269 results on '"Gary S. Nichol"'
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2. Odd and Even Numbered Ferric Wheels
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Daniel J. Cutler, Angelos B. Canaj, Mukesh K. Singh, Gary S. Nichol, David Gracia, Hiroyuki Nojiri, Marco Evangelisti, Jürgen Schnack, and Euan K. Brechin
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FeIII ,even numbered wheel ,odd numbered wheel ,magnetism ,spin frustration ,Science - Abstract
Abstract The structurally related odd and even numbered wheels [FeIII11ZnII4(tea)10(teaH)1(OMe)Cl8] (1) and [FeIII12ZnII4(tea)12Cl8] (2) can be synthesized under ambient conditions by reacting FeIII and ZnII salts with triethanolamine (teaH3), the change in nuclearity being dictated by the solvents employed. An antiferromagnetic exchange between nearest neighbors, J = ‐10.0 cm−1 for 1 and J = −12.0 cm−1 for 2, leads to a frustrated S = 1/2 ground state in the former and an S = 0 ground state in the latter.
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- 2023
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3. The Sensitivity of Structure to Ionic Radius and Reaction Stoichiometry: A Crystallographic Study of Metal Coordination and Hydrogen Bonding in Barbiturate Complexes of All Five Alkali Metals Li–Cs
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William Clegg and Gary S. Nichol
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crystal structure ,alkali metals ,barbituric acid ,coordination ,stoichiometry ,bridging ligands ,Organic chemistry ,QD241-441 - Abstract
A systematic study has been conducted on barbiturate complexes of all five alkali metals, Li–Cs, prepared from metal carbonates or hydroxides in an aqueous solution without other potential ligands present, varying the stoichiometric ratio of metal ion to barbituric acid (BAH). Eight polymeric coordination compounds (two each for Na, K, and Rb and one each for Li and Cs) have been characterised by single-crystal X-ray diffraction. All contain some combination of barbiturate anion BA− (necessarily in a 1:1 ratio with the metal cation M+), barbituric acid, and water. All organic species and water molecules are coordinated to the metal centres via oxygen atoms as either terminal or bridging ligands. Coordination numbers range from 4 (for the Li complex) to 8 (for the Cs complex). Extensive hydrogen bonding plays a significant role in all the crystal structures, almost all of which include pairs of N–H···O hydrogen bonds linking BA− and/or BAH components into ribbons extending in one dimension. Factors influencing the structure adopted by each compound include cation size and reaction stoichiometry as well as hydrogen bonding.
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- 2024
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4. Investigating the Competitive Factors of Metal–Anion Coordination, Coordination by Water, and Hydrogen Bonding in Complexes of Cyanuric Acid with the Alkaline Earth Metals
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William Clegg and Gary S. Nichol
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crystal structure ,alkaline earth metals ,cyanuric acid ,hydrogen bonding ,bridging ligands ,chelate formation ,Crystallography ,QD901-999 - Abstract
A survey of the trends in metal–ligand coordination and hydrogen bonding has been carried out on complexes of singly deprotonated cyanuric acid CY− and alkaline earth metals, synthesised from aqueous solution and characterised by X-ray crystallography. The involvement of cyanurate in metal coordination increases from Mg through Ca and Sr to Ba relative to coordination by water, in parallel with increasing ionic radius and coordination number. The incidence of the bridging of metal centres by both water and cyanurate also increases in this series. The Mg complex [Mg(H2O)6][CY]2·2H2O contains hexaaqua-coordinated cations, uncoordinated CY− anions, and additional water molecules. The Ca and Sr complexes {[Ca(CY)(H2O)3][CY]}∞ and {[Sr(CY)2(H2O)4]}∞ feature polymeric chains of coordinated metal ions, the Ca complex with uncoordinated anions and the Sr complex with all potential ligands coordinated. The Ba complex {[Ba(CY)2(H2O)2]}∞ has a two-dimensional coordination network. Extensive hydrogen bonding plays a key role in generating a three-dimensional network in all four structures. The competition between cyanurate and water for coordination to the alkaline earth metal cations, and that between coordination and the hydrogen bonding propensities of the cyanurate anion, appear to be finely balanced, with the structural outcomes depending on the relative sizes and degrees of hardness of the four cations of the group.
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- 2024
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5. Manganese(I) Diamine Electrocatalysts: Electrochemical Carbon Dioxide Reduction to Carbon Monoxide
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Badrinath Dhakal, Brooke A. Corbin, Alberto Sosa Parada, Jonathan G. Sakai, Emily A. Felton, Lauren T. McDonald, Anthony J. Gross, Gary S. Nichol, and Greg A. N. Felton
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CO2 reduction ,electrocatalyst ,diamine ,manganese compounds ,CO formation ,Inorganic chemistry ,QD146-197 - Abstract
Novel organometallic complexes Mn(benzene-1,2-diamine)(CO)3Br, Mn-1, Mn(3-methylbenzene-1,2-diamine)(CO)3Br, Mn-2, and Re(benzene-1,2-diamine)(CO)3Cl, Re-1, have been synthesized and characterized by IR, UV/Vis, 1H-NMR, EA and HRMS. The structures of Mn-2 and Re-1 were confirmed by X-ray crystallography. The three novel compounds were studied for their electrocatalytic reduction of carbon dioxide to carbon monoxide using cyclic voltammetry in acetonitrile solutions. Controlled potential electrolysis was used to obtain information on faradaic yield, with product formation being confirmed by GC. Using earth-abundant manganese, compounds Mn-1 and Mn-2 display turnover frequencies of 108 s−1 and 82 s−1, respectively, amid selective production of carbon monoxide (faradaic yields ~85%), with minimal co-production of dihydrogen (Re-1, displays no activity as an electrocatalyst for carbon dioxide reduction under identical conditions.
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- 2023
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6. IronIII Half Salen Catalysts for Atom Transfer Radical and Ring-Opening Polymerizations
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Eszter Fazekas, Gary S. Nichol, Jennifer A. Garden, and Michael P. Shaver
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Chemistry ,QD1-999 - Published
- 2018
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7. Unexpected Selective Gas Adsorption on a ‘Non-Porous’ Metal Organic Framework
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Stuart Beveridge, Craig A. McAnally, Gary S. Nichol, Alan R. Kennedy, Edmund J. Cussen, and Ashleigh J. Fletcher
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carbon dioxide ,activated diffusion ,adsorption ,carbon capture ,interpenetration ,Crystallography ,QD901-999 - Abstract
A metal organic framework Cu(tpt)BF4·¾H2O was synthesized as a potential carbon capture material, with the aim being to exploit the Lewis base interaction of the incorporated ligand functionalities with acidic gas. The material displays high thermal stability but an exceptionally low surface area; however, this contrasts starkly with its ability to capture carbon dioxide, demonstrating significant activated diffusion within the framework. The full characterization of the material shows a robust structure, where the CO2 sorption is 120% greater than current industrial methods using liquid amine solutions; the thermal energy required for sorbent regeneration is reduced by 65%, indicating the true industrial potential of the synthesized material.
