Tuning the photoinduced O 2-evolving reactivity of Mn 4O 4 7+, Mn 4O 4 6+, and Mn 4O 3(OH) 6+ manganese-oxo cubane complexes

Jian Zhong Wu, Filippo De Angelis, Thomas G. Carrell, Glenn P A Yap, John Sheats, Roberto Car, G Charles Dismukes

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Abstract

The manganese-oxo "cubane" core complex Mn 4O 4L 1 6 (1, L 1 = Ph 2PO 2 -), a partial model of the photosynthetic water oxidation site, was shown previously to undergo photodissociation in the gas phase by releasing one phosphinate anion, an O 2 molecule, and the intact butterfly core cation (Mn 4O 2L 1 5 +). Herein, we investigate the photochemistry and electronic structure of a series of manganese-oxo cubane complexes: [Mn 4O 4L 2 6] (2), 1 +(ClO 4 -), 2 +(ClO 4 -), and Mn 4O 3(OH)L 1 6 (1H). We report the atomic structure of [Mn 4O 4L 2 6](ClO 4 -), 2 +(ClO 4 -) [L 2 = (4-MeOPh) 2-PO 2 -]. UV photoexcitation of a charge-transfer band dissociates one phosphinate, two core oxygen atoms, and the Mn 4O 2L 5 + butterfly as the dominant (or exclusive) photoreaction of all cubane derivatives in the gas phase, with relative yields: 1H ≫ 2 > 1 > 2 + > 1 +. The photodissociation yield increases upon (1) reducing the core oxidation state by hydrogenation of a corner oxo (1H), (2) increasing the electron donation from the phosphinate ligand (L 2), and (3) reducing the net charge from +1 to 0. The experimental Mn-O bond lengths and Mn-O bond strengths and the calculated ligand binding energy explain these trends in terms of weaker binding of phosphinate L 2 versus L 1 by 14.7 kcal/mol and stronger Mn-(μ3-O)(core) bonds in the oxidized complexes 2 + and 1 + versus 2 and 1. The calculated electronic structure accounts for these trends in terms of the binding energy and antibonding Mn-O(core) and Mn-O′(ligand) character of the degenerate highest occupied molecular orbital (HOMO), including (1) energetic destabilization of the HOMO of 2 relative to 1 by 0.75 eV and (2) depopulation of the antibonding HOMO and increased ionic binding in 1 + and 2 + versus 1 and 2.

Original languageEnglish
Pages (from-to)189-195
Number of pages7
JournalInorganic Chemistry
Volume45
Issue number1
DOIs
Publication statusPublished - Jan 9 2006

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cubane
Molecular orbitals
Manganese
Photodissociation
manganese
reactivity
Tuning
tuning
Ligands
Binding energy
Electronic structure
Gases
Oxidation
molecular orbitals
Photoexcitation
Photochemical reactions
Bond length
photodissociation
ligands
Hydrogenation

ASJC Scopus subject areas

  • Inorganic Chemistry

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Tuning the photoinduced O 2-evolving reactivity of Mn 4O 4 7+, Mn 4O 4 6+, and Mn 4O 3(OH) 6+ manganese-oxo cubane complexes. / Wu, Jian Zhong; De Angelis, Filippo; Carrell, Thomas G.; Yap, Glenn P A; Sheats, John; Car, Roberto; Dismukes, G Charles.

In: Inorganic Chemistry, Vol. 45, No. 1, 09.01.2006, p. 189-195.

Research output: Contribution to journalArticle

Wu, Jian Zhong ; De Angelis, Filippo ; Carrell, Thomas G. ; Yap, Glenn P A ; Sheats, John ; Car, Roberto ; Dismukes, G Charles. / Tuning the photoinduced O 2-evolving reactivity of Mn 4O 4 7+, Mn 4O 4 6+, and Mn 4O 3(OH) 6+ manganese-oxo cubane complexes. In: Inorganic Chemistry. 2006 ; Vol. 45, No. 1. pp. 189-195.
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abstract = "The manganese-oxo {"}cubane{"} core complex Mn 4O 4L 1 6 (1, L 1 = Ph 2PO 2 -), a partial model of the photosynthetic water oxidation site, was shown previously to undergo photodissociation in the gas phase by releasing one phosphinate anion, an O 2 molecule, and the intact butterfly core cation (Mn 4O 2L 1 5 +). Herein, we investigate the photochemistry and electronic structure of a series of manganese-oxo cubane complexes: [Mn 4O 4L 2 6] (2), 1 +(ClO 4 -), 2 +(ClO 4 -), and Mn 4O 3(OH)L 1 6 (1H). We report the atomic structure of [Mn 4O 4L 2 6](ClO 4 -), 2 +(ClO 4 -) [L 2 = (4-MeOPh) 2-PO 2 -]. UV photoexcitation of a charge-transfer band dissociates one phosphinate, two core oxygen atoms, and the Mn 4O 2L 5 + butterfly as the dominant (or exclusive) photoreaction of all cubane derivatives in the gas phase, with relative yields: 1H ≫ 2 > 1 > 2 + > 1 +. The photodissociation yield increases upon (1) reducing the core oxidation state by hydrogenation of a corner oxo (1H), (2) increasing the electron donation from the phosphinate ligand (L 2), and (3) reducing the net charge from +1 to 0. The experimental Mn-O bond lengths and Mn-O bond strengths and the calculated ligand binding energy explain these trends in terms of weaker binding of phosphinate L 2 versus L 1 by 14.7 kcal/mol and stronger Mn-(μ3-O)(core) bonds in the oxidized complexes 2 + and 1 + versus 2 and 1. The calculated electronic structure accounts for these trends in terms of the binding energy and antibonding Mn-O(core) and Mn-O′(ligand) character of the degenerate highest occupied molecular orbital (HOMO), including (1) energetic destabilization of the HOMO of 2 relative to 1 by 0.75 eV and (2) depopulation of the antibonding HOMO and increased ionic binding in 1 + and 2 + versus 1 and 2.",
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T1 - Tuning the photoinduced O 2-evolving reactivity of Mn 4O 4 7+, Mn 4O 4 6+, and Mn 4O 3(OH) 6+ manganese-oxo cubane complexes

