Crystal structure of bis(4-methylimidazole) tetraphenylporphyrinatoiron(III) chloride and related compounds. Correlation of ground state with Fe-N bond lengths

The crystal structure of the title compound is presented and shown to be on e of a class of low-spin iron porphyrin complexes having a ground-state ele ctronic configuration of (d(xy))(2)(d(xz))(2)(d(yz))(1). If their Fe-N bond lengths (average N-porphyrin plotted against average N-axial) are consider ed, this class of low-spin iron(III) porphyrins of general formula [Fe(III) Por(L)(2)]X-+(-) and of B-2 ground state is shown to be distinctly differen t crystallographically from a similar class of compounds with the same gene ral formula but with a E-2 or a (d(xy))(2)(d(xz),d(yz))(3) ground state. A third group of compounds with the same general formula have a (d(xz),d(yz)) (4)(d(xy))(1) ground state and again are in a different region of the plot. Compounds showing intermediate properties can be forecast from the simple relationship presented in this work. The electron paramagenetic resonance d ata are shown to be dependent on the ground state, and those of configurati on (d(xy))(2)(d(xz),d(yz))(3) and the B-2 ground state obey a correlation p reviously suggested in the literature.