Models for the Active Site of Oxygen-Binding Hemoproteins. Dioxygen Binding Properties and the Structures of (2-Methylimidazole)-meso-tetra(α,α,α,α-o-Pivalamidophenyl)porphyrinatoiron(II)-Ethanol and Its Dioxygen Adduct

Geoffrey B. Jameson, Frank S. Molinaro, James A. Ibers, James P. Coliman, John I. Brauman, Eric Rose, Kenneth S. Suslick

Research output: Contribution to journalArticle

Abstract

When crystals of (2-methylimidazole)-mcro-tetra(α,α,α,α-o-pivalamidophenyl)porphyrinatoiron(II)-ethanol, Fe(TpivPP)(2-MeIm)-EtOH, are exposed to dioxygen, the crystals of the resultant dioxygen adduct are still suitable for diffraction studies. The direct, precise determination of the stereochemical changes accompanying oxygenation of an iron(ll)- (porphyrinato)(base) complex has been carried out using conventional X-ray diffraction methods. The structures have been refined by full-matrix, least-squares methods, using 4176 and 5183 reflections for the deoxy and oxy complexes, respectively, to R indices on F2 of 0.162 and 0.120. For the portion of data where F02 > 3σ(F02) the respective indices on F are 0.086 and 0.083. Crystal data for the deoxy compound follow: space group C62h-C2/c, Z = 4, molecular symmetry C2, a = 18.871 (11) Å, b = 19.425 (13) Å, c = 18.434 (11) Å, β = 91.48 (3)°, V = 6755.0 Å3. The oxy complex is nearly isomorphic with Z = 4 in space group C2/c with a cell of dimensions a = 18.864 (5) Å, b = 19.451 (5) Å, c = 18.287 (5) Å, β = 91.45 (2)°, V = 6707.0 Å3. Some selected parameters for the coordination spheres, with those in square brackets pertaining to the dioxygen adduct, follow: Fe-Nporph = 2.068 (5), 2.075 (5) [1.997 (4), 1.995 (4)] Å; Fe-N1m = 2.095 (6) [2.107 (4)] Å. The iron atom is displaced 0.399 [0.086] Å from the least-squares plane of the porphinato nitrogen atoms toward the imidazole ligand. The Fe-O separation is 1.898 (7) Å. The average O-O separation is 1.22 (2) Å and the Fe-O-O angle is 129 (1)°, In the presence of ethanol the deoxy complex binds dioxygen reversibly, noncooperatively, and with lower affinity than when the sample is desolvated- in the latter case dioxygen uptake has been found to be cooperative. The structure and properties of these possible models for T-state deoxy- and oxyhemoglobin are correlated and then compared with the 1-methylimidazole analogue. The sterically active 2-methyl substituent appears to perturb the Fe-O bond but not the Fe-N|m bond.

Original languageEnglish (US)
Pages (from-to)3224-3237
Number of pages14
JournalJournal of the American Chemical Society
Volume102
Issue number9
DOIs
StatePublished - Apr 1980

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ethanol
Reactive Oxygen Species
Catalytic Domain
Ethanol
crystal
Oxygen
oxygen
Crystals
Iron
iron
Atoms
Least-Squares Analysis
Oxygenation
oxygenation
least squares method
diffraction
ligand
symmetry
Diffraction
Oxyhemoglobins

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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Models for the Active Site of Oxygen-Binding Hemoproteins. Dioxygen Binding Properties and the Structures of (2-Methylimidazole)-meso-tetra(α,α,α,α-o-Pivalamidophenyl)porphyrinatoiron(II)-Ethanol and Its Dioxygen Adduct. / Jameson, Geoffrey B.; Molinaro, Frank S.; Ibers, James A.; Coliman, James P.; Brauman, John I.; Rose, Eric; Suslick, Kenneth S.

In: Journal of the American Chemical Society, Vol. 102, No. 9, 04.1980, p. 3224-3237.

