1
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Kopp RO, Kleynemeyer SL, Groth LJ, Ernst MJ, Rupf SM, Weber M, Kershaw Cook LJ, Coles NT, Neale SE, Müller C. Highly selective, reversible water activation by P,N-cooperativity in pyridyl-functionalized phosphinines. Chem Sci 2024; 15:5496-5506. [PMID: 38638216 PMCID: PMC11023035 DOI: 10.1039/d3sc05930h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 03/08/2024] [Indexed: 04/20/2024] Open
Abstract
Tetrapyridyl-functionalized phosphinines were prepared and structurally characterized. The donor-functionalized aromatic phosphorus heterocycles react highly selectively and even reversibly with water. Calculations reveal P,N-cooperativity for this process, with the flanking pyridyl groups serving to kinetically enhance the formal oxidative addition process of H2O to the low-coordinate phosphorus atom via H-bonding. Subsequent tautomerization forms 1,2-dihydrophosphinine derivatives, which can be quantitatively converted back to the phosphinine by applying vacuum, even at room temperature. This process can be repeated numerous times, without any sign of decomposition of the phosphinine. In the presence of CuI·SMe2, dimeric species of the type ([Cu2I2(phosphinine)]2) are formed, in which each phosphorus atom shows the less common μ2-bridging 2e--lone-pair-donation to two Cu(i)-centres. Our results demonstrate that fully unsaturated phosphorus heterocycles, containing reactive P[double bond, length as m-dash]C double bonds, are interesting candidates for the activation of E-H bonds, while the aromaticity of such compounds plays an appreciable role in the reversibility of the reaction, supported by NICS calculations.
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Affiliation(s)
- Richard O Kopp
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Sabrina L Kleynemeyer
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Lucie J Groth
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Moritz J Ernst
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Susanne M Rupf
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Manuela Weber
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
| | - Laurence J Kershaw Cook
- Department of Chemistry and Materials Innovation Factory, University of Liverpool Crown Street Liverpool L69 7ZD UK
| | - Nathan T Coles
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
- School of Chemistry, University of Nottingham, University Park Nottingham NG7 2RD UK
| | - Samuel E Neale
- Department of Chemistry, University of Bath Claverton Down Bath BA2 7AY UK
| | - Christian Müller
- Institute of Chemistry and Biochemistry, Freie Universität Berlin Fabeckstr. 34/36 14195 Berlin Germany
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2
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Jones C, Kershaw Cook LJ, Slater AG, Yufit DS, Steed JW. Scrolling in Supramolecular Gels: A Designer's Guide. Chem Mater 2024; 36:2799-2809. [PMID: 38558920 PMCID: PMC10976645 DOI: 10.1021/acs.chemmater.3c03013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/26/2024] [Accepted: 02/27/2024] [Indexed: 04/04/2024]
Abstract
Gelation by small molecules is a topic of enormous importance in catalysis, nanomaterials, drug delivery, and pharmaceutical crystallization. The mechanism by which gelators self-organize into a fibrous gel network is poorly understood. Herein, we describe the crystal structures and gelation properties of a library of bis(urea) compounds and show, via molecular dynamics simulations, how gelator aggregation progresses from a continuous pattern of supramolecular motifs to a homogeneous fiber network. Our model suggests that lamellae with asymmetric surfaces scroll into uniform unbranched fibrils, while sheets with symmetric surfaces undergo stacking to form crystals. The self-assembly of asymmetric lamellae is associated with specific molecular features, such as the presence of narrow and flexible end groups with high packing densities, and likely represents a general mechanism for the formation of small-molecule gels.
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Affiliation(s)
| | - Laurence J. Kershaw Cook
- Department
of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
| | - Anna G. Slater
- Department
of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
| | - Dmitry S. Yufit
- Department
of Chemistry, Durham University, Durham DH1 3LE, U.K.
