Jameson GB, Molinaro FS, Ibers JA, Collman JP, Brauman JI, Rose E, Suslick KS. . The limiting value of eff is 5.3 B at 302 K, slightly larger than that expected for the spin-only moment. All hydrogen atoms were included in subsequent cycles of least-squares refinement as fixed idealized contributors (C-H = 0.95 , N-H = 0.90 and B(H) = B(C,N) 1.3). This correction is often accomplished by using tabulated values for the diamagnetism of atoms, ions, or whole molecules. The individual N-O bond lengths for the nitrate ligand are given in Table 2. These unusually large quadrupole splitting values likely arise from a significant bonding orbital contribution to the EFG from the anionic axial ligand and that dxy becomes the lowest d-orbital in energy and hence doubly occupied. Granger DL, Taintor RR, Boockvar KS, Hibbs JB.
C6H5Cl. The question of spin state however remains. This bond length is longer in [Fe(TpivPP)(NO3)]- than in the two iron(III) species with monodentate binding of nitrate due to the added electron. Also included in the diagram are the averaged values of the unique bond lengths () and angles (degrees) in the porphyrin core. In iron(III) porphyrin nitrate complexes, bonding of the axial nitrate ligand is exclusively through oxygen, although the denticity varies greatly.
The nitrate is bound in a monodentate fashion with the Fe-O(NO3) vector close to normal to the porphyrin plane and an Fe-O(NO3) bond length of 2.069(4) . Bethesda, MD 20894, Web Policies The species [Fe(TpivPP)(SC6HF4)]- and [Fe(TpivPP)(THF)2] also have the usual, smaller quadrupole splittings of 2 mm/s. Schappacher M, Ricard L, Weiss R, Montiel-Montoya R, Gonser U, Bill E, Trautwein AX. The iron atom displacement for [Fe(TpivPP)(NO3)]- is 0.49 and Fe-Np is 2.070(16) , which is at the low end of the range of Fe-Np bond lengths for high-spin iron(II) porphyrin complexes (2.07 -2.11 ).53. FOIA Summary. An ORTEP drawing of this counterion is given in Figure 4. The iron is significantly displaced out of the 24-atom porphyrin plane toward the nitrate ligand by 0.49 and by 0.42 from the four nitrogen atom plane. Individual bond lengths and angles are given in the Supporting Information. The iron atom is five coordinate, bound to the four porphyrin nitrogen atoms and to a single oxygen atom of the nitrate ligand. The molecular structure of [Fe(TpivPP)(NO3)]- is illustrated in Figure 1. Crystalline [K(222)][Fe(TpivPP)(NO3)] was also studied by solid-state Mssbauer measurements. A new five-coordinate iron(II) anionic porphyrin species has been synthesized and characterized. Thermal probability ellipsoids are drawn at the 50% level. This information is given in Figure 3. Concurrently, the orientation of the nitrate ligand plane with respect to porphyrin plane also varies greatly. The typical quadrupole splitting for a six-coordinate low-spin ferrous porphyrin species is 1 mm/s with decreased values for more -bonding axial ligands (confer Table 3). Consequently, the average Fe-Np bond lengths for high-spin iron(II) complexes are elongated compared to low-spin complexes. Both the cryptand and the KNO3 must be carefully recrystallized to remove halide impurities which bind strongly to iron(II) species. The average K-O(222) distance is 2.82(2) and the average K-N(222) bond length is 3.05(2) . ORTEP diagram of the K(222) cation. Eich RF, Li T, Lemon DD, Doherty DH, Curry SR, Aitken JF, Mathews AJ, Johnson KA, Smith RD, Phillips GN. Systematics of the Stereochemistry of Porphyrins and Metalloporphyrins. Long Fe-L bond lengths characterize high-spin complexes. 8600 Rockville Pike Since there is no structural information on iron coordinated to nitrate in a protein, even though there are proposed intermediates of such species, the structural and magnetic information gathered here will be of use for characterization of future biologically significant molecules of this type. The five-coordinate, high-spin, neutral species, [Fe(TpivPP)(2-MeHIm)], has a Soret band at 436 nm.36 As stated above, the high-spin iron(II) halide and oxyanionic (RO-) species have Soret maxima around 440 nm. Measured magnetic susceptibilities of paramagnetic substances must typically be corrected for their underlying diamagnetism. (Contains 6 tables and 1 figure.). Weak field ligands such as the halides and imidazoles yield high-spin species. Momenteau M, Scheidt WR, Eigenbrot CW, Reed CA. Careers, The publisher's final edited version of this article is available at, GUID:1E86E6FC-C2FA-4F02-A118-42645465835E, Abbreviations used in this paper include Porph, a generalized porphyrin dianion; TpivPP, dianion of ( ,,,-tetrakis(.
