I19-Small Molecule Single Crystal Diffraction
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Emily
Howarth
,
Jordan
Lopez
,
Joseph O.
Ogar
,
Toby J.
Blundell
,
Hiroki
Akutsu
,
Yasuhiro
Nakazawa
,
Shusaku
Imajo
,
Yoshihiko
Ihara
,
Simon J.
Coles
,
Peter N.
Horton
,
Jeppe
Christensen
,
Lee
Martin
Open Access
Abstract: This paper reports the synthesis, crystal structures and conducting properties of the first BEDT-TTF radical-cation salts with D3 symmetry tris-coordinated racemic lanthanide(III) anions. It is also the first crystallographic determination of the nine-coordinate tris(chelidonato)terbate and tris(chelidonato)dysprosate anions (chelidonic acid = clo = 4-oxo-4H-pyran-2,6-dicarboxylic acid). Salt α-(BEDT-TTF)5M(chelidonato)3·EtOH·2H2O is semimetallic for M = Tb, and semiconducting for M = Dy. These conducting properties are consistent with the band structure for both salts.
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Jan 2025
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I24-Microfocus Macromolecular Crystallography
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Rachel
Bolton
,
Moritz M.
Machelett
,
Jack
Stubbs
,
Danny
Axford
,
Nicolas
Caramello
,
Lucrezia
Catapano
,
Martin
Maly
,
Matthew J.
Rodrigues
,
Charlotte
Cordery
,
Graham J.
Tizzard
,
Fraser
Macmillan
,
Sylvain
Engilberge
,
David
Von Stetten
,
Takehiko
Tosha
,
Hiroshi
Sugimoto
,
Jonathan A. R.
Worrall
,
Jeremy S.
Webb
,
Mike
Zubkov
,
Simon
Coles
,
Eric
Mathieu
,
Roberto A.
Steiner
,
Garib
Murshudov
,
Tobias E.
Schrader
,
Allen M.
Orville
,
Antoine
Royant
,
Gwyndaf
Evans
,
Michael A.
Hough
,
Robin L.
Owen
,
Ivo
Tews
Diamond Proposal Number(s):
[15722, 14493, 23570]
Open Access
Abstract: The marine cyanobacterium Prochlorococcus is a main contributor to global photosynthesis, whilst being limited by iron availability. Cyanobacterial genomes generally encode two different types of FutA iron-binding proteins: periplasmic FutA2 ABC transporter subunits bind Fe(III), while cytosolic FutA1 binds Fe(II). Owing to their small size and their economized genome Prochlorococcus ecotypes typically possess a single futA gene. How the encoded FutA protein might bind different Fe oxidation states was previously unknown. Here, we use structural biology techniques at room temperature to probe the dynamic behavior of FutA. Neutron diffraction confirmed four negatively charged tyrosinates, that together with a neutral water molecule coordinate iron in trigonal bipyramidal geometry. Positioning of the positively charged Arg103 side chain in the second coordination shell yields an overall charge-neutral Fe(III) binding state in structures determined by neutron diffraction and serial femtosecond crystallography. Conventional rotation X-ray crystallography using a home source revealed X-ray-induced photoreduction of the iron center with observation of the Fe(II) binding state; here, an additional positioning of the Arg203 side chain in the second coordination shell maintained an overall charge neutral Fe(II) binding site. Dose series using serial synchrotron crystallography and an XFEL X-ray pump–probe approach capture the transition between Fe(III) and Fe(II) states, revealing how Arg203 operates as a switch to accommodate the different iron oxidation states. This switching ability of the Prochlorococcus FutA protein may reflect ecological adaptation by genome streamlining and loss of specialized FutA proteins.
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Mar 2024
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I19-Small Molecule Single Crystal Diffraction
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Jogirdas
Vainauskas
,
Tristan H.
Borchers
,
Mihails
Arhangelskis
,
Laura J.
Mccormick Mcpherson
,
Toni S.
Spilfogel
,
Ehsan
Hamzehpoor
,
Filip
Topić
,
Simon J.
Coles
,
Dmytro F.
Perepichka
,
Christopher J.
