Role of Dicarboxylate Linkers in MnIII-Salicylaldoximate Based Extended Structures: Synthesis, Structures, and Magnetic Behavior

Four new oxo-centered Mn-III-salicylaldoximate triangle-based extended complexes [(Mn6O2)-O-III(salox)(6)(EtOH)(4)(phda)](n)(saloxH(2))(n)(2H(2)O)(n) (1), [(Mn6O2)-O-III(salox)(6)(MeOH)(5)(5-I-isoph)](n)(3MeOH)(n) (2), [(Mn6O2)-O-III(salox)(6)(MeOH)(4)(H2O) (5-N-3-isoph)](n)(4MeOH)(n) (3) and [(Mn3NaO)-Na-III(salox)(3)(MeOH)(4)(5-NO2-isoph)](n)(MeOH)(n) (H2O)(n) (4) [salox=salicylaldoximate, phda=1,3-phenylenediacetate, isoph=isophthalate] have been synthesized under similar reaction conditions. Single crystal X-ray structures show that in 1, only one type of Mn-6 cluster is arranged in 1D, whereas in 2 and 3 there are two types of clusters, differing in the way the triangle units are joined and assembled. In complex4, however, the basic building structure is heteronuclear and based on Mn-3 units extended in 2D. Susceptibility measurements (dc and ac) over a wide range of temperatures and fields show that the complexes1, 2, and 3 behave as single molecule magnets (SMMs) with S=4ground state, while 4 is dominantly antiferromagnetic with a ground spin state S=2. Density functional theory calculations have been performed on model complexes to provide a qualitative theoretical interpretation for their overall magnetic behavior.