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3
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Kulmaczewski R, Kershaw Cook LJ, Pask CM, Cespedes O, Halcrow MA. Iron(II) Complexes of 4-(Alkyldisulfanyl)-2,6-di(pyrazolyl)pyridine Derivatives. Correlation of Spin-Crossover Cooperativity with Molecular Structure Following Single-Crystal-to-Single-Crystal Desolvation. Cryst Growth Des 2022; 22:1960-1971. [PMID: 35431660 PMCID: PMC9007408 DOI: 10.1021/acs.cgd.2c00005] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 01/24/2022] [Indexed: 06/14/2023]
Abstract
The complex salts [Fe(L 1)2]X2 (1X 2 ; L 1 = 4-(isopropyldisulfanyl)-2,6-bis(pyrazolyl)pyridine; X- = BF4 -, ClO4 -) form solvated crystals from common organic solvents. Crystals of 1X 2 ·Me2CO show abrupt spin transitions near 160 K, with up to 22 K thermal hysteresis. 1X 2 ·Me2CO cocrystallizes with other, less cooperative acetone solvates, which all transform into the same solvent-free materials 1X 2 ·sf upon exposure to air, or mild heating. Conversion of 1X 2 ·Me2CO to 1X 2 ·sf proceeds in a single-crystal to single-crystal fashion. 1X 2 ·sf are not isomorphous with the acetone solvates, and exhibit abrupt spin transitions at low temperature with hysteresis loops of 30-38 K (X- = BF4 -) and 10-20 K (X- = ClO4 -), depending on the measurement method. Interestingly, the desolvation has an opposite effect on the SCO temperature and hysteresis in the two salts. The hysteretic spin transitions in 1X 2 ·Me2CO and 1X 2 ·sf do not involve a crystallographic phase change but are accompanied by a significant rearrangement of the metal coordination sphere. Other solvates 1X 2 ·MeNO2, 1X 2 ·MeCN, and 1X 2 ·H2O are mostly isomorphous with each other and show more gradual spin-crossover equilibria near room temperature. All three of these lattice types have similar unit cell dimensions and contain cations associated into chains through pairwise, intermolecular S···π interactions. Polycrystalline [Fe(L 2)2][BF4]2·MeNO2 (2[BF 4 ] 2 ·MeNO2; L 2 = 4-(methyldisulfanyl)-2,6-bis(pyrazolyl)pyridine) shows an abrupt spin transition just above room temperature, with an unsymmetrical and structured hysteresis loop, whose main features are reversible upon repeated thermal scanning.
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Affiliation(s)
- Rafal Kulmaczewski
- School
of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
| | | | - Christopher M. Pask
- School
of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
| | - Oscar Cespedes
- School
of Physics and Astronomy, University of
Leeds, E. C. Stoner
Building, Leeds LS2 9JT, U.K.
| | - Malcolm A. Halcrow
- School
of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K.
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4
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Han G, Vasylenko A, Neale AR, Duff BB, Chen R, Dyer MS, Dang Y, Daniels LM, Zanella M, Robertson CM, Kershaw Cook LJ, Hansen AL, Knapp M, Hardwick LJ, Blanc F, Claridge JB, Rosseinsky MJ. Extended Condensed Ultraphosphate Frameworks with Monovalent Ions Combine Lithium Mobility with High Computed Electrochemical Stability. J Am Chem Soc 2021; 143:18216-18232. [PMID: 34677973 PMCID: PMC8569803 DOI: 10.1021/jacs.1c07874] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Extended anionic
frameworks based on condensation of polyhedral
main group non-metal anions offer a wide range of structure types.
Despite the widespread chemistry and earth abundance of phosphates
and silicates, there are no reports of extended ultraphosphate anions
with lithium. We describe the lithium ultraphosphates Li3P5O14 and Li4P6O17 based on extended layers and chains of phosphate, respectively.
Li3P5O14 presents a complex structure
containing infinite ultraphosphate layers with 12-membered rings that
are stacked alternately with lithium polyhedral layers. Two distinct
vacant tetrahedral sites were identified at the end of two distinct
finite Li6O1626– chains. Li4P6O17 features a new type of loop-branched
chain defined by six PO43– tetrahedra.
