A current area of bioinorganic interest concerns the behavior of ferric porphyrins in solution with nitrogenous bases. PlMR studies have given evidence for (1) low spin (S = +) = high spin (S = 3 or 3) equilibria in certain systems [I, 21, and (2) five coordinate (S = 3) monoimidazole ferric porphyrins in equilibrium with low spin bisimidazoie forms [3] in solution. In contrast, spectrophotometric titrations of Cl-Fe(III)tekaphenylporphin with imidazole in acetone [4] and methylene chloride [5] solvents show an e+libris betvxen only Cl-Fe(III)TPP and (Im)rFe(III)-TPP, Cl-, with no monoimidazole adducts present. me have begun a program of using thermal means to generate 'kmsual" metal ion geometries of metalloporphyrins in the solid state as models of the metalhxnzymes "entatic state" 161. VJe report magnetic, themud and Mossbauer data on a variety of solid hemichromes, which show certain parallel features with the behavior of herniArome in solution. In particular, we havesynthesized by thermal means high spin monoimidazole Fe(III) porphyrin complexes. EXPERIMENTAL Hemichromes with solid nitrogenous bases mere prepared by a mod&a.tion of Conviu's method [7]. The substituted deuterohemin chloride was suspended in a pre-atered saturated solution of the base in benzene and stirred in the absence of light for two hours. The violet solids were recovered by filtration, washed three times xvith hot benzene, and dried under vacuum at 100". Washing with methanol or preparation from methanol solutions gave erratic results. The 2,4 and 2,6 dimethyl pyridine adducts (distilled before use) were made by boiling the porphyrin in the liquid * Correspondence and reprint requests to this author.