Barrett
,
Tomislav
Friscic
Diamond Proposal Number(s):
[26802]
Open Access
Abstract: Carbon, although the central element in organic chemistry, has been traditionally neglected as a target for directional supramolecular interactions. The design of supramolecular structures involving carbon-rich molecules, such as arene hydrocarbons, has been limited almost exclusively to non-directional π-stacking, or derivatisation with heteroatoms to introduce molecular assembly recognition sites. As a result, the predictable assembly of non-derivatised, carbon-only π-systems using directional non-covalent interactions remains an unsolved fundamental challenge of solid-state supramolecular chemistry. Here, we propose and validate a different paradigm for the reliable assembly of carbon-only aromatic systems into predictable supramolecular architectures: not through non-directional π-stacking, but via specific and directional halogen bonding. We present a systematic experimental, theoretical and database study of halogen bonds to carbon-only π-systems (C–I⋯πC bonds), focusing on the synthesis and structural analysis of cocrystals with diversely-sized and -shaped non-derivatised arenes, from one-ring (benzene) to 15-ring (dicoronylene) polycyclic atomatic hydrocarbons (PAHs), and fullerene C60, along with theoretical calculations and a systematic analysis of the Cambridge Structural Database. This study establishes C–I⋯πC bonds as directional interactions to arrange planar and curved carbon-only aromatic systems into predictable supramolecular motifs. In >90% of herein presented structures, the C–I⋯πC bonds to PAHs lead to a general ladder motif, in which the arenes act as the rungs and halogen bond donors as the rails, establishing a unique example of a supramolecular synthon based on carbon-only molecules. Besides fundamental importance in the solid-state and supramolecular chemistry of arenes, this synthon enables access to materials with exciting properties based on simple, non-derivatised aromatic systems, as seen from large red and blue shifts in solid-state luminescence and room-temperature phosphorescence upon cocrystallisation.
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Nov 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[31778]
Open Access
Abstract: The synthesis and characterisation of eleven different 2-(thienyl)quinoxaline species that incorporate different points of functionality, including at the thiophene or quinoxaline rings, are described. These species display variable fluorescence properties in the visible region (λem = 401–491 nm) depending upon the molecular structures and extent of conjugation. The series of 2-(thienyl)quinoxaline species were then investigated as cyclometalating agents for Ir(III) to yield [Ir(C^N)2(bipy)]PF6 (where C^N = the cyclometalated ligand; bipy = 2,2′-bipyridine). Eight complexes were successfully isolated and fully characterised by an array of spectroscopic and analytical techniques. Two Ir(III) examples were structurally characterised in the solid state using single crystal X-ray diffraction; both structures confirmed the proposed formulations and coordination spheres in each case showing that the thiophene coordinates via a Ir–C bond. The photophysical properties of the complexes revealed that each complex is luminescent under ambient conditions with a range of emission wavelengths observed (665–751 nm) indicating that electronic tuning can be achieved via both the thienyl and quinoxaline moieties.
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Oct 2023
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[20876]
Open Access
Abstract: Cyclic porphyrin oligomers have been studied as models for photosynthetic light-harvesting antenna complexes and as potential receptors for supramolecular chemistry. Here, we report the synthesis of unprecedented β,β-directly linked cyclic zinc porphyrin oligomers, the trimer (CP3) and tetramer (CP4), by Yamamoto coupling of a 2,3-dibromoporphyrin precursor. Their three-dimensional structures were confirmed by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and single-crystal X-ray diffraction analyses. The minimum-energy geometries of CP3 and CP4 have propeller and saddle shapes, respectively, as calculated using density functional theory. Their different geometries result in distinct photophysical and electrochemical properties. The smaller dihedral angles between the porphyrin units in CP3, compared with CP4, result in stronger π-conjugation, splitting the ultraviolet–vis absorption bands and shifting them to longer wavelengths. Analysis of the crystallographic bond lengths indicates that the central benzene ring of the CP3 is partially aromatic [harmonic oscillator model of aromaticity (HOMA) 0.52], whereas the central cyclooctatetraene ring of the CP4 is non-aromatic (HOMA –0.02). The saddle-shaped structure of CP4 makes it a ditopic receptor for fullerenes, with affinity constants of (1.1 ± 0.4) × 105 M–1 for C70 and (2.2 ± 0.1) × 104 M–1 for C60, respectively, in toluene solution at 298 K. The formation of a 1:2 complex with C60 is confirmed by NMR titration and single-crystal X-ray diffraction.
