[open quotes]Dimerization[close quotes] of the [Co[sub 2][sup III](OH)[sub 2]] core to the first example of a [Co[sub 4][sup III]O[sub 4]] Cubane. Potential insights into photosynthetic water oxidation

Journal Article · Wed Jul 14 00:00:00 EDT 1993 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00067a077· OSTI ID:5901944

Dimitrou, K; Folting, K; Streib, W E; Christou, G ^[1]

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1. Indiana Univ., Bloomington (United States)

Intense effort is currently directed toward elucidating the structure and mode of action of the Mn[sub 4] aggregate responsible for photosynthetic water oxidation in green plants and cyanobacteria. The arrangement of the metal ions at any of the oxidation levels (S[sub n] states; n =-1 to 4) of this water oxidation center (WOC) is currently unclear. We have extended our WOC modeling studies to encompass Co. The reasoning is that we may obtain Co[sup III] systems that are structurally analogous to, but more stable than, the Mn[sup III]/Mn[sup IV] species present at the highest S[sub n] states or that are intermediates in the O[sub 2] evolution process. For example, Co[sup III] and Mn[sub IV] both favor octahedral geometry and have similar effective ionic radii. Thus, it is a possibility that stable Co[sup III][sub 4] complexes could be structurally analogous to unstable Mn[sup IV][sub 4] complexes at higher S[sub n] states and could thus provide insights into the latter. Similarly, Co[sup III] is known to form stable peroxide complexes, whereas Mn[sub 4]O[sub 2][sup 2] species thought to be formed on oxidation of S[sub 3] are not observed, and only O[sub 2] and regenerated S[sub 0] are found. We herein describe our initial successes in this area, the preparation of Co[sub 2], Co[sub 3], and Co[sub 4] complexes. The Co[sub 3] and Co[sub 4] species possess the first examples of [Co[sub 3]([mu][sub 3]-O)([mu]-OH)[sub 3]][sup 4+] partial cubane and [Co[sub 4]([mu][sub 3]-O)[sub 4]][sup 4+] cubane cores and represent interesting developments in the otherwise well-explored chemistry of Co[sup III]. The Co[sub 4] species is also the first M[sub 4]O[sub 4] cubane complex with biologically-relevant ligands. 16 refs., 2 figs.

• OSTI ID: 5901944
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 115:14; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
CHEMICAL REACTIONS
COBALT COMPLEXES
COMPLEXES
DIMERIZATION
HYDROGEN COMPOUNDS
MANGANESE COMPLEXES
MOLECULAR STRUCTURE
OXIDATION
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
POLYMERIZATION
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
WATER