Ion Pair Charge-Transfer Complexes of Dithiolatocobaltates with Cationic Copper or Nickel Macrocycles: Crystal Structure and Magnetic Properties

Abstract

Abstract The complexes {[M(tim)]2+[Co(mnt)2]2−}, (M = Ni (NiCo), Cu (CuCo), tim = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene, mnt2− = cis-1,2-dicyano-1,2-ethylenedithiolato) have been isolated. NiCo and CuCo have isomorphous crystal structures (P1-), the basic feature of which is the presence of mixed donor–acceptor chains induced by short intrachain distances of 3.15 and 3.03 Å, respectively. For both NiCo and CuCo, an ion pair charge-transfer band is observed at 707 and 843 nm; application of the Hush model affords reorganization energies for electron transfer from the dianion to the dication of 89 and 104 kJ mol−1, respectively. The magnetic properties of the powder samples have been studied in the temperature range of 2 K to 300 K. In NiCo the diamagnetic [Ni(tim)]2+ acceptor induces antiferromagnetic coupling of the spin a half system [Co(mnt)2]2− along the a-axis over a distance of 6.3 Å. From the exchange coupling constant of J = −37 cm−1 a Weiss temperature of 26 K is calculated. Contrary to that, the magnetic orbitals of [Cu(tim)]2+ and [Co(mnt)2]2− remain uncoupled in CuCo.