scholarly journals A Terminal FeIII–Oxo in a Tetranuclear Cluster: Effects of Distal Metal Centers on Structure and Reactivity

2019 ◽  
Vol 141 (24) ◽  
pp. 9479-9484 ◽  
Author(s):  
Christopher J. Reed ◽  
Theodor Agapie
Keyword(s):  
Tetranuclear Cluster ◽  
Metal Centers

Methane activation by ZSM-5-supported transition metal centers

2021 ◽  
Author(s):  
Daniyal Kiani ◽  
Sagar Sourav ◽  
Yadan Tang ◽  
Jonas Baltrusaitis ◽  
Israel E. Wachs
Keyword(s):  
Transition Metal ◽  
Methane Activation ◽  
Group V ◽  
Metal Centers ◽  
Methane Dehydroaromatization

The literature on methane dehydroaromatization (MDA) to benzene using ZSM-5 supported, group V–VIII transition metal-based catalysts (MOx/ZSM-5) is critically reviewed with a focus on in situ and operando molecular insights.

Tuning the Redox Activity of Metal−Organic Frameworks for Enhanced, Selective O2 Binding

2019 ◽  
Author(s):  
Andrew Rosen ◽  
M. Rasel Mian ◽  
Timur Islamoglu ◽  
Haoyuan Chen ◽  
Omar Farha ◽  
...  
Keyword(s):  
Density Functional ◽  
Metal Organic Frameworks ◽  
Redox Activity ◽  
Screening Methods ◽  
Bridging Ligands ◽  
Metal Centers ◽  
Computational Screening ◽  
Open Metal Sites ◽  
Metal Organic ◽  
Unsaturated Metal Sites

<p>Metal−organic frameworks (MOFs) with coordinatively unsaturated metal sites are appealing as adsorbent materials due to their tunable functionality and ability to selectively bind small molecules. Through the use of computational screening methods based on periodic density functional theory, we investigate O<sub>2</sub> and N<sub>2</sub> adsorption at the coordinatively unsaturated metal sites of several MOF families. A variety of design handles are identified that can be used to modify the redox activity of the metal centers, including changing the functionalization of the linkers (replacing oxido donors with sulfido donors), anion exchange of bridging ligands (considering μ-Br<sup>-</sup>, μ-Cl<sup>-</sup>, μ-F<sup>-</sup>, μ-SH<sup>-</sup>, or μ-OH<sup>-</sup> groups), and altering the formal oxidation state of the metal. As a result, we show that it is possible to tune the O<sub>2</sub> affinity at the open metal sites of MOFs for applications involving the strong and/or selective binding of O<sub>2</sub>. In contrast with O<sub>2</sub> adsorption, N<sub>2</sub> adsorption at open metal sites is predicted to be relatively weak across the MOF dataset, with the exception of MOFs containing synthetically elusive V<sup>2+</sup> open metal sites. As one example from the screening study, we predict that exchanging the μ-Cl<sup>-</sup> ligands of M<sub>2</sub>Cl<sub>2</sub>(BBTA) (H<sub>2</sub>BBTA = 1<i>H</i>,5<i>H</i>-benzo(1,2-d:4,5-d′)bistriazole) with μ-OH<sup>-</sup> groups would significantly enhance the strength of O<sub>2</sub> adsorption at the open metal sites without a corresponding increase in the N<sub>2</sub> affinity. Experimental investigation of Co<sub>2</sub>Cl<sub>2</sub>(BBTA) and Co<sub>2</sub>(OH)<sub>2</sub>(BBTA) confirms that the former exhibits only weak physisorption, whereas the latter is capable of chemisorbing O<sub>2</sub> at room temperature. The chemisorption behavior is attributed to the greater electron-donating character of the μ-OH<sup>-</sup><sub> </sub>ligands and the presence of H-bonding interactions between the μ-OH<sup>-</sup> bridging ligands and the O<sub>2</sub> adsorbate.</p>

scholarly journals Structural tuning of heterogeneous molecular catalysts for electrochemical energy conversion

2021 ◽  
Vol 7 (13) ◽  
pp. eabf3989
Author(s):  
Jiong Wang ◽  
Shuo Dou ◽  
Xin Wang
Keyword(s):  
Energy Conversion ◽  
Model Systems ◽  
Structural Variations ◽  
Metal Centers ◽  
Electrochemical Energy Conversion ◽  
Electronic Configurations ◽  
Coordination Spheres ◽  
The Stability ◽  
Molecular Catalysts ◽  
Electrochemical Energy

Heterogeneous molecular catalysts based on transition metal complexes have received increasing attention for their potential application in electrochemical energy conversion. The structural tuning of first and second coordination spheres of complexes provides versatile strategies for optimizing the activities of heterogeneous molecular catalysts and appropriate model systems for investigating the mechanism of structural variations on the activity. In this review, we first discuss the variation of first spheres by tuning ligated atoms; afterward, the structural tuning of second spheres by appending adjacent metal centers, pendant groups, electron withdrawing/donating, and conjugating moieties on the ligands is elaborated. Overall, these structural tuning resulted in different impacts on the geometric and electronic configurations of complexes, and the improved activity is achieved through tuning the stability of chemisorbed reactants and the redox behaviors of immobilized complexes.

