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Theodor Agapie - One of the best experts on this subject based on the ideXlab platform.
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toward models for the full oxygen evolving complex of photosystem ii by ligand coordination to lower the symmetry of the mn3cao4 Cubane demonstration that electronic effects facilitate binding of a fifth metal
Journal of the American Chemical Society, 2014Co-Authors: Jacob S. Kanady, Po-heng Lin, Kurtis M Carsch, Robert J Nielsen, Michael K Takase, William A Goddard, Theodor AgapieAbstract:Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn4CaOn cluster. Herein, low-symmetry MnIV3GdO4 and MnIV3CaO4 Cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing significant Cubane distortions. As a result of increased electron richness and desymmetrization, a specific μ3-oxo moiety of the Mn3CaO4 unit becomes more basic allowing for selective protonation. Coordination of a fifth metal ion, Ag+, to the same site gives a Mn3CaAgO4 cluster that models the topology of the OEC by displaying both a Cubane motif and a “dangler” transition metal. The present synthetic strategy provides a rational roadmap for accessing more accurate models of the biological catalyst.
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a synthetic model of the mn3ca subsite of the oxygen evolving complex in photosystem ii
Science, 2011Co-Authors: Jacob S. Kanady, Emily Y Tsui, Michael W Day, Theodor AgapieAbstract:Within photosynthetic organisms, the oxygen-evolving complex (OEC) of photosystem II generates dioxygen from water using a catalytic Mn_(4)CaOn cluster (n varies with the mechanism and nature of the intermediate). We report here the rational synthesis of a [Mn_(3)CaO_4]^(6+) Cubane that structurally models the trimanganese-calcium–Cubane subsite of the OEC. Structural and electrochemical comparison between Mn_(3)CaO_4 and a related Mn_(4)O_4 Cubane alongside characterization of an intermediate calcium-manganese multinuclear complex reveals potential roles of calcium in facilitating high oxidation states at manganese and in the assembly of the biological cluster.
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a synthetic model of the mn3ca subsite of the oxygen evolving complex in photosystem ii
Science, 2011Co-Authors: Jacob S. Kanady, Emily Y Tsui, Theodor AgapieAbstract:Within photosynthetic organisms, the oxygen-evolving complex (OEC) of photosystem II generates dioxygen from water using a catalytic Mn_(4)CaOn cluster (n varies with the mechanism and nature of the intermediate). We report here the rational synthesis of a [Mn_(3)CaO_4]^(6+) Cubane that structurally models the trimanganese-calcium–Cubane subsite of the OEC. Structural and electrochemical comparison between Mn_(3)CaO_4 and a related Mn_(4)O_4 Cubane alongside characterization of an intermediate calcium-manganese multinuclear complex reveals potential roles of calcium in facilitating high oxidation states at manganese and in the assembly of the biological cluster.
R. H. Holm - One of the best experts on this subject based on the ideXlab platform.
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ligand metathesis as rational strategy for the synthesis of Cubane type heteroleptic iron sulfur clusters relevant to the femo cofactor
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Zheng Wang, Xu-dong Chen, Rong Ling, Jie Zhou, R. H. HolmAbstract:Molybdenum-dependent nitrogenases catalyze the transformation of dinitrogen into ammonia under ambient conditions. The active site (FeMo cofactor) is the structurally and electronically complex weak-field metal cluster [MoFe 7 S 9 C] built of Fe 4 S 3 and MoFe 3 S 3 C portions connected by three sulfur bridges and containing an interstitial carbon atom centered in an Fe 6 trigonal prism. Chemical synthesis of this cluster is a major challenge in biomimetic inorganic chemistry. One synthetic approach of core ligand metathesis has been developed based on the design and synthesis of unprecedented incomplete ([(Tp*)WFe 2 S 3 Q 3 ] − ) and complete ([(Tp*)WFe 3 S 3 Q 4 ] 2− ) Cubane-type clusters containing bridging halide (Q = halide). These clusters are achieved by template-assisted assembly in the presence of sodium benzophenone ketyl reductant; products are controlled by reaction stoichiometry. Incomplete Cubane clusters are subject to a variety of metathesis reactions resulting in substitution of a μ 2 -bridging ligand with other bridges such as N 3 − , MeO − , and EtS − . Reactions of complete Cubanes with Me 3 SiN 3 and S 8 undergo a redox metathesis process and lead to core ligand displacement and formation of [(Tp*)WFe 3 S 3 ( μ 3 -Q)Cl 3 ] − (Q = Me 3 SiN 2− , S 2− ). This work affords entry to a wide variety of heteroleptic clusters derivable from incomplete and complete Cubanes; examples are provided. Among these is the cluster [(Tp*)WFe 3 S 3 ( μ 3 -NSiMe 3 )Cl 3 ] − , one of the very few instances of a synthetic Fe–S cluster containing a light atom (C, N, O) in the core, which constitutes a close mimic of the [MoFe 3 S 3 C] fragment in FeMo cofactor. Superposition of them and comparison of metric information disclose a clear structural relationship [Tp* = tris(3,5-dimethyl-1-pyrazolyl)hydroborate(1−)].