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- 2020
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8. Crystal structure of 2-hydroxy-N-(2-hydroxyethyl)-N-{2-hydroxy-3-[(E)-N-hydroxyethanimidoyl]-5-methylbenzyl}ethanaminium acetate monohydrate
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Gary S. Nichol, Jamie M. Frost, Sergio Sanz, and Euan K. Brechin
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crystal structure ,hydrogen bonding ,hydrate ,organic salt ,magnetism ,Crystallography ,QD901-999 - Abstract
The structure of the title hydrated molecular salt, C14H23N2O4+·C2H3O2−·H2O, was determined as part of a wider study on the use of the molecule as a polydentate ligand in the synthesis of MnIII clusters with magnetic properties. The cation features intramolecular O—H...N and N—H...O hydrogen-bond interactions. The crystal structure features a range of intermolecular hydrogen-bonding interactions, principally O—H...O interactions between all three species in the asymmetric unit. An R24(8) graph-set hydrogen-bonding motif between the anion and water molecules serves as a unit which links to the cation via the diethanolamine group. Each O atom of the acetate anion accepts two hydrogen bonds.
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- 2015
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9. [2-Butyl-4-(4-tert-butylbenzyl)-1,2,4-triazol-3-ylidene]chlorido[(1,2,5,6-η)-cycloocta-1,5-diene]iridium(I)
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Gary S. Nichol, David P. Walton, Laura J. Anna, and Edward Rajaseelan
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Crystallography ,QD901-999 - Abstract
In the title compound, [IrCl(C8H12)(C17H25N3)], the IrI ion has a distorted square-planar coordination geometry. The N-heterocyclic carbene ligand has an extended S-shaped conformation. The butyl group was refined using a two-part 1:1 disorder model. In the crystal, three unique weak C—H...Cl contacts are present. Two of these form a motif described as R21(6) in graph-set notation, while a third forms an R22(8) motif about a crystallographic inversion center. The result is a chain structure which extends parallel to the crystallographic a axis.
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- 2012
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10. 3-[4-(10H-Indolo[3,2-b]quinolin-11-yl)piperazin-1-yl]propan-1-ol
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Gary S. Nichol, Peda V. L. Boddupally, Biswanath De, and Laurence H. Hurley
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Crystallography ,QD901-999 - Abstract
In the title compound, C22H24N4O, the aromatic moiety is essentially planar (r.m.s. deviation of a least-squares plane fitted through all non-H atoms = 0.0386 Å) and is rotated by 89.98 (4)° from the piperazine ring, which adopts the expected chair conformation. The propanol chain is not fully extended away from the piperazine ring. In the crystal, there are two unique hydrogen-bonding interactions. One is an O—H...N interaction which, together with an inversion-related symmetry equivalent, forms a ring motif. The second is an N—H...N interaction which links adjacent molecules by means of a chain motif which propagates in the c-axis direction. Overall, a two-dimensional hydrogen-bonded structure is formed.
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- 2011
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11. [(1,2,5,6-η)-Cycloocta-1,5-diene]bis(1-isopropyl-3-methylimidazolin-2-ylidene)rhodium(I) tetrafluoridoborate
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Gary S. Nichol, Jonathan Rajaseelan, David P. Walton, and Edward Rajaseelan
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Crystallography ,QD901-999 - Abstract
In the title compound, [Rh(C8H12)(C7H12N2)2]BF4, the square-planar Rh complex cation and the BF4− anion are both bisected by a crystallographic twofold rotation axis. The Rh and B atoms lie on this axis and all others are in general positions. In the crystal, two unique C—H...F hydrogen-bonding interactions are present, which involve both imidazolin-2-ylidene H atoms. They form two separate C(5) motifs, the combination of which is a rippled hydrogen-bonded sheet structure in the ab plane.
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- 2011
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12. 3-(2,6-Dimethylanilino)imidazo[1,2-a]pyridin-1-ium perchlorate
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Gary S. Nichol, Anuj Sharma, and Hong-Yu Li
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Crystallography ,QD901-999 - Abstract
The structure of the organic cation in the title compound, C15H16N3+·ClO4−, contains two essentially planar rings. Mean planes fitted through all non-H atoms of each ring system have an r.m.s. deviation of 0.019 Å for the imidazole-based ring and 0.016 Å for the 2,6-dimethylphenyl ring. The angle between the two planes is 86.76 (2)°. In the crystal structure, N—H...O interactions form a one-dimensional chain, which propagates in the b-axis direction. C—H...O interactions are also found in the crystal packing.
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- 2011
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13. N,N′-Bis(5-bromopyridin-2-yl)methanediamine
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Gary S. Nichol, Anuj Sharma, and Hong-Yu Li
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Crystallography ,QD901-999 - Abstract
The V-shaped title compound, C11H10Br2N4, lies on a crystallographic twofold rotation axis which passes through the central C atom. In the crystal, an infinite tape motif, which propagates in the a-axis direction, is formed by inversion-related N—H...N hydrogen-bonding interactions. The structure confirmed the identity of the compound as a reaction side product.
- Published
- 2011
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14. 4-(Piperidin-1-yl)-4H-benzo[b]tetrazolo[1,5-d][1,4]diazepin-5(6H)-one
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Christopher Hulme, Christine E. Kaiser, Zhigang Xu, and Gary S. Nichol
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Crystallography ,QD901-999 - Abstract
There are two crystallographically unique molecules present in the asymmetric unit of the title compound, C14H16N6O; in both molecules, the seven-membered diazepinone ring adopts a boat-like conformation and the chair conformation piperidine ring is an axial substituent on the diazepinone ring. In the crystal, each molecule forms hydrogen bonds with its respective symmetry equivalents. Hydrogen bonding between molecule A and symmetry equivalents forms two ring motifs, the first formed by inversion-related N—H...O interactions and the second formed by C—H...O and C—H...N interactions. The combination of both ring motifs results in the formation of an infinite double tape, which propagates in the a-axis direction. Hydrogen bonding between molecule B and symmetry equivalents forms one ring motif by inversion-related N—H...O interactions and a second ring motif by C—H...O interactions, which propagate as a single tape parallel with the c axis.
