Structural and magnetic investigations on new molecular quantum rings

Abstract

We report on a comparative investigation of the structural and magnetic properties of three oxygen-bridged polynuclear ( N = 6, 8, 10) Cu(II) cyclomethylsiloxanolate complexes, Cu 6 [(MeSiO 2 ) 6 ] 2 ·6DMF ( 1 ), {Cu 8 [(MeSiO 2 ) 8 ] 2 ·8DMF}·EtOH ( 2 ) and {Cu 10 [(MeSiO 2 ) 10 ] 2 ·10DMF}·6DMF ( 3 ). All three molecular complexes have a planar ring-shaped configuration of the copper S = 1/2 spins. The analysis of the magnetic data, with particular emphasis placed on the high-temperature behaviour, together with the structural information enables us to correlate the evolution of the exchange coupling J between the magnetic S = 1/2 centers of the quantum ring as a function of the number N of magnetic sites to the structural changes of the molecular crystals.