimethyl-N,N′-trimethylenedi-(3-formyl-2-hydroxy-5-methylbenzylamine) (H2L), has been prepared. It combines two CuII 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 CuII 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)2•MeCN and [Cu2(L5)](ClO4)2•2MeOH demonstrate a macrocyclic dinuclear core structure with the two CuII 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 NaI ion is accommodated in the aminic site.