The ionic conductivities and electrochemical properties of Li3P5O14 were examined by impedance spectroscopy
combined with DC polarization, NMR spectroscopy, and galvanostatic
plating/stripping measurements. The structure of Li3P5O14 enables three-dimensional lithium migration
that affords the highest ionic conductivity (8.5(5) × 10–7 S cm–1 at room temperature for
bulk), comparable to that of commercialized LiPON glass thin film
electrolytes, and lowest activation energy (0.43(7) eV) among all
reported ternary Li–P–O phases. Both new lithium ultraphosphates
are predicted to have high thermodynamic stability against oxidation,
especially Li3P5O14, which is predicted
to be stable to 4.8 V, significantly higher than that of LiPON and
other solid electrolytes. The condensed phosphate units defining these
ultraphosphate structures offer a new route to optimize the interplay
of conductivity and electrochemical stability required, for example,
in cathode coatings for lithium ion batteries.
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Affiliation(s)
- Guopeng Han
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Andrij Vasylenko
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Alex R Neale
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom.,Stephenson Institute for Renewable Energy, University of Liverpool, Peach Street, Liverpool L69 7ZF, United Kingdom
| | - Benjamin B Duff
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom.,Stephenson Institute for Renewable Energy, University of Liverpool, Peach Street, Liverpool L69 7ZF, United Kingdom
| | - Ruiyong Chen
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Matthew S Dyer
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Yun Dang
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Luke M Daniels
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Marco Zanella
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Craig M Robertson
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Laurence J Kershaw Cook
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Anna-Lena Hansen
- Institute for Applied Materials - Energy Storage Systems, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Michael Knapp
- Institute for Applied Materials - Energy Storage Systems, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
| | - Laurence J Hardwick
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom.,Stephenson Institute for Renewable Energy, University of Liverpool, Peach Street, Liverpool L69 7ZF, United Kingdom
| | - Frédéric Blanc
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom.,Stephenson Institute for Renewable Energy, University of Liverpool, Peach Street, Liverpool L69 7ZF, United Kingdom
| | - John B Claridge
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
| | - Matthew J Rosseinsky
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, United Kingdom
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5
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Abstract
![]()
Many molecular machines
are built from modular components with
well-defined motile capabilities, such as axles and wheels. Hinges
are particularly useful, as they provide the minimum flexibility needed
for a simple and pronounced conformational change. Compounds with
multiple stable conformers are common, but molecular hinges almost
exclusively operate via dihedral rotations rather than truly hinge-like
clamping mechanisms. An ideal molecular hinge would better reproduce
the behavior of hinged devices, such as gates and tweezers, while
remaining soluble, scalable, and synthetically versatile. Herein,
we describe two isomeric macrocycles with clamp-like open and closed
geometries, which crystallize as separate polymorphs but interconvert
freely in solution. An unusual one-pot addition cyclization reaction
was used to produce the macrocycles on a multigram scale from inexpensive
reagents, without supramolecular templating or high-dilution conditions.
Using mechanistic information from NMR kinetic studies and at-line
mass spectrometry, we developed a semicontinuous flow synthesis with
maximum conversions of 85–93% and over 80% selectivity for
a single isomer. The macrocycles feature voids that are sterically
protected from guests, including reactive species such as fluoride
ions, and could therefore serve as chemically inert hinges for adaptive
supramolecular receptors and flexible porous materials.