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- 2011
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15. (S)-Methyl 2-{(S)-2-[bis(4-methoxyphenyl)methylideneamino]-3-hydroxypropanamido}-3-methylbutanoate
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Gary S. Nichol, Robin Polt, and Charles M. Keyari
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Crystallography ,QD901-999 - Abstract
The title compound, C24H30N2O6, a Schiff base, adopts an extended conformation in which the methoxy groups are essentially coplanar with the aromatic ring to which they are bonded (mean planes fitted through the non-H atoms of each methoxyphenyl group have r.m.s. deviations of 0.078 and 0.044 Å) and the angle between mean planes fitted through the aromatic rings is 87.57 (10)°. An intramolecular N—H...N hydrogen bond keeps the imine and amide groups essentially coplanar. A mean plane fitted through these groups has an r.m.s. deviation of 0.0545 Å. Additional O—H...O hydrogen bonding parallel with the a axis links the molecules into a hydrogen-bonded chain in the crystal. C—H...O and C—H...π interactions are found within the crystal packing. The compound has been assigned the S,S configuration on the basis of the chemical synthesis, which used pure homotopic l-amino acids, and we have no reason to believe that the compound has epimerized.
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- 2011
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16. [(1,2,5,6-η)-1,5-Cyclooctadiene](1-isopropyl-3-methylimidazolin-2-ylidene)(triphenylphosphine)iridium(I) tetrafluoridoborate dichloromethane solvate
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Gary S. Nichol, Daniel Stasiw, Laura J. Anna, and Edward Rajaseelan
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Crystallography ,QD901-999 - Abstract
In the title compound, [Ir(C8H12)(C7H12N2)(C18H15P)]BF4·CH2Cl2, the Ir(I) atom has a square-planar conformation with normal bond lengths. One of the phenyl rings, and the solvent dichloromethane molecule, were refined using separate two part disorder models, each in an approximately 1:1 ratio.
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- 2010
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17. 2-Propyl 3,3-dibromo-2-hydroxypyrrolidine-1-carboxylate
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Christopher Hulme, Justin Dietrich, Zhigang Xu, Steven Gunawan, and Gary S. Nichol
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Crystallography ,QD901-999 - Abstract
The title compound, C8H13Br2NO3, crystallizes as a non-merohedral twin with twin law −0.6 0 0.4/0 − 1 0 /1.6 0 0.6, and the structure has a refined twin domain ratio of 0.546 (5). The structure shows a compact conformation, with the ester unit roughly coplanar with a mean plane fitted through the non-H atoms of the pyrrolidine ring [dihedral angle = 8.23 (9)°]. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate an R22(12) motif.
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- 2010
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18. 2-Butyl-11-phenyl-5,10-dihydro-1H-benzo[e]imidazo[1,5-a][1,4]diazepine-1,3(2H)-dione
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Christopher Hulme, Justin Dietrich, Steven Gunawan, and Gary S. Nichol
- Subjects
Crystallography ,QD901-999 - Abstract
The title compound, C21H21N3O2, was obtained following a five-step synthetic procedure yielding weakly diffracting rod and needle-shaped crystals which crystallized concomitantly. Structural analysis of a rod-shaped crystal showed that the central seven-membered heterocyclic ring adopts a conformation that is perhaps best described as a distorted boat, with the H-bearing (CH2 and NH) atoms lying well out of the least-squares mean plane fitted through the other five atoms in the ring (r.m.s. deviation 0.075 Å). In the crystal, the compound packs as a twisted chain, which propagates along the b axis by means of an R12(6) motif formed by one of the carbonyl O atoms acting as a bifurcated acceptor in an N—H...O and C—H...O interaction. No diffraction was observed from the needle-shaped crystals.
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- 2010
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19. 2-[N-(2,4-Difluorophenyl)carbamoyl]-3,4,5,6-tetrafluorobenzoic acid
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Duoli Guo, Gary S. Nichol, James P. Cain, and Samuel H. Yalkowsky
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Crystallography ,QD901-999 - Abstract
The title compound, C14H5F6NO3, was synthesized by condensation of tetrafluorophthalic anhydride and 2,4-difluoroaniline. It was then recrystallized from hexane to give a nonmerohedral twin with two crystallographically unique molecules in the asymmetric unit. The refined twin fraction is 0.460 (3). Torsional differences between the aryl rings and the central amide group account for the presence of two unique molecules. The compound packs as double tapes formed by O—H...O and N—H...O hydrogen-bonding interactions between each unique molecule and its symmetry equivalents.
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- 2009
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20. Diethyl trans-2,5-bis(4-methoxybenzylsulfanyl)-1,4-dimethyl-3,6-dioxopiperazine-2,5-carboxylate
- Author
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Nathan W. Polaske, Gary S. Nichol, and Bogdan Olenyuk
- Subjects
Crystallography ,QD901-999 - Abstract
The title compound, C28H34N2O8S2, was synthesized as part of a project to develop synthetic routes to analogues of sporidesmins, a class of secondary metabolite produced by the filamentous fungi Chaetomium and Pithomyces sp. The complete molecule is generated by crystallographic inversion symmetry: the methoxy group is essentially coplanar with the benzene ring to which it is bonded, a mean plane fitted through the non-H atoms of the aromatic ring and the methoxy group having an r.m.s. deviation of 0.0140 Å. Similarly, the ester group is also essentially planar (r.m.s. deviation of a plane fitted through all non-H atoms is 0.0101 Å). There is only one independent C—H...O interaction, which links together adjacent molecules into a two-dimensional sheet in the bc plane.
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- 2009
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21. 1-(4-Methoxyphenyl)-3-phenyl-1H-pyrazol-5-amine
- Author
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Gary S. Nichol, Victor J. Hruby, and Isuru R. Kumarasinghe
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Crystallography ,QD901-999 - Abstract
The synthesis of the title compound, C16H15N3O, is regiospecific and single-crystal X-ray diffraction provides the only means of unambiguous structural analysis, with the benzene ring bonded to the imine C atom. The phenyl ring and the essentially planar (r.m.s. deviation 0.0354 Å) methoxybenzene group are rotated by 29.41 (5) and 37.01 (5)°, respectively, from the central pyrazole ring. An intermolecular N—H...N hydrogen bond links symmetry-related molecules into a C(5) chain, which runs parallel to the b axis.
- Published
- 2009
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22. Amides as modifiable directing groups in electrophilic borylation
- Author
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Saqib A. Iqbal, Marina Uzelac, Ismat Nawaz, Zhongxing Wang, T. Harri Jones, Kang Yuan, Clement R. P. Millet, Gary S. Nichol, Ghayoor Abbas Chotana, and Michael J. Ingleson
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General Chemistry - Abstract
Amide directed C–H borylation using ≥two equiv. of BBr3 forms borenium cations containing a R2N(R′)C[double bond]O→B(Ar)Br unit which has significant Lewis acidity at the carbonyl carbon. This enables reduction of the amide unit to an amine using hydrosilanes. This approach can be applied sequentially in a one-pot electrophilic borylation–reduction process, which for phenyl-acetylamides generates ortho borylated compounds that can be directly oxidised to the 2-(2-aminoethyl)-phenol. Other substrates amenable to the C–H borylation–reduction sequence include mono and diamino-arenes and carbazoles. This represents a simple method to make borylated molecules that would be convoluted to access otherwise (e.g. N-octyl-1-BPin-carbazole). Substituent variation is tolerated at boron as well as in the amide unit, with diarylborenium cations also amenable to reduction. This enables a double C–H borylation–reduction–hydrolysis sequence to access B,N-polycyclic aromatic hydrocarbons (PAHs), including an example where both the boron and nitrogen centres contain functionalisable handles (N–H and B–OH). This method is therefore a useful addition to the metal-free borylation toolbox for accessing useful intermediates (ArylBPin) and novel B,N-PAHs.
