Controllable antiferromagnetic to ferromagnetic coupling in polynuclear Fe(III)–Co(II) heterobimetallic complexes

Abstract A tetranuclear cluster {[(Tp)Fe(CN) 3 ]Co(pp)H 2 O} 2 ·[(Tp)Fe(CN) 3 ] 2  ⋅ 6H 2 O ( 1 ; Tp = hydrotris(pyrazoly)borate, pp = 2,6-bis(N-pyrazolyl)pyridine) and a hexanuclear cluster {[(pzTp)Fe(CN) 3 ] 2 Co(pp)} 2 ·2H 2 O ( 2 ; pzTp = tetrakis(pyrazoly)borate) have been synthesized via rational assembly of the same (ppCo II ) 2 + unit and different tricyanometalate building blocks with varying proportions of sterically hindered groups. Magnetic measurements reveal that 1 exhibits the dominant antiferromagnetic interactions between Fe(III) and Co(II) ions, while 2 exhibits the dominant ferromagnetic interactions.