No abstract

Measurements are reported of magnetization and the average magnetic susceptibility of manganese (II) phthalocyanine in the range 1.7-300 o K, which confirm that the Mn(II) atom is in an S=3/2 spin state, and that weak ferromagnetic interactions are present in the crystal, presumably between adjacent molecules. Single crystals of MnPc are moderately anisotropic; the principal magnetic moment I'll =4.0 I'B remains constant between 80-300 o K while I'J. increases from 4.4 I'B (300 0 K) to 5.0 I'B (90 0 K). This magnetic anisotropy is consistent with a 4A 2g ground state into which the excited term 4Eg is mixed by spin-orbit couDling. Possible pathways for superexchange are considered.

No abstract

No abstract

Magnetic susceptibility results and extensive electronic, infrared, and Mossbauer spectral data are presented for enH2[(FeHEDTA)20] • 6H20, Na4[(FeEDTA)20] • 12H20, FeHEDTA H20, and NaFeEDTA • 3H20 (HEDTA = '-hydroxoethylethylenediaminetriacetate, EDTA = ethylenediaminetetraacetate, and enH22+ = ethylenediammonium cation). The magnetic and spectral data establish an electronic structural model for the oxo-bridged dimers in which pairs of S = 5/2 Fe(III) ions interact antiferromagnetically, with / --95 cm-1. The oxo-bridged dimers show marked intensity enhancement of the one-center Fe(III) ligand-field bands. There are also several uv bands which are interpreted as arising from simultaneous electronic excitations of Fe(III) pairs. A simple high-spin ligand-field model modified by spin-spin interaction is judged to be considerably more appropriate than the Dunitz-Orgel molecular orbital approach as a vehicle for describing oxo-bridged Fe(III) dimers.here has recently been considerable interest in oxobridged iron(III) dimeric systems. Several complexes of this type have been synthesized and characterized by magnetic susceptibility measurements and Mossbauer spectra.4-8 Infrared frequencies associated with the oxo-bridging unit have been identified,4•9 and in certain cases X-ray structures have been obtained.10-13 Particular importance can be attached to these model complexes in view of the presence of dimeric and polymeric species in the aqueous chemistry of Fe(III) and the probable occurrence of dimeric Fe(III) species in biochemical systems such as the protein hemerythrin.14 Dimeric ferriporphyrins containing the Fe-O-Fe structural unit have also been characterized.13• 15•16 (1) Rutgers University.