MODELS OF THE CYTOCHROMES-B - LOW-SPIN BIS-LIGATED (PORPHINATO)IRON(III) COMPLEXES WITH UNUSUAL MOLECULAR-STRUCTURES AND NMR, EPR, AND MOSSBAUER-SPECTRA

被引:171
作者
SAFO, MK
GUPTA, GP
WATSON, CT
SIMONIS, U
WALKER, FA
SCHEIDT, WR
机构
[1] UNIV NOTRE DAME, DEPT CHEM & BIOCHEM, NOTRE DAME, IN 46556 USA
[2] PENN STATE UNIV, DEPT PHYS, University Pk, PA 16802 USA
[3] UNIV ARIZONA, DEPT CHEM, TUCSON, AZ 85721 USA
[4] SAN FRANCISCO STATE UNIV, DEPT CHEM & BIOCHEM, SAN FRANCISCO, CA 94132 USA
关键词
D O I
10.1021/ja00044a017
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The synthesis and characterization of the following bis-pyridine and bis-imidazole complexes of (tetramesityl-porphinato)iron(III) are reported: [Fe(TMP)(4-NH2PY)2]ClO4, 1, [Fe(TMP)(3-EtPy)2]ClO4, 2, [Fe(TMP)(3-ClPY)2]ClO4, 3, [Fe(TMP)(2-MeHIm)2]ClO4,4, [Fe(TMP)(4-CNPY)2]ClO4, 5, and [Fe(TMP)(3-CNPY)2]ClO4,6. The crystal structures of complexes 2, 3, and 5 are reported. All three complexes have relative perpendicular alignment of the axial ligands with bond lengths consistent with low-spin iron(III). The porphinato cores are strongly S4 ruffled; the Fe-N(p) bonds show a commensurate shortening. EPR investigations reveal "large g(max)" type EPR spectra for complexes 1-4, with complexes 2, 3, and 4 having unusually low g values (<3.2). Complex 1 has a "normal" "large g(max)" g value of 3.40. Complexes 5 and 6 have axial EPR spectra with g(perpendicular-to) = 2.53 and g(parallel-to) = 1.56 or g(perpendicular-to) = 2.62 and g(parallel-to) unresolved, which result from a substantial change in the usual ground state of low-spin (porphinato)iron(III) complexes, (d(xy))2(d(xz),d(yz))3, to that having a predominantly (d(x2),d(yz))4(d(xy))1 ground state. Complexes 2, 3, 4, and 5 have been characterized by Mossbauer spectroscopy. The Mossbauer isomer shifts (delta) range from 0. 1 8 to 0.20 mm/s and the quadrupole splittings (DELTA-E(Q)) from 0.97 to 1.48 mm/s. The quadrupole splittings, like the EPR g values of these complexes, are unusually low, compared with DELTA-E(Q) values of approximately 1.7-1.8 mm/s expected for imidazole complexes with perpendicular axial ligand orientation. The H-1 NMR isotropic shifts at -80-degrees-C (193 K) of the pyrrole protons of all complexes except 1 and 2, but including additional low-spin bis-pyridine complexes with 4-NMe2, 3,4-Me2, 3,5-Me2, 4-Me, and 3-Me substituents and pyridine itself as axial ligands, varied from -39.5 ppm (4-NMe2PY) to -6.5 ppm (4-CNPy) through this series. This result indicates a smooth change from an electronic ground state which is largely (d(xy))2(d(xz),d(yz))3 to one which is at least 50% (d(xz),d(yz))4(d(xy))1 in nature at 193 K for the (4-CNPy)2 complex, supporting the conclusions reached on the basis of the variation of EPR and Mossbauer parameters observed at 77 K and below.
引用
收藏
页码:7066 / 7075
页数:10
相关论文
共 104 条
[21]   ISOTROPIC NUCLEAR MAGNETIC-RESONANCE SHIFTS IN LOW-SPIN IRON(III) PORPHYRIN AND HEMIN SYSTEMS - THEORETICAL INTERPRETATION OF TEMPERATURE DEPENDENCIES [J].
HORROCKS, WD ;
GREENBERG, ES .
MOLECULAR PHYSICS, 1974, 27 (04) :993-999
[22]   EVALUATION OF DIPOLAR NUCLEAR MAGNETIC-RESONANCE SHIFTS IN LOW-SPIN HEMIN SYSTEM - FERRICYTOCHROME C AND METMYOGLOBIN CYANIDE [J].
HORROCKS, WD ;
GREENBER.ES .
BIOCHIMICA ET BIOPHYSICA ACTA, 1973, 322 (01) :38-44
[23]  
HUYNH BH, 1984, J BIOL CHEM, V259, P5373
[24]  
HUYNH BH, 1982, J BIOL CHEM, V257, P9576
[25]  
HUYNH BH, COMMUNICATION
[26]   THE ELECTRONIC-STRUCTURE OF HIGHLY ANISOTROPIC LOW-SPIN FERRIC PORPHYRIN COMPLEXES BASED ON SINGLE-CRYSTAL ELECTRON-PARAMAGNETIC-RES MEASUREMENTS [J].
INNISS, D ;
SOLTIS, SM ;
STROUSE, CE .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1988, 110 (17) :5644-5650
[27]   MOSSBAUER STUDY OF IMIDAZOLE AND N-HETEROCYCLIC COMPLEXES OF PENTACYANOIRON(II) AND PENTACYANOIRON(III) [J].
JOHNSON, CR ;
SHEPHERD, RE .
INORGANIC CHEMISTRY, 1983, 22 (24) :3506-3513
[28]   PHOTOELECTRON-SPECTRA OF TETRAPHENYLPORPHINE AND SOME METALLOTETRAPHENYLPORPHYRINS [J].
KHANDELWAL, SC ;
ROEBBER, JL .
CHEMICAL PHYSICS LETTERS, 1975, 34 (02) :355-359
[29]   PHOTOELECTRON SPECTROSCOPIC STUDY ON METALLOOCTAETHYLPORPHYRINS [J].
KITAGAWA, S ;
MORISHIMA, I ;
YONEZAWA, T ;
SATO, N .
INORGANIC CHEMISTRY, 1979, 18 (05) :1345-1349
[30]   EXTENDED X-RAY ABSORPTION FINE-STRUCTURE STUDIES OF CYTOCHROMES-C - STRUCTURAL ASPECTS OF OXIDATION REDUCTION [J].
KORSZUN, ZR ;
MOFFAT, K ;
FRANK, K ;
CUSANOVICH, MA .
BIOCHEMISTRY, 1982, 21 (09) :2253-2258