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May 2023
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I03-Macromolecular Crystallography
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Arathy
Jose
,
Daniel
Guest
,
Remi
Legay
,
Graham J.
Tizzard
,
Simon
Coles
,
Mariliza
Derveni
,
Edward
Wright
,
Lester
Marrison
,
Alpha A.
Lee
,
Aaron
Morris
,
Matt
Robinson
,
Frank
Von Delft
,
Daren
Fearon
,
Lizbe
Koekemoer
,
Tetiana
Matviuk
,
Anthony
Aimon
,
Christopher J.
Schofield
,
Tika R.
Malla
,
Nir
London
,
Barnaby W.
Greenland
,
Mark C.
Bagley
,
John
Spencer
Diamond Proposal Number(s):
[19301]
Open Access
Abstract: The pentafluorosulfanyl (-SF5) functional group is of increasing interest as a bioisostere in medicinal chemistry. A library of SF5-containing compounds, including amide, isoxazole, and oxindole derivatives, was synthesised using a range of solution-based and solventless methods, including microwave and ball-mill techniques. The library was tested against targets including human dihydroorotate dehydrogenase (HDHODH). A subsequent focused approach led to synthesis of analogues of the clinically used disease modifying anti-rheumatic drugs (DMARDs), Teriflunomide and Leflunomide, considered for potential COVID-19 use, where SF5 bioisostere deployment led to improved inhibition of HDHODH compared with the parent drugs. The results demonstrate the utility of the SF5 group in medicinal chemistry.
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Feb 2022
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I19-Small Molecule Single Crystal Diffraction
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John D.
Wallis
,
Gregory J
Rees
,
Mateusz B.
Pitak
,
Alberth
Lari
,
Stephen P.
Day
,
Jonathan R.
Yates
,
Peter
Gierth
,
Kristian
Barnsley
,
Mark E.
Smith
,
Simon J.
Coles
,
John V.
Hanna
Diamond Proposal Number(s):
[8521]
Open Access
Abstract: A combination of charge density studies and solid state nuclear magnetic resonance (NMR) 1 J NC coupling measurements supported by periodic density functional theory (DFT) calculations is used to characterise the transition from an n - π * interaction to bond formation between a nucleophilic nitrogen atom and an electrophilic sp 2 carbon atom in a series of crystalline peri-substituted naphthalenes. As the N···C distance reduces there is a sharp decrease in the Laplacian derived from increasing charge density between the two groups at ca. N···C:1.8 Å, with the periodic DFT calculations predicting, and heteronuclear spin-echo NMR measurements confirming, the 1 J NC couplings of ~2-5 Hz for long C-N bonds (1.60-1.65 Å), and 1 J NC couplings of <1 Hz for N···C > 2.1 Å.
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Aug 2021
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Zahraa S.
Al-Taie
,
Joseph M.
Anderson
,
Laura
Bischoff
,
Jeppe
Christensen
,
Simon J.
Coles
,
Richard
Froom
,
Mari E.
Gibbard
,
Leigh F.
Jones
,
F. F. J.
De Kleijne
,
Patrick J.
Murphy
,
Emma C.
Thompson
Abstract: We report the preparation of a range of N-protected amino acid derived guanidine organocatalysts and their application to the Michael addition of 2-hydroxy-1,4-napthoquinone to β-nitrostyrene, achieving a maximum ee of 26%. Whilst these catalysts gave poor ees, the structural variation together with the X-ray crystallographic study of the intra- and intermolecular hydrogen bonding reported suggest that the C2-symmetric catalyst are lead compounds for the further development of this methodology.
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Apr 2021
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I19-Small Molecule Single Crystal Diffraction
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Alexander J.
Bukvic
,
Arron L.
Burnage
,
Graham J.
Tizzard
,
Antonio J.
Martinez-Martinez
,
Alasdair I.
Mckay
,
Nicholas H.
Rees
,
Bengt E.
