A study of pyridyl nitrosyl iron(II) tetraphenyl N-15(4)-porphyrin. NO geometry and spin coupling to the pyrrole nitrogens

Spin coupling with pyrrole nitrogens and NO geometry in pyridyl-NO-Fe(II) t etraphenyl-N-15(4)-porphyrin, examined with hyperfine sublevel correlation spectroscopy (HYSCORE), was studied because of renewed interest in diatomic molecule bound ferrous hemes, e.g. the physiologically important NO syntha se. Dipolar coupling locates the effective electron spin position (0.109 +/ - 0.008 nm from the ring center, 0.106 +/- 0.006 nm above the ring plane an d projecting 37 +/- 2 degrees from the nearest pyrrole nitrogen). The NO pr ojection in an X-ray study of the di-methyl piperidine complex is 38.6 degr ees. The negative pyrrole nitrogen spin densities induced by the NO obey a sinusoidal angular relationship. (C) 1999 Elsevier Science B.V. All rights reserved.