M2δ to ligand π-conjugation

Testbeds for current theories of mixed valence in ground and photoexcited states of molecular systems

Malcolm H. Chisholm, Benjamin James Lear

Research output: Contribution to journalReview article

57 Citations (Scopus)

Abstract

Redox active quadruply bonded units, M2, can be combined so that they either (i) are bridged by an organic linker or (ii) function as a bridge between two identical organic ligands. When two M2 units are linked together by an organic group that affords M2δ-bridge π-conjugation the electronic structure of each M2 unit is perturbed by the other in the ground state, the photoexcited states, and the mixed valence oxidized form. Similarly when a M2 center links two organic π systems represented by L, the two organic units are coupled by Lπ*-M2δ-Lπ* interactions in their ground state, their photoexcited states, and the mixed valence reduced state. The photoexcited states of the neutral complexes (both case i and ii) provide examples of excited state mixed valence. In case (i), the positive charge may be localized on one dinuclear center or may be delocalized over both M2 units. Similarly in (ii), the electron may be localized on one ligand or delocalized over both. In this tutorial review, spectroscopic studies (UV-vis-NIR absorption, steady state emission, EPR, and time resolved infrared) of these mixed valence systems employing carboxylate tethers are described and the data are discussed in terms of contemporary theories of mixed valence ions.

Original languageEnglish (US)
Pages (from-to)5254-5265
Number of pages12
JournalChemical Society Reviews
Volume40
Issue number11
DOIs
StatePublished - Nov 1 2011

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Testbeds
Ground state
Ligands
Excited states
Electronic structure
Paramagnetic resonance
Ions
Infrared radiation
Electrons
Oxidation-Reduction

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

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M2δ to ligand π-conjugation : Testbeds for current theories of mixed valence in ground and photoexcited states of molecular systems. / Chisholm, Malcolm H.; Lear, Benjamin James.

In: Chemical Society Reviews, Vol. 40, No. 11, 01.11.2011, p. 5254-5265.

Research output: Contribution to journalReview article

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AB - Redox active quadruply bonded units, M2, can be combined so that they either (i) are bridged by an organic linker or (ii) function as a bridge between two identical organic ligands. When two M2 units are linked together by an organic group that affords M2δ-bridge π-conjugation the electronic structure of each M2 unit is perturbed by the other in the ground state, the photoexcited states, and the mixed valence oxidized form. Similarly when a M2 center links two organic π systems represented by L, the two organic units are coupled by Lπ*-M2δ-Lπ* interactions in their ground state, their photoexcited states, and the mixed valence reduced state. The photoexcited states of the neutral complexes (both case i and ii) provide examples of excited state mixed valence. In case (i), the positive charge may be localized on one dinuclear center or may be delocalized over both M2 units. Similarly in (ii), the electron may be localized on one ligand or delocalized over both. In this tutorial review, spectroscopic studies (UV-vis-NIR absorption, steady state emission, EPR, and time resolved infrared) of these mixed valence systems employing carboxylate tethers are described and the data are discussed in terms of contemporary theories of mixed valence ions.

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