Structural Trends in a 3 d-4 f System: Ln(NO3)(3)-Cu(2,2-bipyridine)(2)(NO3)(2) (Ln=La-Nd, Sm-Yb)

A series of thirteen complexes which may be formally considered as assembled from Cu(bpy)(2)(NO3)(2) and Ln(NO3)(3) (Ln=La-Yb excluding Pm, bpy=2,2'-bipyridine) have been characterized. The crystals may be grouped into four classes: A, [Cu-2(bpy)(4)(mu-NO3)][Ln(NO3)(6)] (Ln=La-Nd); B, [Cu(bpy)(2)(NO3)](2)[Ln(NO3)(4)(OH2)(2)](NO3) (Ln=Sm-Dy); C, [Cu(bpy)(2)(NO3)](2)[Ln(NO3)(5)] (Ln=Ho-Tm); D, [Cu(bpy)(2)(NO3)](2) [Ln(NO3)(3)(OH2)(3)](NO3)(2)center dot 2H(2)O (Ln=Yb). The coordination numbers of the nitrato or aquonitrato lanthanide anions range from 9 to 12. The dinuclear cation in Class A having a linear monoatomic nitrate bridge is new and is seen to produce weak antiferromagnetic coupling in these compounds. The other classes contain distortion isomers of [Cu(bpy)(2)NO3](+). The structural trends are analysed in terms of lanthanide contraction and non-covalent interactions in the crystals. EPR and electronic spectral characteristics are discussed for the four classes of compounds.