RECENT PUBLICATIONS

Emeritus Professor Noel Hush et al

Emeritus Professor Noel Hush

E/Prof Noel Hush

Posted 28 April 2017
Competition of van der Waals and chemical forces on gold-sulfur surfaces and nanoparticles
Nature Reviews Chemistry, 1 (0017), 1-12, 2017.

Abstract:
Chemists generally believe that covalent and ionic bonds form much stronger links between atoms than the van der Waals force does. However, this is not always so. We present cases in which van der Waals dispersive forces introduce new competitive bonding possibilities rather than just modulating traditional bonding scenarios. Although the new possibilities could arise from any soft–soft chemical interaction, we focus on bonding between gold atoms and alkyl or arylsulfur ligands, RS. Consideration of all the interactions at play in sulfur-protected gold surfaces and gold nanoparticles is necessary to understand their structural, chemical and spectroscopic properties. In turn, such knowledge opens pathways to new chemical entities and innovative nanotechnological devices. Such experimentation is complemented by modern theory, and presented here is a broad overview of computational methods appropriate to fields ranging from gas-phase chemistry to device physics and biochemistry.


Professor Phil Gale et al

Professor Phil Gale

Prof Phil Gale

Posted 19 April 2017
Cyclic peptide unguisin A is an anion receptor with high affinity for phosphate and pyrophosphate
Organic & Biomolecular Chemistry, 15 (14), 2962-2967, 2017.

Abstract:
Unguisin A (1) is a marine-derived, GABA-containing cyclic heptapeptide. The biological function of this flexible macrocycle is obscure. Here we show that compound 1 lacks any detectable activity in antimicrobial growth inhibition assays, a result that runs contrary to a previous report. However, we find that 1 functions as a promiscuous host molecule in a variety of anion-binding interactions, with high affinity particularly for phosphate and pyrophosphate. We also show that a series of rigidified, backbone-fluorinated analogues of 1 displays altered affinity for chloride ions.


Ms Anna Safitri, Dr Aviva Levina, Dr Joonsup Lee, Dr Elizabeth Carter and Prof Peter Lay

Professor Peter Lay

Prof Peter Lay

Posted 19 April 2017
Biospectroscopy for studying the influences of anti-diabetic metals (V, Cr, Mo, and W) to the insulin signaling pathway
AIP Conference Proceeding, 1823, 020019, 2017.

Abstract:
The prevalence of diabetes, particularly with respect to type 2 diabetes, has reached epidemic proportions and continues to grow worldwide. One of the potential therapeutic targets in the treatment of type 2 diabetes involves the role of protein tyrosine phosphatases in the negative regulation of insulin signaling. The complexes of V(V/IV), Cr(III), W(VI), and Mo(VI), have all been proposed as possible drugs in the treatment of diabetes mellitus. Anti-diabetic activities of V(V/IV), Cr(III), Mo(VI), and W(VI) compounds are likely to be based on similar mechanisms, which involve phosphorylation/dephosphorylation reactions in the glucose uptake and metabolism. In order to clearly understand biological activities and phosphorylation/dephosphorylation reactions involved in anti-diabetic actions of Cr(III), V(V/IV), Mo(VI), and W(VI) complexes, the current research involves the use of cultured insulin-sensitive cells treated with these compounds. These reactions were investigated through vibrational spectroscopy. Protein phosphorylation/dephosphorylation induced conformational changes in secondary protein structure from α-helix to β-sheet, and these changes were detected by the IR spectra, which showed changes in the wavenumber and intensities of signals within the composite protein amide I band.


Ms Michelle Yu, Dr Paula Kayser-Gonzalez and Prof Brendan Kennedy et al

Professor Brendan Kennedy

Prof Brendan Kennedy

Posted 19 April 2017
Structure and magnetism in Sr1-xAxTcO3 perovskites: Importance of the A-site cation
Physical Review B, 95 (5), 054430, 2017.

