ORCID Profile
0000-0002-8110-4535
Current Organisation
University of St Andrews
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Publisher: Wiley
Date: 15-02-2021
DOI: 10.1002/MRC.5140
Abstract: Characterising the local structures (e.g., the cation distribution) of mixed‐metal ceramics by NMR spectroscopy is often challenging owing to the unfavourable properties (low γ , large quadrupole moment and/or low abundance) of many metal nuclei. 17 O is an attractive option owing to the prevalence of oxygen within ceramics. The moderate γ and small quadrupole moment of 17 O mean that the greatest barrier to accessing the information available from this nucleus is isotopic enrichment. We explore the challenges of ensuring uniform isotopic enrichment with 17 O 2 (g) for the pyrochlore solid solutions, Y 2 Sn x Ti 2– x O 7 , La 2 Sn x Zr 2– x O 7 and La 2 Sn x Hf 2– x O 7 , demonstrating that high enrichment temperatures (900 °C for 12 hr) are required. In addition, for sites with very high symmetry (such as the tetrahedral OY4 and OLa4 sites with C Q ≈ 0 present here), we demonstrate that quantitative 17 O NMR spectra require correction for the differing contributions from the centreband of the satellite transitions, which can be as high as a factor of ~3.89. It is common to use first‐principles calculations to aid in interpreting NMR spectra of disordered solids. Here, we use an ensemble modelling approach to ensure that all possible cation arrangements are modelled in the minimum possible number of calculations. By combining uniform isotopic enrichment, quantitative NMR spectroscopy and a comprehensive computational approach, we are able to show that the cation distribution in Y 2 Sn x Ti 2– x O 7 is essentially random, whereas in La 2 Sn x Zr 2– x O 7 and La 2 Sn x Hf 2– x O 7 , OLa2SnZr and OLa2SnHf sites are slightly energetically disfavoured, leading to a weak preference for clustering of like cations.
Publisher: American Chemical Society (ACS)
Date: 09-07-2020
Publisher: American Chemical Society (ACS)
Date: 24-01-2019
DOI: 10.1021/JACS.8B11519
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.SSNMR.2019.05.005
Abstract: NMR spectroscopy of paramagnetic materials (pNMR) has the potential to provide great structural insight, but many challenges remain in interpreting the spectra in detail. This work presents a study of a series of structurally analogous metal-organic frameworks (MOFs) based on 5-substituted isophthalate linkers and Cu(II) paddlewheel dimers, of interest owing to their "crumple zone" structural rearrangement on dehydration/rehydration.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2TA09253K
Abstract: Continuous flow synthesis of hypercrosslinked polymers (HCPs) was achieved within 5 minutes, 99% faster than a batch reaction, improving productivity rates by 32-fold. The faster kinetics also enhanced microporosity, increasing CO 2 /N 2 selectivity by 850%.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CC03731D
Abstract: By replacing Lewis acids with Brønsted acids as catalysts, continuous flow synthesis of hypercrosslinked polymers is achieved within 10% of the time required for a typical batch reaction. Compared with batch-synthesised polymers, the flow-produced materials take up 24% more CO2, precluding the need for lengthy reaction protocols to yield high-performance hypercrosslinked polymers for carbon capture.
Publisher: American Chemical Society (ACS)
Date: 05-05-2015
DOI: 10.1021/JACS.5B03353
Abstract: Solid-state NMR spectra of new P-Se heterocycles based on peri-substituted naphthalene motifs show the presence of unusual J couplings between Se and P. These couplings are between atoms in adjacent molecules and occur "through space", rather than through conventional covalent bonds. Experimental measurements are supported by relativistic DFT calculations, which confirm the presence of couplings between nonbonded atoms, and provide information on the pathway of the interaction. This observation improves the understanding of J couplings and offers insight into the factors that affect crystal packing in solids, for future synthetic exploitation.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8RA00596F
Abstract: Investigation of the conditions required for quantitative isotopic enrichment and the acquisition of quantitative 17 O NMR spectra of ceramic oxides.
Publisher: Wiley
Date: 28-06-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0NJ02969F
Abstract: Hosting a BODIPY dye in a crystalline sponge bathochromically shifts luminescent emission.
Publisher: American Chemical Society (ACS)
Date: 20-08-2014
DOI: 10.1021/JO5015678
Abstract: The synthesis of rigid symmetric polyradical model systems with inter-spin distances between 1.4 and 4 nm and their room temperature continuous wave (CW) EPR spectra are reported. Conditions for attachment of the spin-label via esterification have been optimized on the direct synthesis of polyradicals from commercially available polyphenols and the carboxylic acid functionalized nitroxide TPC. A common synthetic protocol utilizing 4-hydroxy-4'-iodobiphenyl as a key building block has been used to synthesize an equilateral biradical and a triradical in only two steps from commercially available starting materials. The first synthesis of a tetraradical based upon an adamantane core bearing six equivalent nitroxide-nitroxide distances is also reported. These systems are very promising candidates for studying multi-spin effects in pulsed EPR distance measurements.
Publisher: Springer Science and Business Media LLC
Date: 13-08-2018
DOI: 10.1038/S41557-018-0104-X
Abstract: Highly porous metal-organic frameworks (MOFs), which have undergone exciting developments over the past few decades, show promise for a wide range of applications. However, many studies indicate that they suffer from significant stability issues, especially with respect to their interactions with water, which severely limits their practical potential. Here we demonstrate how the presence of 'sacrificial' bonds in the coordination environment of its metal centres (referred to as hemilability) endows a dehydrated copper-based MOF with good hydrolytic stability. On exposure to water, in contrast to the indiscriminate breaking of coordination bonds that typically results in structure degradation, it is non-structural weak interactions between the MOF's copper paddlewheel clusters that are broken and the framework recovers its as-synthesized, hydrated structure. This MOF retained its structural integrity even after contact with water for one year, whereas HKUST-1, a compositionally similar material that lacks these sacrificial bonds, loses its crystallinity in less than a day under the same conditions.
Publisher: American Chemical Society (ACS)
Date: 06-09-2016
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Daniel Dawson.