Scheme 2.

Crystal structure of [Fe(OEP)(NO)] (1) from monoclinic (left; form I) and triclinic (right, form II) crystals taken from ref. 14. In form I, 5 neighboring ethyl groups of OEP point to one face of the porphyrin, whereas the remaining 3 point in the opposite direction. In contrary, in form II, 4 neighboring ethyl groups point to each face of the porphyrin core as indicated on the right. (Reprinted with permission from Ref. 14. Copyright 1997 and 2000, American Chemical Society.) (Comment: permission request will be submitted when needed)