The effect of pressure on the mossbauer resonance in hemin and iron phthalocyanine.

The effect of pressure on the M6ssbauer resonance in hemin and in iron phthalocyanine has been measured. In these initial studies unenriched compounds were used. The hemin was material supplied by Dr. Lowell Hager of the Division of Biochemistry. The iron phthalocyanine was obtained from E. I. DuPont de Nemours Company and was resublimed in our laboratory. The high-pressure M6ssbauer techniques have been described elsewhere.' The results on hemin are related to previous observations2 3 that both high-spin and low-spin ferric ions tend to reduce reversibly with increasing pressure. Normally, samples were run diluted with amorphous boron powder, but the behavior was the same whether the material was diluted with powdered A1203 or was run pure. In all cases, peak locations and areas were determined by computer fits with the appropriate combinations of Lorentzian curves. For Fe3+ ion in hemin the data were fit with two peaks of equal area but of width (in general unequal) determined to give the best fit to the data. The Fe2+ in hemin was fit with two peaks of equal area and width. For phthalocyanine the low-spin peaks were fit as two peaks with equal areas and widths. The same sort of fit was made to the high-spin pair. All isomer shifts are reported relative to metallic iron.