AU - Wu, Jian Zhong

AU - De Angelis, Filippo

AU - Carrell, Thomas G.

AU - Yap, Glenn P A

AU - Sheats, John

AU - Car, Roberto

AU - Dismukes, G Charles

PY - 2006/1/9

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N2 - The manganese-oxo "cubane" core complex Mn 4O 4L 1 6 (1, L 1 = Ph 2PO 2 -), a partial model of the photosynthetic water oxidation site, was shown previously to undergo photodissociation in the gas phase by releasing one phosphinate anion, an O 2 molecule, and the intact butterfly core cation (Mn 4O 2L 1 5 +). Herein, we investigate the photochemistry and electronic structure of a series of manganese-oxo cubane complexes: [Mn 4O 4L 2 6] (2), 1 +(ClO 4 -), 2 +(ClO 4 -), and Mn 4O 3(OH)L 1 6 (1H). We report the atomic structure of [Mn 4O 4L 2 6](ClO 4 -), 2 +(ClO 4 -) [L 2 = (4-MeOPh) 2-PO 2 -]. UV photoexcitation of a charge-transfer band dissociates one phosphinate, two core oxygen atoms, and the Mn 4O 2L 5 + butterfly as the dominant (or exclusive) photoreaction of all cubane derivatives in the gas phase, with relative yields: 1H ≫ 2 > 1 > 2 + > 1 +. The photodissociation yield increases upon (1) reducing the core oxidation state by hydrogenation of a corner oxo (1H), (2) increasing the electron donation from the phosphinate ligand (L 2), and (3) reducing the net charge from +1 to 0. The experimental Mn-O bond lengths and Mn-O bond strengths and the calculated ligand binding energy explain these trends in terms of weaker binding of phosphinate L 2 versus L 1 by 14.7 kcal/mol and stronger Mn-(μ3-O)(core) bonds in the oxidized complexes 2 + and 1 + versus 2 and 1. The calculated electronic structure accounts for these trends in terms of the binding energy and antibonding Mn-O(core) and Mn-O′(ligand) character of the degenerate highest occupied molecular orbital (HOMO), including (1) energetic destabilization of the HOMO of 2 relative to 1 by 0.75 eV and (2) depopulation of the antibonding HOMO and increased ionic binding in 1 + and 2 + versus 1 and 2.

AB - The manganese-oxo "cubane" core complex Mn 4O 4L 1 6 (1, L 1 = Ph 2PO 2 -), a partial model of the photosynthetic water oxidation site, was shown previously to undergo photodissociation in the gas phase by releasing one phosphinate anion, an O 2 molecule, and the intact butterfly core cation (Mn 4O 2L 1 5 +). Herein, we investigate the photochemistry and electronic structure of a series of manganese-oxo cubane complexes: [Mn 4O 4L 2 6] (2), 1 +(ClO 4 -), 2 +(ClO 4 -), and Mn 4O 3(OH)L 1 6 (1H). We report the atomic structure of [Mn 4O 4L 2 6](ClO 4 -), 2 +(ClO 4 -) [L 2 = (4-MeOPh) 2-PO 2 -]. UV photoexcitation of a charge-transfer band dissociates one phosphinate, two core oxygen atoms, and the Mn 4O 2L 5 + butterfly as the dominant (or exclusive) photoreaction of all cubane derivatives in the gas phase, with relative yields: 1H ≫ 2 > 1 > 2 + > 1 +. The photodissociation yield increases upon (1) reducing the core oxidation state by hydrogenation of a corner oxo (1H), (2) increasing the electron donation from the phosphinate ligand (L 2), and (3) reducing the net charge from +1 to 0. The experimental Mn-O bond lengths and Mn-O bond strengths and the calculated ligand binding energy explain these trends in terms of weaker binding of phosphinate L 2 versus L 1 by 14.7 kcal/mol and stronger Mn-(μ3-O)(core) bonds in the oxidized complexes 2 + and 1 + versus 2 and 1. The calculated electronic structure accounts for these trends in terms of the binding energy and antibonding Mn-O(core) and Mn-O′(ligand) character of the degenerate highest occupied molecular orbital (HOMO), including (1) energetic destabilization of the HOMO of 2 relative to 1 by 0.75 eV and (2) depopulation of the antibonding HOMO and increased ionic binding in 1 + and 2 + versus 1 and 2.

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