The quadrupole splitting for high-spin iron(II) complexes however, varies greatly. Mashiko T, Kastner ME, Spartalian K, Scheidt WR, Reed CA. The ligand plane nearly bisects the two shorter Fe-Np bonds. These values and other selected bond lengths are given in Table 1. The negative charge of the [Fe(TpivPP)(NO3)]- anion is balanced by a potassium-222 counterion. Although definitive structural data are not available, it appears that some iron(III) porphyrinate species can adopt either monodentate or bidentate nitrate coordination modes. Schappacher M, Ricard L, Fischer J, Weiss R, Montiel-Montoya R, Bill E, Trautwein AX. Final cycles of full-matrix least-squares used anisotropic temperature factors for all heavy atoms. Safo MK, Nesset MJM, Walker FA, Debrunner PG, Scheidt WR. Illustrated are the displacements of each atom from the mean plane of the 24-atom core in units of 0.01 . The position of the Soret band is red-shifted compared to the iron(III) nitrate species, [Fe(TPP)(NO3)], which appears at 412 nm in methylene chloride.20 Similar red shifts are seen when comparing iron(III) vs iron(II) chloride and also acetate species.
The magnetic susceptibility for [K(222)][Fe(TpivPP)(NO3)] was measured between 1.91 and 302 K. A plot of the magnetic data is shown in Figure 5. Hydrogen atoms have been omitted for clarity. Blood Substitutes: Physiological Basis of Efficacy. This figure shows the core atom displacements (in units of 0.01 ) from the 24-atom mean porphyrin plane. The N(8)-H(N8)O(12) hydrogen bond distance is 2.33 . ORTEP diagram of [Fe(TpivPP)(NO3)]- showing the position of the nitrate ligand in the pocket of the picket fence porphyrin. Porphyrin species with isomer shift values of 0.8-1 mm/s are expected for high-spin iron(II).54 Indeed, the isomer shift for [Fe(TpivPP)(NO3)]- of 0.98 mm/s at 77 K strongly supports a high-spin state assignment for this species. At convergence, R1 = 0.074 and R2 = 0.093, the error of fit was 1.88 and the final data/variable ratio was 20.1. The synthesis of the iron(II) species, [K(222)][Fe(TpivPP)(NO3)], involves the addition of [FeIITpivPP] (made by reduction of the triflate complex, [Fe(TpivPP)(SO3CF3)(H2O)] with zinc amalgam) to excess potassium nitrate solubilized by the cryptand, Kryptofix-222 under strict anaerobic conditions. Crystalline [K(222)][Fe(TpivPP)(NO3)] was then obtained by slow diffusion of pentane into the chlorobenzene solution. Thermal probability ellipsoids are drawn at the 50% level. At the beginning of our investigation, before an adequate recrystallization of the Kryptofix-222 and KNO. Schappacher M, Weiss R, Montiel-Montoya R, Trautwein A, Tabard A. Inorg Chem. There is a hydrogen bond between a nitrate anion oxygen atom and one of the picket amido groups.
In five-coordinate iron(II) porphyrinates, the nature of the axial ligand determines the spin state. The molecular structure, specifically the geometry at iron, can be a strong indicator of spin state. In the iron(III) derivative, [Fe(TpivPP)(NO3)], there are also two long and two short Fe-Np bonds but the nitrate ligand nearly eclipses the two long bonds which are across from each other.19 The significance of the varied modes of binding of the nitrate ligand are not clear but likely result in different electronic structures at iron which may in turn affect the reactivity of the different iron species. We thank the National Institutes of Health for support of this research under Grants GM-38401 (WRS), and HL-16860 (GL). These low-spin iron(II) species are also characterized with decreased isomer shifts (Fe < 0.5 mm/s). For instance, high-spin iron(II) five-coordinate complexes have typical Fe out-of-plane displacements of 0.5 and high-spin six-coordinate species have expanded porphyrin cores.
. The temperature dependence, displayed in Figure 5, is consistent with a significant zero field splitting parameter of 10 cm-1. INOR 29. Positive values of displacement are toward the nitrate ligand. HHS Vulnerability Disclosure, Help Previous studies28,31,55,56 suggest that species of the general formula [Fe(Porph)(X)]- where X is a halide ion, or an anionic oxygen-donor ligand have distinctively large quadrupole splittings ( EQ 3.5-4 mm/s).
