Neutral bis-macrocyclic nickel(II) and copper(II) complexes as π-donor receptors

A new type of hetero- and homo-polynuclear complexes of copper(II) and nickel(II) containing 1,2,3-triazole groups in polymethylene chains have been synthesized and characterized using NMR and electrochemical methods. The triazole link facilitates the synthesis of hetero-dinuclear macrocyclic complexes. Introducing the triazole unit into the complex structure can lead to increased stability of the bis-macrocyclic system and to obtain electroactive receptors for electron-deficient molecules. Intermolecular interactions between new bis-macrocyclic donors and a chosen acceptor--7,7,8,8-tetracyanoquinodimethane (TCNQ) have been studied by voltammetry. Normal pulse voltammetry with varying initial potentials, E(i), was found to be a convenient tool to follow subtle changes of the electrochemical behavior of the redox centers due to interactions between the π-donor, bis-macrocyclic complex, and the acceptor, TCNQ molecule. The copper(II) bis-macrocyclic compound functions as a receptor able to accommodate the small organic compound in the macrocyclic cavity. This brings together transition metal ions and organic substrates within the same supramolecular structure.