Resonance Raman (rR) spectroscopy of metalloporphyrins can provide detailed information about the oxidation state, coordination number, and spin state of the central metal ion : These data have been of particular value in the study of natural and model heme systems. Core-size correlations, plots of the porphyrin-ring center to pyrrole nitrogen (Ct-N) distances versus rR frequencies, are frequently utilized to assess structural properties or to confirm spectral assignments. However, in most cases, such plots for beta-pyrrole-substituted porphyrins are limited by the use of Ct-N distances derived from the crystal structures of meso-tetraphenylporphyrins. Because of well-documented structural and spectroscopic differences in these two classes of porphyrins, the utility of such core-size correlations may be impaired. Here we report the crystal structures of three new octaethylporphyrin (OEP) complexes : (1) Fe(OEP)(NCS). C7H8, triclinic, P1 ($) over bar, a = 11.669(2) Angstrom, b = 12.151(2) Angstrom, c = 14.251(3) Angstrom, alpha = 73.77(1)degrees, beta = 87.41(1)degrees, gamma = 82.07(1)degrees, Z = 2, T = -130(1)degrees C; (2) [Fe(OEP)(N-MeIm)(2)][Ag(N-MeIm)(2)][PF6](2), P1 ($) over bar, a = 10.577(2) Angstrom, b = 11.322(2) Angstrom, c = 13.205(2) Angstrom, alpha = 66.61(2)degrees, beta = 82.43(2)degrees, gamma = 77.51(2)degrees, Z = 1, T = -100(1)degrees C; (3) [Fe(OEP)(DMSO)(2)][PF6], monoclinic, C2/c, a = 21.877(4) Angstrom, b = 14.680(3) Angstrom, c = 14.593(3) Angstrom, beta = 93.43(3)degrees, Z = 4, T = -100(1)degrees C. : These data have been of particular value in the study of natural and model heme systems. Core-size correlations, plots of the porphyrin-ring center to pyrrole nitrogen (Ct-N) distances versus rR frequencies, are frequently utilized to assess structural properties or to confirm spectral assignments. However, in most cases, such plots for beta-pyrrole-substituted porphyrins are limited by the use of Ct-N distances derived from the crystal structures of meso-tetraphenylporphyrins. Because of well-documented structural and spectroscopic differences in these two classes of porphyrins, the utility of such core-size correlations may be impaired. Here we report the crystal structures of three new octaethylporphyrin (OEP) complexes : (1) Fe(OEP)(NCS). C7H8, triclinic, P1 ($) over bar, a = 11.669(2) Angstrom, b = 12.151(2) Angstrom, c = 14.251(3) Angstrom, alpha = 73.77(1)degrees, beta = 87.41(1)degrees, gamma = 82.07(1)degrees, Z = 2, T = -130(1)degrees C; (2) [Fe(OEP)(N-MeIm)(2)][Ag(N-MeIm)(2)][PF6](2), P1 ($) over bar, a = 10.577(2) Angstrom, b = 11.322(2) Angstrom, c = 13.205(2) Angstrom, alpha = 66.61(2)degrees, beta = 82.43(2)degrees, gamma = 77.51(2)degrees, Z = 1, T = -100(1)degrees C; (3) [Fe(OEP)(DMSO)(2)][PF6], monoclinic, C2/c, a = 21.877(4) Angstrom, b = 14.680(3) Angstrom, c = 14.593(3) Angstrom, beta = 93.43(3)degrees, Z = 4, T = -100(1)degrees C.