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- 2023
23. Boron-Catalyzed, Diastereo- and Enantioselective Allylation of Ketones with Allenes
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Kieran Nicholson, Yuxuan Peng, Natalia Llopis, Dominic R. Willcox, Gary S. Nichol, Thomas Langer, Alejandro Baeza, Stephen P. Thomas, Universidad de Alicante. Departamento de Química Orgánica, Universidad de Alicante. Instituto Universitario de Síntesis Orgánica, and Alternative Methodologies In Chemistry (AMIC)
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Allylation ,General Chemistry ,Ketone ,Catalysis ,Boron ,Transborylation - Abstract
The diastereo- and enantioselective allylation of ketones remains a synthetic challenge, with transition metal catalysis offering the most applied methods. Here, a boron-catalyzed allylation of ketones with allenes is presented. Excellent yield, regioselectivity, and diastereoselectivity were found across functionalized substrates. The reaction was further developed to accommodate an enantioenriched boron catalyst and thus gave asymmetric ketone allylation in good yield, diastereoselectivity, and enantioselectivity. Mechanistic studies supported a hydroboration–allylation–transborylation pathway. S.P.T. acknowledges the Royal Society for a University Research Fellowship (URF/R/191015). S.P.T. and K.N. thank AstraZeneca and EPSRC for an iCase PhD studentship.
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- 2022
24. Utilizing Raman Spectroscopy as a Tool for Solid- and Solution-Phase Analysis of Metalloorganic Cage Host–Guest Complexes
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Helen M. O’Connor, William J. Tipping, Julia Vallejo, Gary S. Nichol, Karen Faulds, Duncan Graham, Euan K. Brechin, and Paul J. Lusby
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Inorganic Chemistry ,QD ,Physical and Theoretical Chemistry - Abstract
The host-guest chemistry of coordination cages continues to promote significant interest, not least because confinement effects can be exploited for a range of applications, such as drug delivery, sensing, and catalysis. Often a fundamental analysis of noncovalent encapsulation is required to provide the necessary insight into the design of better functional systems. In this paper, we demonstrate the use of various techniques to probe the host-guest chemistry of a novel Pd2L4 cage, which we show is preorganized to selectively bind dicyanoarene guests with high affinity through hydrogen-bonding and other weak interactions. In addition, we exemplify the use of Raman spectroscopy as a tool for analyzing coordination cages, exploiting alkyne and nitrile reporter functional groups that are contained within the host and guest, respectively.
- Published
- 2022
25. Enhanced N-directed electrophilic C–H borylation generates BN–[5]- and [6]helicenes with improved photophysical properties
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Agnieszka Nowak-Król, Michael J. Ingleson, Gary S. Nichol, Daniel Volland, Marina Uzelac, Sven Kirschner, and Kang Yuan
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chemistry.chemical_compound ,Helicene ,chemistry ,Stereochemistry ,Electrophile ,Helix ,Enantioselective synthesis ,Supramolecular chemistry ,Protonation ,General Chemistry ,Racemization ,Borylation - Abstract
Helicenes are chiral polycyclic aromatic hydrocarbons (PAHs) of significant interest e.g. in supramolecular chemistry, materials science and asymmetric catalysis. Herein an enhanced N-directed electrophilic C-H borylation methodology has been developed that provides access to azaborine containing helicenes (BN-helicenes). This borylation process proceeds via protonation of an aminoborane with bistriflimidic acid. DFT calculations reveal the borenium cation formed by protonation to be more electrophilic than the product derived from aminoborane activation with BBr3. The synthesised helicenes include BN-analogues of archetypal all carbon [5]- and [6]helicenes. The replacement of a CC with a BN unit (that has a longer bond) on the outer helix increases the strain in the BN congeners and the racemization half-life for a BN-[5]helicene relative to the all carbon [5]helicene. BN incorporation also increases the fluorescence efficency of the helicenes, a direct effect of BN incorporation altering the distribution of the key frontier orbitals across the helical backbone relative to carbo-helicenes.
- Published
- 2022
26. Influence of alkali metal cations on the formation of the heterobimetallic actinide
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Andreas, Lichtenberg, Markus, Zegke, Gary S, Nichol, Aida, Raauf, and Sanjay, Mathur
- Abstract
Heterobimetallic
- Published
- 2023
27. Influence of alkali metal cations on the formation of the heterobimetallic actinide tert-butoxides [AnM3(OtBu)7] and [AnM2(OtBu)6] (AnIV = Th, U; MI = Li, Na, K, Rb, Cs)
- Author
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Andreas Lichtenberg, Markus Zegke, Gary S. Nichol, Aida Raauf, and Sanjay Mathur
- Subjects
Inorganic Chemistry - Abstract
Heterobimetallic tert-butoxides of alkali metal cations with tetravalent actinide centers exhibit two distinctive structural motifs, [AnM2(OtBu)6] and [AnM3(OtBu)7] (AnIV = Th, U and MI = Li, Na, K, Rb, Cs), evidently governed by the size of the alkali metal ions. Both [AnM3(OtBu)7] AnM3 (AnIV = U, MI = Li; AnIV = Th, MI = Li, Na) and [AnM2(OtBu)6] AnM2 (AnIV = U, MI = Na-Cs; AnIV = Th, MI = K-Cs) compounds are obtained in nearly quantitative yields by reacting actinide and alkali metal silyl amides with an excess of tert-butyl alcohol. The AnM3 complexes form a cubane-type coordination motif, whereas the AnM2 complexes display a geometry resembling two face-shared bipyramids. The sodium derivatives of thorium and uranium (ThNa3 and UNa2) allow the determination of the structural transition threshold as a function of the ratio of the ionic radii ri(AnIV)/ri(MI). The AnM3 complexes are formed for ratios above 0.92 and the AnM2 type is formed for ratios below 0.87. All compounds are unambiguously characterized in both solution and solid states by NMR and IR spectroscopic studies and single crystal X-ray diffraction analyses, respectively.
