Nitric oxide complexes of manganese and chromium tetraphenylporphyrin

B. B. Wayland, Larry Olson, Z. U. Siddiqui

Research output: Contribution to journalArticle

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Abstract

Nitric oxide forms 1:1 low spin complexes with CrIITPP, CrIIITPP(X), MnIITPP, and MnIIITPP(X) species. MnTPP(X)(NO) (X- = Cl-, CH3CO2-, CN-) and CrTPP(NO) complexes have the S = 1/2 ground state and EPR spectra diagnostic for the odd electron occupying a molecular orbital of predominantly metal dxy character. MnTPP(X)(NO) complexes and the isoelectronic CrTPP(NO) species are assigned the (dxz,yz)4 (dxy)1 ground configuration. Narrow lines in the isptropic EPR spectrum of CrTPP(NO) permit resolution of nitrogen-14 hyperfine from both nitric oxide (6.5 G) and the porphyrin pyrrole nitrogens (3.15 G). The metal nuclear hyperfine coupling constants in these complexes 〈A 55Mn〉 = 88.3 G and 〈A 53Cr〉 = 21.2 G are indicative of the odd electron being relatively localized on the metal. All of these nitric oxide complexes are formulated as M-NO+ species, although dπ → π* bonding substantially reduces this charge separation. Within isoelectronic sets such as (d5) MnTPP(Cl)(NO) (νNO = 1830 cm-1), CrTPP(NO) (νNO = 1700 cm-1), or (d6) FeTPP(Cl)(NO) (νNO = 1880 cm-1), MnTPP(NO) (νNO = 1760 cm-1), the nitric oxide stretching frequencies are substantially smaller for the complex where the metal has the lower formal oxidation state. Electronic spectra for the chromium porphyrin species are typical for metalloporphyrins, while spectra for MnTPP(X) and MnTPP(X)(NO) complexes are highly irregular. VOTPP fails to form a nitric oxide complex even in the low temperature glass media.

Original languageEnglish (US)
Pages (from-to)94-98
Number of pages5
JournalJournal of the American Chemical Society
Volume98
Issue number1
StatePublished - 1976
Externally publishedYes

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Nitric oxide
Chromium
Manganese
Nitric Oxide
Metals
Porphyrins
Paramagnetic resonance
Nitrogen
Metalloporphyrins
Electrons
Pyrroles
Coordination Complexes
Molecular orbitals
Ground state
Stretching
Glass
tetraphenylporphyrin
manganese tetraphenylporphyrin
Oxidation
Temperature

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Nitric oxide complexes of manganese and chromium tetraphenylporphyrin. / Wayland, B. B.; Olson, Larry; Siddiqui, Z. U.

In: Journal of the American Chemical Society, Vol. 98, No. 1, 1976, p. 94-98.