Tegner
,
Tobias
Krämer
,
Heather
Fish
,
Mark R.
Warren
,
Simon J.
Coles
,
Stuart A.
Macgregor
,
Andrew S.
Weller
Diamond Proposal Number(s):
[20300, 17308]
Open Access
Abstract: Using solid-state molecular organometallic (SMOM) techniques, in particular solid/gas single-crystal to single-crystal reactivity, a series of σ-alkane complexes of the general formula [Rh(Cy2PCH2CH2PCy2)(ηn:ηm-alkane)][BArF4] have been prepared (alkane = propane, 2-methylbutane, hexane, 3-methylpentane; ArF = 3,5-(CF3)2C6H3). These new complexes have been characterized using single crystal X-ray diffraction, solid-state NMR spectroscopy and DFT computational techniques and present a variety of Rh(I)···H–C binding motifs at the metal coordination site: 1,2-η2:η2 (2-methylbutane), 1,3-η2:η2 (propane), 2,4-η2:η2 (hexane), and 1,4-η1:η2 (3-methylpentane). For the linear alkanes propane and hexane, some additional Rh(I)···H–C interactions with the geminal C–H bonds are also evident. The stability of these complexes with respect to alkane loss in the solid state varies with the identity of the alkane: from propane that decomposes rapidly at 295 K to 2-methylbutane that is stable and instead undergoes an acceptorless dehydrogenation to form a bound alkene complex. In each case the alkane sits in a binding pocket defined by the {Rh(Cy2PCH2CH2PCy2)}+ fragment and the surrounding array of [BArF4]− anions. For the propane complex, a small alkane binding energy, driven in part by a lack of stabilizing short contacts with the surrounding anions, correlates with the fleeting stability of this species. 2-Methylbutane forms more short contacts within the binding pocket, and as a result the complex is considerably more stable. However, the complex of the larger 3-methylpentane ligand shows lower stability. Empirically, there therefore appears to be an optimal fit between the size and shape of the alkane and overall stability. Such observations are related to guest/host interactions in solution supramolecular chemistry and the holistic role of 1°, 2°, and 3° environments in metalloenzymes.
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Mar 2021
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I19-Small Molecule Single Crystal Diffraction
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Aaron J
Scott
,
Euan K.
Brechin
,
Stergios
Piligkos
,
Gopalan
Rajaraman
,
Mark
Murrie
,
Simon
Coles
,
Wim T.
Klooster
,
Gary S.
Nichol
,
Paul
Lusby
,
Lucy
Smythe
,
Arup
Sarkar
,
Julia
Vallejo
,
Emma
Regincos Marti
Diamond Proposal Number(s):
[22240]
Open Access
Abstract: Reaction of Ni(OTf)2 with the bisbidentate quaterpyridine ligand L results in the self-assembly of a tetrahedral, paramagnetic cage [NiII4L6]8+. By selectively exchanging the bound triflate from [OTf⊂NiII4L6](OTf)7 (1), we have been able to prepare a series of host-guest complexes that feauture an encapsulated paramagnetic tetrahalometallate ion inside this paramagnetic host giving [MIIX4⊂NiII4L6](OTf)6, where MIIX42− = MnCl42− (2), CoCl42− (5), CoBr42− (6), NiCl42− (7), CuBr42− (8) or [MIIIX4⊂NiII4L6](OTf)7, where MIIIX4− = FeCl4− (3), FeBr4− (4). Triflate-to-tetrahalometallate exchange occurs in solution and can also be accomplished through single-crystal-to-single-crystal transformations. Host-guest complexes 1-8 all crystallise as homochiral racemates in monoclinic space groups, wherein the four {NiN6} vertex within a single Ni4L6 unit possess the same Δ or Λ stereochemistry. Magnetic susceptibility and magnetisation data show that the magnetic exchange between metal ions in the host [NiII4] complex, and between the host and the MX4n- guest, are of comparable magnitude and antiferromagnetic in nature. Theoretically derived values for the magnetic exchange are in close agreement with experiment, revealing that large spin densities on the electronegative X-atoms of particular {MX4}n− guest molecules leads to stronger host-guest magnetic exchange interactions.
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Mar 2021
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