Metal-organic ion pairs with dithiooxalate d8 metal donors and viologens. Spectroscopic, structural and electronic characterization

Molecular self-assemblies of a π-conjugated redox-active bipyridinium cation with magnetic dimetallic oxalate-bridged trimeric clusters

A series of molecular assemblies constructed from a pi-conjugated redox-active bipyridinium cation, 1,4-bis(4'-pyridyl-1'-pyridinio)phthalazine (Bpyph), and magnetic dimetallic oxalate-bridged trimeric clusters, has been synthesized and characterized by elemental analysis, IR, TGA, X-ray single-crystal diffraction and magnetic susceptibility studies. The molecular assemblies formulated as (Bpyph)2{M(II)(H2O)2[M(III)(C2O4)3]2}.12.5H2O [for M(III) = Fe; M(II) = Mn (1) or Co (2); for M(III) = Cr; M(II) = Mn (3) or Co4] are isostructural, their structures feature an alternative arrangement of Bpyph2+ cations and the linear trimeric oxalate complexes {M(II)(H2O)2[M(III)(C2O4)3]2} along all three crystallographic axes, in which the dimetallic trimers form two distinct homo-chiral helices along the b axis via intermolecular hydrogen bonding interactions. Within each trimeric cluster, the two M(III) sites have opposite chirality (Delta and Lambda). Studies on the magnetic properties reveal the presence of antiferromagnetic exchange interactions within the trimeric clusters for the Fe2M and ferromagnetic for the Cr2M series.