School of Chemistry - Research Publications

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    Effects of Hydrostatic Pressure on the Surface Plasmon Resonance of Gold Nanocrystals
    Martin-Sanchez, C ; Antonio Barreda-Argueso, J ; Seibt, S ; Mulvaney, P ; Rodriguez, F (American Chemical Society, 2019-01)
    The surface plasmon resonances of gold nanospheres and nanorods have been measured as a function of hydrostatic pressure up to 17 GPa in methanol-ethanol 4:1 solvent and up to 10 GPa in paraffin. Both the sphere resonance and the longitudinal rod resonance exhibit redshifts, whereas the transverse rod mode shows an extremely weak redshift or blueshift depending on the nanorod aspect ratio. Solidification of the solvent around 11 GPa causes some aggregation of the particles, readily identified through broadening of the surface plasmon band and further redshifting. Spectra collected during loading and unloading cycles exhibit only minimal hysteresis if the pressure remains below 11 GPa. The surface plasmon shifts are the result of two competing effects. Compression of the conduction electrons in the metals increases the bulk plasma frequency, which causes a blueshift. However, the increase in the solvent density under hydrostatic load leads to an increase in the solvent refractive index, which in turn leads to a redshift. We find that after accounting for the solvent contribution, we can spectroscopically determine the bulk modulus of the gold nanoparticles with a precision of 10%. The value obtained of K0 = 190 GPa is significantly higher than the value for bulk gold (167 GPa). Furthermore, we show that pressure-induced solidification causes a significant broadening and anomalous shift of the surface plasmon band that we attribute to aggregation and nanorod deformation.
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    Chiral 1-D coordination polymer chains featuring 1,1′-binaphthyl
    Tay, HM ; Thoonen, S ; Hua, C (CSIRO Publishing, 2024)
    Four 1-D chain coordination polymers containing bent 1,1′-binaphthyl ligands were synthesised with NiII, CuII and AgI. The use of (R)-4,4′-(2,2′-diethoxy-[1,1′-binaphthalene]-6,6′)dipyridine as a ligand yielded isostructural 1-D looping chains with NiII and CuII, whereas the use of AgI yielded both linear and helical 1-D chains. Changing the dipyridyl coordination groups to dicarboxylates in (S)-6,6′-dicarboxyl-2,2′-diethoxy-1,1′-binaphthalene yielded a 1-D looping chain with a CuII paddlewheel motif. The AgI 1-D chain features two crystallographically distinct 1-D chain morphologies with a triple helix and linear strips. The packing arrangement of the 1-D chains differs because of the intermolecular interactions present, with the steric bulk of the ethoxy substituent on the 1,1′-binaphthyl enabling the formation of large void spaces.
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    Regioselective metal-free synthesis of sulfostyril-quinoline hybrid framework: Experimental and computational mechanistic insights
    Munir, R ; Khan, I ; Siddiqui, L ; Javid, N ; Zia-ur-Rehman, M ; Ali, HS ; Saeed, M ; Zaib, S ; Awwad, NS ; Ibrahium, HA ; Yeow, CHS ; White, JM ; Dera, AA (Elsevier, 2024-11-05)
    Polycyclic sultams are widely encountered in both natural products and bioactive drug candidates. In cognizance to their synthetic and medicinal chemistry applications, the exploration of facile approaches remains at high demand. In the present work, a straightforward, efficient and operationally simple methodology has been developed. The coupling of β-chloroaldehyde with a diverse range of anilines as bis-nucleophile containing N–C–C fragment was achieved to deliver a sulfostyril-quinoline hybrid framework. The formation of target scaffolds bearing various substituents avoiding the need of column chromatographic purification represents one of the key advantages associated with this transformation. The exclusive regioselectivity achieved for the formation of linear tetracyclic products over angular products was corroborated with density functional theory (DFT) calculations as well as single crystal X-ray analysis. Furthermore, the density functional theory calculations allowed us to understand the formation of tetracyclic sulfostyril-quinoline hybrid skeleton, and are in fair agreement with the observed regioselectivity of this reaction.
