Solid state reactions of hemin and imidazole were performed by milling the crystalline materials in an agate mortar.
The process was monitored by i.r., x.r.d. and MoÈ ssbauer spectroscopies. Samples with di erent hemin to imidazole
molar ratios were studied. The interactions of imidazole with the central Fe atom and with the propionic acid
groups in the periphery of the hemin molecule were detected. The latter interactions are suppressed by washing with
MeOH. Complexes with 1:2 and 1:4 hemin-to-imidazole molar ratios were identi®ed
