A copper–cyclen coordination complex associated with a polyoxometalate anion: Synthesis, crystal structure and electrochemistry of [Cu(cyclen)(MeCN)][W6O19]

The reaction between Cu(NO3)2·3H2O and a tetra-aza macrocycle, more specifically, cyclen in 1:1 MeCN–MeOH solvent mixture forms a Cu2+–cyclen coordination complex in situ, that has been reacted with an isopolyanion [W6O19]2− in a slow diffusion technique, resulting in the isolation of an ion-pair solid [Cu(cyclen)(MeCN)][W6O19] (1). Single crystal structural investigation on 1 shows a square pyramidal geometry around the metal centre (copper ion) with an axially bound MeCN solvent molecule. The title compound 1 is the first crystallographically characterized ion-pair compound, in which a transition metal coordination complex of a tetra-aza-crown ether (cyclen) has been associated with a polyoxometalate cluster anion. This communication deals with synthesis, spectroscopic, structural and electrochemical analyses of compound 1.