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    Selenoproteins in Health
    Ng, K ; Ziqi, Q ; Duan, A (MDPI AG, 2023-12-25)
    Selenium (Se) is a naturally occurring essential micronutrient that is required for human health. The existing form of Se includes inorganic and organic. In contrast to the inorganic Se, which has low bioavailability and high cytotoxicity, organic Se exhibits higher bioavailability, lower toxicity, and has a more diverse composition and structure. This review presents the nutritional benefits of Se by listing and linking selenoprotein (SeP) functions to evidence of health benefits. The research status of SeP from foods in recent years is introduced systematically, particularly the sources, biochemical transformation and speciation, and the bioactivities. These aspects are elaborated with references for further research and utilization of organic Se compounds in the field of health.
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    Predicting valence tautomerism in diverse cobalt-dioxolene complexes: elucidation of the role of ligands and solvent
    Zahir, FZM ; Hay, MA ; Janetzki, JT ; Gable, RW ; Goerigk, L ; Boskovic, C (ROYAL SOC CHEMISTRY, 2024-04-17)
    The ability of molecular switches to reversibly interconvert between different forms promises potential applications at the scale of single molecules up to bulk materials. One type of molecular switch comprises cobalt-dioxolene compounds that exhibit thermally-induced valence tautomerism (VT) interconversions between low spin Co(iii)-catecholate (LS-CoIII-cat) and high spin Co(ii)-semiquinonate (HS-CoII-sq) forms. Two families of these compounds have been investigated for decades but have generally been considered separately: neutral [Co(diox)(sq)(N2L)] and cationic [Co(diox)(N4L)]+ complexes (diox = generic dioxolene, N2L/N4L = bidentate/tetradentate N-donor ancillary ligand). Computational identification of promising new candidate compounds prior to experimental exploration is beneficial for environmental and cost considerations but requires a thorough understanding of the underlying thermochemical parameters that influence the switching. Herein, we report a robust approach for the analysis of both cobalt-dioxolene families, which involved a quantitative density functional theory-based study benchmarked with reliable quasi-experimental references. The best-performing M06L-D4/def2-TZVPP level of theory has subsequently been verified by the synthesis and experimental investigation of three new complexes, two of which exhibit thermally-induced VT, while the third remains in the LS-CoIII-cat form across all temperatures, in agreement with prediction. Valence tautomerism in solution is markedly solvent-dependent, but the origin of this has not been definitively established. We have extended our computational approach to elucidate the correlation of VT transition temperature with solvent stabilisation energy and change in dipole moment. This new understanding may inform the development of VT compounds for applications in soft materials including films, gels, and polymers.
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    Ab initio-based determination of lanthanoid-radical exchange as visualised by inelastic neutron scattering
    Dunstan, MA ; Giansiracusa, MJ ; Calvello, S ; Sorace, L ; Krause-Heuer, AM ; Soncini, A ; Mole, RA ; Boskovic, C (ROYAL SOC CHEMISTRY, 2024-03-20)
    Magnetic exchange coupling can modulate the slow magnetic relaxation in single-molecule magnets. Despite this, elucidation of exchange coupling remains a significant challenge for the lanthanoid(iii) ions, both experimentally and computationally. In this work, the crystal field splitting and 4f-π exchange coupling in the erbium-semiquinonate complex [ErTp2dbsq] (Er-dbsq; Tp- = hydro-tris(1-pyrazolyl)borate, dbsqH2 = 3,5-di-tert-butyl-1,2-semiquinone) have been determined by inelastic neutron scattering (INS), magnetometry, and CASSCF-SO ab initio calculations. A related complex with a diamagnetic ligand, [ErTp2trop] (Er-trop; tropH = tropolone), has been used as a model for the crystal field splitting in the absence of coupling. Magnetic and INS data indicate antiferromagnetic exchange for Er-dbsq with a coupling constant of Jex = -0.23 meV (-1.8 cm-1) (-2Jex formalism) and good agreement is found between theory and experiment, with the low energy magnetic and spectroscopic properties well modelled. Most notable is the ability of the ab initio modelling to reproduce the signature of interference between localised 4f states and delocalised π-radical states that is evident in the Q-dependence of the exchange excitation. This work highlights the power of combining INS with EPR and magnetometry for determination of ground state properties, as well as the enhanced capability of CASSCF-SO ab initio calculations and purposely developed ab initio-based theoretical models. We deliver an unprecedentedly detailed representation of the entangled character of 4f-π exchange states, which is obtained via an accurate image of the spin-orbital transition density between the 4f-π exchange coupled wavefunctions.