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Selenium as a Structural Surrogate of Sulfur: Template-Assisted Assembly of Five Types of Tungsten–Iron–Sulfur/Selenium Clusters and the Structural Fate of Chalcogenide Reactants
2016Co-Authors: Bo Zheng, Xu-dong Chen, Shao-liang Zheng, R. H. HolmAbstract:Syntheses of five types of tungsten–iron–sulfur/selenium clusters, namely, incomplete Cubanes, single Cubanes, edge-bridged double Cubanes (EBDCs), PN-type clusters, and double-cuboidal clusters, have been devised using the concept of template-assisted assembly. The template reactant is six-coordinate [(Tp*)WVIS3]1– [Tp* = tris(3,5-dimethylpyrazolyl)hydroborate(1−)], which in the assembly systems organizes Fe2+/3+ and sulfide/selenide into cuboidal [(Tp*)WFe2S3] or Cubane [(Tp*)WFe3S3Q] (Q = S, Se) units. With appropriate terminal iron ligation, these units are capable of independent existence or may be transformed into higher-nuclearity species. Selenide is used as a surrogate for sulfide in cluster assembly in order to determine by X-ray structures the position occupied by an external chalcogenide nucleophile or an internal chalcogenide atom in the product clusters. Specific incorporation of selenide is demonstrated by the formation of [WFe3S3Se]2+/3+ Cubane cores. Reductive dimerization of the Cubane leads to the EBDC core [W2Fe6S6Se2]2+ containing μ4-Se sites. Reaction of these species with HSe– affords the PN-type cores [W2Fe6S6Se3]1+, in which selenide occupies μ6-Se and μ2-Se sites. The reaction of [(Tp*)WS3]1–, FeCl2, and Na2Se yields the double-cuboidal [W2Fe4S6Se3]2+/0 core with μ2-Se and μ4-Se bridges. It is highly probable that in analogous sulfide-only assembly systems, external and internal sulfide reactants occupy corresponding positions in the cluster products. The results further demonstrate the viability of template-assisted cluster synthesis inasmuch as the reduced (Tp*)WS3 unit is present in all of the clusters. Structures, zero-field Mössbauer data, and redox potentials are presented for each cluster type
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heterometal Cubane type mfe3s4 clusters m mo v trigonally symmetrized with hydrotris pyrazolyl borate 1 and tris pyrazolyl methanesulfonate 1 capping ligands
Inorganic Chemistry, 2002Co-Authors: Dmitry V Fomitchev, Craig C Mclauchlan, R. H. HolmAbstract:A series of heterometal Cubane-type clusters containing [VFe3S4]2+ and [MoFe3S4]3+,2+ cores has been prepared. Ligand substitution of [(DMF)3VFe3S4Cl3]- affords [(Tpms)VFe3S4L3]2- (L = Cl- (8), EtS- (9), p-MeC6H4S-, p-MeC6H4O-). A new procedure for the preparation of molybdenum single Cubanes is introduced by the reaction of recently reported [(Tp)MoS(S4)]- with FeCl2/NaSEt to afford [(Tp)MoFe3S4Cl3]- (1, 75% yield). This procedure is more efficient that the existing multistep synthesis of single Cubanes, which generally affords clusters of mirror symmetry. Also prepared were [(Tp)MoFe3S4L3]- (L = EtS- (2), p-MeC6H4S-). Reduction of 1 with borohydride gives [(Tp)MoFe3S4Cl3]2- (5, 67%). Owing to the nature of the heterometal ligand, all clusters have idealized trigonal symmetry, reflected in their 1H NMR spectra. Trigonal structures are demonstrated by crystallography of (Bu4N)[1,2], (Bu4N)2[5]·MeCN, and (Me4N)2[8,9]. The availability of 1 and 5 allows the first comparison of structures and 57Fe isomer shi...
Jacob S. Kanady - One of the best experts on this subject based on the ideXlab platform.
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toward models for the full oxygen evolving complex of photosystem ii by ligand coordination to lower the symmetry of the mn3cao4 Cubane demonstration that electronic effects facilitate binding of a fifth metal
Journal of the American Chemical Society, 2014Co-Authors: Jacob S. Kanady, Po-heng Lin, Kurtis M Carsch, Robert J Nielsen, Michael K Takase, William A Goddard, Theodor AgapieAbstract:Synthetic model compounds have been targeted to benchmark and better understand the electronic structure, geometry, spectroscopy, and reactivity of the oxygen-evolving complex (OEC) of photosystem II, a low-symmetry Mn4CaOn cluster. Herein, low-symmetry MnIV3GdO4 and MnIV3CaO4 Cubanes are synthesized in a rational, stepwise fashion through desymmetrization by ligand substitution, causing significant Cubane distortions. As a result of increased electron richness and desymmetrization, a specific μ3-oxo moiety of the Mn3CaO4 unit becomes more basic allowing for selective protonation. Coordination of a fifth metal ion, Ag+, to the same site gives a Mn3CaAgO4 cluster that models the topology of the OEC by displaying both a Cubane motif and a “dangler” transition metal. The present synthetic strategy provides a rational roadmap for accessing more accurate models of the biological catalyst.
