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 CuII3 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.