The Dioxygen Adduct of meso-Tetraphenylporphyrinmanganese(II), a Synthetic Oxygen Carrier

Brian M Hoffman; Charles J. Weschler; Fred Basolo

doi:10.1021/ja00434a012

The Dioxygen Adduct of meso-Tetraphenylporphyrinmanganese(II), a Synthetic Oxygen Carrier

Brian M Hoffman^*, Charles J. Weschler, Fred Basolo

^*Corresponding author for this work

Chemistry

Research output: Contribution to journal › Article › peer-review

184 Scopus citations

Abstract

In toluene solutions (–79 °C) dioxygen reversibly binds to Mn(TPP)(py) with replacement of the pyridine to form a five-coordinate complex, rather than by addition to yield a six-coordinate species. The resulting Mn(TPP)(O₂) complex surprisingly exhibits the S = 3/2 spin state (D = –2.48 ± 0.07 cm^-1; λ = E/D = 0.3257 ± 0.0003; A_z = –53.1 (±0.5) × 10⁴ cm^-1; Ay = –82.0 (±0.5) × 10^-4cm ^-1; A¹⁷_O = B¹⁷_O = 0). The experimental results, in combination with qualitative bonding considerations, indicate (i) extensive Mn ⟶ O₂ charge transfer and (ii) the appropriateness of an Mn^1v(O₂^2-) valency formalism in which the Mn(IV) is in the ⁴(t₂³) ground state. A linear geometry for the complex can be ruled out. Although further definite conclusions as to structure are not presently possible, we tentatively favor the symmetric, “edge-on” mode of binding.

Original language	English (US)
Pages (from-to)	5473-5482
Number of pages	10
Journal	Journal of the American Chemical Society
Volume	98
Issue number	18
DOIs	https://doi.org/10.1021/ja00434a012
State	Published - Sep 1 1976

ASJC Scopus subject areas

Catalysis
Chemistry(all)
Biochemistry
Colloid and Surface Chemistry

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title = "The Dioxygen Adduct of meso-Tetraphenylporphyrinmanganese(II), a Synthetic Oxygen Carrier",

abstract = "In toluene solutions (–79 °C) dioxygen reversibly binds to Mn(TPP)(py) with replacement of the pyridine to form a five-coordinate complex, rather than by addition to yield a six-coordinate species. The resulting Mn(TPP)(O2) complex surprisingly exhibits the S = 3/2 spin state (D = –2.48 ± 0.07 cm-1; λ = E/D = 0.3257 ± 0.0003; Az = –53.1 (±0.5) × 104 cm-1; Ay = –82.0 (±0.5) × 10-4cm -1; A17O = B17O = 0). The experimental results, in combination with qualitative bonding considerations, indicate (i) extensive Mn ⟶ O2 charge transfer and (ii) the appropriateness of an Mn1v(O22-) valency formalism in which the Mn(IV) is in the 4(t23) ground state. A linear geometry for the complex can be ruled out. Although further definite conclusions as to structure are not presently possible, we tentatively favor the symmetric, “edge-on” mode of binding.",

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AU - Hoffman, Brian M

AU - Weschler, Charles J.

AU - Basolo, Fred

PY - 1976/9/1

Y1 - 1976/9/1

N2 - In toluene solutions (–79 °C) dioxygen reversibly binds to Mn(TPP)(py) with replacement of the pyridine to form a five-coordinate complex, rather than by addition to yield a six-coordinate species. The resulting Mn(TPP)(O2) complex surprisingly exhibits the S = 3/2 spin state (D = –2.48 ± 0.07 cm-1; λ = E/D = 0.3257 ± 0.0003; Az = –53.1 (±0.5) × 104 cm-1; Ay = –82.0 (±0.5) × 10-4cm -1; A17O = B17O = 0). The experimental results, in combination with qualitative bonding considerations, indicate (i) extensive Mn ⟶ O2 charge transfer and (ii) the appropriateness of an Mn1v(O22-) valency formalism in which the Mn(IV) is in the 4(t23) ground state. A linear geometry for the complex can be ruled out. Although further definite conclusions as to structure are not presently possible, we tentatively favor the symmetric, “edge-on” mode of binding.

AB - In toluene solutions (–79 °C) dioxygen reversibly binds to Mn(TPP)(py) with replacement of the pyridine to form a five-coordinate complex, rather than by addition to yield a six-coordinate species. The resulting Mn(TPP)(O2) complex surprisingly exhibits the S = 3/2 spin state (D = –2.48 ± 0.07 cm-1; λ = E/D = 0.3257 ± 0.0003; Az = –53.1 (±0.5) × 104 cm-1; Ay = –82.0 (±0.5) × 10-4cm -1; A17O = B17O = 0). The experimental results, in combination with qualitative bonding considerations, indicate (i) extensive Mn ⟶ O2 charge transfer and (ii) the appropriateness of an Mn1v(O22-) valency formalism in which the Mn(IV) is in the 4(t23) ground state. A linear geometry for the complex can be ruled out. Although further definite conclusions as to structure are not presently possible, we tentatively favor the symmetric, “edge-on” mode of binding.

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The Dioxygen Adduct of meso-Tetraphenylporphyrinmanganese(II), a Synthetic Oxygen Carrier

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