Pentanuclear and Octanuclear Manganese Helices

Two helical manganese complexes, [Mn-5(L)(3)((3)-O)(NO3)(OMe)(2)(MeOH)](NO3)4MeOHH(2)O (1) and [Mn-8(L)(6)((3)-Cl)(2)]Cl(2)3C(2)H(4)Cl(2)60H(2)O2DMF (2, DMF = N,N-dimethylformamide), were obtained by the reaction of the multidentate polypyridine ligand 2,6-bis[5-(2-pyridinyl)-1H-pyrazole-3-yl]-pyridine (H2L) with manganese nitrate and chloride, respectively. The compounds were characterized by elemental analyses and single-crystal X-ray structural analyses. The pentanuclear complex 1 is composed of three ligands and five manganese ions with (3)-oxido bridges, whereas the octanuclear complex 2 is constructed from six ligands and eight manganese ions with two (3)-chlorido bridges. Both compounds have helix-type structures. The manganese ions in 1 are present in a mixture of +2 and +3 valence states, whereas 2 is homovalent and contains only +2 ions. The magnetic properties of both compounds were investigated in the temperature range 1.8-300 K, and antiferromagnetic interactions between the manganese ions are dominant in both complexes.