Synthesis, crystal structures and magnetic properties of cyanide-bridged heterobimetallic trinuclear Cr2IIIMnII complexes based on the cis-dicyanidemetalate [Cr(2,2′-bipy)2(CN)2]ClO4 building block

A structurally characterized cis-dicyanidemetalate [Cr(2,2′-bipy)2(CN)2]ClO4 (1) building block and two mononuclear seven-coordinate macrocyclic manganese(II) complexes have been employed to assemble two cyanide-bridged heterometallic CrIII–MnIII complexes: {[Mn(L1)][Cr(2,2′-bipy)2(CN)2]2}{ClO4}4·H2O (2) and {[Mn(L2)][Cr(2,2′-bipy)2(CN)2]2}{ClO4}4·2H2O (3) (L1 = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, L2 = 2,13-dimethyl-6,9-dioxa-3,12,18-triazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene). Single-crystal X-ray diffraction analysis shows that 2 and 3 have similar cyanide-bridged cationic trinuclear Cr2Mn structures with free ClO4− as balancing anions, in which the cyanide precursor acts as a monodentate ligand to connect the macrocyclic manganese(II) units. The coordination geometry of the manganese(II) centers in the two complexes is slightly distorted pentagonal-bipyramidal, with two cyanide nitrogen atoms at the trans-positions and N5 or N3O2 donor sets in the equatorial plane provided by the macrocyclic ligand. Investigation of the magnetic properties reveals antiferromagnetic magnetic coupling between the cyanide-bridged Cr(III) and Mn(II) centers. A best-fit analysis of the magnetic susceptibility leads to the magnetic coupling constants J = −1.15 and −1.08 cm−1 for complexes 2 and 3, respectively.