- Published
- 2023
28. A low-symmetry monothiatruxene-based hole transport material for planar n–i–p perovskite solar cells with 18.9% efficiency
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Ellie Tanaka, Gyu Min Kim, Michał R. Maciejczyk, Ayumi Ishii, Gary S. Nichol, Tsutomu Miyasaka, and Neil Robertson
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Materials Chemistry ,General Chemistry - Abstract
Hole transport materials (HTMs) based on truxene cores have emerged as promising candidates in recent years. They are noted by properties such as higher hole mobility and higher glass transition temperature than the 2,2′,7,7′-tetrakis (N,N-di-p-methoxyphenamine)-9,9′-spirobiflourene (spiro-MeOTAD), as well as good hydrophobicity and energy alignment. Truxene derivatives have been studied for application in transistors, OLEDs, lasers, supercapacitors, etc., however, there are only a few studies on their use as HTMs in perovskite solar cells (PSCs). In this study, we synthesised a novel small organic molecule HTM with a monothiatruxene (TrxS) core, namely TrxS-2MeOTAD, and characterised its basic properties and ability as an HTM in n–i–p planar PSCs. The TrxS-2MeOTAD showed suitable electrochemical, optical, structural and thermal properties for an HTM, such as a relatively high glass transition temperature (145 °C) and stable amorphous nature when deposited as films. The PSCs using TrxS-2MeOTAD achieved 18.9% power conversion efficiency (PCE) compared to the reference spiro-MeOTAD at 19.3% PCE. The unencapsulated TrxS-2MeOTAD devices showed better operational stability than spiro-MeOTAD, with a 1.5 times longer lifetime under constant AM1.5G illumination. Our results suggest that small molecules based on the TrxS core can be a promising direction for the development of alternative HTMs.
- Published
- 2023
29. Iron‐catalysed C(sp2)‐H Borylation with Expanded Functional Group Tolerance
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Luke Britton, Jamie H. Docherty, Gary S. Nichol, Andrew P. Dominey, and Stephen P. Thomas
- Subjects
C-H borylation ,Photochemistry ,Iron ,Earth-abundant ,General Chemistry ,Boron - Abstract
Arene C(sp2)-H bond borylation offers direct and efficient access to aryl boronic esters. Using in situ catalyst activation and photoirradiation, the iron-catalysed C(sp2)-H borylation reaction of carboarenes, pyrroles, and indoles has been developed using only bench-stable pre-catalysts and reagents. Good functional group tolerance was observed including those not tolerated under previous methods (ArNH2, ArOH, ArSiR3, ArP(O)(OR)2, ArC(O)NR2). Mechanistic studies revealed iron-catalysed reductive deoxygenation, C-F protodefluorination, and a demethylation of aryl methyl ethers by C-O sigma bond hydroboration.
- Published
- 2022
30. Diastereoselective, Catalytic Access to Cross‐Aldol Products Directly from Esters and Lactones
- Author
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Adrián Moreno González, Kieran Nicholson, Natalia Llopis, Gary S. Nichol, Thomas Langer, Alejandro Baeza, Stephen P. Thomas, Universidad de Alicante. Departamento de Química Orgánica, Universidad de Alicante. Instituto Universitario de Síntesis Orgánica, and Alternative Methodologies In Chemistry (AMIC)
- Subjects
Aldol ,General Medicine ,General Chemistry ,C−C bond ,Catalysis ,Boron ,Main-group Catalysis ,Transborylation - Abstract
High oxidation-state carbonyl coupling partners including esters and lactones were reacted with enones to give aldol-type products directly using two-fold organoborane catalysis. This new retrosynthetic disconnection to aldol-type products is compatible with enolisable coupling partners, without self-condensation, and couples the high reactivity of secondary dialkylboranes with the stability of pinacolboronic esters. Excellent chemoselectivity, substrate scope (including those containing reducible functionalities and free alcohols) and diastereocontrol were achieved to access both the syn- and anti-aldol-type products. Mechanistic studies confirmed the two-fold catalytic role of the single secondary borane catalyst for boron enolate formation and formation of an aldehyde surrogate from the ester or lactone coupling partner.
- Published
- 2022
31. C–H Borylation Catalysis of Heteroaromatics by a Rhenium Boryl Polyhydride
- Author
-
Teresa Faber, Liam J. Donnelly, Carole A. Morrison, Stephen P. Thomas, Gary S. Nichol, and Jason B. Love
- Subjects
chemistry ,Polymer chemistry ,chemistry.chemical_element ,General Chemistry ,Rhenium ,Borylation ,Catalysis - Abstract
Transition metal complexes bearing metal–boron bonds are of particular relevance to catalytic C–H borylation reactions, with iridium polyboryl and polyhydrido-boryl complexes the current benchmark catalysts for these transformations. Herein, we demonstrate that polyhydride boryl phosphine rhenium complexes are accessible and catalyze the C–H borylation of heteroaromatic substrates. Reaction of [K(DME)(18-c-6)][ReH4(Bpin)(η2-HBpin)(κ2-H2Bpin)] 1 with 1,3-bis(diphenylphosphino)propane (dppp) produced [K(18-c-6)][ReH4(η2-HBpin)(dppp)] 2 through substitution of two equivalents of HBpin, and protonation of 2 formed the neutral complex [ReH6(Bpin)(dppp)] 3. Combined X-ray crystallographic and DFT studies show that 2 is best described as a σ-borane complex, whereas 3 is a boryl complex. Significantly, the boryl complex 3 acted as a catalyst for the C(sp2)–H borylation of a variety of heteroarenes (14 examples including furan, thiophene, pyrrole and indole derivatives) and displayed similar reactivity to the iridium analogues.
- Published
- 2021
32. Design, Synthesis, and Analytical Evaluation of Fsp3‐Inspired Raman Probes for Cellular Imaging
- Author
-
Craig F. Steven, Martin Lee, Gary S. Nichol, Paul R. J. Davey, Elisabetta Chiarparin, Valerie G. Brunton, and Alison N. Hulme
- Subjects
Organic Chemistry ,Physical and Theoretical Chemistry - Abstract
The fraction of sp 3 -hybdrised carbons (Fsp 3 ) in drug candidates and other biologically relevant compounds has been proposed to be an important physicochemical consideration within medicinal chemistry. Currently available small-molecule probes for Raman imaging are not optimised for biological applications. We sought to improve upon the highly Raman-active, yet rigid, lipophilic, and aggregative, bisarylbutadiyne (BADY) motif by introducing Fsp 3 character. BADY analogues were designed, efficiently synthesised, and analysed by mass spectrometry – revealing a statistical correlation between compound aggregation and cLog P , but no correlation with sp 3 . However, X-ray crystallography demonstrated that the modifications to the BADY structure had a marked effect on crystal packing, suggesting Fsp 3 may still be important in reducing intermolecular stacking, and thus aggregation, of BADY. Cellular imaging by stimulated Raman scattering (SRS) microscopy allowed comparison of the intracellular distribution of the tags, guiding the design of future Raman probes.
