87 results on '"Prior TJ"'
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2. Synthesis and characterization of two metallic spin-glass phases of FeMo4Ge3
- Author
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Baker, PJ, Battle, PD, Blundell, SJ, Grandjean, F, Lancaster, T, Long, GJ, Oldham, SE, and Prior, TJ
- Subjects
Physics - Abstract
Polycrystalline samples of Fe Mo4 Ge3 have been synthesized by the reduction of an oxide mixture at 1248 K and characterized by a combination of diffraction, muon spin relaxation (μ+ SR), Mössbauer spectroscopy, magnetometry, transport, and heat-capacity measurements. The compound adopts a tetragonal W5 Si3 structure (space group I4 mcm); the iron and molybdenum atoms are disordered over two crystallographic sites, 16k and either 4a or 4b. The synthesis conditions determine which fourfold site is selected; occupation of either leads to the presence of one-dimensional chains of transition metals in the structure. In both cases, the electrical resistivity below 200 K is ∼175 μΩ cm. The dc magnetization rapidly rises below 35 K (Fe Mo on 16k and 4b sites) or 16 K (16k and 4a sites), and a magnetization of 1 μB or 0.8 μB per Fe atom is observed in 4 T at 2 K. The ac susceptibility and the heat capacity both suggest that these are glasslike magnetic transitions, although the transition shows a more complex temperature dependence (with two maxima in χ″) when the 4b sites are partially occupied by iron. No long-range magnetic order is thought to be present at 5 K in either structural form; this has been proven by neutron diffraction and μ+ SR for the case when Fe and Mo occupy the 16k and 4b sites. © 2008 The American Physical Society.
- Published
- 2016
3. Crystal structure of poly[[mu]-acetato-bis[[mu]-2-oxo-2-(quinolin-8-yl)ethanoato]trisodium]
- Author
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Nicholls, RL, Pask, CM, Nguyen, NB, and Prior, TJ
- Abstract
The title compound [Na3(C11H6NO3)2(C2H3O2)]n, crystallized through diffusion of diethyl ether into methanol as needles. There are three crystallographically independent Na+ cations present, each exhibiting a distorted octahedral coordination geometry, two through coordination by five O atoms and one N atom, and one through coordination by six O atoms. A series of intermolecular O...Na and N...Na contacts leads to the formation of chains along the a-axis direction.
- Published
- 2014
4. Rigid Macrocycle Metal Complexes as CXCR4 Chemokine Receptor Antagonists: Influence of Ring Size.
- Author
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Renard I, D'huys T, Burke BP, Ajoleza T, Cain AN, Funwie NL, Khan A, Maples DL, Maples RD, Matz DL, McRobbie G, Ullom R, Prior TJ, Linder DP, Van Loy T, Hubin TJ, Schols D, and Archibald SJ
- Abstract
Understanding the role of chemokine receptors in health and disease has been of increasing interest in recent years. Chemokine receptor CXCR4 has been extensively studied because of its defined role in immune cell trafficking, HIV infection, inflammatory diseases, and cancer progression. We have developed high affinity rigidified CXCR4 antagonists that incorporate metal ions to optimize the binding interactions with the aspartate side chains at the extracellular surface of the CXCR4 chemokine receptor and increase the residence time. Cross- and side-bridged tetraazamacrocylic complexes offer significant advantages over the non-bridged molecular structures in terms of receptor affinity, potential for radiolabelling, and use in therapeutic applications. Our investigation has been extended to the influence of the ring size on bridged tetraazamacrocyclic compounds with the addition of two novel chelators (bis-cross-bridged homocyclen and bis-cross-bridged cyclen) to compare to the bis-bridged cyclam, along with novel metal complexes formed with copper(II) or zinc(II). The in vitro biological assays showed that all of the zinc(II) complexes are high affinity antagonists with a marked increase in CXCR4 selectivity for the bis-cross-bridged cyclen complex, whereas the properties of the copper(II) complexes are highly dependent on metal ion geometry. X-ray crystal structural data and DFT computational studies allow for the rationalisation of the relative affinities and the aspartate residue interactions on the protein surface. Changing the ring size from 14-membered can increase the selectivity for the CXCR4 receptor whilst retaining potent inhibitory activity, improving the key pharmacological characteristics.
- Published
- 2024
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5. EVIDENCE meta-analysis: evaluating minimal residual disease as an intermediate clinical end point for multiple myeloma.
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Landgren O, Prior TJ, Masterson T, Heuck C, Bueno OF, Dash AB, Einsele H, Goldschmidt H, Knop S, Li C, Mellqvist UH, McFadden I, Oprea C, Ross JA, Talpes M, Hydren JR, Ahlstrom JM, Kazandjian D, Weinhold N, Zhang R, Stetler-Stevenson M, Marti G, and Devlin SM
- Subjects
- Humans, Randomized Controlled Trials as Topic, Progression-Free Survival, Prognosis, Neoplasm, Residual diagnosis, Multiple Myeloma mortality, Multiple Myeloma diagnosis, Multiple Myeloma drug therapy, Multiple Myeloma therapy, Multiple Myeloma pathology
- Abstract
Abstract: Estimating progression-free survival (PFS) and overall survival superiority during clinical trials of multiple myeloma (MM) has become increasingly challenging as novel therapeutics have improved patient outcomes. Thus, it is imperative to identify earlier end point surrogates that are predictive of long-term clinical benefit. Minimal residual disease (MRD)-negativity is a common intermediate end point that has shown prognostic value for clinical benefit in MM. This meta-analysis was based on the US Food and Drug Administration guidance for considerations for a meta-analysis of MRD as a clinical end point and evaluates MRD-negativity as an early end point reasonably likely to predict long-term clinical benefit. Eligible studies were phase 2 or 3 randomized controlled clinical trials measuring MRD-negativity as an end point in patients with MM, with follow-up of ≥6 months following an a priori-defined time point of 12 ± 3 months after randomization. Eight newly diagnosed MM studies evaluating 4907 patients were included. Trial-level associations between MRD-negativity and PFS were R2WLSiv, 0.67 (95% confidence interval [CI], 0.43-0.91) and R2copula 0.84 (0.64 to >0.99) at the 12-month time point. The individual-level association between 12-month MRD-negativity and PFS resulted in a global odds ratio (OR) of 4.02 (95% CI, 2.57-5.46). For relapse/refractory MM, there were 4 studies included, and the individual-level association between 12-month MRD-negativity and PFS resulted in a global OR of 7.67 (4.24-11.10). A clinical trial demonstrating a treatment effect on MRD is reasonably likely to eventually demonstrate a treatment effect on PFS, suggesting that MRD may be an early clinical end point reasonably likely to predict clinical benefit in MM, that may be used to support accelerated approval and thereby, expedite the availability of new drugs to patients with MM.
- Published
- 2024
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6. Layered rare-earth hydroxides as multi-modal medical imaging probes: particle size optimisation and compositional exploration.
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Strimaite M, Wells CJR, Prior TJ, Stuckey DJ, Wells JA, Davies GL, and Williams GR
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- Magnetic Resonance Imaging, Multimodal Imaging, Humans, Particle Size, Hydroxides chemistry, Metals, Rare Earth chemistry
- Abstract
Recently, layered rare-earth hydroxides (LRHs) have received growing attention in the field of theranostics. We have previously reported the hydrothermal synthesis of layered terbium hydroxide (LTbH), which exhibited high biocompatibility, reversible uptake of a range of model drugs, and release-sensitive phosphorescence. Despite these favourable properties, LTbH particles produced by the reported method suffered from poor size-uniformity (670 ± 564 nm), and are thus not suitable for therapeutic applications. To ameliorate this issue, we first derive an optimised hydrothermal synthesis method to generate LTbH particles with a high degree of homogeneity and reproducibility, within a size range appropriate for in vivo applications (152 ± 59 nm, n = 6). Subsequently, we apply this optimised method to synthesise a selected range of LRH materials (R = Pr, Nd, Gd, Dy, Er, Yb), four of which produced particles with an average size under 200 nm (Pr, Nd, Gd, and Dy) without the need for further optimisation. Finally, we incorporate Gd and Tb into LRHs in varying molar ratios (1 : 3, 1 : 1, and 3 : 1) and assess the combined magnetic relaxivity and phosphorescence properties of the resultant LRH materials. The lead formulation, LGd
1.41 Tb0.59 H, was demonstrated to significantly shorten the T2 relaxation time of water ( r2 = 52.06 mM-1 s-1 ), in addition to exhibiting a strong phosphorescence signal (over twice that of the other LRH formulations, including previously reported LTbH), therefore holding great promise as a potential multi-modal medical imaging probe.- Published
- 2024
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7. Inorganic Chemistry of the Tripodal Picolinate Ligand Tpaa with Gallium(III) and Radiolabeling with Gallium-68.
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Price TW, Wagner L, Rosecker V, Havlíčková J, Prior TJ, Kubíček V, Hermann P, and Stasiuk GJ
- Abstract
We report here the improved synthesis of the tripodal picolinate chelator Tpaa , with an overall yield of 41% over five steps, in comparison to the previously reported 6% yield. Tpaa was investigated for its coordination chemistry with Ga(III) and radiolabeling properties with gallium-68 (
68 Ga). The obtained crystal structure for [Ga( Tpaa )] shows that the three picolinate arms coordinate to the Ga(III) ion, fully occupying the octahedral coordination geometry. This is supported by1 H NMR which shows that the three arms are symmetrical when coordinated to Ga(III). Assessment of the thermodynamic stability through potentiometry gives log KGa- Tpaa = 21.32, with a single species being produced across the range of pH 3.5-7.5. Tpaa achieved >99% radiochemical conversion with68 Ga under mild conditions ([ Tpaa ] = 6.6 μM, pH 7.4, 37 °C) with a molar activity of 3.1 GBq μmol-1 . The resulting complex, [68 Ga][Ga( Tpaa )], showed improved stability over the previously reported [68 Ga][Ga( Dpaa )(H2 O)] in a serum challenge, with 32% of [68 Ga][Ga( Tpaa )] remaining intact after 30 min of incubation with fetal bovine serum.- Published
- 2023
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8. Earth Abundant Oxidation Catalysts for Removal of Contaminants of Emerging Concern from Wastewater: Homogeneous Catalytic Screening of Monomeric Complexes.