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Affiliation(s)
- Christopher D Jones
- Department of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Laurence J Kershaw Cook
- Department of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - David Marquez-Gamez
- Department of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Konstantin V Luzyanin
- Department of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Jonathan W Steed
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, U.K
| | - Anna G Slater
- Department of Chemistry and Materials Innovation Factory, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
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6
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Vriza A, Canaj AB, Vismara R, Kershaw Cook LJ, Manning TD, Gaultois MW, Wood PA, Kurlin V, Berry N, Dyer MS, Rosseinsky MJ. One class classification as a practical approach for accelerating π-π co-crystal discovery. Chem Sci 2020; 12:1702-1719. [PMID: 34163930 PMCID: PMC8179233 DOI: 10.1039/d0sc04263c] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The implementation of machine learning models has brought major changes in the decision-making process for materials design. One matter of concern for the data-driven approaches is the lack of negative data from unsuccessful synthetic attempts, which might generate inherently imbalanced datasets. We propose the application of the one-class classification methodology as an effective tool for tackling these limitations on the materials design problems. This is a concept of learning based only on a well-defined class without counter examples. An extensive study on the different one-class classification algorithms is performed until the most appropriate workflow is identified for guiding the discovery of emerging materials belonging to a relatively small class, that being the weakly bound polyaromatic hydrocarbon co-crystals. The two-step approach presented in this study first trains the model using all the known molecular combinations that form this class of co-crystals extracted from the Cambridge Structural Database (1722 molecular combinations), followed by scoring possible yet unknown pairs from the ZINC15 database (21 736 possible molecular combinations). Focusing on the highest-ranking pairs predicted to have higher probability of forming co-crystals, materials discovery can be accelerated by reducing the vast molecular space and directing the synthetic efforts of chemists. Further on, using interpretability techniques a more detailed understanding of the molecular properties causing co-crystallization is sought after. The applicability of the current methodology is demonstrated with the discovery of two novel co-crystals, namely pyrene-6H-benzo[c]chromen-6-one (1) and pyrene-9,10-dicyanoanthracene (2). Machine learning using one class classification on a database of existing co-crystals enables the identification of co-formers which are likely to form stable co-crystals, resulting in the synthesis of two co-crystals of polyaromatic hydrocarbons.![]()
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Affiliation(s)
- Aikaterini Vriza
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK .,Leverhulme Research Centre for Functional Materials Design, University of Liverpool Oxford Street Liverpool L7 3NY UK
| | - Angelos B Canaj
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK
| | - Rebecca Vismara
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK
| | - Laurence J Kershaw Cook
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK
| | - Troy D Manning
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK
| | - Michael W Gaultois
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK .,Leverhulme Research Centre for Functional Materials Design, University of Liverpool Oxford Street Liverpool L7 3NY UK
| | - Peter A Wood
- Cambridge Crystallographic Data Centre 12 Union Road Cambridge CB2 1EZ UK
| | - Vitaliy Kurlin
- Materials Innovation Factory, Computer Science Department, University of Liverpool Liverpool L69 3BX UK
| | - Neil Berry
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK
| | - Matthew S Dyer
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK .,Leverhulme Research Centre for Functional Materials Design, University of Liverpool Oxford Street Liverpool L7 3NY UK
| | - Matthew J Rosseinsky
- Department of Chemistry and Materials Innovation Factory, University of Liverpool 51 Oxford Street Liverpool L7 3NY UK .,Leverhulme Research Centre for Functional Materials Design, University of Liverpool Oxford Street Liverpool L7 3NY UK
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7
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8
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Bagherzadeh M, Bayrami A, Kia R, Amini M, Cook LJK, Raithby PR. Two new copper(II) complexes with chelating N,O-type bidentate ligands: Synthesis, characterization, crystal structure and catalytic activity in azide–alkyne cycloaddition reaction. Inorganica Chim Acta 2017. [DOI: 10.1016/j.ica.2017.06.046] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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9
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Kulmaczewski R, Trzop E, Kershaw Cook LJ, Collet E, Chastanet G, Halcrow MA. The role of symmetry breaking in the structural trapping of light-induced excited spin states. Chem Commun (Camb) 2017; 53:13268-13271. [DOI: 10.1039/c7cc07990g] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Six isostructural compounds show differing agreement with the correlation T(LIESST) = T0 − 0.3T1/2 (red line; LIESST = Light-Induced Excited Spin-State Trapping). This reflects crystallographic symmetry breaking under LIESST conditions, exhibited by one of the compounds but not by two others.