- Published
- 2022
33. Guest-induced magnetic exchange in paramagnetic [M
- Author
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Mukesh K, Singh, Alvaro, Etcheverry-Berríos, Julia, Vallejo, Sergio, Sanz, José, Martínez-Lillo, Gary S, Nichol, Paul J, Lusby, and Euan K, Brechin
- Abstract
Paramagnetic complexes that possess magnetically switchable properties show promise in a number of applications. A significantly underdeveloped approach is the use of metallocages, whose magnetic properties can be modulated through host-guest chemistry. Here we show such an example that utilises a simple [Cu
- Published
- 2022
34. Dissecting Solvent Effects on Hydrogen Bonding
- Author
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Nicole Y. Meredith, Stefan Borsley, Ivan V. Smolyar, Gary S. Nichol, Christopher M. Baker, Kenneth B. Ling, and Scott L. Cockroft
- Subjects
Solvents ,Thermodynamics ,Hydrogen Bonding ,General Chemistry ,General Medicine ,Amides ,Catalysis - Abstract
The experimental isolation of H-bond energetics from the typically dominant influence of the solvent remains challenging. Here we use synthetic molecular balances to quantify amine/amide H-bonds in competitive solvents. Over 200 conformational free energy differences were determined using 24 H-bonding balances in 9 solvents spanning a wide polarity range. The correlations between experimental interaction energies and gas-phase computed energies exhibited wild solvent-dependent variation. However, excellent correlations were found between the same computed energies and the experimental data following empirical dissection of solvent effects using Hunter’s α/β solvation model. In addition to facilitating the direct comparison of experimental and computational data, changes in the fitted donor and acceptor constants reveal the energetics of secondary local interactions such as competing H-bonds.
- Published
- 2022
35. Instantaneous and Phosphine-Catalyzed Arene Binding and Reduction by U(III) Complexes
- Author
-
Polly L. Arnold, Gary S. Nichol, Connor J. V. Halliday, and Laura Puig-Urrea
- Subjects
010405 organic chemistry ,Chemistry ,Ligand ,Actinide ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,Spectral line ,3. Good health ,0104 chemical sciences ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Redistribution (chemistry) ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Benzene ,Phosphine - Abstract
Neutral arenes such as benzene have never been considered suitable ligands for electropositive actinide cations, yet we find that even simple UIII UX3 aryloxide complexes such as U(ODipp)3 bind and reduce arenes spontaneously at room temperature, forming inverse arene sandwich (IAS) complexes XnU(μ-C6D6)UXm (X = ODipp, n=2, m=3; X = OBMes2 n=m=2 or 3) (ODipp = OC6H3iPr2-2,6; Mes = 2,4,6-Me3-C6H2). In some of these cases, further arene reduction has occured as a result of X ligand redistribution. These unexpected spontaneous reactions explain the anomalous spectra and reported lack of further reactivity of strongly reducing UIII centers of U(ODipp)3. Phosphines that are not considered suitable ligands for actinides can catalyze the formation of the IAS complexes. This enables otherwise inaccessible asymmetric and less congested IAS complexes to be isolated and the bonding in this series compared.
- Published
- 2021
36. Borane-Catalyzed C(sp3)–F Bond Arylation and Esterification Enabled by Transborylation
- Author
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Gary S. Nichol, Stephen P. Thomas, and Dominic R. Willcox
- Subjects
010405 organic chemistry ,Bond ,chemistry.chemical_element ,General Chemistry ,Borane ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Surface modification ,Boron ,Stoichiometry ,Bond cleavage - Abstract
The activation and functionalization of carbon–fluorine bonds represent a significant synthetic challenge, given the high thermodynamic barrier to C–F bond cleavage. Stoichiometric hydridoborane-mediated C–F functionalization has recently emerged, but is yet to be rendered catalytic. Herein, the borane-catalyzed coupling of alkyl fluorides with arenes (carbon–carbon bond formation) and carboxylic acids (carbon–oxygen bond formation) has been developed using transborylation reactions to achieve catalytic turnover. Successful C–C and C–O coupling across a variety of structurally and electronically differentiated arenes and carboxylic acids was achieved using 9-borabicyclo[3.3.1]nonane (H-B-9-BBN) as the catalyst and pinacolborane (HBpin), with broad functional group tolerance. Experimental and computational studies suggest a mechanistic dichotomy for the carbon–carbon and carbon–oxygen coupling reactions. B–F transborylation (B–F/B–H metathesis) between F-B-9-BBN and HBpin enabled catalytic turnover for carbon–carbon bond formation, whereas direct exchange between the alkyl fluoride and acyloxyboronic ester (C–F/B–O metathesis) was proposed for carbon–oxygen coupling, where H-B-9-BBN catalyzed the dehydrocoupling of the carboxylic acid with HBpin.
- Published
- 2021
37. Formation of a hydride containing amido-zincate using pinacolborane
- Author
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Marina Uzelac, Kang Yuan, Gary S. Nichol, and Michael J. Ingleson
- Subjects
010405 organic chemistry ,Hydride ,Borane ,010402 general chemistry ,01 natural sciences ,Medicinal chemistry ,0104 chemical sciences ,3. Good health ,Inorganic Chemistry ,Chemistry ,chemistry.chemical_compound ,Deprotonation ,chemistry ,Amide ,Electrophile ,Reactivity (chemistry) ,Catecholborane ,Zincate - Abstract
Amido-zincates containing hydrides are underexplored yet potentially useful complexes. Attempts to access this type of zincate through combining amido-organo zincates and pinacolborane (HBPin) via Zn–C/H–BPin exchange led instead to preferential formation of amide–BPin and/or [amide–BPin(Y)]− (Y = Ph, amide, H), when the amide is hexamethyldisilazide or 2,2,6,6-tetramethylpiperidide and the hydrocarbyl group was phenyl or ethyl. In contrast, the use of a dipyridylamide (dpa) based arylzinc complex led to Zn–C/H–BPin metathesis being the major outcome. Independent synthesis and full characterisation of two LnLi[(dpa)ZnPh2] (L = THF, n = 3; L = PMDETA, n = 1) complexes, 1 and 3, respectively, enabled reactivity studies that demonstrated that these species display zincate type reactivity (by comparison to the lower reactivity of the neutral complex (Me-dpa)ZnPh2, 4, Me-dpa = 2,2′-dipyridyl-N-methylamine). This included 1 performing the rapid deprotonation of 4-ethynyltoluene and also phenyl transfer to α,α,α-trifluoroacetophenone in contrast to neutral complex 4. Complex 1 reacted with one equivalent of HBPin to give predominantly PhBPin (ca. 90%) and a lithium amidophenylzincate containing a hydride unit, complex 7-A, as the major zinc containing product. Complex 7-A transfers hydride to an electrophile preferentially over phenyl, indicating it reacts as a hydridozincate. Attempts to react 1 with >1 equivalent of HBPin or with catecholborane led to more complex outcomes, which included significant borane and dpaZn substituent scrambling, two examples of which were crystallographically characterised. While this work provides proof of principle for Zn–C/H–BPin exchange as a route to form an amido-zincate containing a hydride, amido-organozincates that undergo more selective Zn–C/H–BPin exchange still are required., Careful tuning of the nature of the amide ligand in amido-zincates allows for selective Zn–C over Zn–N exchange with HBPin affording a hydride containing amido-zincate. The mixed hydrido-phenyl zincate preferentially transfers hydride over phenyl.