Abstract:
The Sr1-xBaxTcO3 (x=0, 0.1, 0.2) oxides were prepared and their solid-state and magnetic structure studied as a function of temperature by x-ray and neutron powder diffraction. The refined Tc moments at room temperature and Néel temperatures for Ba0.1Sr0.9TcO3 and Ba0.2Sr0.8TcO3 were 2.32(14)μβ and 2.11(13)μβ and 714oC and 702oC, respectively. In contrast to expectations, the Néel temperature in the series Sr1-xAxTcO3 decreases with increasing Ba content. This observation is consistent with previous experimental measurements for the two series AMO3 (M=Ru, Mn; A=Ca, Sr, Ba) where the maximum magnetic ordering temperature was observed for A=Sr. Taken with these previous results the current work demonstrates the critical role of the A-site cation in the broadening of the pi* bandwidth and ultimately the magnetic ordering temperature.


Ms Lisa Cattelan and Professor Thomas Maschmeyer et al

Professor Thomas Maschmeyer

Prof Thomas Maschmeyer

Posted 19 April 2017
Continuous-flow O-alkylation of biobased derivatives with dialkyl carbonates in the presence of magnesium- aluminium hydrotalcites as catalyst precursors
ChemSusChem, 10 (7), 1571-1583, 2017.

Abstract:
The base-catalysed reactions of OH-bearing biobased derivatives (BBDs) including glycerol formal, solketal, glycerol carbonate, furfuryl alcohol and tetrahydrofurfuryl alcohol with non-toxic dialkyl carbonates (dimethyl and diethyl carbonate) were explored under continuous-flow (CF) conditions in the presence of three Na-exchanged Y- and X-faujasites (FAUs) and four Mg–Al hydrotalcites (HTs). Compared to previous etherification protocols mediated by dialkyl carbonates, the reported procedure offers substantial improvements not only in terms of (chemo)selectivity but also for the recyclability of the catalysts, workup, ease of product purification and, importantly, process intensification. Characterisation studies proved that both HT30 and KW2000 hydrotalcites acted as catalyst precursors: during the thermal activation pre-treatments, the typical lamellar structure of the hydrotalcite was broken down gradually into a MgO-like phase (periclase) or rather a magnesia–alumina solid solution, which was the genuine catalytic phase.


Dr George Bacskay et al

Dr George Bacskay

Dr George Bacskay

Posted 19 April 2017
First observation of the 33Πg state of C2: Born-Oppenheimer breakdown
The Journal of Chemical Physics, 146 (13), 134306, 2017.

Abstract:
The 33Πg state of the dicarbon molecule, C2, has been identified for the first time by a combination of resonant ionization spectroscopy, mass spectrometry, and high-level ab initio quantum chemical calculations. This marks the discovery of the final valence triplet state of C2 spectroscopically accessible from the lowest triplet state. It is found to be vibronically coupled to the recently discovered 43Πg state, necessitating vibronic calculations beyond the Born-Oppenheimer approximation to reconcile calculated rotational constants with observations. The 33Πg state of C2 is observed to have a much shorter fluorescence lifetime than expected, possibly pointing to predissociation by coupling to the unbound d3Πg state.


Professor Maxim Avdeev et al

Professor Maxim Avdeev

Prof Maxim Avdeev

Posted 19 April 2017
Synthesis and structural characterization of the hexagonal anti-perovskite Na2CaVO4F
Journal of Solid State Chemistry, 250, 134-139, 2017.

Abstract:
The structural details of the ordered hexagonal oxyfluoride Na2CaVO4F prepared by solid-state synthesis using stoichiometric amounts of V2O5, CaCO3, Na2CO3 and NaF were characterized using high-resolution neutron powder diffraction. The structural changes between 25 °C and 750 °C revealed that the two structural subunits in this material behave different when heated: there is an expansion of the face-shared FNa4Ca2 octahedra while the VO4 tetrahedra due to increased thermal disorder reveal marginal bond contractions. Bond valences and the global instability index point to significant structural disorder at 750 °C.


Dr Anna Renfrew*

Dr Anna Renfrew

Dr Anna Renfrew

Posted 4 April 2017
Spectroscopic approaches to tracking metal-based drugs in cells and tissue
Chimia, 71 (3), 112-119, 2017.

Abstract:
Metal-based drugs with novel targets and modes of action are increasingly being developed as alternatives to classical platinum(ii) chemotherapeutics. Imaging methods in tumour cells and tissues offer valuable insights into the behaviour of these novel complexes; however, mapping the distribution of metal ions and complexes within cellular environments remains challenging. The advantages and limitations of three modes of imaging: synchrotron radiation-induced X-ray fluorescence, mass spectrometry, and fluorescence microscopy are discussed in this review, with particular emphasis on their use in imaging ruthenium-based drugs.


