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.

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Magnetic anisotropy, magnetization, and average magnetic susceptibility have been measured for iron (II) phthalocyanine. The anisotropy was measured from the room temperature to about 90°K, the average susceptibility from 296 to 1.57°K, and the magnetization was measured at 1.57°K for field strengths between 1100 and 15 000 Oe. The results are interpreted in terms of a B2g3 ground state with a zero-field splitting parameter D = 64 cm−1, and g‖ = g⊥ = 2.74. Iron (II) phthalocyanine is an unusual example in which a large magnetic anisotropy arises entirely from the zero-field splitting. The danger inherent in the existing method of evaluation of ligand-field parameters from the average magnetic susceptibility data has been highlighted, and the advantages of magnetic anisotropy studies in deducing the ligand-field parameters and the electronic structures are discussed. A change of about 70° of the “setting angle” between 290 and 90°K is observed in this crystal when measured with b axis vertical. It is shown that this change is not indicative of a change in the ligand-field parameters with temperature, as generally assumed previously, but depends on the temperature dependence of the ratio of principal susceptibilities.

Detailed crystal field calculations are presented to ddermine the ground and excited states of mangane~e(Il) phthalocyanine which belongs to the rare spin S = 3/2 state. It is deduced that the ground state of Mn(II) ion is predominantly 4A i± 112) while 4A ,(± 3/2) state lies above 40 cm 1 above it. It is shown that 6 A I(± 1/2) lies fairly close to the ground state (600 cm I) and appreciably mixes with it. Two magnetic exchange models are investigated, and their effects are superimposed over the crystal field to quantitatively explain the low temperature experimental data.B, C, and t, i.e., 960, 3360, and 300 cm-I, respec-962

Diamagnetic susceptibilities and anisotropies of metal-free, nickel(II), and zinc(II) phthalocyanines are reported. Calculations based on Pauling's semiclassical model give very poor agreement with the experimental results. The results are interpreted following the procedure of Amos and Roberts from which it emerges that only part of the total anisotropy can be attributed to the π-electron macrocyclic ring.