Research output: Contribution to journalArticle

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title = "Models for the Active Site of Oxygen-Binding Hemoproteins. Dioxygen Binding Properties and the Structures of (2-Methylimidazole)-meso-tetra(α,α,α,α-o-Pivalamidophenyl)porphyrinatoiron(II)-Ethanol and Its Dioxygen Adduct",
abstract = "When crystals of (2-methylimidazole)-mcro-tetra(α,α,α,α-o-pivalamidophenyl)porphyrinatoiron(II)-ethanol, Fe(TpivPP)(2-MeIm)-EtOH, are exposed to dioxygen, the crystals of the resultant dioxygen adduct are still suitable for diffraction studies. The direct, precise determination of the stereochemical changes accompanying oxygenation of an iron(ll)- (porphyrinato)(base) complex has been carried out using conventional X-ray diffraction methods. The structures have been refined by full-matrix, least-squares methods, using 4176 and 5183 reflections for the deoxy and oxy complexes, respectively, to R indices on F2 of 0.162 and 0.120. For the portion of data where F02 > 3σ(F02) the respective indices on F are 0.086 and 0.083. Crystal data for the deoxy compound follow: space group C62h-C2/c, Z = 4, molecular symmetry C2, a = 18.871 (11) {\AA}, b = 19.425 (13) {\AA}, c = 18.434 (11) {\AA}, β = 91.48 (3)°, V = 6755.0 {\AA}3. The oxy complex is nearly isomorphic with Z = 4 in space group C2/c with a cell of dimensions a = 18.864 (5) {\AA}, b = 19.451 (5) {\AA}, c = 18.287 (5) {\AA}, β = 91.45 (2)°, V = 6707.0 {\AA}3. Some selected parameters for the coordination spheres, with those in square brackets pertaining to the dioxygen adduct, follow: Fe-Nporph = 2.068 (5), 2.075 (5) [1.997 (4), 1.995 (4)] {\AA}; Fe-N1m = 2.095 (6) [2.107 (4)] {\AA}. The iron atom is displaced 0.399 [0.086] {\AA} from the least-squares plane of the porphinato nitrogen atoms toward the imidazole ligand. The Fe-O separation is 1.898 (7) {\AA}. The average O-O separation is 1.22 (2) {\AA} and the Fe-O-O angle is 129 (1)°, In the presence of ethanol the deoxy complex binds dioxygen reversibly, noncooperatively, and with lower affinity than when the sample is desolvated- in the latter case dioxygen uptake has been found to be cooperative. The structure and properties of these possible models for T-state deoxy- and oxyhemoglobin are correlated and then compared with the 1-methylimidazole analogue. The sterically active 2-methyl substituent appears to perturb the Fe-O bond but not the Fe-N|m bond.",
author = "Jameson, {Geoffrey B.} and Molinaro, {Frank S.} and Ibers, {James A.} and Coliman, {James P.} and Brauman, {John I.} and Eric Rose and Suslick, {Kenneth S.}",
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T1 - Models for the Active Site of Oxygen-Binding Hemoproteins. Dioxygen Binding Properties and the Structures of (2-Methylimidazole)-meso-tetra(α,α,α,α-o-Pivalamidophenyl)porphyrinatoiron(II)-Ethanol and Its Dioxygen Adduct

AU - Jameson, Geoffrey B.

AU - Molinaro, Frank S.

AU - Ibers, James A.

AU - Coliman, James P.

AU - Brauman, John I.

AU - Rose, Eric

AU - Suslick, Kenneth S.