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Affiliation(s)
| | - Elzbieta Trzop
- Institut de Physique de Rennes
- Université de Rennes 1
- UMR UR1-CNRS 6251
- F-35000 Rennes
- France
| | | | - Eric Collet
- Institut de Physique de Rennes
- Université de Rennes 1
- UMR UR1-CNRS 6251
- F-35000 Rennes
- France
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10
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Kershaw Cook LJ, Kulmaczewski R, Mohammed R, Dudley S, Barrett SA, Little MA, Deeth RJ, Halcrow MA. A Unified Treatment of the Relationship Between Ligand Substituents and Spin State in a Family of Iron(II) Complexes. Angew Chem Int Ed Engl 2016; 55:4327-31. [PMID: 26929084 PMCID: PMC4804750 DOI: 10.1002/anie.201600165] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Indexed: 11/10/2022]
Abstract
The influence of ligands on the spin state of a metal ion is of central importance for bioinorganic chemistry, and the production of base-metal catalysts for synthesis applications. Complexes derived from [Fe(bpp)2 ](2+) (bpp=2,6-di{pyrazol-1-yl}pyridine) can be high-spin, low-spin, or spin-crossover (SCO) active depending on the ligand substituents. Plots of the SCO midpoint temperature (T1/2 ) in solution vs. the relevant Hammett parameter show that the low-spin state of the complex is stabilized by electron-withdrawing pyridyl ("X") substituents, but also by electron-donating pyrazolyl ("Y") substituents. Moreover, when a subset of complexes with halogeno X or Y substituents is considered, the two sets of compounds instead show identical trends of a small reduction in T1/2 for increasing substituent electronegativity. DFT calculations reproduce these disparate trends, which arise from competing influences of pyridyl and pyrazolyl ligand substituents on Fe-L σ and π bonding.
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Affiliation(s)
- Laurence J Kershaw Cook
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
- Department of Chemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | | | | | - Stephen Dudley
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
| | - Simon A Barrett
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
| | - Marc A Little
- School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK
- Department of Chemistry, University of Liverpool, Crown Street, Liverpool, L69 7ZD, UK
| | - Robert J Deeth
- Inorganic Computational Chemistry Group, Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.
- School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, UK.
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11
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Kershaw Cook LJ, Kearsey R, Lamb JV, Pace EJ, Gould JA. Efficient and chromatography-free methodology for the modular synthesis of oligo-(1 H -pyrazol-4-yl)-arenes with controllable size, shape and steric bulk. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.01.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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12
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Chappell S, Brooke C, Nichols RJ, Kershaw Cook LJ, Halcrow M, Ulstrup J, Higgins SJ. Evidence for a hopping mechanism in metal|single molecule|metal junctions involving conjugated metal–terpyridyl complexes; potential-dependent conductances of complexes [M(pyterpy)2]2+ (M = Co and Fe; pyterpy = 4′-(pyridin-4-yl)-2,2′:6′,2′′-terpyridine) in ionic liquid. Faraday Discuss 2016; 193:113-131. [DOI: 10.1039/c6fd00080k] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Extensive studies of various families of conjugated molecules in metal|molecule|metal junctions suggest that the mechanism of conductance is usually tunnelling for molecular lengths < ca. 4 nm, and that for longer molecules, coherence is lost as a hopping element becomes more significant. In this work we present evidence that, for a family of conjugated, redox-active metal complexes, hopping may be a significant factor for even the shortest molecule studied (ca. 1 nm between contact atoms). The length dependence of conductance for two series of such complexes which differ essentially in the number of conjugated 1,4-C6H4- rings in the structures has been studied, and it is found that the junction conductances vary linearly with molecular length, consistent with a hopping mechanism, whereas there is significant deviation from linearity in plots of log(conductance) vs. length that would be characteristic of tunnelling, and the slopes of the log(conductance)–length plots are much smaller than expected for an oligophenyl system. Moreover, the conductances of molecular junctions involving the redox–active molecules, [M(pyterpy)2]2+/3+ (M = Co, Fe) have been studied as a function of electrochemical potential in ionic liquid electrolyte, and the conductance–overpotential relationship is found to fit well with the Kuznetsov–Ulstrup relationship, which is essentially a hopping description.
