The preparation and characterization of the low-spin bis(pyridine)iron(III) porphyrinate complex [Fe(TPP)(4-CNPy)2]C10(4) is reported. Consistent with the expected effect from the strong pi-acceptor character of the axial4-cyanopyridine ligands, the X-ray structure o f the complex shows that the two axial ligands have relative perpendicular orientations along with an extensivelyS(4)-ruffled porphyrin core. The S-4 ruffling is among the largest found for bis(pyridine) complexes and leads to the extremely short average Fe-Np bond distance of 1.952(7) Angstrom. The axial Fe-N bond distances average to 2.002(8) Angstrom. Molecular mechanics calculations indicate that the ruffling observed in this and other bis(pyridine) complexes of Fe(III) porphyrins is not simply a result of steric interactions between the phenyl rings and the pyridine ligands, since the minimized energies of bis(pyridine) complexes of the non-phenyl-containing system, [Fe(porphine)(pyridine)(2)](+), as a function of the angular orientation of two perpendicularly aligned pyridine ligands with respect to the N-Fe-N axes of the porphyrin ring, are within experimental error of those of [Fe(TPP)-(pyridine)(2)](+). Therefore, the observed strong S-4 ruffling of the porphyrinato core must be due to electronic rather than steric factors. This electronic contribution is likely the partial delocalization of the d(xy) unpaired electron into the alpha(2u)(pi) orbital of the porphyrin ring, which is made possible by the twisting of the nitrogen p(z) orbitals out of the mean plane of the porphyrin ring as a result of the strong S-4 ruffling. The Mossbauer spectrum of the complex has an isomer shift of 0.19(1) mm/s and an unusually small quadrupole splitting (Delta E(q)) of 0.65(1) mm/s. The EPR spectra in both solid and solution phases are axial, with g(perpendicular to) greater than or equal to 2.62 and g(parallel to) less than or equal to 0.92 at 4.2 K, Sigma g(2) similarto 14.6. The [Fe(TPP)(4-cnpY)(2)]ClO4 complex is thus a case in which a large amount of the d orbital angular momentum of the metal is quenched, and hence Sigma g(2) is much lower than 16, and is, in fact,midway between that value and the minimum possible value of 12 that is expected for a pure (d(xy))(1) unpaired electron. Single crystal EPR spectra show a strong broadening of the EPR signal near the g(parallel to) turning point that is indicative of what has been called by some researchers "g-strain," as was previously observed in the "large g(max)" type of rhombic EPR signals of low-spin Fe(III) porphyrin systems having perpendicularly aligned planar axial ligands and a (d(xy))(2)(d(xz),d(yz))(3) electronic ground state (Walker, F.A.; Huynh, B. H.; Scheidt, W. R.; Osvath, S. R. J. Am. Chem. Soc. 1986, 108, 5288-5297).