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Structural diversities in heterometallic Mn-Ca cluster chemistry from the use of salicylhydroxamic acid: {MnIII4Ca2}, {MnII/III6Ca2}, {MnIII/IV8Ca}, and {MnIII8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex

Structural diversities in heterometallic Mn-Ca cluster chemistry from the use of salicylhydroxamic acid: {MnIII4Ca2}, {MnII/III6Ca2}, {MnIII/IV8Ca}, and {MnIII8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex
Structural diversities in heterometallic Mn-Ca cluster chemistry from the use of salicylhydroxamic acid: {MnIII4Ca2}, {MnII/III6Ca2}, {MnIII/IV8Ca}, and {MnIII8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex

One-pot reactions between the [Mn3O(O2CPh)6(py)x]+/0 triangular precursors and either CaBr2·xH2O or CaCl2·6H2O, in the presence of salicylhydroxamic acid (shaH2), have afforded the heterometallic complexes [MnIII4Ca2(O2CPh)4(shi)4(H2O)3(Me2CO)] (1) and (pyH)[MnII2MnIII4Ca2Cl2(O2CPh)7(shi)4(py)4] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO3)2·4H2O/Ca(NO3)2·4H2O and Mn(O2CPh)2·2H2O/Ca(ClO4)2·4H2O "metal blends" and shaH2, in the presence of external base NEt3, led to the new complexes (NHEt3)2[MnIII4MnIV4Ca(OEt)2(shi)10(EtOH)2] (3) and (NHEt3)4[MnIII8Ca2(CO3)4(shi)8] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi3-), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH2, was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a Mn4Ca2 octahedron bound to an additional Mn2 unit, 3 consists of a Mn8 "ring" surrounding a CaII atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two CaII atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

0020-1669
10760-10774
Alaimo, Alysha A.
d821e91b-f52a-46e0-9b7e-3bcdaca1dd8e
Koumousi, Evangelia S.
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Cunha-Silva, Luís
3fc69292-bef4-493e-ae40-cacdc99b9f77
McCormick, Laura J.
f1c2f8cd-adcc-4bbf-9289-0b33a006d2bb
Teat, Simon J.
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Psycharis, Vassilis
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Raptopoulou, Catherine P.
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Mukherjee, Shreya
33d7385e-7417-4ecf-9fed-ea3b48ab2ac1
Li, Chaoran
97cbe705-d308-4102-a9e7-ae99536c0cd1
Gupta, Sayak Das
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Escuer, Albert
b0ec9089-81bf-4f1a-9093-a7c032d02f76
Christou, George
081d51bc-30ff-495b-b52d-03735b1bb600
Stamatatos, Theocharis C.
c6138182-7c91-44b6-bcaf-45dd70f1e910
Alaimo, Alysha A.
d821e91b-f52a-46e0-9b7e-3bcdaca1dd8e
Koumousi, Evangelia S.
49aa45b0-9fc6-432b-a9bf-8bd302102c2c
Cunha-Silva, Luís
3fc69292-bef4-493e-ae40-cacdc99b9f77
McCormick, Laura J.
f1c2f8cd-adcc-4bbf-9289-0b33a006d2bb
Teat, Simon J.
fd6e6d90-b0c2-4463-91d2-5c72e212d414
Psycharis, Vassilis
09079574-89d2-4571-b359-6b7c93828cba
Raptopoulou, Catherine P.
9bd1f70c-2922-4e14-a86b-5a23174f5b97
Mukherjee, Shreya
33d7385e-7417-4ecf-9fed-ea3b48ab2ac1
Li, Chaoran
97cbe705-d308-4102-a9e7-ae99536c0cd1
Gupta, Sayak Das
9c36a0e4-a99c-49a0-8dc8-ac33edb36730
Escuer, Albert
b0ec9089-81bf-4f1a-9093-a7c032d02f76
Christou, George
081d51bc-30ff-495b-b52d-03735b1bb600
Stamatatos, Theocharis C.
c6138182-7c91-44b6-bcaf-45dd70f1e910

