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Zhao TY, Greenstein EP, Peczak IL, Poeppelmeier KR, Perras FA. Observing the Surface Termination of LaScO 3 Perovskite Using Solid-State Nuclear Magnetic Resonance. J Am Chem Soc 2024; 146:23487-23496. [PMID: 39112441 DOI: 10.1021/jacs.4c07055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/22/2024]
Abstract
Materials with well-defined surfaces are drawing increased attention for the design of bespoke catalysts and nanomaterials. Gaining a detailed understanding of the surfaces of these materials is an important challenge, which is often complicated by surface polymorphism and dynamic restructuring. We introduce the use of surface-enhanced NMR spectroscopy for the observation of such surfaces, focusing on LaScO3 as an example. We show that double-resonance NMR experiments correlating surface oxygen and probe molecules to the 139La and 45Sc nuclei at the surface reveal the material to be terminated by a ScOx monolayer. Surface-selective 17O and 45Sc NMR experiments further showed the material to be hydroxyl terminated and that the surface may be prone to dynamic restructuring as a result of moisture exposure. Perhaps most interestingly, surface-selective 139La NMR experiments revealed the existence of previously undetected surface lanthanum defects, suggesting that surface-enhanced NMR may be useful as a guide in the synthesis of defect-free surfaces in the design of various nanomaterials.
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Affiliation(s)
- Tommy Yunpu Zhao
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, Iowa 50011, United States
| | - Emily P Greenstein
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Ian L Peczak
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Kenneth R Poeppelmeier
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Frédéric A Perras
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, Iowa 50011, United States
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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2
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Erastova V, Evans IR, Glossop WN, Guryel S, Hodgkinson P, Kerr HE, Oganesyan VS, Softley LK, Wickins HM, Wilson MR. Unravelling Guest Dynamics in Crystalline Molecular Organics Using 2H Solid-State NMR and Molecular Dynamics Simulation. J Am Chem Soc 2024; 146:18360-18369. [PMID: 38935813 PMCID: PMC11240262 DOI: 10.1021/jacs.4c03246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2024] [Revised: 05/30/2024] [Accepted: 05/30/2024] [Indexed: 06/29/2024]
Abstract
2H solid-state NMR and atomistic molecular dynamics (MD) simulations are used to understand the disorder of guest solvent molecules in two cocrystal solvates of the pharmaceutical furosemide. Traditional approaches to interpreting the NMR data fail to provide a coherent model of molecular behavior and indeed give misleading kinetic data. In contrast, the direct prediction of the NMR properties from MD simulation trajectories allows the NMR data to be correctly interpreted in terms of combined jump-type and libration-type motions. Time-independent component analysis of the MD trajectories provides additional insights, particularly for motions that are invisible to NMR. This allows a coherent picture of the dynamics of molecules restricted in molecular-sized cavities to be determined.
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Affiliation(s)
- Valentina Erastova
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
- Department
of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster
Road, Edinburgh EH9 3FJ, U.K.
| | - Ivana R. Evans
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | - William N. Glossop
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | - Songül Guryel
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | - Paul Hodgkinson
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | - Hannah E. Kerr
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | | | - Lorna K. Softley
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | - Helen M. Wickins
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
| | - Mark R. Wilson
- Department
of Chemistry, Durham University, Stockton Road, Durham DH1 3LE, U.K.
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Southern SA, Perras FA. Comparison of methods for the NMR measurement of motionally averaged dipolar couplings. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2024; 364:107710. [PMID: 38901172 DOI: 10.1016/j.jmr.2024.107710] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 05/31/2024] [Accepted: 06/07/2024] [Indexed: 06/22/2024]
Abstract
Motionally averaged dipolar couplings are an important tool for understanding the complex dynamics of catalysts, polymers, and biomolecules. While there is a plethora of solid-state NMR pulse sequences available for their measurement, in can be difficult to gauge the methods' strengths and weaknesses. In particular, there has not been a comprehensive comparison of their performance in natural abundance samples, where 1H homonuclear dipolar couplings are important and the use of large MAS rotors may be required for sensitivity reasons. In this work, we directly compared some of the more common methods for measuring C-H dipolar couplings in natural abundance samples using L-alanine (L-Ala) and the N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLF) tripeptide as model systems. We evaluated their performance in terms of accuracy, resolution, sensitivity, and ease of implementation. We found that, despite the presence of 1H homonuclear dipolar interactions, all methods, with the exception of REDOR, were able to yield the reasonable dipolar coupling strengths for both mobile and static moieties. Of these methods, PDLF provides the most convenient workflow and precision at the expense of low sensitivity. In low-sensitivity cases, MAS-PISEMA and DIPSHIFT appear to be the better options.