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Garcia L, Koper MR, Mondal S, Priddle JT, Truong WA, Allbritton EMA, McAdoo AG, Cannon-Smith DJ, Funwie NL, Hoang T, Kim I, Hubin DJ, Krause JA, Oliver AG, Prior TJ, and Hubin TJ
- Abstract
Twenty novel Mn, Fe, and Cu complexes of ethylene cross-bridged tetraazamacrocycles with potentially copolymerizable allyl and benzyl pendant arms were synthesized and characterized. Multiple X-ray crystal structures demonstrate the cis-folded pseudo-octahedral geometry forced by the rigidifying ethylene cross-bridge and show that two cis coordination cites are available for interaction with substrate and oxidant. The Cu complexes were used to determine kinetic stability under harsh acidic and high-temperature conditions, which revealed that the cyclam-based ligands provide superior stabilization with half-lives of many minutes or even hours in 5 M HCl at 50-90 °C. Cyclic voltammetry studies of the Fe and Mn complexes reveal reversible redox processes indicating stabilization of Fe
2+ /Fe3+ and Mn2+ /Mn3+ /Mn4+ oxidation states, indicating the likelihood of catalytic oxidation for these complexes. Finally, dye-bleaching experiments with methylene blue, methyl orange, and rhodamine B demonstrate efficient catalytic decolorization and allow selection of the most successful monomeric catalysts for copolymerization to produce future heterogeneous water purification materials.- Published
- 2023
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9. A Bridge too Far? Comparison of Transition Metal Complexes of Dibenzyltetraazamacrocycles with and without Ethylene Cross-Bridges: X-ray Crystal Structures, Kinetic Stability, and Electronic Properties.
- Author
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Walker AN, Ayala MA, Mondal S, Bergagnini MC, Bui PJD, Chidester SN, Doeden CI, Esjornson L, Sweany BR, Garcia L, Krause JA, Oliver AG, Prior TJ, and Hubin TJ
- Abstract
Tetraazamacrocycles, cyclic molecules with four nitrogen atoms, have long been known to produce highly stable transition metal complexes. Cross-bridging such molecules with two-carbon chains has been shown to enhance the stability of these complexes even further. This provides enough stability to use the resulting compounds in applications as diverse and demanding as aqueous, green oxidation catalysis all the way to drug molecules injected into humans. Although the stability of these compounds is believed to result from the increased rigidity and topological complexity imparted by the cross-bridge, there is insufficient experimental data to exclude other causes. In this study, standard organic and inorganic synthetic methods were used to produce unbridged dibenzyl tetraazamacrocycle complexes of Co, Ni, Cu, and Zn that are analogues of known cross-bridged tetraazamacrocycles and their transition metal complexes to allow direct comparison of molecules that are identical except for the cross-bridge. The syntheses of the known tetraazamacrocycles and the new transition metal complexes were successful with high yields and purity. Initial chemical characterization of the complexes was conducted by UV-Visible spectroscopy, while cyclic voltammetry showed more marked differences in electronic properties from bridged versions. Direct comparison studies of the unbridged and bridged compounds' kinetic stabilities, as demonstrated by decomposition using high acid concentration and elevated temperature, showed that the cyclen-based complex stability did not benefit from cross-bridging. This is likely due to poor complementarity with the Cu
2+ ion while cyclam-based complexes benefited greatly. We conclude that ligand-metal complementarity must be maintained in order for the topological and rigidity constraints imparted by the cross-bridge to contribute significantly to complex robustness.- Published
- 2023
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10. Synthesis and Characterization of Late Transition Metal Complexes of Mono-Acetate Pendant Armed Ethylene Cross-Bridged Tetraazamacrocycles with Promise as Oxidation Catalysts for Dye Bleaching.
- Author
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Hoang T, Mondal S, Allen MB, Garcia L, Krause JA, Oliver AG, Prior TJ, and Hubin TJ
- Subjects
- Crystallography, X-Ray, Ethylenes chemistry, Ligands, Oxidation-Reduction, Coordination Complexes chemistry, Cyclams, Transition Elements
- Abstract
Ethylene cross-bridged tetraazamacrocycles are known to produce kinetically stable transition metal complexes that can act as robust oxidation catalysts under harsh aqueous conditions. We have synthesized ligand analogs with single acetate pendant arms that act as pentadentate ligands to Mn, Fe, Co, Ni, Cu, and Zn. These complexes have been synthesized and characterized, including the structural characterization of four Co and Cu complexes. Cyclic voltammetry demonstrates that multiple oxidation states are stabilized by these rigid, bicyclic ligands. Yet, redox potentials of the metal complexes are modified compared to the "parent" ligands due to the pendant acetate arm. Similarly, gains in kinetic stability under harsh acidic conditions, compared to parent complexes without the pendant acetate arm, were demonstrated by a half-life seven times longer for the cyclam copper complex. Due to the reversible, high oxidation states available for the Mn and Fe complexes, the Mn and Fe complexes were examined as catalysts for the bleaching of three commonly used pollutant model dyes (methylene blue, methyl orange, and Rhodamine B) in water with hydrogen peroxide as oxidant. The efficient bleaching of these dyes was observed.
- Published
- 2022
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11. Bn 2 DT3A , a Chelator for 68 Ga Positron Emission Tomography: Hydroxide Coordination Increases Biological Stability of [ 68 Ga][Ga(Bn 2 DT3A)(OH)] .
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Price TW, Renard I, Prior TJ, Kubíček V, Benoit DM, Archibald SJ, Seymour AM, Hermann P, and Stasiuk GJ
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- Animals, Rats, Tissue Distribution, Positron-Emission Tomography methods, Hydroxides, Radiopharmaceuticals chemistry, Gallium Radioisotopes chemistry, Chelating Agents chemistry
- Abstract
The chelator Bn
2 DT3A was used to produce a novel68 Ga complex for positron emission tomography (PET). Unusually, this system is stabilized by a coordinated hydroxide in aqueous solutions above pH 5, which confers sufficient stability for it to be used for PET. Bn2 DT3A complexes Ga3+ in a hexadentate manner, forming a mer-mer complex with log K ([Ga( Bn2 DT3A )]) = 18.25. Above pH 5, the hydroxide ion coordinates the Ga3+ ion following dissociation of a coordinated amine. Bn2 DT3A radiolabeling displayed a pH-dependent speciation, with [68 Ga][Ga( Bn2 DT3A )(OH)]- being formed above pH 5 and efficiently radiolabeled at pH 7.4. Surprisingly, [68 Ga][Ga( Bn2 DT3A )(OH)]- was found to show an increased stability in vitro (for over 2 h in fetal bovine serum) compared to [68 Ga][Ga( Bn2 DT3A )]. The biodistribution of [68 Ga][Ga( Bn2 DT3A )(OH)]- in healthy rats showed rapid clearance and excretion via the kidneys, with no uptake seen in the lungs or bones.- Published
- 2022
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12. Heterometallic cobalt(ii) calix[6 and 8]arenes: synthesis, structure and electrochemical activity.
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Ignaszak A, Patterson N, O'Brien C, True A, Elsegood MRJ, Prior TJ, and Redshaw C
- Abstract
Heterometallic cobalt p-tert -butylcalix[6 and 8]arenes have been generated from the in situ reaction of lithium reagents ( n -BuLi or t -BuOLi) or NaH with the parent calix[ n ]arene and subsequent reaction with CoBr
2 . The reverse route, involving the addition of in situ generated Li[Co(O t -Bu)3 ] to p-tert -butylcalix[6 and 8]arene, has also been investigated. X-ray crystallography reveals the formation of complicated products incorporating differing numbers of cobalt and lithium or sodium centers, often with positional disorder, as well as, in some cases, the retention of halide. The electrochemical analysis revealed several oxidation events related to the subsequent oxidation of Co(ii) centers and the reduction of the metal cation at negative potentials. Moreover, the electrochemical activity of the phenol moieties of the parent calix[ n ]arenes resulted in dimerized products or quinone derivatives, leading to insoluble oligomeric products that deposit and passivate the electrode. Preliminary screening for electrochemical proton reduction revealed good activity for a number of these systems. Results suggest that [Co6 Na(NCMe)6 (μ-O)( p-tert -butylcalix[6]areneH)2 Br]·7MeCN (6·7MeCN) is a promising molecular catalyst for electrochemical proton reduction, with a mass transport coefficient, catalytic charge transfer resistance and current magnitude at the catalytic turnover region that are comparable to those of the reference electrocatalyst (Co(ii)Cl2 )., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2022
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13. pH-dependent concatenation of an inorganic complex results in solid state helix formation.
