Hemin modification. Different hemin derivatives were synthesized and typically purified by column chromatography. The NMR spectrum was consistent with that obtained by , relating to a six coordinate high-spin system. Following hemin modification, all the 1 H-NMR spectra were observed within a narrow detection range, in contrast to the wide range in the case of hemin itself (fig. ). These differences relate to either one or more of the following factors: (1) effects of the substituent groups and whether they work as electron-withdrawing or donating groups;