Alaimo, Alysha A., Koumousi, Evangelia S., Cunha-Silva, Luís, McCormick, Laura J., Teat, Simon J., Psycharis, Vassilis, Raptopoulou, Catherine P., Mukherjee, Shreya, Li, Chaoran, Gupta, Sayak Das, Escuer, Albert, Christou, George and Stamatatos, Theocharis C. (2017) Structural diversities in heterometallic Mn-Ca cluster chemistry from the use of salicylhydroxamic acid: {MnIII4Ca2}, {MnII/III6Ca2}, {MnIII/IV8Ca}, and {MnIII8Ca2} Complexes with Relevance to Both High- and Low-Valent States of the Oxygen-Evolving Complex. Inorganic Chemistry, 56 (17), 10760-10774. (doi:10.1021/acs.inorgchem.7b01740).

Record type: Article

Abstract

One-pot reactions between the [Mn3O(O2CPh)6(py)x]+/0 triangular precursors and either CaBr2·xH2O or CaCl2·6H2O, in the presence of salicylhydroxamic acid (shaH2), have afforded the heterometallic complexes [MnIII4Ca2(O2CPh)4(shi)4(H2O)3(Me2CO)] (1) and (pyH)[MnII2MnIII4Ca2Cl2(O2CPh)7(shi)4(py)4] (2), respectively, in good yields. Further reactions but using a more flexible synthetic scheme comprising the Mn(NO3)2·4H2O/Ca(NO3)2·4H2O and Mn(O2CPh)2·2H2O/Ca(ClO4)2·4H2O "metal blends" and shaH2, in the presence of external base NEt3, led to the new complexes (NHEt3)2[MnIII4MnIV4Ca(OEt)2(shi)10(EtOH)2] (3) and (NHEt3)4[MnIII8Ca2(CO3)4(shi)8] (4), respectively. In all reported compounds, the anion of the tetradentate (N,O,O,O)-chelating/bridging ligand salicylhydroxime (shi3-), resulting from the in situ metal-ion-assisted amide-iminol tautomerism of shaH2, was found to bridge both Mn and Ca atoms. Complexes 1-4 exhibit a variety of different structures, metal stoichiometries, and Mn oxidation-state descriptions; 1 possesses an overall octahedral metal arrangement, 2 can be described as a Mn4Ca2 octahedron bound to an additional Mn2 unit, 3 consists of a Mn8 "ring" surrounding a CaII atom, and 4 adopts a rectangular cuboidal motif of eight Mn atoms accommodating two CaII atoms. Solid-state direct-current magnetic susceptibility studies revealed the presence of predominant antiferromagnetic exchange interactions between the Mn centers, leading to S = 0 spin ground-state values for all complexes. From a bioinorganic chemistry perspective, the reported compounds may demonstrate some relevance to both high-valent scheme (3) and lower-oxidation-level species (1, 2, and 4) of the catalytic cycle of the oxygen-evolving complex.

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e-pub ahead of print date: 17 August 2017
Published date: 5 September 2017

Identifiers

Local EPrints ID: 439014
URI: http://eprints.soton.ac.uk/id/eprint/439014
ISSN: 0020-1669
PURE UUID: e4e5374d-d10f-4ea1-aabf-ede2214c5b0c
ORCID for Laura J. McCormick: ORCID iD orcid.org/0000-0002-6634-4717

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Date deposited: 31 Mar 2020 16:32
Last modified: 07 Oct 2020 02:27

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Contributors

Author: Alysha A. Alaimo
Author: Evangelia S. Koumousi
Author: Luís Cunha-Silva
Author: Simon J. Teat
Author: Vassilis Psycharis
Author: Catherine P. Raptopoulou
Author: Shreya Mukherjee
Author: Chaoran Li
Author: Sayak Das Gupta
Author: Albert Escuer
Author: George Christou
Author: Theocharis C. Stamatatos

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