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Hoffer E, Niebuhr BP, Pota K, Schwartz TM, Burnett ME, Prior TJ, Puschmann H, and Green KN
- Abstract
Growth of the library of tetraaza macrocyclic pyridinophane ligands is a result of the potential to treat neurodegenerative diseases by binding unregulated redox active metal-ions, scavenging radicals, and reducing oxidative stress. As part of this work, the copper complex of
OH PyN3 Cu (3,6,9,15-tetraazabicyclo[9.3.1]penta-deca-1(15),11,13-trien-13-ol) was previously identified as a discrete molecule in the solid state when isolated at lower pH values. However, here we report thatOH PyN3 Cu forms a helical structure upon crystallization around pH 6.5. Several properties of the ligand and complex were evaluated to understand the driving forces that led to the concatenation and formation of this solid-state helix. DFT studies along with a comparison of keto/enol tautomerization stability and bond lengths were used to determine the keto-character of the C=O within each subunit. This pH dependent keto-enol tautomerization is responsible for the solid state intermolecular C=O···Cu bonds observed in this metallohelix ( Cu1H ) when produced around pH 6.5. Perchlorate templating that occurs through hydrogen bonding between perchlorate counter ions and each Cu1H unit is the primary driving factor for the twist that leads to the helix structure. Cu1H does not exhibit the typical factors that stabilize the formation of helices, such as intra-strand hydrogen bonding or π-stacking. The helix structure further highlights the diversity of inorganic metallohelices and demonstrates the importance of tautomerization and pH that occurs with the pyridinophane ligand used in this study. To our knowledge and although these phenomenon have been observed individually, this is the first example of a pH dependent keto-enol tautomerization in an azamacrocycle being the driving force for the formation of a metallohelix solid state structure and is a particularly unique observation for pyridinophane complexes., Competing Interests: Conflicts of interest There are no conflicts to declare.- Published
- 2022
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14. Pd-Immobilized Schiff Base Double-Layer Macrocycle: Synthesis, Structures, Peroxidase Mimic Activity, and Antibacterial Performance.
- Author
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Wang K, Chen K, Prior TJ, Feng X, and Redshaw C
- Subjects
- Anti-Bacterial Agents chemistry, Anti-Bacterial Agents metabolism, Biocompatible Materials chemistry, Biocompatible Materials metabolism, Cell Line, Density Functional Theory, Humans, Materials Testing, Microbial Sensitivity Tests, Molecular Structure, Palladium chemistry, Palladium metabolism, Particle Size, Peroxidase chemistry, Schiff Bases chemistry, Schiff Bases metabolism, Schiff Bases pharmacology, Anti-Bacterial Agents pharmacology, Biocompatible Materials pharmacology, Escherichia coli drug effects, Palladium pharmacology, Peroxidase metabolism, Staphylococcus aureus drug effects
- Abstract
Di-, tri-, and tetra-aldehydes have been employed to access new [2 + 2] [2 + 3] and [2 + 4] double-layer Schiff base macrocycles. The [2 + 3] compound has been used for the immobilization of Pd and the resulting composite has been employed as a peroxidase-like mimetic using 3,3',5,5'-tetramethylbenzidine (TMB) as the substrate; the optimum conditions together with the catalytic kinetics of the enzyme-like activity is discussed. Based on the peroxidase-like catalytic activity, the Pd@Schiff base composite was found to exhibit excellent bactericidal activity against both Escherichia coli (Gram-negative bacterium) and Staphylococcus aureus (Gram-positive bacterium) in the presence of relatively low concentrations of H
2 O2 . Furthermore, cytotoxicity measurements illustrate the biosafety of the Pd composite. The above-mentioned findings have the potential to guide the innovation of new Pd-based composites as enzyme mimetics and antibacterial materials.- Published
- 2022
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15. Lead calix[ n ]arenes ( n = 4, 6, 8): structures and ring opening homo-/co-polymerization capability for cyclic esters.
- Author
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Xing T, Prior TJ, and Redshaw C
- Abstract
Reaction of [LiPb(O i Pr)
3 ]2 (generated in situ ) with either p-tert -butylcalix[4]areneH4 (L4 H4 ) or p-tert -butylcalix[6]areneH6 (L6 H6 ) resulted in the heterometallic lithium/lead complexes [Pb4 Li2 (L4 )4 H6 (MeCN)3 ]·4.5MeCN (1·4.5MeCN) and [Pb8 Li10 Cl2 (L6 H2 )3 (L6 )(OH)2 (O)2 (H2 O)2 (MeCN)4 ]·14MeCN (2·14MeCN), respectively. Use of the dimethyleneoxa-bridged p-tert -butyltetrahomodioxacalix[6]areneH6 (L6' H6 ) with five equivalents of [Pb(O i Pr)2 ] afforded [Pb13 (L6' )3 O4 ( i PrOH)]·11MeCN (3·11MeCN). Use of the larger p-tert -butylcalix[8]areneH8 (L8 H8 ) with [Pb(O t Bu)2 ] or {Pb[N(TMS)2 ]} (TMS = SiMe3 ) afforded the products [Pb12 (L8 )2 O4 ]·8.7C7 H8 (4·8.7C7 H8 ) or [Pb6 (SiMe3 )2 (L8 )O2 Cl2 ] (5), respectively. Reaction of {Pb[N(TMS)2 ]} (generated in situ from (Me3 Si)2 NH, n BuLi and PbCl2 ) with L6 H6 afforded, after work-up (MeCN), the mixed-metal complex [Pb10 Li2 (L6 )2 (OH)Cl(O)4 ]·9.5MeCN (6·9.5MeCN). Reaction of distilled {Pb[N(TMS)2 ]} (six equivalents) with L8 H8 resulted in the complex [Pb12 (L8 )2 O4 ]·12MeCN (7·12MeCN). Complexes 1-7, Pb(O i Pr)2 and [Pb(N(TMS)2 )2 ] have been screened for their potential to act as pre-catalysts in the ring opening polymerization (ROP) of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) and the copolymerization thereof. Generally, the lithiated complexes 1 and 2 exhibited better activities than the other pre-catalysts screened herein. For ε-CL and δ-VL, moderate activity at 130 °C over 24 h was observed for 1-7. In the case of the co-polymerization of ε-CL with δ-VL, 1-7, Pb(O i Pr)2 and [Pb(N(TMS)2 )2 ] afforded reasonable conversions and high molecular weight polymers. The systems 1-7, Pb(O i Pr)2 and [Pb(N(TMS)2 )2 ] also proved to be active in the ROP of the rac -lactide ( r -LA); the activity trend was found to be 1 > 2 ≈ Pb(O i Pr)2 ≈ [Pb(N(TMS)2 )2 ] > 4 > 5 ≈ 6 ≈ 7 > 3.- Published
- 2021
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16. Mechanistic Insights into Iron-Catalyzed C-H Bond Activation and C-C Coupling.
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Brewer SM, Schwartz TM, Mekhail MA, Turan LS, Prior TJ, Hubin TJ, Janesko BG, and Green KN
- Abstract
Iron-catalyzed C-C coupling reactions of pyrrole provide a unique alternative to the traditional Pd-catalyzed counterpart. However, many details regarding the actual mechanism remain unknown. A series of macrocyclic iron(III) complexes were used to evaluate specifics related to the role of O
2 , radicals, and μ -oxodiiron-complex participation in the catalytic cycle. It was determined that the mononuclear tetra-azamacrocyclic complex is a true catalyst and not a stoichiometric reagent, while more than one equivalent of a sacrificial oxidant is needed. Furthermore, the reaction does not proceed through an organic radical pathway. μ -Oxodiiron complexes are not involved in the main catalytic pathway, and the dimers are, in fact, off-cycle species that decrease catalytic efficiency., Competing Interests: The authors declare no competing financial interest.- Published
- 2021
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17. Scandium calix[ n ]arenes ( n = 4, 6, 8): structural, cytotoxicity and ring opening polymerization studies.
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Alshamrani AFA, Santoro O, Prior TJ, Alamri MA, Stasiuk GJ, Elsegood MRJ, and Redshaw C
- Subjects
- Antineoplastic Agents chemistry, Antineoplastic Agents pharmacology, Antineoplastic Agents toxicity, Calixarenes pharmacology, Calixarenes toxicity, Cell Survival drug effects, HCT116 Cells, HT29 Cells, Humans, Models, Molecular, Polymerization, Scandium pharmacology, Scandium toxicity, Calixarenes chemistry, Scandium chemistry
- Abstract
Interaction of [Sc(OR)3] (R = iPr or triflate) with p-tert-butylcalix[n]arenes, where n = 4, 6, or 8, affords a number of intriguing structural motifs, which are relatively non-toxic (cytotoxicity evaluated against cell lines HCT116 and HT-29) and a number were capable of the ring opening polymerization (ROP) of cyclohexene oxide.
- Published
- 2021
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18. Coordination chemistry of [2 + 2] Schiff-base macrocycles derived from the dianilines [(2-NH 2 C 6 H 4 ) 2 X] (X = CH 2 CH 2 , O): structural studies and ROP capability towards cyclic esters.
- Author
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Wang K, Prior TJ, Hughes DL, Arbaoui A, and Redshaw C
- Abstract
Reaction of the [2 + 2] Schiff-base macrocycles {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][CH2CH2(2-C6H4N)2]}2 (R = Me, L1H2; tBu, L2H2) with FeBr2 afforded the complexes [FeBr(L1H2)]2[(FeBr3)2O]·2MeCN (1·2MeCN), [FeBr(L2H2)][X] (X = 0.5(FeBr3)2O, 2·0.5MeCN, X = Br, 3·5.5MeCN), respectively. Reaction of L2H2 with [KFe(OtBu)3(THF)] (formed in situ from FeBr2 and KOtBu), following work-up, led to the isolation of the complex [Fe(L2)(L2H)]·3MeCN (4·3MeCN), whilst with [CuBr2] afforded [CuBr(L2H2)][CuBr2]·2MeCN (5·2MeCN). Attempts to form mixed Co/Ti species by reaction of [CoBrL2][CoBr3(NCMe)] with TiCl4 resulted in [L2H4][CoBr4]·2MeCN (6·2MeCN). Use of the related oxy-bridged Schiff-base macrocycles {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][O(2-C6H4N)2]}2 (R = Me, L3H2; tBu, L4H2) with CoBr2 led to the isolation of the complexes [(CoBr)2(L3)]·2C3H6O (7·2C3H6O), [Co(NCMe)2(L4H2)][CoBr4]·5MeCN (8·5MeCN), [Co(NCMe)6][CoBr3(MeCN)]2·2MeCN (9·2MeCN). For comparative structural/polymerisation studies, the complexes {CoBr(NCMe)L5}2·2MeCN (10·2MeCN) and [Co(NCMe)2L5]2[CoBr3(NCMe)]2 (11), [FeBr(NCMe)L5]2·2MeCN (12·2MeCN) where L5H = 2,6-(CHO)2-4-tBu-C6H2OH, as well as the chelate-free salt [Fe(NCMe)6][FeBr3OFeBr3] (13) have been isolated and structurally characterized. The ability of these complexes to act as catalysts for the ring opening polymerisation (ROP) of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL) was investigated, as well as co-polymerisation of ε-CL with rac-lactide (r-LA) and vice versa.