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Affiliation(s)
- Sarah Chappell
- Department of Chemistry
- University of Liverpool
- Liverpool L69 7ZD
- UK
| | - Carly Brooke
- Department of Chemistry
- University of Liverpool
- Liverpool L69 7ZD
- UK
| | | | | | | | - Jens Ulstrup
- Department of Chemistry
- Technical University of Denmark
- DK-2800 Kgs. Lyngby
- Denmark
| | - Simon J. Higgins
- Department of Chemistry
- University of Liverpool
- Liverpool L69 7ZD
- UK
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13
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Cook LJK, Kulmaczewski R, Cespedes O, Halcrow MA. Different Spin-State Behaviors in Isostructural Solvates of a Molecular Iron(II) Complex. Chemistry 2015; 22:1789-99. [DOI: 10.1002/chem.201503989] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Indexed: 11/07/2022]
Affiliation(s)
- Laurence J. Kershaw Cook
- School of Chemistry; University of Leeds; Woodhouse Lane Leeds LS2 9JT UK), Fax
- Department of Chemistry; University of Bath; Claverton Down Bath BA2 7AY UK)
| | - Rafal Kulmaczewski
- School of Chemistry; University of Leeds; Woodhouse Lane Leeds LS2 9JT UK), Fax
| | - Oscar Cespedes
- School of Physics and Astronomy; University of Leeds; E.C. Stoner Building Leeds LS2 9JT UK)
| | - Malcolm A. Halcrow
- School of Chemistry; University of Leeds; Woodhouse Lane Leeds LS2 9JT UK), Fax
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14
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Kershaw Cook LJ, Thorp-Greenwood FL, Comyn TP, Cespedes O, Chastanet G, Halcrow MA. Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn- Teller Distortion. Inorg Chem 2015; 54:6319-6330. [PMID: 26351707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The synthesis of 4-methyl-2,6-di(pyrazol-1-yl)pyridine (L) and four salts of [FeL2]X2 (X– = BF(4)(–), 1; X– = ClO(4)(–), 2; X– = PF(6)(–), 3; X– = CF3SO(3)(–), 4) are reported. Powder samples of 1 and 2 both exhibit abrupt, hysteretic spin-state transitions on cooling, with T(1/2)↓ = 204 and T(1/2)↑ = 209 K (1), and T(1/2)↓ = 175 and T(1/2)↑ = 193 K (2). The 18 K thermal hysteresis loop for 2 is unusually wide for a complex of this type. Single crystal structures of 2 show it to exhibit a Jahn–Teller-distorted six-coordinate geometry in its high-spin state, which would normally inhibit spin-crossover. Bulk samples of 1 and 2 are isostructural by X-ray powder diffraction, and undergo a crystallographic phase change during their spin-transitions. At temperatures below T(1/2), exposing both compounds to 10(–5) Torr pressure inside the powder diffractometer causes a reversible transformation back to the high-temperature crystal phase. Consideration of thermodynamic data implies this cannot be accompanied by a low → high spin-state change, however. Both compounds also exhibit the LIESST effect, with 2 exhibiting an unusually high T(LIESST) of 112 K. The salts 3 and 4 are respectively high-spin and low-spin between 3 and 300 K, with crystalline 3 exhibiting a more pronounced version of the same Jahn–Teller distortion.