The monodentate iron-oxygen bond length is 2.069(4) and the average equatorial Fe-Np bond length is 2.070(16) . The unusually large quadrupole splitting value found in the Mssbauer spectrum is similar to those found for other species of the type [Fe(Porph)(X)]- but distinctly different in magnitude and sign than those found for deoxymyoglobin, deoxyhemoglobin, and their model compounds.
Collman JP, Hoard JL, Kim N, Lang G, Reed CA. Caron C, Mitschler A, Riviere G, Schappacher M, Weiss RJ. Also shown in this figure are the individual iron-porphyrin nitrogen bond lengths and the closest interaction between a pivolyl group of the picket fence porphyrin and the nitrate ligand. Hu C, Roth A, Ellison MK, An J, Ellis CM, Schulz CE, Scheidt WR. This material is available free of charge via the Internet at http://pubs.acs.org. National Library of Medicine 31 The remaining axial ligand and solvent atoms were found from a difference Fourier calculation.32. Interestingly however, the Soret maximum for the low-spin iron(II) anionic species, [Fe(TpivPP)(NO2)]-, is also in this area at 444 nm.15,16. Magnetic susceptibility of [K(222)][Fe(TpivPP)(NO3)] over the temperature range of 1.91 to 302 K. Solid-State Mssbauer Parameters for[Fe(TpivPP)(NO3)]- and Related Derivatives, Although there are several iron(III) porphyrin nitrate species of the general formula [Fe(Porph)-(NO3)] structurally characterized,19-22 [Fe(TpivPP)(NO3)]- is the first such iron(II) species characterized. American Society for Biochemistry and Molecular Biology, Biochemical and Biophysical Research Communications, Journal of agricultural and food chemistry. The large iron out-of-plane displacement and long Fe-Np bond lengths shows a high-spin state assignment for this species. Formal diagram of the porphyrinato core of [Fe(TpivPP)(NO3)]-. Reed CA, Mashiko T, Scheidt WR, Spartalian K, Lang GJ. The magnetic data confirm this assignment. April 1974; Washington, D. C.: American Chemical Society; Abstracts of Papers. Picket fence porphyrin was used to provide a protective binding pocket thought to reduce the risk of O-atom transfer chemistry known to occur in iron(III) nitrite species.52 A solution electronic spectrum confirmed the synthesis, and persistence in solution, of a new species with a Soret band at 438 nm in chlorobenzene.
The eight-coordinate potassium ion is bonded to six oxygen atoms and two nitrogen atoms. 2006 Jul 10; 45(14): 52845290. We thank Prof. C. A. Reed for assistance in obtaining the magnetic susceptibility data. The nitrate ligand in [Fe(TPP)(O2NO)] is bound in a near symmetrical bidentate fashion.22 In [Fe(TpivPP)(O2NO)] the nitrate ligand is bound in a more symmetrical bidentate fashion; that is the two Fe-O bond lengths are nearly equivalent.19 The large denticity range from monodentate to a nearly symmetrical bidentate fashion in these iron(III) nitrate species results in a large range of Fe-O bond lengths (1.966-2.323 ). Collman JP, Kim N, Hoard JL, Lang G, Radonovich LJ, Reed CA. ORTEP diagram of [Fe(TpivPP)(NO3)]- looking onto the porphyrin plane from the pocket side of the picket fence porphyrin. This new compound has been characterized by UV-vis and Mssbauer spectroscopies, magnetic susceptibility, and a single-crystal X-ray structure determination. The synthesis of [Fe(TpivPP)(NO3)]- involves addition of excess KNO3 solubilized with a cryptand to the four coordinate iron(II) species, [Fe(TpivPP)], under anaerobic conditions. Scheidt WR, Brinegar AC, Ferro EB, Kirner JF. In: Kadish KM, Smith K, Guilard R, editors. In the iron(II) species, [Fe(TpivPP)(NO3)]-, the nitrate anion is in the pocket of the picket fence porphyrin as is almost always the case for complexes of the general formula [Fe(TpivPP)(X)]0/-, where X is an anionic ligand.