- Published
- 2021
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19. A Single-Pot Template Reaction Towards a Manganese-Based T 1 Contrast Agent.
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Anbu S, Hoffmann SHL, Carniato F, Kenning L, Price TW, Prior TJ, Botta M, Martins AF, and Stasiuk GJ
- Abstract
Manganese-based contrast agents (MnCAs) have emerged as suitable alternatives to gadolinium-based contrast agents (GdCAs). However, due to their kinetic lability and laborious synthetic procedures, only a few MnCAs have found clinical MRI application. In this work, we have employed a highly innovative single-pot template synthetic strategy to develop a MnCA, MnL
Me , and studied the most important physicochemical properties in vitro. MnLMe displays optimized r1 relaxivities at both medium (20 and 64 MHz) and high magnetic fields (300 and 400 MHz) and an enhanced r1 b =21.1 mM-1 s-1 (20 MHz, 298 K, pH 7.4) upon binding to BSA (Ka =4.2×103 M-1 ). In vivo studies show that MnLMe is cleared intact into the bladder through renal excretion and has a prolonged blood half-life compared to the commercial GdCA Magnevist. MnLMe shows great promise as a novel MRI contrast agent., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)- Published
- 2021
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20. Titanium complexes bearing oxa- and azacalix[4, 6]arenes: structural studies and use in the ring opening homo-/co-polymerization of cyclic esters.
- Author
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Xing T, Prior TJ, Chen K, and Redshaw C
- Abstract
Reaction of excess [Ti(OiPr)
4 ] with p-tert-butyltetrahomodioxacalix[6]areneH6 (L1 H6 ) afforded, after work-up (MeCN), the complex [Ti2 (OiPr)2 (MeCN)L1 ]·3.5MeCN (1·3.5MeCN), whilst the oxo complex [Ti4 (μ3 -O)2 (H2 O)(L1 )2 ]·MeCN (2·MeCN) was isolated via a fortuitous synthesis involving the use of two equivalents of [Ti(OiPr)4 ]. Reactions of p-methyl-dimethyldiazacalix[6]areneH6 (L2 H6 ) with [TiF4 ] (four equivalents), [TiCl4 (THF)2 ] (two equivalents) or [TiBr4 ] (>four equivalents) resulted in the titanium-based azacalix[n]arene complexes [Ti4 F14 L2 H2 (H)2 ]·2.5MeCN (3·2.5MeCN), [Ti2 X4 (H2 O)2 OL2 H2 (H)2 ] (X = Cl (4·5MeCN), Br (5·4.5MeCN) and [Ti4 Br12 L2 (H)2 (MeCN)6 ]·7MeCN (6·7MeCN), respectively. Reaction of four equivalents of [TiF4 ] with L3 H4 (L3 H4 = p-methyl-dimethyldiazacalix[4]areneH4 ) afforded the product [Ti2 F2 (μ-F)3 L3 (H)2 (SiF5 )]·2MeCN (7·2MeCN). These complexes have been screened for their potential to act as pre-catalysts in the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and rac-lactide (r-LA). Generally, the titanium complexes bearing oxacalixarene exhibited better activities than the azacalixarene-based pre-catalysts. For ε-CL, δ-VL and r-LA, moderate activity at 130 °C over 24 h was observed for 1-6. In the case of the co-polymerization of ε-CL with r-LA, 1-6 afforded reasonable conversions and high molecular weight polymers; 7 exhibited lower catalytic performance due to low solubility. None of the complexes proved to be active in the polymerization of ω-pentadecalactone (ω-PDL) under the conditions employed herein.- Published
- 2021
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21. Group sequential monitoring based on the maximum of weighted log-rank statistics with the Fleming-Harrington class of weights in oncology clinical trials.
- Author
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Prior TJ
- Subjects
- Humans, Proportional Hazards Models, Survival Analysis, Treatment Outcome, Medical Oncology, Neoplasms drug therapy
- Abstract
Clinical trials in oncology often involve the statistical analysis of time-to-event data such as progression-free survival or overall survival to determine the benefit of a treatment or therapy. The log-rank test is commonly used to compare time-to-event data from two groups. The log-rank test is especially powerful when the two groups have proportional hazards. However, survival curves encountered in oncology studies that differ from one another do not always differ by having proportional hazards; in such instances, the log-rank test loses power, and the survival curves are said to have "non-proportional hazards". This non-proportional hazards situation occurs for immunotherapies in oncology; immunotherapies often have a delayed treatment effect when compared to chemotherapy or radiation therapy. To correctly identify and deliver efficacious treatments to patients, it is important in oncology studies to have available a statistical test that can detect the difference in survival curves even in a non-proportional hazards situation such as one caused by delayed treatment effect. An attempt to address this need was the "max-combo" test, which was originally described only for a single analysis timepoint; this article generalizes that test to preserve type I error when there are one or more interim analyses, enabling efficacious treatments to be identified and made available to patients more rapidly.
- Published
- 2020
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22. Mechanistic In Situ and Ex Situ Studies of Phase Transformations in Molecular Co-Crystals.
- Author
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Clout AE, Buanz ABM, Pang Y, Tsui WM, Yan D, Parkinson G, Prior TJ, Bučar DK, Gaisford S, and Williams GR
- Abstract
Co-crystallisation is widely explored as a route to improve the physical properties of pharmaceutical active ingredients, but little is known about the fundamental mechanisms of the process. Herein, we apply a hyphenated differential scanning calorimetry-X-ray diffraction technique to mimic the commercial hot melt extrusion process, and explore the heat-induced synthesis of a series of new co-crystals containing isonicotinamide. These comprise a 1:1 co-crystal with 4-hydroxybenzoic acid, 2:1 and 1:2 systems with 4-hydroxyphenylacetic acid and a 1:1 crystal with 3,4-dihydroxyphenylactic acid. The formation of co-crystals during heating is complex mechanistically. In addition to co-crystallisation, conversions between polymorphs of the co-former starting materials and co-crystal products are also observed. A subsequent study exploring the use of inkjet printing and milling to generate co-crystals revealed that the synthetic approach has a major effect on the co-crystal species and polymorphs produced., (© 2020 The Authors. Published by Wiley-VCH GmbH.)
- Published
- 2020
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23. Homo- and Hetero-dinuclear Arene-Linked Osmium(II) and Ruthenium(II) Organometallics: Probing the Impact of Metal Variation on Reactivity and Biological Activity.
- Author
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Wilson CS, Prior TJ, Sandland J, Savoie H, Boyle RW, and Murray BS
- Subjects
- Cell Line, Tumor, HEK293 Cells, HT29 Cells, Humans, Ligands, Magnetic Resonance Spectroscopy, X-Ray Diffraction, Antineoplastic Agents pharmacology, Organometallic Compounds pharmacology, Osmium, Ruthenium
- Abstract
Dinuclear metallodrugs offer much potential in the development of novel anticancer chemotherapeutics as a result of the distinct interactions possible with bio-macromolecular targets and the unique biological activity that can result. Herein, we describe the development of isostructural homo-dinuclear Os
II -OsII and hetero-dinuclear OsII -RuII organometallic complexes formed from linking the arene ligands of [M(η6 -arene)(C2 O4 )(PTA)] units (M=Os/Ru; PTA=1,3,5-triaza-7-phosphaadamantane). Using these complexes together with the known RuII -RuII analogue, a chromatin-modifying agent, we probed the impact of varying the metal ions on the structure, reactivity and biological activity of these complexes. The complexes were structurally characterised by X-ray diffraction experiments, their stability and reactivity were examined by using1 H and31 P NMR spectroscopy, and their biological activity was assessed, alongside that of mononuclear analogues, through MTT assays and cell-cycle analysis (HT-29 cell line). The results revealed high antiproliferative activity in each case, with cell-cycle profiles of the dinuclear complexes found to be similar to that for untreated cells, and similar but distinct profiles for the mononuclear complexes. These results indicate these complexes impact on cell viability predominantly through a non-DNA-damaging mechanism of action. The new OsII -OsII and OsII -RuII complexes reported here are further examples of a family of compounds operating via mechanisms of action atypical of the majority of metallodrugs, and which have potential as tools in chromatin research., (© 2020 Wiley-VCH GmbH.)- Published
- 2020
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24. An ethylene cross-bridged pentaazamacrocycle and its Cu 2+ complex: constrained ligand topology and excellent kinetic stability.
- Author
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Shircliff AD, Burke BP, Davilla DJ, Burgess GE, Okorocha FA, Shrestha A, Allbritton EMA, Nguyen PT, Lamar RL, Jones DG, Gorbet MJ, Allen MB, Eze JI, Fernandez AT, Ramirez D, Archibald SJ, Prior TJ, Krause JA, Oliver AG, and Hubin TJ
- Abstract
Rigid and topologically constrained ethylene cross-bridged tetraazamacrocycles have been increasingly utilised for thirty years as they form remarkably stable transition metal complexes for catalysis, biomedical imaging, and inorganic drug molecule applications. Extending these benefits to pentaazamacrocycles has been achieved and a first transition metal complex prepared and structurally characterized.