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Affiliation(s)
- Scott A Southern
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA
| | - Frédéric A Perras
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA; Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
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Perras FA, Culver DB. On the use of NMR distance measurements for assessing surface site homogeneity. Dalton Trans 2023. [PMID: 38015038 DOI: 10.1039/d3dt03201a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
The past few decades have seen tremendous growth in the area of single-site heterogeneous catalysis, which aims to combine the best aspects of homogeneous and heterogeneous catalysis, namely molecular-level site control and ease of separation/recycling. Despite this, we still do not have a means of assessing site homogeneity and whether the produced catalyst is indeed a "single-site". Recent developments have enabled the use of NMR-based distance measurements to determine the conformations and configurations of surface sites, leading to the question whether such measurements can be used to distinguish materials containing either single or multiple surface sites with otherwise indistinguishable NMR properties. We describe a Monte Carlo-based multi-structure search algorithm and its application to the determination of multi-site structures from supported metal complexes. The sensitivity of REDOR data to the existence of multiple sites is assessed using synthetic data and prior literature examples are revisited to determine whether the single-site approximation was indeed appropriate. We lastly apply this new methodology to differentiate the configurations of zirconocene complexes grafted onto alumina supports that were thermally treated at different temperatures.
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Affiliation(s)
- Frédéric A Perras
- Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
- Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50011, USA
| | - Damien B Culver
- Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
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5
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Southern SA, Liu DJ, Chatterjee P, Li Y, Perras FA. 1H chemical shift anisotropy: a high sensitivity solid-state NMR dynamics probe for surface studies? Phys Chem Chem Phys 2023; 25:5348-5360. [PMID: 36399032 DOI: 10.1039/d2cp04406d] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Dynamics play significant roles in chemistry and biochemistry-molecular motions impact both large- and small-scale chemical reactions in addition to biochemical processes. In many systems, including heterogeneous catalysts, the characterization of dynamics remains a challenge. The most common approaches involve the solid-state NMR measurement of anisotropic interactions, in particular 2H quadrupolar coupling and 1H-X dipolar coupling, which generally require isotope enrichment. Due to the high sensitivity of 1H NMR, 1H chemical shift anisotropy (CSA) is a particularly enticing, and underexplored, dynamics probe. We carried out 1H CSA and 1H-13C dipolar coupling measurements in a series of model supported complexes to understand how 1H CSA can be leveraged to gain dynamic information for heterogeneous catalysts. Mathematical descriptions are given for the dynamic averaging of the CSA tensor, and its dependence on orientation and asymmetry. The variability of the orientation of the tensor in the molecular frame, in addition to its magnitude and asymmetry, negatively impacts attempts to extract quantitative dynamic information. Nevertheless, 1H CSA measurements can reveal useful qualitative insights into the motions of a particularly dilute site, such as from a surface species.
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Affiliation(s)
- Scott A Southern
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
| | - Da-Jiang Liu
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
| | - Puranjan Chatterjee
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA. .,Department of Chemistry, Iowa State University, Ames, IA 50014, USA
| | - Yuting Li
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
| | - Frédéric A Perras
- Division of Chemical and Biological Sciences, Ames National Laboratory, Ames, IA 50014, USA.
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Bekyarova E, Conley MP. The coordination chemistry of oxide and nanocarbon materials. Dalton Trans 2022; 51:8557-8570. [PMID: 35586978 DOI: 10.1039/d2dt00459c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding how a ligand affects the steric and electronic properties of a metal is the cornerstone of the inorganic chemistry enterprise. What happens when the ligand is an extended surface? This question is central to the design and implementation of state-of-the-art functional materials containing transition metals. This perspective will describe how these two very different sets of extended surfaces can form well-defined coordination complexes with metals. In the Green formalism, functionalities on oxide surfaces react with inorganics to form species that contain X-type or LX-type interactions between the metal and the oxide. Carbon surfaces are neutral L-type ligands; this perspective focuses on carbons that donate six electrons to a metal. The nature of this interaction depends on the curvature, and thereby orbital overlap, between the metal and the extended π-system from the nanocarbon.
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Affiliation(s)
- Elena Bekyarova
- Department of Chemistry, University of California, Riverside, California 92521, USA.
| | - Matthew P Conley
- Department of Chemistry, University of California, Riverside, California 92521, USA.
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Perras FA, Kanbur U, Paterson AL, Chatterjee P, Slowing II, Sadow AD. Determining the Three-Dimensional Structures of Silica-Supported Metal Complexes from the Ground Up. Inorg Chem 2021; 61:1067-1078. [PMID: 34962783 DOI: 10.1021/acs.inorgchem.1c03200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The immobilization of molecularly precise metal complexes to substrates, such as silica, provides an attractive platform for the design of active sites in heterogeneous catalysts. Specific steric and electronic variations of the ligand environment enable the development of structure-activity relationships and the knowledge-driven design of catalysts. At present, however, the three-dimensional environment of the precatalyst, much less the active site, is generally not known for heterogeneous single-site catalysts. We explored the degree to which NMR-based surface-to-complex interatomic distances could be used to solve the three-dimensional structures of three silica-supported metal complexes. The structure solution revealed unexpected features related to the environment around the metal that would be difficult to discern otherwise. This approach appears to be highly robust and, due to its simplicity, is readily applied to most single-site catalysts with little extra effort.
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Affiliation(s)
| | - Uddhav Kanbur
- US DOE, Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | | | - Puranjan Chatterjee
- US DOE, Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Igor I Slowing
- US DOE, Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Aaron D Sadow
- US DOE, Ames Laboratory, Ames, Iowa 50011, United States.,Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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