Research output: Contribution to journalArticle

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title = "Nitric oxide complexes of manganese and chromium tetraphenylporphyrin",
abstract = "Nitric oxide forms 1:1 low spin complexes with CrIITPP, CrIIITPP(X), MnIITPP, and MnIIITPP(X) species. MnTPP(X)(NO) (X- = Cl-, CH3CO2-, CN-) and CrTPP(NO) complexes have the S = 1/2 ground state and EPR spectra diagnostic for the odd electron occupying a molecular orbital of predominantly metal dxy character. MnTPP(X)(NO) complexes and the isoelectronic CrTPP(NO) species are assigned the (dxz,yz)4 (dxy)1 ground configuration. Narrow lines in the isptropic EPR spectrum of CrTPP(NO) permit resolution of nitrogen-14 hyperfine from both nitric oxide (6.5 G) and the porphyrin pyrrole nitrogens (3.15 G). The metal nuclear hyperfine coupling constants in these complexes 〈A 55Mn〉 = 88.3 G and 〈A 53Cr〉 = 21.2 G are indicative of the odd electron being relatively localized on the metal. All of these nitric oxide complexes are formulated as M-NO+ species, although dπ → π* bonding substantially reduces this charge separation. Within isoelectronic sets such as (d5) MnTPP(Cl)(NO) (νNO = 1830 cm-1), CrTPP(NO) (νNO = 1700 cm-1), or (d6) FeTPP(Cl)(NO) (νNO = 1880 cm-1), MnTPP(NO) (νNO = 1760 cm-1), the nitric oxide stretching frequencies are substantially smaller for the complex where the metal has the lower formal oxidation state. Electronic spectra for the chromium porphyrin species are typical for metalloporphyrins, while spectra for MnTPP(X) and MnTPP(X)(NO) complexes are highly irregular. VOTPP fails to form a nitric oxide complex even in the low temperature glass media.",
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N2 - Nitric oxide forms 1:1 low spin complexes with CrIITPP, CrIIITPP(X), MnIITPP, and MnIIITPP(X) species. MnTPP(X)(NO) (X- = Cl-, CH3CO2-, CN-) and CrTPP(NO) complexes have the S = 1/2 ground state and EPR spectra diagnostic for the odd electron occupying a molecular orbital of predominantly metal dxy character. MnTPP(X)(NO) complexes and the isoelectronic CrTPP(NO) species are assigned the (dxz,yz)4 (dxy)1 ground configuration. Narrow lines in the isptropic EPR spectrum of CrTPP(NO) permit resolution of nitrogen-14 hyperfine from both nitric oxide (6.5 G) and the porphyrin pyrrole nitrogens (3.15 G). The metal nuclear hyperfine coupling constants in these complexes 〈A 55Mn〉 = 88.3 G and 〈A 53Cr〉 = 21.2 G are indicative of the odd electron being relatively localized on the metal. All of these nitric oxide complexes are formulated as M-NO+ species, although dπ → π* bonding substantially reduces this charge separation. Within isoelectronic sets such as (d5) MnTPP(Cl)(NO) (νNO = 1830 cm-1), CrTPP(NO) (νNO = 1700 cm-1), or (d6) FeTPP(Cl)(NO) (νNO = 1880 cm-1), MnTPP(NO) (νNO = 1760 cm-1), the nitric oxide stretching frequencies are substantially smaller for the complex where the metal has the lower formal oxidation state. Electronic spectra for the chromium porphyrin species are typical for metalloporphyrins, while spectra for MnTPP(X) and MnTPP(X)(NO) complexes are highly irregular. VOTPP fails to form a nitric oxide complex even in the low temperature glass media.

AB - Nitric oxide forms 1:1 low spin complexes with CrIITPP, CrIIITPP(X), MnIITPP, and MnIIITPP(X) species. MnTPP(X)(NO) (X- = Cl-, CH3CO2-, CN-) and CrTPP(NO) complexes have the S = 1/2 ground state and EPR spectra diagnostic for the odd electron occupying a molecular orbital of predominantly metal dxy character. MnTPP(X)(NO) complexes and the isoelectronic CrTPP(NO) species are assigned the (dxz,yz)4 (dxy)1 ground configuration. Narrow lines in the isptropic EPR spectrum of CrTPP(NO) permit resolution of nitrogen-14 hyperfine from both nitric oxide (6.5 G) and the porphyrin pyrrole nitrogens (3.15 G). The metal nuclear hyperfine coupling constants in these complexes 〈A 55Mn〉 = 88.3 G and 〈A 53Cr〉 = 21.2 G are indicative of the odd electron being relatively localized on the metal. All of these nitric oxide complexes are formulated as M-NO+ species, although dπ → π* bonding substantially reduces this charge separation. Within isoelectronic sets such as (d5) MnTPP(Cl)(NO) (νNO = 1830 cm-1), CrTPP(NO) (νNO = 1700 cm-1), or (d6) FeTPP(Cl)(NO) (νNO = 1880 cm-1), MnTPP(NO) (νNO = 1760 cm-1), the nitric oxide stretching frequencies are substantially smaller for the complex where the metal has the lower formal oxidation state. Electronic spectra for the chromium porphyrin species are typical for metalloporphyrins, while spectra for MnTPP(X) and MnTPP(X)(NO) complexes are highly irregular. VOTPP fails to form a nitric oxide complex even in the low temperature glass media.

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