- Published
- 2021
38. A [Mn18] wheel-of-wheels
- Author
-
Marco Coletta, Gary S. Nichol, Thomais G. Tziotzi, Constantinos J. Milios, Mark Gray, Mukesh Kumar Singh, and Euan K. Brechin
- Subjects
Magnetization ,Materials science ,Condensed matter physics ,Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,General Chemistry ,Magnetic susceptibility ,Catalysis ,Square (algebra) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion - Abstract
A [Mn18] wheel of wheels is obtained from the reaction of MnBr2·4H2O and LH3 in MeOH. The metallic skeleton reveals two asymmetric [MnIII6MnII2] square wheels connected into a larger wheel via two MnII ions. Magnetic susceptibility and magnetisation data reveal competing exchange interactions, supported by computational studies.
- Published
- 2021
39. Incorporating Sodium to Boost the Activity of Aluminium TrenSal Complexes towards rac‐Lactide Polymerisation
- Author
-
Yali Zhou, Gary S. Nichol, and Jennifer A. Garden
- Subjects
Inorganic Chemistry - Abstract
Four novel homo- and heterometallic sodium and/or aluminium complexes based on the TrenSal ligand, [LH3], have been synthesised and fully characterised, including by single-crystal X-ray diffraction experiments. While [LAl] was completely inactive towards rac-lactide ring-opening polymerisation, incorporating sodium to form heterometallic [LNaAlMe] changes the aluminium geometry from octahedral to tetrahedral, leading to good catalytic activity in the presence of co-initiator BnOH (kobs=3.19×10−2 min−1; room temperature, toluene solvent) and good polymerisation control. Under identical conditions, homometallic sodium complexes showed higher activities in rac-lactide polymerisation than [LNaAlMe], with [LNa3] being extremely active (kobs=1.21 min−1) but displaying unusual second-order monomer dependency and poor polymerisation control. 1H NMR spectroscopic studies suggest that polymerisation with [LNaAlMe] or [LH2Na]/BnOH follows an activated monomer mechanism, whereas [LNa3] operates via simultaneous coordination-insertion and activated monomer mechanisms. Overall, heterometallic [LNaAlMe] provides a balance of good activity and control compared to the homometallic analogues.
- Published
- 2022
40. Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions
- Author
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Stefan Borsley, Catherine Adam, Kenneth Ling, Kamila B. Muchowska, Dominic J. Pascoe, Ivan V. Smolyar, Ioulia K. Mati, Scott L. Cockroft, and Gary S. Nichol
- Subjects
010402 general chemistry ,01 natural sciences ,Catalysis ,noncovalent interactions ,Delocalized electron ,Molecular recognition ,Protein structure ,Noncovalent Interactions | Hot Paper ,conformation analysis ,Non-covalent interactions ,Molecular orbital ,Lone pair ,Research Articles ,chemistry.chemical_classification ,Physics ,delocalization ,010405 organic chemistry ,General Medicine ,General Chemistry ,electrostatic interactions ,Electrostatics ,computational chemistry ,0104 chemical sciences ,Dipole ,chemistry ,Chemical physics ,Research Article - Abstract
Interactions between carbonyl groups are prevalent in protein structures. Earlier investigations identified dominant electrostatic dipolar interactions, while others implicated lone pair n→π* orbital delocalisation. Here these observations are reconciled. A combined experimental and computational approach confirmed the dominance of electrostatic interactions in a new series of synthetic molecular balances, while also highlighting the distance‐dependent observation of inductive polarisation manifested by n→π* orbital delocalisation. Computational fiSAPT energy decomposition and natural bonding orbital analyses correlated with experimental data to reveal the contexts in which short‐range inductive polarisation augment electrostatic dipolar interactions. Thus, we provide a framework for reconciling the context dependency of the dominance of electrostatic interactions and the occurrence of n→π* orbital delocalisation in C=O⋅⋅⋅C=O interactions., Carbonyls reconciled: Electrostatics and orbital interactions have both been implicated in governing carbonyl interactions. A combined experimental and computational approach reconciles these conflicting explanations of the physiochemical origin of the interaction, demonstrating that orbital delocalisation augments electrostatic control, but for very close carbonyl contacts.
- Published
- 2020
41. Characterization of the Zwitterionic Intermediate in 1,1‐Carboboration of Alkynes
- Author
-
Michael J. Cowley, Alessandro Bismuto, Fernanda Duarte, Gary S. Nichol, and Stephen P. Thomas
- Subjects
chemistry.chemical_classification ,Reaction mechanism ,010405 organic chemistry ,Alkyne ,General Medicine ,General Chemistry ,Borane ,010402 general chemistry ,01 natural sciences ,Combinatorial chemistry ,Catalysis ,Frustrated Lewis pair ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Zwitterion ,Intramolecular force ,Reactivity (chemistry) ,Vinyl cation - Abstract
The reaction of a Lewis acidic borane with an alkyne is a key step in a diverse range of main group transformations. Alkyne 1,1-carboboration, the Wrackmeyer reaction, is an archetypal transformation of this kind. 1,1-Carboboration has been proposed to proceed through a zwitterionic intermediate. We report the isolation and spectroscopic, structural and computational characterization of the zwitterionic intermediates generated by reaction of B(C6 F5 )3 with alkynes. The stepwise reactivity of the zwitterion provides new mechanistic insight for 1,1-carboboration and wider B(C6 F5 )3 catalysis. Making use of intramolecular stabilization by a ferrocene substituent, we have characterized the zwitterionic intermediate in the solid state and diverted reactivity towards alkyne cyclotrimerization.
- Published
- 2020
42. Kinetic selection of Pd4L2 metallocyclic and Pd6L3 trigonal prismatic assemblies
- Author
-
Gary S. Nichol, Euan K. Brechin, Alvaro Etcheverry-Berrios, Marco Coletta, Paul J. Lusby, and Helen M. O'Connor
- Subjects
Crystallography ,Materials science ,Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,General Chemistry ,Trigonal prismatic molecular geometry ,Kinetic energy ,Catalysis ,Selection (genetic algorithm) ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
The self-assembly of Pd4L2 metallocylcic and Pd6L3 trigonal prismatic assemblies are described. The selection of one species over the other has been achieved by careful choice of ancilliary ligands, which switch the dynamics of the Pd-pyridine bonds such that a highly unusual and distorted smaller assembly can be kinetically trapped en route to the more energetically favourable larger species. Both assemblies provide promise as easy to access multicavity reaction vessels.