ChemInform Abstract: Intramolecular Alkane Dehydrogenation and Functionalization at Niobium Metal Centers.

ChemInform ◽  
2010 ◽  
Vol 22 (6) ◽  
pp. no-no
Author(s):  
J. S. YU ◽  
P. E. FANWICK ◽  
I. P. ROTHWELL
Keyword(s):  
Alkane Dehydrogenation ◽  
Metal Centers

Dioxygen splitting at room temperature over distant binuclear transition metal centers in zeolites for direct oxidation of methane to methanol

2021 ◽  
Author(s):  
Kinga Mlekodaj ◽  
Mariia Lemishka ◽  
Stepan Sklenak ◽  
Jiri Dedecek ◽  
Edyta Tabor
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
Direct Oxidation ◽  
Metal Centers ◽  
Oxidation Of Methane ◽  
First Time

Here we demonstrate for the first time the splitting of dioxygen at RT over distant binuclear transition metal (M = Ni, Mn, and Co) centers stabilized in ferrierite zeolite. Cleaved...

scholarly journals Iron(II) complexes of dimethyltriazacyclophane

2018 ◽  
Vol 74 (12) ◽  
pp. 1641-1649
Author(s):  
Wei-Tsung Lee ◽  
Matthias Zeller ◽  
David Upp ◽  
Yuliya Politanska ◽  
Doug Steinman ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Dft Calculations ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Coordination Mode ◽  
Functional Theory ◽  
Metal Centers ◽  
Bonding Interaction

Treatment of the ortho-triazacyclophane 1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-triene [(C6H5)3(NH)(NCH3)2, L1] with Fe[N(SiMe3)2]2 yields the dimeric iron(II) complex bis(μ-1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-trien-7-ido)bis[(μ-1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-trien-7-ido)iron(II)], [Fe(C20H18N3)4] or Fe2(L1)4 (9). Dissolution of 9 in tetrahydrofuran (THF) results in solvation by two THF ligands and the formation of a simpler monoiron complex, namely bis(μ-1,4-dimethyltribenzo[b,e,h][1,4,7]triazacyclonona-2,5,8-trien-7-ido-κN 7)bis(tetrahydrofuran-κO)iron(II), [Fe(C20H18N3)2(C4H8O)2] or (L1)2Fe(THF)2 (10). The reaction is reversible and 10 reverts in vacuo to diiron complex 9. In the structures of both 9 and 10, the monoanionic triazacyclophane ligand L1− is observed in only the less-symmetric saddle conformation. No bowl-shaped crown conformers are observed in the solid state, thus preventing chelating κ3-coordination to the metal as had been proposed earlier based on density functional theory (DFT) calculations. Instead, the L1− ligands are bound in either a η2-chelating fashion through the amide and one amine donor (for one of the four ligands of 9), or solely through their amide N atoms in an even simpler monodentate η1-coordination mode. Density functional calculations on dimer 9 revealed nearly full cationic charges on each Fe atom and no bonding interaction between the two metal centers, consistent with the relatively long Fe...Fe distance of 2.912 (1) Å observed in the solid state.

Metal-organic frameworks for electrochemical reduction of carbon dioxide: The role of metal centers

2020 ◽  
Vol 40 ◽  
pp. 156-170 ◽  
Author(s):  
Ping Shao ◽  
Luocai Yi ◽  
Shumei Chen ◽  
Tianhua Zhou ◽  
Jian Zhang
Keyword(s):  
Carbon Dioxide ◽  
Electrochemical Reduction ◽  
Metal Organic Frameworks ◽  
Metal Centers ◽  
Metal Organic

A dinuclear Ru(ii) complex capable of photoinduced ligand exchange at both metal centers

2015 ◽  
Vol 51 (92) ◽  
pp. 16522-16525 ◽  
Author(s):  
B. A. Albani ◽  
B. Peña ◽  
S. Saha ◽  
J. K. White ◽  
A. M. Schaeffer ◽  
...  
Keyword(s):  
Ligand Exchange ◽  
Metal Centers

{[Ru(CH3CN)3]2(tppz)}4+ (tppz = tetra-2-pyridylpyrazine) undergoes photoinduced CH3CN exchange with λirr ≥ 610 nm in H2O from both metal centers.

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