Determination of Ligand-Field Parameters and f-Electronic Structures of Double-Decker Bis(phthalocyaninato)lanthanide Complexes

The f-electronic structures of the ground states of anionic bis(phthalocyaninato)lanthanides, [Pc(2)Ln](-) (Pc = dianion of phthalocyanine, Ln = Tb(3+), Dy(3+), Ho(3+), Er(3+), Tm(3+), or Yb(3+)), are determined. Magnetic susceptibilities of the powder samples of [Pc(2)Ln]TBA (TBA = tetra-n-butylammonium cation) in the range 1.8-300 K showed characteristic temperature dependences which resulted from splittings of the ground-state multiplets. NMR signals for the two kinds of protons on the Pc rings at room temperature were shifted to lower frequency with respect to the diamagnetic Y complex in Ln = Tb, Dy, and Ho cases, and to higher frequency in Er, Tm, and Yb cases. The ratios of the paramagnetic shifts of the two positions were near constant in the six cases. This indicates that the shifts are predominantly caused by the magnetic dipolar term, which is determined by the anisotropy of the magnetic susceptibility of the lanthanide ion. Using a multidimensional nonlinear minimization algorithm, we determined a set of ligand-field parameters that reproduces both the NMR and the magnetic susceptibility data of the six complexes simultaneously. Each ligand-field parameter was assumed to be a linear function of atomic number of the lanthanide. The energies and wave functions of the sublevels of the multiplets are presented. Temperature dependences of anisotropies in the magnetic susceptibilities are theoretically predicted for the six complexes.