- Published
- 2020
43. An [Fe III 34 ] Molecular Metal Oxide
- Author
-
Alice E. Dearle, Daniel J. Cutler, Hector W. L. Fraser, Sergio Sanz, Edward Lee, Sourav Dey, Ismael F. Diaz‐Ortega, Gary S. Nichol, Hiroyuki Nojiri, Marco Evangelisti, Gopalan Rajaraman, Jürgen Schnack, Leroy Cronin, and Euan K. Brechin
- Subjects
General Medicine - Published
- 2019
44. A Lewis Base Nucleofugality Parameter
- Author
-
Nicholas P, Taylor, Jorge A, Gonzalez, Gary S, Nichol, Andrés, García-Domínguez, Andrew G, Leach, and Guy C, Lloyd-Jones
- Subjects
Kinetics ,Hydrolysis ,Lewis Bases ,Boranes - Abstract
The kinetics of quinuclidine displacement of BH
- Published
- 2021
45. A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
- Author
-
Nicholas P. Taylor, Jorge A. Gonzalez, Gary S. Nichol, Andrés García-Domínguez, Andrew G. Leach, and Guy C. Lloyd-Jones
- Subjects
Organic Chemistry - Abstract
The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3–nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
- Published
- 2021
46. An [FeIII30] molecular metal oxide
- Author
-
Daniel J. Cutler, Alice E. Dearle, Marco Coletta, Gopalan Rajaraman, Gary S. Nichol, Hector W. L. Fraser, Sergio Sanz, Jürgen Schnack, Sourav Dey, Edward S. Lee, Euan K. Brechin, and Leroy Cronin
- Subjects
Materials science ,Metals and Alloys ,Oxide ,General Chemistry ,Mass spectrometry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Metal ,chemistry.chemical_compound ,Crystallography ,Octahedron ,chemistry ,visual_art ,ddc:540 ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Cluster (physics) ,Antiferromagnetism ,Acetonitrile ,Dissolution - Abstract
Dissolution of FeBr3 in a mixture of acetonitrile and 3,4-lutidine in the presence of an amine results in the formation of an [Fe30] molecular metal oxide containing alternating layers of tetrahedral and octahedral FeIII ions. Mass spectrometry suggests the cluster is formed quickly and remains stable in solution, while magnetic measurements and DFT calculations reveal competing antiferromagnetic exchange interactions.
- Published
- 2021
47. Lithium Half‐Salen Complexes: Synthesis, Structural Characterization and Studies as Catalysts for rac‐Lactide Ring‐Opening Polymerization
- Author
-
Jennifer A. Garden, Gary S. Nichol, and Yali Zhou
- Subjects
chemistry.chemical_compound ,Reaction mechanism ,Lactide ,Chemistry ,Organic Chemistry ,Polymer chemistry ,chemistry.chemical_element ,Lithium ,Physical and Theoretical Chemistry ,Ring-opening polymerization ,Catalysis ,Characterization (materials science) - Abstract
Seven lithium complexes supported by sterically and electronically diverse phenoxyimine ligands were synthesized and characterized by X-ray diffraction, NMR spectroscopy and elemental microanalysis. These complexes show high activity (kobs ≤7.43×10−2 s−1) for rac-lactide ring-opening polymerization (ROP) in the presence of co-initiator benzyl alcohol (BnOH), with the exception of Li4 which features an unusual polymeric ladder structure. Overall, the catalyst activity correlates to the aggregation state; the catalysts with low aggregation states display increased propagation rates attributed to improved metal accessibility and kinetic mobility. The nature of the ligand substituents and solvent influence the catalyst aggregation in both the solid- and solution-state. While the lithium complexes can initiate rac-lactide ROP without BnOH, the addition of this co-initiator significantly increases the polymerization rate by switching the mechanism from a coordination-insertion to an activated monomer pathway, changing the resultant poly(lactic acid) architecture from cyclic to linear.
- Published
- 2021
48. Reversible Dissociation of a Dialumene
- Author
-
Michael J. Cowley, Gary S. Nichol, Rosalyn L. Falconer, Tobias Krämer, and Keelan M Byrne
- Subjects
010405 organic chemistry ,Chemistry ,aluminium ,multiple bonds ,General Medicine ,General Chemistry ,aluminium(I) compounds ,low-valent atoms ,010402 general chemistry ,01 natural sciences ,Bond order ,Bond-dissociation energy ,Multiple bonds ,Catalysis ,Dissociation (chemistry) ,0104 chemical sciences ,3. Good health ,chemistry.chemical_compound ,Crystallography ,Monomer ,Aluminium Compounds | Very Important Paper ,Reactivity (chemistry) ,Research Articles ,dialumene ,Research Article - Abstract
Dialumenes are neutral AlI compounds with Al=Al multiple bonds. We report the isolation of an amidophosphine‐supported dialumene. Our X‐ray crystallographic, spectroscopic, and computational DFT analyses reveal a long and extreme trans‐bent Al=Al bond with a low dissociation energy and bond order. In solution, the dialumene can dissociate into monomeric AlI species. Reactivity studies reveal two modes of reaction: as dialumene or as aluminyl monomers., A highly trans‐bent dialumene has marginal Al=Al double‐bond character and, in solution, can dissociate into monomeric aluminyl fragments. Reactivity studies reveal that both the dialuminene and aluminyl monomer can be trapped by varying the reaction partner. DFT calculations elaborate the origins of the extreme trans‐bending, weak Al=Al bond, and define substituent effects in dialumenes.
- Published
- 2021
49. [Fe
- Author
-
Daniel J, Cutler, Mukesh K, Singh, Gary S, Nichol, Marco, Evangelisti, Jürgen, Schnack, Leroy, Cronin, and Euan K, Brechin
- Abstract
The combination of two different Fe
- Published
- 2021
50. [Fe15]: A Frustrated, Centred Tetrakis Hexahedron
- Author
-
Gary S. Nichol, Jürgen Schnack, Daniel J. Cutler, Marco Evangelisti, Euan K. Brechin, Leroy Cronin, Mukesh Kumar Singh, Engineering and Physical Sciences Research Council (UK), European Commission, Ministerio de Ciencia e Innovación (España), Agencia Estatal de Investigación (España), and Ministerio de Ciencia, Innovación y Universidades (España)
- Subjects
Materials science ,Magnetism ,010405 organic chemistry ,Metals and Alloys ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Solvothermal reaction ,Catalysis ,0104 chemical sciences ,3. Good health ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,Triethanolamine ,Materials Chemistry ,Ceramics and Composites ,Cluster (physics) ,medicine ,Tetrakis hexahedron ,Symmetry (geometry) ,medicine.drug - Abstract
The combination of two different FeIII salts in a solvothermal reaction with triethanolamine results in the formation of a high symmetry [FeIII15] cluster whose structure conforms to a centred, tetrakis hexahedron., EKB and LC thank U21/EPSRC for funding a studentship (DJC). MKS would like to thank Edinburgh Compute and Data Facility (ECDF), and the European Union Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 832488. ME thanks the Spanish Ministry of Science and Innovation (Project RTI2018-098537-B-C22).
- Published
- 2021
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