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

Two new hexanuclear oxamatocopper(II) complexes <b>3</b> and <b>4</b> have been synthesized from the binuclear copper(II) complexes of the <i>meta</i>- and <i>para</i>-phenylenebis(oxamate) ligands, respectively. Complexes <b>3</b> and <b>4</b> 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 <i>meta</i>- and <i>para</i>-cyclophane type, respectively. They show different ground spin states, <i>S</i> = 1 (<b>3</b>) or <i>S</i> = 0 (<b>4</b>), depending on the substitution pattern in the aromatic spacers. The triplet state molecule <b>3</b> containing two spin doublet Cu^II₃ units connected by two <i>m</i>-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.