Ms Hazel Chan, Ms Joy Ghrayche, Ms Jianhua Wei and Dr Anna Renfrew*

Dr Anna Renfrew

Dr Anna Renfrew

Posted 4 April 2017
Photolabile ruthenium(II)-purine complexes: Phototoxicity, DNA binding, and light-triggered drug release
European Journal of Inorganic Chemistry, 2017 (12), 1679-1686, 2017.

Abstract:
Photoactivated chemotherapy is gaining increasing interest as a potentially selective treatment of cancer, and bacterial and viral infections. In this approach a therapeutic can be administered as a nontoxic prodrug and then converted to its active form in the diseased tissue by the localized application of light. Here we report the first example of a photolabile ruthenium prodrug that releases a purine ligand when irradiated with visible light. A series of ruthenium(II) polypyridyl complexes were prepared with the anticancer agent 6-mercaptopurine as a ligand. The nature of the polypyridyl ligand was found to strongly influence the properties of the complexes, including absorbance maxima, photostability, and the binding mode of 6-mercaptopurine. The lead complex is stable in solution in the dark but releases 6-mercapoturine when irradiated with visible light, leading to a significant increase in toxicity towards breast cancer cells.


Mr Jack Markham, Mr Jun Liang, Dr Aviva Levina, Dr Rachel Mak and Prof Peter Lay* et al

Professor Peter Lay

Prof Peter Lay

Posted 4 April 2017
(Pentamethylcyclopentadienato)rhodium complexes for delivery of the curcumin anticancer drug
European Journal of Inorganic Chemistry, 2017 (12), 1812-1823, 2017.

Abstract:
[RhIII(*Cp)Cl(X,Y)]n+ complexes {X, Y = Cl, PTA, n = 0 (2); X, Y = en, n = 1 (3, Cl– salt; 4, PF6– salt); X, Y = acac, n = 0 (5); X, Y = cur, n = 0 (6), where *Cp = pentamethylcyclopentadienato, curH = curcumin; PTA = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane; en = 1,2-ethanediamine; acac = acetylacetonato = 2,4-pentanedionato(1–)} were synthesized from [Rh(*Cp)(µ-Cl)Cl]2 (1). While 2–5 were inactive against human epithelial A549 lung-cancer cells in assays of cytotoxicity, and antimetastatic and proapoptotic behaviors, 6 had a cytotoxic activity similar to that of curH over 72 h, but at 24 h in real-time cell migration assays, it was less active, showing slow release of curH. All complexes underwent ligand-exchange reactions with biomolecules and cells within the timeframes of the assays (X-ray absorption spectroscopy). Intracellular elemental distributions (X-ray fluorescence microscopy) showed that 6 effectively delivered curH to cells, where it was released. Other elemental distributions and caspase activities were consistent with preapoptotic activities. As such, 6 is a promising delivery agent for bioactive ligands, such as curH. However, pure curcumin itself showed a previously unrecognized ability to promote migration of A549 cells at subtoxic concentrations in the presence of endothelial growth factor, which may be a concern for its widespread use as a nutritional supplement and as a potential drug. This aspect warrants further research.


Dr Behnam Nikoobakht et al

Dr Behnam Nikoobakht

Dr Behnam Nikoobakht

Posted 4 April 2017
Theoretical description of circular dichroism in photoelectron angular distributions of randomly oriented chiral molecules after multi-photon photoionization
The Journal of Chemical Physics, 146 (2), 024306, 2017.

Abstract:
Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem., Int. Ed. 51, 4755 (2012) and C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionization of the photoselected molecules. It combines perturbation theory for the light-matter interaction with ab initio calculations for the two-photon absorption and a single-center expansion of the photoelectron wavefunction in terms of hydrogenic continuum functions. It is verified that the model correctly reproduces the basic symmetry behavior expected under exchange of handedness and light helicity. When applied to fenchone and camphor, semi-quantitative agreement with the experimental data is found, for which a sufficient d wave character of the electronically excited intermediate state is crucial.