- Published
- 2020
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25. Water-Soluble Rhenium Phosphine Complexes Incorporating the Ph 2 C(X) Motif (X = O - , NH - ): Structural and Cytotoxicity Studies.
- Author
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Alshamrani AF, Prior TJ, Burke BP, Roberts DP, Archibald SJ, Higham LJ, Stasiuk G, and Redshaw C
- Subjects
- Cell Line, Tumor, Coordination Complexes chemical synthesis, HEK293 Cells, Humans, Molecular Structure, Organotechnetium Compounds chemical synthesis, Organotechnetium Compounds chemistry, Phosphines chemical synthesis, Phosphines chemistry, Phosphines toxicity, Rhenium chemistry, Solubility, Water chemistry, Coordination Complexes chemistry, Coordination Complexes toxicity
- Abstract
Reaction of [ReOCl
3 (PPh3 )2 ] or [ReO2 I(PPh3 )2 ] with 2,2'-diphenylglycine (dpgH2 ) in refluxing ethanol afforded the air-stable complex [ReO(dpgH)(dpg)(PPh3 )] ( 1 ). Treatment of [ReO(OEt)I2 (PPh3 )2 ] with 1,2,3-triaza-7-phosphaadamantane (PTA) afforded the complex [ReO(OEt)I2 (PTA)2 ] ( 2 ). Reaction of [ReOI2 (PTA)3 ] with dpgH2 led to the isolation of the complex [Re(NCPh2 )I2 (PTA)3 ]·0.5EtOH ( 3 ·0.5EtOH). A similar reaction but using [ReOX2 (PTA)3 ] (X = Cl, Br) resulted in the analogous halide complexes [Re(NCPh2 )Cl2 (PTA)3 ]·2EtOH ( 4 ·2EtOH) and [Re(NCPh2 )(PTA)3 Br2 ]·1.6EtOH ( 5 ·1.6EtOH). Using benzilic acid (2,2'-diphenylglycolic acid, benzH) with 2 afforded the complex [ReO(benz)2 (PTA)][PTAH]·EtOH ( 6 ·EtOH). The potential for the formation of complexes using radioisotopes with relatively short half-lives suitable for nuclear medicine applications by developing conditions for [Re(NCPh2 )(dpg)I(PTA)3 ] ( 7 )[ReO4 ]- in a 4 h time scale was investigated. A procedure for the technetium analog of complex [Re(NCPh2 )I2 (PTA)3 ] ( 3 ) from99m Tc[TcO4 ]- was then investigated. The molecular structures of 1 - 7 are reported; complexes 3 - 7 have been studied using in vitro cell assays (HeLa, HCT116, HT-29, and HEK 293) and were found to have IC50 values in the range of 29-1858 μM.- Published
- 2020
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26. The Application of Reversible Intramolecular Sulfonamide Ligation to Modulate Reactivity in Organometallic Ruthenium(II) Diamine Complexes.
- Author
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Kemp SA, Prior TJ, Savoie H, Boyle RW, and Murray BS
- Subjects
- Antineoplastic Agents pharmacology, Cell Survival drug effects, Chelating Agents chemistry, Coordination Complexes chemical synthesis, Coordination Complexes toxicity, Crystallography, X-Ray, Diamines pharmacology, Ethylenediamines chemistry, Ethylenediamines pharmacology, Guanosine Monophosphate metabolism, HT29 Cells, Humans, Hydrogen-Ion Concentration, Kinetics, Ligands, Models, Molecular, Organometallic Compounds chemistry, Ruthenium pharmacology, Sulfonamides pharmacology, Antineoplastic Agents chemistry, Coordination Complexes chemistry, Coordination Complexes pharmacology, Diamines chemistry, Organometallic Compounds pharmacology, Ruthenium chemistry, Sulfonamides chemistry
- Abstract
Metallation of biomacromolecular species forms the basis for the anticancer activity of many metallodrugs. A major limitation of these compounds is that their reactivity is indiscriminate and can, in principle, occur in healthy tissue as well as cancerous tissue, potentially leading to side effects in vivo. Here we present pH-dependent intramolecular coordination of an arene-tethered sulfonamide functionality in organometallic ruthenium(II) ethylenediamine complexes as a route to controlling the coordination environment about the central metal atom. Through variation of the sulfonamide R group and the length of the tether linking it to the arene ligand the acidity of the sulfonamide NH group, and hence the pH-region over which regulation of metal coordination occurs, can be modulated. Intramolecular sulfonamide ligation controlled the reactivity of complex 4 within the physiologically relevant pH-region, rendering it more reactive towards 5'-GMP in mildly acidic pH-conditions typical of tumour tissue compared to the mildly alkaline pH-conditions typical of healthy tissue. However, the activation of 4 by ring-opening of the chelate was found to be a slow process relative to the timescale of typical cell culture assays and members of this series of complexes were found not to be cytotoxic towards the HT-29 cell line. These complexes provide the basis for the development of analogues of increased potency where intramolecular sulfonamide ligation regulates reactivity and therefore cytotoxicity in a pH-dependent, and potentially, tissue-dependent manner.
- Published
- 2020
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27. Turning on ROP activity in a bimetallic Co/Zn complex supported by a [2+2] Schiff-base macrocycle.
- Author
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Wang K, Prior TJ, and Redshaw C
- Abstract
Homo-dinuclear Co and Zn complexes derived from the macrocycle LH2, {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][CH2CH2(2-C6H4N)2]}2 (R = Me, tBu), revealed near inactivity for the ring opening polymerization (ROP) of the cyclic esters δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL). By contrast, the hetero-bimetallic complexes [LCo(NCMe)(μ-Br)ZnBr]·nMeCN (n = 3 or 3.25) were found to be efficient catalysts for the ROP of ε-CL and δ-VL.
- Published
- 2019
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28. Crystal structures and Hirshfeld surface analysis of transition-metal complexes of 1,3-azolecarboxylic acids.
- Author
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Meundaeng N, Prior TJ, and Rujiwatra A
- Abstract
The crystal structures of five new transition-metal complexes synthesized using thiazole-2-carboxylic acid (2-Htza), imidazole-2-carboxylic acid (2-H
2 ima) or 1,3-oxazole-4-carboxylic acid (4-Hoxa), namely diaquabis(thiazole-2-carboxylato-κ2 N,O)cobalt(II), [Co(C4 H2 NO2 S)2 (H2 O)2 ], 1, diaquabis(thiazole-2-carboxylato-κ2 N,O)nickel(II), [Ni(C4 H2 NO2 S)2 (H2 O)2 ], 2, diaquabis(thiazole-2-carboxylato-κ2 N,O)cadmium(II), [Cd(C4 H2 NO2 S)2 (H2 O)2 ], 3, diaquabis(1H-imidazole-2-carboxylato-κ2 N3 ,O)cobalt(II), [Co(C4 H2 N2 O2 )2 (H2 O)2 ], 4, and diaquabis(1,3-oxazole-4-carboxylato-κ2 N,O4 )cobalt(II), [Co(C4 H2 NO3 )2 (H2 O)2 ], 5, are reported. The influence of the nature of the heteroatom and the position of the carboxyl group in relation to the heteroatom on the self-assembly process are discussed based upon Hirshfeld surface analysis and used to explain the observed differences in the single-crystal structures and the supramolecular frameworks and topologies of complexes 1-5.- Published
- 2019
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29. Tetraazamacrocyclic derivatives and their metal complexes as antileishmanial leads.
- Author
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Hubin TJ, Walker AN, Davilla DJ, Freeman TNC, Epley BM, Hasley TR, Amoyaw PNA, Jain S, Archibald SJ, Prior TJ, Krause JA, Oliver AG, Tekwani BL, and Khan MOF
- Abstract
A total of 44 bis-aryl-monocyclic polyamines, monoaryl-monocyclic polyamines and their transition metal complexes were prepared, chemically characterized, and screened in vitro against the Leishmania donovani promastigotes, axenic amastigotes and intracellular amastigotes in THP1 cells. The IC
50 and/or IC90 values showed that 10 compounds were similarly active at about 2-fold less potent than known drug pentamidine against promastigotes. The most potent compound had an IC50 of 2.82 μM (compared to 2.93 μM for pentamidine). Nine compounds were 1.1-13.6-fold more potent than pentamidine against axenic amastigotes, the most potent one being about 2-fold less potent than amphotericin B. Fourteen compounds were about 2-10 fold more potent than pentamidine, the most potent one is about 2-fold less potent than amphotericin B against intracellular amastigotes in THP1 cells. The 2 most promising compounds (Fe L7 Cl2 and Mn L7 Cl2 ), with strong activity against both promastigotes and amastigotes and no observable toxicity against the THP1 cells are the Fe2+ - and Mn2+ - complexes of a dibenzyl cyclen derivative. Only 2 of the 44 compounds showed observable cytotoxicity against THP1 cells. Tetraazamacrocyclic monocyclic polyamines represent a new class of antileishmanial lead structures that warrant follow up studies.- Published
- 2019
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30. Acetate as a model for aspartate-based CXCR4 chemokine receptor binding of cobalt and nickel complexes of cross-bridged tetraazamacrocycles.
