Spin Control in Ladderlike Hexanuclear Copper(II) Complexes with Metallacyclophane Cores

Two new hexanuclear oxamatocopper(II) complexes 3 and 4 have been synthesized from the binuclear copper(II) complexes of the meta- and para-phenylenebis(oxamate) ligands, respectively. Complexes 3 and 4 possess an overall ladderlike structure made up of two oxamate-bridged linear trinuclear units (“rails”) connected through two phenylenediamidate bridges (“rungs”) between the central copper atoms to give metallacyclic cores of the meta- and para-cyclophane type, respectively. They show different ground spin states, S = 1 (3) or S = 0 (4), depending on the substitution pattern in the aromatic spacers. The triplet state molecule 3 containing two spin doublet Cu^II₃ units connected by two m-phenylenediamidate bridges represents a successful extension of the concept of “ferromagnetic coupling units” to metal complexes, which is a well-known approach toward high spin organic radicals.