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    John Atherton Young 1936–2004
    Rae, ID (CSIRO Publishing, 2024)
    John Atherton Young (1936–2004) graduated in medicine at the University of Queensland and undertook research in physiology at the Kanematsu Institute in Sydney for which he was awarded his PhD. After postdoctoral studies in Germany, he joined the department of physiology at the University of Sydney, rising to professor, then Dean of the Faculty of Medicine and finally Pro-Vice-Chancellor for Health Sciences. His research on the physiology of epithelial ducts, beginning with those of the kidney but later centring on salivary glands and the pancreas, brought him international recognition as a leader in the field. He made significant contributions to professional societies and was recognised with international and national awards including membership of the Order of Australia. A bronze portrait head of Young by sculptor Dan Lake is displayed in the foyer of the Edward Ford building at the University of Sydney. He was a man of great culture, a witty conversationalist and a great scientist.
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    Identification and Evaluation of Olive Phenolics in the Context of Amine Oxidase Enzyme Inhibition and Depression: In Silico Modelling and In Vitro Validation
    Karagiannis, TC ; Ververis, K ; Liang, JJ ; Pitsillou, E ; Liu, S ; Bresnehan, SM ; Xu, V ; Wijoyo, SJ ; DUAN, X ; Ng, K ; Hung, A ; Goebel, E ; El-Osta, A (MDPI AG, 2024)
    The Mediterranean diet well known for its beneficial health effects, including mood enhancement, is characterised by the relatively high consumption of extra virgin olive oil (EVOO), which is rich in bioactive phenolic compounds. Over 200 phenolic compounds have been associated with Olea europaea, and of these, only a relatively small fraction have been characterised. Utilising the OliveNetTM library, phenolic compounds were investigated as potential inhibitors of the epigenetic modifier lysine-specific demethylase 1 (LSD1). Furthermore, the compounds were screened for inhibition of the structurally similar monoamine oxidases (MAOs) which are directly implicated in the pathophysiology of depression. Molecular docking highlighted that olive phenolics interact with the active site of LSD1 and MAOs. Protein–peptide docking was also performed to evaluate the interaction of the histone H3 peptide with LSD1, in the presence of ligands bound to the substrate-binding cavity. To validate the in silico studies, the inhibitory activity of phenolic compounds was compared to the clinically approved inhibitor tranylcypromine. Our findings indicate that olive phenolics inhibit LSD1 and the MAOs in vitro. Using a cell culture model system with corticosteroid-stimulated human BJ fibroblast cells, the results demonstrate the attenuation of dexamethasone- and hydrocortisone-induced MAO activity by phenolic compounds. The findings were further corroborated using human embryonic stem cell (hESC)-derived neurons stimulated with all-trans retinoic acid. Overall, the results indicate the inhibition of flavin adenine dinucleotide (FAD)-dependent amine oxidases by olive phenolics. More generally, our findings further support at least a partial mechanism accounting for the antidepressant effects associated with EVOO and the Mediterranean diet.
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    Resolving conjugated polymer film morphology with polarised transmission and time-resolved emission microscopy
    Xu, Y ; Sun, L ; Ghiggino, KP ; Smith, TA (IOP Publishing, 2024-07-01)
    The alignment of chromophores plays a crucial role in determining the optoelectronic properties of materials. Such alignment can make interpretation of fluorescence anisotropy microscopy (FAM) images somewhat ambiguous. The time-resolved emission behaviour can also influence the fluorescence anisotropy. This is particularly the case when probing excitation energy migration between chromophores in a condensed phase. Ideally information concerning the chromophoric alignment, emission decay kinetics and fluorescence anisotropy can be recorded and correlated. We report on the use of polarised transmission imaging (PTI) coupled with both steady-state and time-resolved FAM to enable accurate identification of chromophoric alignment and morphology in thin films of a conjugated polydiarylfluorene. We show that the combination of these three imaging modes presents a comprehensive methodology for investigating the alignment and morphology of chromophores in thin films, particularly for accurately mapping the distribution of amorphous and crystalline phases within the thin films, offering valuable insights for the design and optimization of materials with enhanced optoelectronic performance.