Five-coordinate nitrosyl iron(II) tetraphenylporphyrin exhibits porphyrin ring N-14 symmetry about the Fe-N-O plane: a hyperfine sublevel correlationspectroscopy study

Hyperfine sublevel correlation experiments were performed on five-coordinat e nitrosyl iron(II) tetraphenylporphyrin (ON-FeTPP) in frozen toluene solut ion. The spectrum exhibits pairs of equivalent pyrrole nitrogens N-1,N-2 an d N-3,N-4. The quadrupole parameters agree with literature values for other pyrrole nitrogens. N 2s spin densities of -0.0021 to -0.0022 and -0.00096 on N-1,N-2 and N-3,N-4, respectively, are found. The anisotropic hyperfine interaction results from magnetic dipole interactions between the pyrrole N -14 nuclei and electron spin located in the Fe 3d(z2)-type orbital and in t he N 2p orbitals in the (yz) plane bisecting the pyrrole C-N-C angles. The spin density in the Fe 3d(z2)-type orbital along the normal to the porphyri n plane (y axis) is similar to0.7. The two pyrrole N 2p orbitals are quanti zed along axes y' and z', 9-10 degrees from y and z, respectively. The N 2p (y') and N 2p(z') spin densities range from -0.005 to -0.009 and +0.007 to +0.010, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.