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a synthetic model of the mn3ca subsite of the oxygen evolving complex in photosystem ii
Science, 2011Co-Authors: Jacob S. Kanady, Emily Y Tsui, Michael W Day, Theodor AgapieAbstract:Within photosynthetic organisms, the oxygen-evolving complex (OEC) of photosystem II generates dioxygen from water using a catalytic Mn_(4)CaOn cluster (n varies with the mechanism and nature of the intermediate). We report here the rational synthesis of a [Mn_(3)CaO_4]^(6+) Cubane that structurally models the trimanganese-calcium–Cubane subsite of the OEC. Structural and electrochemical comparison between Mn_(3)CaO_4 and a related Mn_(4)O_4 Cubane alongside characterization of an intermediate calcium-manganese multinuclear complex reveals potential roles of calcium in facilitating high oxidation states at manganese and in the assembly of the biological cluster.
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a synthetic model of the mn3ca subsite of the oxygen evolving complex in photosystem ii
Science, 2011Co-Authors: Jacob S. Kanady, Emily Y Tsui, Theodor AgapieAbstract:Within photosynthetic organisms, the oxygen-evolving complex (OEC) of photosystem II generates dioxygen from water using a catalytic Mn_(4)CaOn cluster (n varies with the mechanism and nature of the intermediate). We report here the rational synthesis of a [Mn_(3)CaO_4]^(6+) Cubane that structurally models the trimanganese-calcium–Cubane subsite of the OEC. Structural and electrochemical comparison between Mn_(3)CaO_4 and a related Mn_(4)O_4 Cubane alongside characterization of an intermediate calcium-manganese multinuclear complex reveals potential roles of calcium in facilitating high oxidation states at manganese and in the assembly of the biological cluster.
Enbo Wang - One of the best experts on this subject based on the ideXlab platform.
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polyoxometalate assisted synthesis of transition metal Cubane clusters as artificial mimics of the oxygen evolving center of photosystem ii
Coordination Chemistry Reviews, 2016Co-Authors: Zhujun Liu, Xinlong Wang, Chao Qin, Zhiming Zhang, Weilin Chen, Enbo WangAbstract:Abstract The {Mn 4 O 5 Ca} cluster of photosystem II is a well-known Cubane-like transition-metal (TM) cluster that plays important roles in solar energy conversion. The artificial synthesis of Cubane-like TM clusters and their interesting potential applications have been widely studied. Most of them were isolated by use of organic ligands, and therefore their potential applications were essentially restricted to organic solvents because of their limited stability in aqueous solution. In recent decades, lacunary polyoxometalates (POMs) composed of W VI /Mo VI centers have been used to replace organic ligands as stable and oxidative-resistant pure-inorganic multidentate ligands to construct water-soluble and water-stable molecular clusters. In the course of the mimicking of the {Mn 4 O 5 Ca} subsite of photosystem II, significant advances have already been made in POM-assisted artificial synthesis of TM Cubanes. Compared with classic Cubane-like TM clusters, these POM-based TM Cubane clusters can not only dissolve in organic solvents by virtue of a simple phase-transfer reaction but also display excellent aqueous stability. Consequently, the synthesis of these pure-inorganic Cubane clusters offers a great opportunity for expanding the applications of Cubane-like TM clusters. This review focuses on the synthetic strategies for, structures of, and applications of these POM-based TM Cubane clusters, particularly highlighting how POMs can be used as the inorganic ligands to construct Cubane-like TM clusters. The purpose of this review is to give a representative and comprehensive overview of the work done so far in this emerging field.
Stefano Brenna - One of the best experts on this subject based on the ideXlab platform.
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Hydroxo-bridged copper(II) Cubane complexes
Coordination Chemistry Reviews, 2016Co-Authors: G. Attilio Ardizzoia, Stefano BrennaAbstract:Abstract Oxygen-bridged tetranuclear copper complexes having a Cu4O4 Cubane-like core represent a really fascinating class of compounds, due to their similarity to copper oxidase active sites or to their molecular magnetism. Among these, hydroxo-bridged copper(II) Cubanes are a restricted category when compared to alkoxo-bridged ones, {Cu4(μ3-OH)4}-based compounds structurally described via X-ray being only 18 (to the end of 2014), to the best of our knowledge. In this review, the key features of these compounds will be highlighted, with attention to their structural characterization and classification, their syntheses and their magnetic behavior.