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    Synthesis and reactivity of α-diazo-β-keto sulfonamides
    (Georg Thieme Verlag KG, 2024-06-19) Maguire, Anita R.; Judge, Evan; O'Shaughnessy, Keith A.; Lawrence, Simon E.; Collins, Stuart G.; Science Foundation Ireland; Irish Research Council; Higher Education Authority; Synthesis and Solid State Pharmaceutical Centre; European Regional Development Fund
    Copper mediated reactions of α-diazo-β-keto sulfonamides 1 leads to a range of products including the alkyne sulfonamides 5, the enamines 6, and the α-halosulfonamides 7 and 11 with no evidence for intramolecular C–H insertion in any of the reactions, in contrast to the reactivity of the comparable α-diazo-β-keto sulfones. Use of copper(II) triflate (5 mol%) led to isolation of a series of alkyne sulfonamides 5 (up to 12%) and enamines 6 (up to 64%). Use of copper(II) chloride (5 mol%) formed, in addition, the α-halosulfonamides 7; use of stoichiometric amounts of copper(II) chloride/bromide enables facile halogenation of the β-keto sulfonamide to form the α-halosulfonamides 7 and 11 (up to 63%).
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    Photochemistry of 2-butenedial and 4-oxo-2-pentenal under atmospheric boundary layer conditions
    (Royal Society of Chemistry, 2018-12-21) Newland, Mike J.; Rea, Gerard J.; Thüner, Lars P.; Henderson, Alistair P.; Golding, Bernard T.; Rickard, Andrew R.; Barnes, Ian; Wenger, John; Horizon 2020; Natural Environment Research Council
    Unsaturated 1,4-dicarbonyl compounds, such as 2-butenedial and 4-oxo-2-pentenal are produced in the atmospheric boundary layer from the oxidation of aromatic compounds and furans. These species are expected to undergo rapid photochemical processing, affecting atmospheric composition. In this study, the photochemistry of (E)-2-butenedial and both E and Z isomers of 4-oxo-2-pentenal was investigated under natural sunlight conditions at the large outdoor atmospheric simulation chamber EUPHORE. Photochemical loss rates, relative to j(NO2), are determined to be j((E)-2-butenedial)/j(NO2) = 0.14 (±0.02), j((E)-4-oxo-2-pentenal)/j(NO2) = 0.18 (±0.01), and j((Z)-4-oxo-2-pentenal)/j(NO2) = 0.20 (±0.03). The major products detected for both species are a furanone (30–42%) and, for (E)-2-butenedial, maleic anhydride (2,5-furandione) (12–14%). The mechanism appears to proceed predominantly via photoisomerization to a ketene–enol species following γ-H abstraction. The lifetimes of the ketene–enol species in the dark from 2-butenedial and 4-oxo-2-pentenal are determined to be 465 s and 235 s, respectively. The ketene–enol can undergo ring closure to yield the corresponding furanone, or further unimolecular rearrangement which can subsequently form maleic anhydride. A minor channel (10–15%) also appears to form CO directly. This is presumed to be via a molecular elimination route of an initial biradical intermediate formed in photolysis, with an unsaturated carbonyl (detected here but not quantified) as co-product. α-Dicarbonyl and radical yields are very low, which has implications for ozone production from the photo-oxidation of unsaturated 1,4-dicarbonyls in the boundary layer. Photochemical removal is determined to be the major loss process for these species in the boundary layer with lifetimes of the order of 10–15 minutes, compared to >3 hours for reaction with OH.
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    Guanidine functionalized porous SiO2 as heterogeneous catalysts for microwave depolymerization of PET and PLA
    (Royal Society of Chemistry, 2024-03-06) Casey, Éadaoin; Breen, Rachel; Pareras, Gerard; Rimola, Albert; Holmes, Justin D.; Collins, Gillian; Science Foundation Ireland
    Chemical recycling is an important strategy to tackle the growing global problem of plastic waste pollution. The development of metal-free catalysts for depolymerization of plastics is attractive as it avoids the use of metal salts, which are potentially damaging to the environment. Here we report a metal-free heterogeneous catalyst for the glycolysis of polyethylene terephthalate (PET) and methanolysis of polylactic acid (PLA). The catalysts are synthesized by covalent surface modification of mesoporous silica (SiO2) with guanidine ligands and evaluated under conventional thermal and microwave-assisted heating. A surface bound cyanoguanidine ligand was found to be the best catalyst leading to 100% PET conversion with 80% BHET yield. The nature of the catalyst support material influenced the catalytic performance of the guanidine ligands with porous SiO2 supports outperforming activated carbon in conventional thermal glycolysis, while the opposite trend was observed with microwave assisted glycolysis. Dedicated density functional theory (DFT) computations were performed to simulate the depolymerization processes, obtain the free energy profiles of the reaction mechanisms, and identify the important role of hydrogen bonding in the reaction mechanism.
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    3D printed rechargeable aqueous and non-aqueous lithium-ion batteries: Evolution of design and performance
    (Electrochemical Society, 2023-12-12) Egorov, Vladimir; Gulzar, Umair; O'Dwyer, Colm; Horizon 2020; European Regional Development Fund; Irish Research Council; Enterprise Ireland; Higher Education Authority
    Here we describe the modeling and design evolution of vat polimerized (Vat-P) stereolithographic apparatus (SLA) 3D printed coin cell-type aqueous and non-aqueous rechargeable lithium-ion batteries, cases and current collectors. We detail the rationale for design evolution that improved performance, handling and assembly of the printed batteries. Some guidance into the modeling, 3D printing process, material choice, chemical and electrochemical stability, assembly, sealing, and performance of 3D printed Li-ion batteries is outlined. 3D printed Li-ion batteries demonstrated promising results in terms of gravimetric capacity, rate capability, and capacity per unit footprint area compared to conventional coin cells in both aqueous and non-aqueous systems. For aqueous cells, the cell level capacity is a factor of 2–3x higher than similar metal coin cells due to the lighter weight and better rate response. We also outline design requirements for a Vat-P printed battery that are compatible with organic carbonate-based electrolytes, where the cell provides 115 mAh g−1 specific capacity using an LiCoO2–graphite chemistry, which is only ∼20% less than the maximum reversible capacity of LCO. Despite the challenges faced in optimizing the design and materials for 3D printed Li-ion batteries, this study provides valuable information for future research and development.
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    Asymmetrical optical response of opal photonic crystals with graded thickness
    (IOP Publishing, 2023-11-27) Grant, Alex; O'Dwyer, Colm; Irish Research Council
    The influence of thickness gradient and structural order on the spectral response of opal photonic crystals (PhCs) grown by evaporation-induced self-assembly (EISA) are presented. SEM imaging and angle resolved optical transmission spectroscopy are used to investigate the evolution of the PBG along a thickness gradient for opals grown from five different colloidal sphere concentrations at two different evaporation rates. The degradation of structural order along the thickness gradient is demonstrated, the occurrence of which attenuates the PBG with the thinning of the opal film and results in asymmetrical angle-resolved transmission spectra. The asymmetry in transmission intensity becomes more pronounced for opals grown from lower volume fractions, where secondary Bragg reflections also appear at low incident angles.