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Kershaw Cook LJ, Thorp-Greenwood FL, Comyn TP, Cespedes O, Chastanet G, Halcrow MA. Unexpected Spin-Crossover and a Low-Pressure Phase Change in an Iron(II)/Dipyrazolylpyridine Complex Exhibiting a High-Spin Jahn–Teller Distortion. Inorg Chem 2015; 54:6319-30. [DOI: 10.1021/acs.inorgchem.5b00614] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | - Tim P. Comyn
- Institute
for Materials Research, School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, E. C. Stoner Building, Leeds LS2 9JT, United Kingdom
| | | | - Malcolm A. Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, United Kingdom
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Santoro A, Kershaw Cook LJ, Kulmaczewski R, Barrett SA, Cespedes O, Halcrow MA. Iron(II) complexes of tridentate indazolylpyridine ligands: enhanced spin-crossover hysteresis and ligand-based fluorescence. Inorg Chem 2015; 54:682-93. [PMID: 25563430 DOI: 10.1021/ic502726q] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reaction of 2,6-difluoropyridine with 2 equiv of indazole and NaH at room temperature affords a mixture of 2,6-bis(indazol-1-yl)pyridine (1-bip), 2-(indazol-1-yl)-6-(indazol-2-yl)pyridine (1,2-bip), and 2,6-bis(indazol-2-yl)pyridine (2-bip), which can be separated by solvent extraction. A two-step procedure using the same conditions also affords both 2-(indazol-1-yl)-6-(pyrazol-1-yl)pyridine (1-ipp) and 2-(indazol-2-yl)-6-(pyrazol-1-yl)pyridine (2-ipp). These are all annelated analogues of 2,6-di(pyrazol-1-yl)pyridine, an important ligand for spin-crossover complexes. Iron(II) complexes [Fe(1-bip)2](2+), [Fe(1,2-bip)2](2+), and [Fe(1-ipp)2](2+) are low-spin at room temperature, reflecting sterically imposed conformational rigidity of the 1-indazolyl ligands. In contrast, the 2-indazolyl complexes [Fe(2-bip)2](2+) and [Fe(2-ipp)2](2+) are high-spin in solution at room temperature, whereas salts of [Fe(2-bip)2](2+) exhibit thermal spin transitions in the solid state. Notably, [Fe(2-bip)2][BF4]2·2MeNO2 adopts a terpyridine embrace lattice structure and undergoes a spin transition near room temperature after annealing, resulting in thermal hysteresis that is wider than previously observed for this structure type (T1/2 = 266 K, ΔT = 16-20 K). This reflects enhanced mechanical coupling between the cations in the lattice through interdigitation of their ligand arms, which supports a previously proposed structure/function relationship for spin-crossover materials with this form of crystal packing. All of the compounds in this work exhibit blue fluorescence in solution under ambient conditions. In most cases, the ligand-based emission maxima are slightly red shifted upon complexation, but there is no detectable correlation between the emission maximum and the spin state of the iron centers.
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Affiliation(s)
- Amedeo Santoro
- School of Chemistry, University of Leeds , Woodhouse Lane, Leeds LS2 9JT, United Kingdom
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Kershaw Cook LJ, Kulmaczewski R, Barrett SA, Halcrow MA. Iron(ii) complexes of 4-sulfanyl-, 4-sulfinyl- and 4-sulfonyl-2,6-dipyrazolylpyridine ligands. A subtle interplay between spin-crossover and crystallographic phase changes. Inorg Chem Front 2015. [DOI: 10.1039/c5qi00083a] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The compound shown exhibits an abrupt thermal spin-transition, with an accompanying crystallographic phase change at slightly lower temperature which is visible as a shoulder on the susceptibility curve.
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Kershaw Cook LJ, Fisher J, Harding LP, Halcrow MA. An iron(ii) spin-crossover metallacycle from a back-to-back bis-[dipyrazolylpyridine]. Dalton Trans 2015; 44:9417-25. [DOI: 10.1039/c5dt00732a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Iron(ii) and zinc(ii) complexes of bis[2,6-di(pyrazol-1-yl)pyrid-4-yl]disulfide assemble into tetranuclear metallacycles according to ES-MS, DOSY NMR and conductivity data. The iron complex exhibits a thermal spin-state equilibrium in solution, which the iron centres appear to undergo independently of each other.
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Affiliation(s)
| | - Julie Fisher
- School of Chemistry
- University of Leeds
- Leeds
- UK LS2 9JT
| | - Lindsay P. Harding
- Department of Chemical and Biological Sciences
- University of Huddersfield
- Huddersfield
- UK HD1 3DH
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Roberts TD, Little MA, Kershaw Cook LJ, Halcrow MA. Iron(ii) complexes of 2,6-di(1H-pyrazol-3-yl)-pyridine derivatives with hydrogen bonding and sterically bulky substituents. Dalton Trans 2014; 43:7577-88. [PMID: 24705977 DOI: 10.1039/c4dt00355a] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Thomas D Roberts
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
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