- Author
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Cain AN, Carder Freeman TN, Roewe KD, Cockriel DL, Hasley TR, Maples RD, Allbritton EMA, D'Huys T, van Loy T, Burke BP, Prior TJ, Schols D, Archibald SJ, and Hubin TJ
- Abstract
A number of disease states including WHIM syndrome, HIV infection and cancer have been linked to the chemokine receptor CXCR4. High-affinity CXCR4 antagonist transition metal complexes of configurationally restricted bis-tetraazamacrocyclic ligands have been identified in previous studies. Recently synthesised and structurally characterised Co2+/Co3+ and Ni2+ acetate complexes of mono-macrocycle cross-bridged ligands have been used to mimic their known coordination interaction with the aspartate side chains on binding to CXCR4. Here, X-ray crystal structures for three Co2+/Co3+ acetate complexes and five Ni2+ acetate complexes are presented and demonstrate flexibility in the mode of binding to the acetate ligand concomitantly with the requisite cis-V-configured cross-bridged tetraazamacrocyle. Complexes of the smaller Co3+ metal ion exclusively bind acetate by chelating both oxygens of acetate. Larger Co2+ and Ni2+ metal ions in cross-bridged tetraazamacrocycles show a clear tendency to coordinate acetate in a monodentate fashion with a coordinated water molecule completing the octahedral coordination sphere. However, in unbridged tetraazamacrocycle acetate structures reported in the literature, the coordination preference is to chelate both acetate oxygens. We conclude that the short ethylene cross-bridge restricts the equatorial bulk of the macrocycle, prompting the metal ion to fill the equator with the larger monodentate acetate plus water ligand set. In unbridged ligand examples, the flexible macrocycle expands equatorially and generally only allows chelation of the sterically smaller acetate alone. These results provide insight for generation of optimised bis-macrocyclic CXCR4 antagonists utilising cobalt and nickel ions.
- Published
- 2019
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31. Mono-oxo molybdenum(vi) and tungsten(vi) complexes bearing chelating aryloxides: synthesis, structure and ring opening polymerization of cyclic esters.
- Author
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Sun Z, Zhao Y, Prior TJ, Elsegood MRJ, Wang K, Xing T, and Redshaw C
- Abstract
The mono-oxo aryloxide complexes [M(O)(L1)2] (M = Mo (1·hexane), W(2·2MeCN)) have been prepared from [Mo(O)(Cl)4] or [W(O)(Ot-Bu)4] and two equivalents of the di-phenol 2,2'-ethylidenebis(4,6-di-tert-butylphenol) L1H2, respectively. Use of in situ generated [Mo(O)(Ot-Bu)4] with two equivalents of L1H2 also led to the isolation of 1·2MeCN. In the presence of adventitious oxygen, attempts to generate in situ [Mo(O)(Ot-Bu)4] and reaction with one equivalent of L1H2 afforded the bi-metallic complex [Mo(O)(L1)(μ-O)Li(THF)(MeCN)]2·2MeCN (3·2MeCN). Use of the tetra-phenol α,α,α',α'-tetrakis(3,5-di-tert-butyl-2-hydroxyphenyl)-p-xyleneH4 (L2H4) with [Mo(O)(Oi-Pr)4] led to the isolation of {[Mo(O)]L2}2 (4), whilst the analogous tungsten complex {[W(O)]L2}2 (5) was isolated from the reaction of L2H4 with [W(O)(Ot-Bu)4]. Similar reaction of p-tert-butylcalix[4]areneH4 (L3H4) with [Mo(O)(Oi-Pr)4] afforded ([Mo(O)L3(NCMe)]·3MeCN (6). Modifications of known routes were employed to access complexes [W(Cl)2L3]·3.5MeCN (7·3.5MeCN) and [W(O)L3(NCMe)] (8), whilst use of [WO(Ot-Bu)4] with L3H4 unexpectedly afforded [W(Ot-Bu)2L3]·MeCN (9·MeCN). The molecular crystal structures for 1-9 are reported, and the ability of these complexes to act as catalysts for the ring opening polymerization (ROP) of ε-caprolactone (ε-CL), δ-valerolactone (δ-VL) and ω-pentadecalactone (ω-PDL) has been investigated. The molybdenum complexes 1 and 4 were the best performers for ε-Cl and δ-VL, but all complexes exhibited poor control and were also inactive toward the ROP of PDL.
- Published
- 2019
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32. Erratum: Chen, L.X., et al. Synthesis and Structure of the Inclusion Complex {NdQ[5]K@Q[10](H₂O)₄}•4NO₃•20H₂O. Molecules 2017, 22 , 1147.
- Author
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Chen LX, Kan JL, Cong H, Prior TJ, Tao Z, Xiao X, and Redshaw C
- Abstract
The authors wish to make the following correction to their paper [...].
- Published
- 2019
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33. Crystal structure of (1,3-thia-zole-2-carboxyl-ato-κ N )(1,3-thia-zole-2-carb-oxy-lic acid-κ N )silver(I).
- Author
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Meundaeng N, Rujiwatra A, and Prior TJ
- Abstract
The linear two-coordinate silver (I) complex [Ag(C
4 H2 NO2 S)(C4 H3 NO2 S)] or [Ag(2-Htza)(2-tza)] is reported (2-Htza = 1,3-thia-zole-2-carb-oxy-lic acid). The AgI ion is coordinated by two heterocyclic N atoms from two ligands in a linear configuration, forming a discrete coordination complex. There is an O-H⋯O hydrogen bond between 2-tza- and 2tzaH of adjacent complexes. The hydrogen atom is shared between the two oxygen atoms. This inter-action produces a hydrogen-bonded tape parallel to the [110] direction, which is augmented through inter-molecular C-H⋯O hydrogen-bonding inter-actions between the bound thia-zole groups. There is a further rather long Ag⋯O inter-action [2.8401 (13) Å, compared with a mean of 2.54 (11) Å for 23 structures in the CSD] that assembles these tapes into columns, between which there are C-H⋯π inter-actions, leading to the formation of a three-dimensional supra-molecular architecture.- Published
- 2019
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34. A Study of the Interaction Between Cucurbit[8]uril and Alkyl-Substituted 4-Pyrrolidinopyridinium Salts.
- Author
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Xu W, Kan J, Yang B, Prior TJ, Bian B, Xiao X, Tao Z, and Redshaw C
- Abstract
The interaction between cucuribit[8]uril (Q[8]) and a series of 4-pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4-(C
4 H8 N)C5 H5 NRBr, where R=Et (g1), n-butyl (g2), n-pentyl (g3), n-hexyl (g4), n-octyl (g5), n-dodecyl (g6), has been studied in aqueous solution by1 H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. Single crystal X-ray diffraction revealed the structure of the host-guest complexes for g1, g2, g3, and g5. In each case, the Q[8] contains two guest molecules in a centrosymmetric dimer. The orientation of the guest molecule changes as the alkyl chain increases in length. Interestingly, in the solid state, the inclusion complexes identified are different from those observed in solution, and furthermore, in the case of g3, Q[8] exhibits two different interactions with the guest. In solution, the length of the alkyl chain plays a significant role in determining the type of host-guest interaction present., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2019
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35. Vanadyl sulfates: molecular structure, magnetism and electrochemical activity.
- Author
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Ignaszak A, Patterson N, Radtke M, Elsegood MRJ, Frese JWA, Lipman JLZF, Yamato T, Sanz S, Brechin EK, Prior TJ, and Redshaw C
- Abstract
Reaction of differing amounts of vanadyl sulfate with p-tert-butylthiacalix[4]areneH4 and base allows access to the vanadyl-sulfate species [NEt4]4[(VO)4(μ3-OH)4(SO4)4]·½H2O (1), [HNEt3]5[(VO)5(μ3-O)4(SO4)4]·4MeCN (2·4MeCN) and [NEt4]2[(VO)6(O)2(SO4)4(OMe)(OH2)]·MeCN (3·MeCN). Similar use of p-tert-butylsulfonylcalix[4]areneH4, p-tert-butylcalix[8]areneH8 or p-tert-butylhexahomotrioxacalix[3]areneH3 led to the isolation of [HNEt3]2[H2NEt2]2{[VO(OMe)]2p-tert-butylcalix[8-SO2]areneH2} (4), [HNEt3]2[V(O)2p-tert-butylcalix[8]areneH5] (5) and [HNEt3]2[VIV2VV4O11(OMe)8] (6), respectively. Dc magnetic susceptibility measurements were performed on powdered microcrystalline samples of 1-3 in the T = 300-2 K temperature range. Preliminary screening for electrochemical water oxidation revealed some activity for 2 with turnover frequency (TOF) and number (TON) of 2.2 × 10-4 s-1 and 6.44 × 10-6 (mmol O2/mmol cat.), respectively. The compound 3 showed an improved electrochemical activity in the presence of water. This is related to the increased number and the rate of electrons exchanged during oxidation of V4+ species, facilitated by protons generated in the water discharge process.
- Published
- 2018
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36. Recovery of Al, Cr and V from steel slag by bioleaching: Batch and column experiments.
- Author
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Gomes HI, Funari V, Mayes WM, Rogerson M, and Prior TJ
- Subjects
- Industrial Waste, Recycling, Aluminum isolation & purification, Chromium isolation & purification, Steel, Vanadium isolation & purification
- Abstract
Steel slag is a major by-product of the steel industry and a potential resource of technology critical elements. For this study, a basic oxygen furnace (BOF) steel slag was tested for bacterial leaching and recovery of aluminium (Al), chromium (Cr), and vanadium (V). Mixed acidophilic bacteria were adapted to the steel slag up to 5% (w/v). In the batch tests, Al, Cr, and V were bioleached significantly more from steel slag than in control treatments. No statistical difference was observed arising from the duration of the leaching (3 vs 6 d) in the batch tests. Al and Cr concentrations in the leachate were higher for the smaller particle size of the steel slag (<75 μm), but no difference was observed for V. In the column tests, no statistical difference was found for pH, Al, Cr and V between the live culture (one-step bioleaching) and the supernatant (two-step bioleaching). The results show that the culture supernatant can be effectively used in an upscaled industrial application for metal recovery. If bioleaching is used in the 170-250 million tonnes of steel slag produced per year globally, significant recoveries of metals (100% of Al, 84% of Cr and 8% of V) can be achieved, depending on the slag composition. The removal and recovery percentages of metals from the leachate with Amberlite
® IRA-400 are relatively modest (<67% and <5%, respectively), due to the high concentration of competing ions (SO4 2- , PO4 3- ) in the culture medium. Other ion exchange resins can be better suited for the leachate or methods such as selective precipitation could improve the performance of the resin. Further research is needed to minimise interference and maximise metal recovery., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)- Published
- 2018
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37. Increase of Direct C-C Coupling Reaction Yield by Identifying Structural and Electronic Properties of High-Spin Iron Tetra-azamacrocyclic Complexes.
