Bicyclam [6,6′-bi(1,4,8,11-tetra-azacyclotetradecane)]: a ditopic receptor for homo- and hetero-bimetallic complexes

Abstract

Bicyclam [6,6′-bi(1,4,8,11-tetra-azacyclotetradecane)](L²) was prepared by reducing 6,6′-bi(1,4,8,11-tetra-azacyclotetradecan-5,7-dione)(L¹) with B₂H₆ in bis(2-methoxyethyl) ether. Ligand L² forms homo- and hetero-binuclear complexes with Cu²⁺ and Ni²⁺, the spectral properties and the electrochemistry of which have been studied. Whereas the visible spectra are very similar to those of the mononuclear complexes with cyclam (1,4,8,11-tetra-azacyclotetradecane), the electrochemistry indicates a weak interaction between the metal ions co-ordinated by bicyclam, as shown by a shift of the second oxidation potential M²⁺→ M³⁺ to more positive values.