Christina M. Klug

Pacific Northwest National Laboratory

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Matthew P. Shores

Colorado State University

R. Morris Bullock

Pacific Northwest National Laboratory

Eric S. Wiedner

Pacific Northwest National Laboratory

Stephanie R. Fiedler

Colorado State University

A.M. McDaniel

Colorado State University

Kelsey A. Schulte

Texas A&M University

Brooke Newell

Lawrence Berkeley National Laboratory

Indrani Bhowmick

Colorado State University

Molly O’Hagan

Montana State University

Aaron M. Appel

Pacific Northwest National Laboratory

Cooperative Institutions

Pacific Northwest National Laboratory

Richland College

Battelle

Colorado State University

Physical Sciences (United States)

University of North Carolina at Chapel Hill

Communities In Schools of Orange County

Environmental Molecular Sciences Laboratory

University of Idaho

Washington State University

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CCDC 884193: Experimental Crystal Structure Determination

The Cambridge Structural Database (2012)

Christina M. Klug A.M. McDaniel Stephanie R. Fiedler Kelsey A. Schulte Brooke Newell

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

10.5517/ccyp2c1

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CCDC 892318: Experimental Crystal Structure Determination

The Cambridge Structural Database (2012)

Christina M. Klug A.M. McDaniel Stephanie R. Fiedler Kelsey A. Schulte Brooke Newell

10.5517/ccyyjgv

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CCDC 1030389: Experimental Crystal Structure Determination

The Cambridge Structural Database (2019)

Christina M. Klug Tarik J. Ozumerzifon Indrani Bhowmick Brooke N. Livesay Anthony K. Rappé

10.5517/ccdc.csd.cc13l6c8

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CCDC 1030390: Experimental Crystal Structure Determination

The Cambridge Structural Database (2019)

Christina M. Klug Tarik J. Ozumerzifon Indrani Bhowmick Brooke N. Livesay Anthony K. Rappé

10.5517/ccdc.csd.cc13l6d9

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Spin‐State Switching in Solution

Matthew P. Shores Christina M. Klug Stephanie R. Fiedler

This chapter focuses on solution studies of systems where spin events are localized to single, isolated metal centers. It summarizes the kinds of information, such as spin-crossover (SC), and methods available for solution-phase spin switching investigations. The methods include NMR characterization, SQUID magnetometry, and electronic absorption spectroscopy. The chapter surveys recent literature, focusing on effects of solvent and ions, ligand distortions and complex isomerizations, and noncoordinating anion-cation interactions on spin-state switching behavior. It finally highlights several challenges and opportunities of spin-state switching in solution. Solution investigations presented in the chapter emphasize chemical-interaction-based spin-state switching. Spin-state switching in solution is sensitive to small environmental changes. Extensive efforts have been devoted to exploring the influence of solvent, anions and/or salts on SC properties, and some useful structure-property correlations have been obtained.

Spin Crossover

Spin states

10.1002/9781118519301.ch10

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Citations (38)

CCDC 892044: Experimental Crystal Structure Determination

The Cambridge Structural Database (2012)

Christina M. Klug A.M. McDaniel Stephanie R. Fiedler Kelsey A. Schulte Brooke Newell

10.5517/ccyy7mq

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CCDC 865554: Experimental Crystal Structure Determination

The Cambridge Structural Database (2012)

Christina M. Klug A.M. McDaniel Stephanie R. Fiedler Kelsey A. Schulte Brooke Newell

10.5517/ccy1p3r

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Impact of Weak Agostic Interactions in Nickel Electrocatalysts for Hydrogen Oxidation

Organometallics (2017)

Christina M. Klug Molly O’Hagan R. Morris Bullock Aaron M. Appel Eric S. Wiedner

To understand how H2 binding and oxidation is influenced by [Ni(PR2NR′2)2]2+ catalysts with H2 binding energies close to thermoneutral, two [Ni(PPh2NR′2)2]2+ (R = Me, C14H29) complexes with phenyl substituents on phosphorus and varying alkyl chain lengths on the pendant amine were studied. In the solid state, [Ni(PPh2NMe2)2]2+ exhibits a weak agostic interaction between the Ni(II) center and the a C–H bond of the pendant N–CH3 group. DFT computations and variable-temperature 31P NMR experiments suggest that the agostic interaction persists in solution. The equilibrium constants for H2 addition to these complexes were measured by 31P NMR spectroscopy, affording free energies of H2 addition (ΔG°H2) of −0.8 kcal mol–1 in benzonitrile and −1.7 to −2.7 kcal mol–1 in THF. The agostic interaction contributes to the low driving force for H2 binding by stabilizing the four-coordinate Ni(II) species prior to binding of H2. The pseudo-first-order rate constants for addition of H2 (1 atm) were measured by variable-scan rate cyclic voltammetry and were found to be similar for both complexes, with rate constants of 3–6 s–1 in THF and less than 0.2 s–1 in benzonitrile. In the presence of exogenous base and H2, turnover frequencies of electrocatalytic H2 oxidation were measured to be less than 0.2 s–1 in benzonitrile and 4–6 s–1 in THF. These complexes are slower electrocatalysts for H2 oxidation in comparison to previously studied [Ni(PR2NR′2)2]2+ complexes because of a competition between H2 binding and formation of the agostic bond. However, the decrease in catalytic rate is accompanied by a beneficial 130 mV decrease in overpotential.

Agostic interaction

Benzonitrile

10.1021/acs.organomet.7b00103

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Synthesis of Functionalized Hexadentate Iminopyridine Fe^II Complexes – Toward Anion‐Dependent Spin Switching in Polar Media

European Journal of Inorganic Chemistry (2013)

A.M. McDaniel Christina M. Klug Matthew P. Shores

Abstract We report the syntheses and characterizations of low‐spin Fe II complexes of hexadentate ligands poised for anion‐triggered spin‐state switching in polar solutions: [Fe(L 5‐OH )](BF 4 ) 2 ( 1 ) and [Fe(L 5‐ONH t Bu )](BF 4 ) 2 ( 3 ), in which L 5‐OH and L 5‐ONH t Bu are tripodal iminopyridine ligands that contain methanolic or tert ‐butylamide functional groups, respectively, bound meta to the pyridyl N donor atom. Solid‐state evidence for strong hydrogen bonding between Cl – anions and all three amide functional groups in [Fe(L 5‐ONH t Bu )] 2+ is provided by the crystal structure of {[Fe(L 5‐ONH t Bu )]⊂Cl} 2 [FeCl 4 ] ( 2 ). In ambient‐temperature acetonitrile solutions of 1 and 3 , chloride ion titrations produce marked changes in the 1 H NMR spectra, including large downfield shifts for the amide NH and hydroxy OH resonances, which indicates strong anion binding events. Interestingly, for amide‐containing 3 , we observe small changes in magnetic susceptibility as ( n Bu 4 N)Cl is added, which suggests that spin‐state control by anion–cation interactions may be accessible for related compounds with weaker ligand fields.

Amide

Spin states

10.1002/ejic.201201086

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Citations (24)

CCDC 1860784: Experimental Crystal Structure Determination

The Cambridge Structural Database (2019)

Qian Liao Tianbiao Liu Samantha I. Johnson Christina M. Klug Eric S. Wiedner

10.5517/ccdc.csd.cc20g993

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