- Author
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Brewer SM, Wilson KR, Jones DG, Reinheimer EW, Archibald SJ, Prior TJ, Ayala MA, Foster AL, Hubin TJ, and Green KN
- Abstract
Macrocyclic ligands have been explored extensively as scaffolds for transition metal catalysts for oxygen and hydrogen atom transfer reactions. C-C reactions facilitated using earth abundant metals bound to macrocyclic ligands have not been well-understood but could be a green alternative to replacing the current expensive and toxic precious metal systems most commonly used for these processes. Therefore, the yields from direct Suzuki-Miyaura C-C coupling of phenylboronic acid and pyrrole to produce 2-phenylpyrrole facilitated by eight high-spin iron complexes ([Fe
3+ L1(Cl)2 ]+ , [Fe3+ L4(Cl)2 ]+ , [Fe2+ L5(Cl)]+ , [Fe2+ L6(Cl)2 ], [Fe3+ L7(Cl)2 ]+ , [Fe3+ L8(Cl)2 ]+ , [Fe2+ L9(Cl)]+ , and [Fe2+ L10(Cl)]+ ) were compared to identify the effect of structural and electronic properties on catalytic efficiency. Specifically, catalyst complexes were compared to evaluate the effect of five properties on catalyst reaction yields: (1) the coordination requirements of the catalyst, (2) redox half-potential of each complex, (3) topological constraint/rigidity, (4) N atom modification(s) increasing oxidative stability of the complex, and (5) geometric parameters. The need for two labile cis-coordination sites was confirmed based on a 42% decrease in catalytic reaction yield observed when complexes containing pentadentate ligands were used in place of complexes with tetradentate ligands. A strong correlation between iron(III/II) redox potential and catalytic reaction yields was also observed, with [Fe2+ L6(Cl)2 ] providing the highest yield (81%, -405 mV). A Lorentzian fitting of redox potential versus yields predicts that these catalysts can undergo more fine-tuning to further increase yields. Interestingly, the remaining properties explored did not show a direct, strong relationship to catalytic reaction yields. Altogether, these results show that modifications to the ligand scaffold using fundamental concepts of inorganic coordination chemistry can be used to control the catalytic activity of macrocyclic iron complexes by controlling redox chemistry of the iron center. Furthermore, the data provide direction for the design of improved catalysts for this reaction and strategies to understand the impact of a ligand scaffold on catalytic activity of other reactions.- Published
- 2018
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38. Host-Guest Interaction of Cucurbit[8]uril with N-(3-Aminopropyl)cyclohexylamine: Cyclohexyl Encapsulation Triggered Ternary Complex.
- Author
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Xia Y, Wang CZ, Tian M, Tao Z, Ni XL, Prior TJ, and Redshaw C
- Subjects
- Calorimetry, Crystallography, X-Ray, Magnetic Resonance Spectroscopy, Models, Molecular, Molecular Structure, Thermodynamics, Bridged-Ring Compounds chemistry, Cyclohexylamines chemistry, Imidazoles chemistry
- Abstract
The host-guest interaction of a series of cyclohexyl-appended guests with cucurbit[8]uril (Q[8]) was studied by ¹H NMR spectroscopy, isothermal titration calorimetry (ITC), and X-ray crystallography. The X-ray structure revealed that two cycloalkane moieties can be simultaneously encapsulated in the hydrophobic cavity of the Q[8] host to form a ternary complex for the first time., Competing Interests: The authors declare no conflict of interest.
- Published
- 2018
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39. Amino acid based gallium-68 chelators capable of radiolabeling at neutral pH.
- Author
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Price TW, Gallo J, Kubíček V, Böhmová Z, Prior TJ, Greenman J, Hermann P, and Stasiuk GJ
- Abstract
Gallium-68 (
68 Ga) has been the subject of increasing interest for its potential in the production of radiotracers for diagnosis of diseases. In this work we report the complexation of68 Ga by the amino acid based tripodal chelate H3 Dpaa, and two bifunctional derivatives, H3 Dpaa.dab and H4 Dpaa.ga, under a range of conditions with particular emphasis on the rapid complexation of68 Ga at pH 7.4. 100 μM H3 Dpaa achieved a radiochemical yield of 95% at pH 7.4 in 5 minutes at 37 °C. The bifunctional derivatives H4 Dpaa.ga and H3 Dpaa.dab achieved 94% and 84% radiochemical yields, respectively, under the same conditions. The resulting Ga(iii) complexes show thermodynamic stabilities of log KGaDpaa = 18.53, log KGaDpaa.dab = 22.08, log KGaDpaa.ga = 18.36. Unfortunately, the resulting radiolabelled species do not present sufficient serum stability for in vivo application. Herein we show a flexible synthesis for bifunctional chelators based on amino acids that rapidly complex68 Ga under physiological conditions.- Published
- 2017
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40. Interconvertible geometric isomers of Plasmodium falciparum dihydroorotate dehydrogenase inhibitors exhibit multiple binding modes.
- Author
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McConkey GA, Bedingfield PTP, Burrell DR, Chambers NC, Cunningham F, Prior TJ, Fishwick CWG, and Boa AN
- Subjects
- Acrylates chemical synthesis, Acrylates chemistry, Dihydroorotate Dehydrogenase, Dose-Response Relationship, Drug, Molecular Docking Simulation, Molecular Structure, Oxidoreductases Acting on CH-CH Group Donors genetics, Oxidoreductases Acting on CH-CH Group Donors metabolism, Structure-Activity Relationship, Acrylates pharmacology, Oxidoreductases Acting on CH-CH Group Donors antagonists & inhibitors, Plasmodium falciparum enzymology
- Abstract
Two new tricyclic β-aminoacrylate derivatives (2e and 3e) have been found to be inhibitors of Plasmodium falciparum dihydroorotate dehydrogenase (PfDHODH) with Ki 0.037 and 0.15μM respectively.
1 H and13 C NMR spectroscopic data show that these compounds undergo ready cis-trans isomerisation at room temperature in polar solvents. In silico docking studies indicate that for both molecules there is neither conformation nor double bond configuration which bind preferentially to PfDHODH. This flexibility is favourable for inhibitors of this channel that require extensive positioning to reach their binding site., (Copyright © 2017 Elsevier Ltd. All rights reserved.)- Published
- 2017
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41. Synthesis and Structure of the Inclusion Complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O.
- Author
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Chen LX, Kan JL, Cong H, Prior TJ, Tao Z, Xiao X, and Redshaw C
- Subjects
- Amantadine chemical synthesis, Crystallography, X-Ray methods, Molecular Structure, Photoelectron Spectroscopy methods, X-Ray Diffraction methods, Amantadine analogs & derivatives, Amantadine chemistry, Coordination Complexes chemistry, Neodymium chemistry
- Abstract
Heating a mixture of Nd(NO₃)₃·6H₂O, KCl, Q[10] and Q[5] in HCl for 10 min affords the inclusion complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O. The structure of the inclusion complex has been investigated by single crystal X-ray diffraction and by X-ray Photoelectron spectroscopy (XPS)., Competing Interests: The authors declare no conflict of interest.
- Published
- 2017
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42. Crystal structures of N '-amino-pyridine-2-carboximidamide and N '-{[1-(pyridin-2-yl)ethyl-idene]amino}-pyridine-2-carboximidamide.
- Author
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Eya'ane Meva F, Prior TJ, Evans DJ, and Mang ER
- Abstract
The crystal structures of N '-amino-pyridine-2-carboximidamide (C
6 H8 N4 ), 1 , and N '-{[1-(pyridin-2-yl)ethyl-idene]amino}-pyridine-2-carboximidamide (C13 H13 N5 ), 2 , are described. The non-H atoms in compound 1 are nearly planar (r.m.s. deviation from planarity = 0.0108 Å), while 2 is twisted about the central N-N bond by 17.8 (2)°. Both mol-ecules are linked by inter-molecular N-H⋯N hydrogen-bonding inter-actions; 1 forms a two-dimensional hydrogen-bonding network and for 2 the network is a one-dimensional chain. The bond lengths of these mol-ecules are similar to those in other literature reports of azine and di-imine systems.- Published
- 2017
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43. On the high-pressure phase stability and elastic properties of β-titanium alloys.
- Author
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Smith D, Joris OP, Sankaran A, Weekes HE, Bull DJ, Prior TJ, Dye D, Errandonea D, and Proctor JE
- Abstract
We have studied the compressibility and stability of different β-titanium alloys at high pressure, including binary Ti-Mo, Ti-24Nb-4Zr-8Sn (Ti2448) and Ti-36Nb-2Ta-0.3O (gum metal). We observed stability of the β phase in these alloys to 40 GPa, well into the ω phase region in the P-T diagram of pure titanium. Gum metal was pressurised above 70 GPa and forms a phase with a crystal structure similar to the η phase of pure Ti. The bulk moduli determined for the different alloys range from 97 ± 3 GPa (Ti2448) to 124 ± 6 GPa (Ti-16.8Mo-0.13O).
