Spin admixed iron porphyrins

The magnetic properties of the iron porphyrins may be considered in terms of their tetragonal symmetry, which results in the existence of three possible spin states. For the ds Fe111 centre these are the low-spin S = 3 state, the intermediate-spin S = state and the high-spin S = state. Examples of each type are given in Table 15, with information on bond lengths. The S = state can couple to a nearby S = f state to give a new admixed intermediate state (S = , ), which must not be viewed as a spin equilibrium. 

Figure 2 Possible oxidation and spin states of iron porphyrins and the d orbital configurations expected in each case. AU of these states (excluding high-spin d, which is not included in the figure) have been observed for iron porphyrins, and are discussed in this article. In addition, the spin-admixed 5 = 3/2,5/2 state of Fe " and the alternative orbital configuration for low-spin Fe , with dxy higher in energy than dxi,dyz are also discussed...

A relatively high contribution of the S=3/2 spin state in the spin-admixed state of the studied highly n atively charged iron(III) porphyrins is nicely reflected in the kinetic behavior of the latter complexes concerning... 

There has been a report of bridged dinitrogen complexes of iron(III) and chromium(lll) complexes, formed by reaction of the metallo(IlI)porphyrinate triftate with [Re(N2)(PMe2Ph)4Cl] to make the Fe-N-N-Re or Cr-N-N-Re bridged complexes. The Fe complex has a magnetic moment of about 4.4 /u-b at room temperature, consistent with a S = 312,512 admixed spin state for the iron(lll), and a pyrrole-H shift of -3.23 ppm, consistent with the expected weak-fteld nature of the N2 ligand. The stracture shows a linear Fe-N-N-Re unit (Fe-Nl-N2 = 170°, Nl-N2-Re = 177°) with Fe-N bond length of 1.93 similar to that of the TPPFe -azide complex (1.953 A). 

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