Trinuclear magnetic clusters based on cyanide metal complexes:: synthesis, crystal structures, and magnetic properties of four new [MnII2MIII] complexes (M = Cr, Fe, Co)

Four new cyano-bridged [Mn-II M-III Mn-II] heterotrinuclear complexes (M-III = Cr, Fe, Co) have been synthesized and crystallographically characterized: {[(H2O) L-1 Mn - NC - Cr(CN)(4) - CN-MnL1( H2O)]}(3)[Cr(CN)(6)] center dot 10H(2)O 1, [(H2O) L-2 Mn - NC - M(CN)(4) - CN - MnL2(NCS)] center dot 2H(2)O 2, [(H2O) L-2 Mn - NC - Fe(CN)(4) - CN - MnL2(H2O)](NCS) center dot 1.5H(2)O 3, and [(H2O) L-2 Mn - NC-Co( CN)(4) - CN - MnL2(H2O)](NCS) center dot 1.5H(2)O 4 (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). The crystal structure of 1 consists of independent [MnCrMn] monocations whose charges are counterbalanced by [Cr(CN)(6)](3-) anions. The crystal structure of 2 consists of neutral heterotrinuclear [ MnCrMn] species, with the isothiocyanato ion coordinated to one of the manganese atoms. Compounds 3 and 4 are isomorphous. Their crystal structure consists of centrosymmetric [MnMMn] entities, uncoordinated NCS 2 ions, and solvent molecules. The magnetic properties of the four complexes have been investigated. Compounds 1 and 2 are new examples of systems with an irregular spin state structure, exhibiting the characteristic minimum on the the chi T-M versus T curves. The exchange interaction between the chromium(III) and the manganese(II) ions is antiferromagnetic (1: J = -9.8 cm(-1); 2: J = -6.52 cm(-1)). For compound 3, the exchange interaction between manganese( II) and iron( III) was found to be ferromagnetic.