- Published
- 2017
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44. Simultaneous Differential Scanning Calorimetry-Synchrotron X-ray Powder Diffraction: A Powerful Technique for Physical Form Characterization in Pharmaceutical Materials.
- Author
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Clout A, Buanz AB, Prior TJ, Reinhard C, Wu Y, O'Hare D, Williams GR, and Gaisford S
- Subjects
- Phase Transition, Stereoisomerism, Sulfathiazole, Temperature, Calorimetry, Differential Scanning methods, Glutarates chemistry, Powder Diffraction methods, Sulfathiazoles chemistry, X-Ray Diffraction methods
- Abstract
We report a powerful new technique: hyphenating synchrotron X-ray powder diffraction (XRD) with differential scanning calorimetry (DSC). This is achieved with a simple modification to a standard laboratory DSC instrument, in contrast to previous reports which have involved extensive and complex modifications to a DSC to mount it in the synchrotron beam. The high-energy X-rays of the synchrotron permit the recording of powder diffraction patterns in as little as 2 s, meaning that thermally induced phase changes can be accurately quantified and additional insight on the nature of phase transitions obtained. Such detailed knowledge cannot be gained from existing laboratory XRD instruments, since much longer collection times are required. We demonstrate the power of our approach with two model systems, glutaric acid and sulfathiazole, both of which show enantiotropic polymorphism. The phase transformations between the low and high temperature polymorphs are revealed to be direct solid-solid processes, and sequential refinement against the diffraction patterns obtained permits phase fractions at each temperature to be calculated and unit cell parameters to be accurately quantified as a function of temperature. The combination of XRD and DSC has further allowed us to identify mixtures of phases which appeared phase-pure by DSC.
- Published
- 2016
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45. Stabilisation of metastable polymorphs: the case of paracetamol form III.
- Author
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Telford R, Seaton CC, Clout A, Buanz A, Gaisford S, Williams GR, Prior TJ, Okoye CH, Munshi T, and Scowen IJ
- Abstract
The design of a melt synthesis of the first air-stable formulation of the metastable form III of paracetamol is derived from thermo-spectroscopic and thermo-diffraction experiments. Melt crystallisation in the presence of β-1,4-saccharides produces form III selectively and the excipients appear to act as stabilising 'active' templates of the metastable polymorph.
- Published
- 2016
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46. Structural studies of Schiff-base [2 + 2] macrocycles derived from 2,2'-oxydianiline and the ROP capability of their organoaluminium complexes.
- Author
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Yang W, Zhao KQ, Prior TJ, Hughes DL, Arbaoui A, Elsegood MR, and Redshaw C
- Abstract
The molecular structures of a number of solvates of the [2 + 2] Schiff-base macrocycles {[2-(OH)-5-(R)-C6H2-1,3-(CH)2][O(2-C6H4N)2]}2 (R = Me L(1)H2, tBu L(2)H2, Cl L(3)H2), formed by reacting 2,6-dicarboxy-4-R-phenol with 2,2'-oxydianiline (2-aminophenylether), (2-NH2C6H4)2O, have been determined. Reaction of L(n)H2 with two equivalents of AlR'3 (R' = Me, Et) afforded dinuclear alkylaluminium complexes [(AlR'2)2L(1-3)] (R = R' = Me (1), R = tBu, R' = Me (2), R = Cl, R' = Me (3), R = Me, R' = Et (4), R = tBu, R' = Et (5), R = Cl, R' = Et (6)). For comparative studies, reactions of two equivalents of AlR'3 (R' = Me, Et) with the macrocycle derived from 2,2'-ethylenedianiline and 2,6-dicarboxy-R-phenols (R = Me L(4)H2, tBu L(5)H2) were conducted; the complexes [(AlMe)(AlMe2)L(5)]·2¼MeCN (7·2¼MeCN) and [(AlEt2)2L(4)] (8) were isolated. Use of limited AlEt3 with L(3)H2 or L(5)H2 afforded mononuclear bis(macrocyclic) complexes [Al(L(3))(L(3)H)]·4toluene (9·4toluene) and [Al(L(5))(L(5)H)]·5MeCN (10·5MeCN), respectively. Use of four equivalents of AlR'3 led to transfer of alkyl groups and isolation of the complexes [(AlR'2)4L(1'-3')] (R = L(2'), R' = Me (11); L(3'), R' = Me (12); L(1'), R' = Et (13); L(2'), R' = Et (14); L(3'), R' = Et (15)), where L(1'-3') is the macrocycle resulting from double alkyl transfer to imine, namely {[2-(O)-5-(R)C6H2-1-(CH)-3-C(R')H][(O)(2-(N)-2'-C6H4N)2]}2. Molecular structures of complexes 7·2¼MeCN, 8, 9·4toluene, 10·5MeCN and 11·1¾toluene·1¼hexane are reported. These complexes act as catalysts for the ring opening polymerisation (ROP) of ε-caprolactone and rac-lactide; high conversions were achieved over 30 min at 80 °C for ε-caprolactone, and 110 °C over 12 h for rac-lactide.
- Published
- 2016
- Full Text
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47. Crystal structure of 4-carbamoylpyridinium chloride.
- Author
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Fellows SM and Prior TJ
- Abstract
The hydro-chloride salt of isonicotinamide, C6H7N2O(+)·Cl(-), has been synthesized from a dilute solution of hydro-chloric acid in aceto-nitrile. The compound displays monoclinic symmetry (space group C2/c) at 150 K, similar to the related hydro-chloride salt of nicotinamide. The asymmetric unit contains one protonated isonicotinamide mol-ecule and a chloride anion. An array of hydrogen-bonding inter-actions, including a peculiar bifurcated pyridinium-chloride inter-action, results in linear chains running almost perpendicularly in the [150] and [1-50] directions within the structure. A description of the hydrogen-bonding network and comparison with similar compounds are presented.
- Published
- 2016
- Full Text
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48. Mono- and Bis-Alkylation of Glyoxal-Bridged Tetraazamacrocycles Using Mechanochemistry.
- Author
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Abdulwahaab BH, Burke BP, Domarkas J, Silversides JD, Prior TJ, and Archibald SJ
- Abstract
Glyoxal-bridged bisaminal tetraazamacrocyclic derivatives of 1,4,7,10-tetraazacyclododecane (cyclen) and 1,4,8,11-tetraazacyclotetradecane (cyclam) can be N-functionalized to incorporate coordinating groups or for conjugation to biomolecules. Herein, we present an improved N-functionalization methodology using mechanochemistry which reduces reaction times in comparison with conventional synthetic routes. A range of six alkyl halides were reacted with cyclen and cyclam bisaminal derivatives in various ratios to form mono- and bis-functionalized quaternary ammonium salts. Cross-bridged cyclam, a key intermediate for CB-TE2A, a commonly used chelator in positron emission tomography medical imaging with (64)Cu, has been synthesized using nonconventional synthetic methodologies (grinding and microwave heating) with intermediates characterized by 2D NMR and single crystal XRD. The overall synthesis time of CB-TE2A from cyclam could be shortened to 5 days from the 35 days required for the conventional synthesis.
- Published
- 2016
- Full Text
- View/download PDF
49. Synthesis, structural studies, and oxidation catalysis of the manganese(II), iron(II), and copper(II) complexes of a 2-pyridylmethyl pendant armed side-bridged cyclam.
- Author
-
Shircliff AD, Wilson KR, Cannon DJ, Jones DG, Zhang Z, Chen Z, Yin G, Prior TJ, and Hubin TJ
- Abstract
The first 2-pyridylmethyl pendant armed structurally reinforced cyclam ligand has been synthesized and successfully complexed to Mn
2+ , Fe2+ , and Cu2+ cations. X-ray crystal structures were obtained for the diprotonated ligand and its Cu2+ complex demonstrating pentadentate binding of the ligand with trans-II configuration of the side-bridged cyclam ring, leaving a potential labile binding site cis to the pyridine donor for interaction of the complex with oxidants and/or substrates. The electronic properties of these complexes were determined by means of solid state magnetic moment, with a low value of μ = 3.10 μB for the Fe2+ complex suggesting it has a trigonal bipyramidal coordination geometry, matching the crystal structure of the Cu2+ complex, while the μ = 5.52 μB value for the Mn2+ complex suggests it is high spin octahedral. Cyclic voltammetry in acetonitrile revealed reversible redox processes in all three complexes, suggesting catalytic reactivity involving electron transfer processes are possible for these complexes. Screening for oxidation catalysis using hydrogen peroxide as the terminal oxidant identified the Fe2+ complex as the oxidation catalysts most worthy of continued development.- Published
- 2015
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50. Crystal structure of di-chlorido-(4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-deca-ne)iron(III) hexa-fluorido-phosphate.
- Author
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Funwie NL, Cain AN, Fanning BZ, Hageman SA, Mullens M, Roberts TK, Turner DJ, Valdez CN, Vaughan RW, Ermias HG, Silversides JD, Archibald SJ, Hubin TJ, and Prior TJ
- Abstract
The title compound, [FeCl2(C14H30N4)]PF6, contains Fe(3+) coordinated by the four nitro-gen atoms of an ethyl-ene cross-bridged cyclam macrocycle and two cis chloride ligands in a distorted octa-hedral environment. In contrast to other similar compounds this is a monomer. Inter-molecular C-H⋯Cl inter-actions exist in the structure between the complex ions. Comparison with the mononuclear Fe(2+) complex of the same ligand shows that the smaller Fe(3+) ion is more fully engulfed by the cavity of the bicyclic ligand. Comparison with the μ-oxido dinuclear complex of an unsubstituted ligand of the same size demonstrates that the methyl groups of 4,11-dimethyl-1,4,8,11-tetra-aza-bicyclo-[6.6.2]hexa-decane prevent dimerization upon oxidation.
- Published
- 2015
- Full Text
- View/download PDF
Catalog
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