Synthesis, crystal structures and magnetic properties of cyanide-bridged heterobimetallic trinuclear Cr 2 III MnII 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 Cr-III-Mn-III complexes: {[Mn(L-1)][Cr(2,2'-bipy)(2)(CN)(2)](2)}{ClO4}(4)center dot H2O (2) and {[Mn(L-2)][Cr(2,2'-bipy)(2)(CN)(2)](2)}{ClO4}(4)center dot 2H(2)O (3) (L-1 = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene, L-2 = 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 N-5 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.