The dihedral angle between the nitrate plane and the closest Np-Fe-O angle ranges from 10 to 45 (Table 2). The nitrate ligand plane nearly bisects an Np-Fe-Np angle as can be seen in Figure 2. Complete crystallographic details, atomic coordinates, anisotropic thermal parameters, and fixed hydrogen atom coordinates are included in the Supporting Information. Iron-axial ligand bond lengths are also indicative of spin state. Wyllie GRA, Munro OQ, Schulz CE, Scheidt WR. This bidentate nitrate possibility for iron(II) is being explored. Strong axial ligands such as NO and CS result in low-spin complexes. These tabulated values can be problematic since many sources contain incomplete and conflicting data. Iron(II) porphyrinates with oxyanionic ligands are either high- or low-spin. Acknowledgments. The quadrupole splitting and isomer shift were found to be 3.59 mm/s and 0.98 mm/s respectively, at 77 K and 3.56 and 0.98 mm/s at 4.2 K. These values of EQ and Fe are given in Table 3 along with Mssbauer data for related iron(II) and iron(III) porphyrin species. Scheidt WR.
Supporting Information Available: Tables S1-S6 giving complete crystallographic information. The diagram also gives the averaged values of each distinct bond distance and angle in the porphyrinato core. Final difference Fourier maps were judged to be significantly free of features.
Hydrogen atoms have been omitted for clarity except for the amide hydrogen atom nearest the nitrate ligand. Bominaar EL, Ding X-Q, Gismelseed A, Bill E, Winkler H, Trautwein AX, Nasri H, Fischer J, Weiss R. Kent TA, Spartalian K, Lang G, Yonetani T, Reed CA, Collman JP. Further exploration of possible classes of high-spin iron(II) porphyrinates is in progress.57. The porphyrin core is modestly ruffled and there is a small (0.07 ) doming toward the nitrate ligand. Indeed the quadrupole splitting for [Fe(TpivPP)(NO3)]- at 3.59 mm/s is consistent with their findings. Mssbauer spectroscopy was used to characterize the electronic structure of [Fe(TpivPP)-(NO3)]-. The nitrate ligand is bound inside the pocket formed by the pivalamide groups of the picket fence porphyrin. 167th National Meeting of the American Chemical Society; Los Angeles, CA. So the question remains, will nitrate result in a low-spin or high-spin species? From the single-crystal structure determination, the nitrate ligand is found to be bound in a monodentate fashion. The neutral five-coordinate imidazole species, [Fe(Porph)(RIm)], as well as deoxyhemoglobin and -myoglobin have values for the quadrupole splitting of 2 mm/s and are negative in sign. For example, in the two crystalline forms of [Fe(OEP)(NO3)], the nitrate is bound in a monodentate fashion.21,22 However, in the triclinic form the Fe-O bond length is significantly longer than in the monoclinic form (confer Table 2). Nasri H, Fischer J, Weiss R, Bill E, Trautwein A. Mandon D, Ott-Woelfel F, Fischer J, Weiss R, Bill E, Trautwein AX. For example, nitrite yields an N-bound low-spin species16 and methoxide,31 acetate,42 and phenolate23 yield high-spin species. The S = 2 spin state has also been confirmed from the measurement of the temperature-dependent magnetic susceptibility. Selected Bond Parameters () for Five-coordinate Iron(II) Porphyrin Derivatives, Summary of Bond Parameters for Iron(II) and Iron(III) Nitrate-Coordinated Porphyrin Derivatives. Accessibility As can be seen from Figure 2, the oxygen atom is directly over the iron atom which corresponds to a long FeO(NO3) distance to the next closest oxygen atom of the nitrate ligand.
Nasri H, Wang Y, Huynh BH, Walker FA, Scheidt WR. Selected bond lengths are given (in ). Polam JR, Wright JL, Christensen KA, Walker FA, Flint H, Winkler H, Grodzicki M, Trautwein AX. After isotropic least-squares refinement had been carried to convergence, difference Fourier syntheses suggested possible locations for all hydrogen atoms. Nasri H, Haller KJ, Wang Y, Huynh BH, Scheidt WR. For instance, the Soret for [Fe(TPP)Cl] is at 417 nm with that for [Fe(TpivPP)Cl]- at 446 nm28 and the Soret of [Fe(TpivPP)(O2CCH3)] at 414 nm shifts to 448 nm for [Fe(TpivPP)(O2CCH3)]- in chlorobenzene.31 So, the solution electronic spectrum for [Fe(TpivPP)(NO3)]- alone suggests the formation of a new iron(II) porphyrin species. This article presents an explanation for the origin of the diamagnetic correction factors, organized tables of constants compiled from many sources, a simple method for estimating the correct order of magnitude for the diamagnetic correction for any given compound, a clear explanation of how to use the tabulated constants to calculate the diamagnetic susceptibility, and a worked example for the magnetic susceptibility of copper acetate. Nasri H, Ellison MK, Krebs C, Huynh BH, Scheidt WR.