PY - 1980/4

Y1 - 1980/4

N2 - When crystals of (2-methylimidazole)-mcro-tetra(α,α,α,α-o-pivalamidophenyl)porphyrinatoiron(II)-ethanol, Fe(TpivPP)(2-MeIm)-EtOH, are exposed to dioxygen, the crystals of the resultant dioxygen adduct are still suitable for diffraction studies. The direct, precise determination of the stereochemical changes accompanying oxygenation of an iron(ll)- (porphyrinato)(base) complex has been carried out using conventional X-ray diffraction methods. The structures have been refined by full-matrix, least-squares methods, using 4176 and 5183 reflections for the deoxy and oxy complexes, respectively, to R indices on F2 of 0.162 and 0.120. For the portion of data where F02 > 3σ(F02) the respective indices on F are 0.086 and 0.083. Crystal data for the deoxy compound follow: space group C62h-C2/c, Z = 4, molecular symmetry C2, a = 18.871 (11) Å, b = 19.425 (13) Å, c = 18.434 (11) Å, β = 91.48 (3)°, V = 6755.0 Å3. The oxy complex is nearly isomorphic with Z = 4 in space group C2/c with a cell of dimensions a = 18.864 (5) Å, b = 19.451 (5) Å, c = 18.287 (5) Å, β = 91.45 (2)°, V = 6707.0 Å3. Some selected parameters for the coordination spheres, with those in square brackets pertaining to the dioxygen adduct, follow: Fe-Nporph = 2.068 (5), 2.075 (5) [1.997 (4), 1.995 (4)] Å; Fe-N1m = 2.095 (6) [2.107 (4)] Å. The iron atom is displaced 0.399 [0.086] Å from the least-squares plane of the porphinato nitrogen atoms toward the imidazole ligand. The Fe-O separation is 1.898 (7) Å. The average O-O separation is 1.22 (2) Å and the Fe-O-O angle is 129 (1)°, In the presence of ethanol the deoxy complex binds dioxygen reversibly, noncooperatively, and with lower affinity than when the sample is desolvated- in the latter case dioxygen uptake has been found to be cooperative. The structure and properties of these possible models for T-state deoxy- and oxyhemoglobin are correlated and then compared with the 1-methylimidazole analogue. The sterically active 2-methyl substituent appears to perturb the Fe-O bond but not the Fe-N|m bond.

AB - When crystals of (2-methylimidazole)-mcro-tetra(α,α,α,α-o-pivalamidophenyl)porphyrinatoiron(II)-ethanol, Fe(TpivPP)(2-MeIm)-EtOH, are exposed to dioxygen, the crystals of the resultant dioxygen adduct are still suitable for diffraction studies. The direct, precise determination of the stereochemical changes accompanying oxygenation of an iron(ll)- (porphyrinato)(base) complex has been carried out using conventional X-ray diffraction methods. The structures have been refined by full-matrix, least-squares methods, using 4176 and 5183 reflections for the deoxy and oxy complexes, respectively, to R indices on F2 of 0.162 and 0.120. For the portion of data where F02 > 3σ(F02) the respective indices on F are 0.086 and 0.083. Crystal data for the deoxy compound follow: space group C62h-C2/c, Z = 4, molecular symmetry C2, a = 18.871 (11) Å, b = 19.425 (13) Å, c = 18.434 (11) Å, β = 91.48 (3)°, V = 6755.0 Å3. The oxy complex is nearly isomorphic with Z = 4 in space group C2/c with a cell of dimensions a = 18.864 (5) Å, b = 19.451 (5) Å, c = 18.287 (5) Å, β = 91.45 (2)°, V = 6707.0 Å3. Some selected parameters for the coordination spheres, with those in square brackets pertaining to the dioxygen adduct, follow: Fe-Nporph = 2.068 (5), 2.075 (5) [1.997 (4), 1.995 (4)] Å; Fe-N1m = 2.095 (6) [2.107 (4)] Å. The iron atom is displaced 0.399 [0.086] Å from the least-squares plane of the porphinato nitrogen atoms toward the imidazole ligand. The Fe-O separation is 1.898 (7) Å. The average O-O separation is 1.22 (2) Å and the Fe-O-O angle is 129 (1)°, In the presence of ethanol the deoxy complex binds dioxygen reversibly, noncooperatively, and with lower affinity than when the sample is desolvated- in the latter case dioxygen uptake has been found to be cooperative. The structure and properties of these possible models for T-state deoxy- and oxyhemoglobin are correlated and then compared with the 1-methylimidazole analogue. The sterically active 2-methyl substituent appears to perturb the Fe-O bond but not the Fe-N|m bond.

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