Structural and magnetic diversity in cyano-bridged bi- and trimetallic complexes assembled from cyanometalates and [M(rac-CTH)]n+ building blocks (CTH = d, l-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)

Seven new cyano-bridged heterometallic systems have been prepared by assembling [M'(rac-CTH)](n+) complexes (M' = Cr-III, Ni-II, Cu-II), which have two cis available coordination positions, and [M(CN)(6)](3-) (M = Fe-III, Cr-III) and [Fe(CN)(2)(bpy)(2)](+) cyanometalate building blocks. The assembled systems, which have been characterized by X-ray crystallography and magnetic investigations, are the molecular squares (meso-CTH-H-2)[{Ni( rac-CTH)}(2){Fe(CN)(6))}(2)](.)5H(2)O (2) and [{Ni( rac-CTH)}(2){Fe(CN)(2)(bpy)(2)}(2)(ClO4)(4)(H2O)-H-. (5), the bimetallic chain [{Ni(rac-CTH)}(2){Cr(CN)(6))}(2)Ni-(meso-CTH)](.)4H(2)O (3), the trimetallic chain [{Ni(rac-CTH)}(2){Fe(CN)(6))}(2)Cu(cyclam)](.)6H(2)O (4), the pentanuclear complexes [{Cu(rac-CTH)}(3){Fe(CN)(6))}(2)](.)2H(2)O (6) and [{Cu(rac-CTH)}(3){Cr(CN)(6))}(2)](.)2H(2)O (7), and the dinuclear complex [Cr(rac-CTH)(H2O)Fe(CN)(6)](.)2H(2)O (8). With the exception of 5, all compounds exhibit ferromagnetic interaction between the metal ions (J(FeNi) = 12.8(2) cm(-1) for 2; J(1FeCu) = 13.8(2) cm(-1) and J(2FeCu) = 3.9(4) cm(-1) for 6; J(1CrCu) = 6.95(3) cm(-1) and J(2CrCu) = 1.9(2) cm(-1) for 7; J(CrFe) = 28.87(3) cm(-1) for 8). Compound 5 exhibits the end of a transition from the high-spin to the low-spin state of the octahedral FeII ions. The bimetallic chain 3 behaves as a metamagnet with a critical field H-c = 300 G, which is associated with the occurrence of week antiferromagnetic interactions between the chains. Although the trimetallic chain 4 shows some degree of spin correlation along the chain, magnetic ordering does not occur. The sign and magnitude of the magnetic exchange interaction between CrIII and FeIII in compound 8 have been justified by DFT type calculations.