• Ab initio RAFT emulsion polymerization mediated by small cationic RAFT agents to form polymers with low molar mass dispersity

      Stace, Sarah J; Vanderspikken, Jochen; Howard, Shaun C; Li, Guoxin; Muir, Benjamin W; Fellows, Christopher M; Keddie, Daniel J; Moad, Graeme (Royal Society of Chemistry (RSC), 2019-07-29)
      We report on low molar mass cationic RAFT agents that provide predictable molar mass and low molar mass dispersities (Đm) in ab initio emulsion polymerization. Thus RAFT emulsion polymerization of styrene in the presence of the protonated RAFT agent, ((((cyanomethyl)thio)carbonothioyl)(methyl)amino)pyridin-1-ium toluenesulfonate (4), and the analogous methyl-quaternized RAFT agents, 4-((((cyanomethyl)thio)carbonothioyl)(methyl)amino)-1-methylpyridin-1-ium dodecyl sulfate (6), provide low dispersity polystyrene with Đm 1.2–1.4 for Mn ∼ 20 000. We postulate that the success of ab initio emulsion polymerization with 4 is due to the hydrophilicity of the pyridinium group, which is such that the water soluble RAFT agent partitions predominantly into the aqueous phase under the conditions of the experiment and that 4 provides little retardation. With 6, when the counterion is dodecyl sulfate, we can achieve “surfactant-free” RAFT emulsion polymerization to provide a low Đm polystyrene. However, the RAFT end-group is lost on isolation of the polymer. Preliminary results show that this class of RAFT agent is broadly applicable in ab initio emulsion polymerization of other more-activated monomers (e.g., butyl acrylate, butyl methacrylate). Furthermore, cyanomethyl(pyridin-4-yl)carbamodithioate (3, the RAFT agent in neutral form) provides molar mass control and Đm < 1.8 in ab initio emulsion polymerization of less activated monomers, specifically, the vinyl esters, vinyl acetate and vinyl benzoate.
    • Assessment of ATR-FTIR spectroscopy with multivariate analysis to investigate the binding mechanisms of Ag and TiO2 nanoparticles to Chelex®-100 or Metsorb™ for the DGT technique

      Pouran, Hamid; Perez Colodrero, Rosario; Wu, Shuang; Hix, Gary; Zakharova, Julia; Zhang, Hao (Royal Society of Chemistry (RSC), 2020-01-09)
      Studying nanomaterials' ecotoxicology is not new but there are still gaps in our understanding of their fate in the environment. A major challenge is lack of reliable tools to measure available concentrations of nanoparticles (NPs) in soil and water. Diffusive gradients in thin-films (DGT) is a robust technique for measuring the concentrations of trace metals in the environment. We have also shown that it could be potentially developed for measuring ZnO NPs. To further investigate the suitability of DGT for measuring the available concentrations of NPs in soil and water we selected two model nanoparticles, Ag and TiO2, which are widely used and incorporated in different commercial products. We aimed to understand (1) if two of the DGT binding agents, Chelex®-100 and Metsorb™, could irreversibly retain our model NPs and if yes (2) what might be the differences between bound Ag and TiO2 NPs and Ag+ and Ti4+ cations. We used ATR-FTIR spectroscopy for this purpose and analysed the IR spectra using principal component analysis and linear discriminant analysis (PCA-LDA), as our pattern recognition tool. The results show that the DGT resins form chemical bonds with silver and titanium nanoparticles and their ionic forms. PCA-LDA demonstrates that the binding mechanisms are statistically different (95% confidence level) among the treatments. This study indicates DGT's potential for measuring the available concentrations of NPs in the environment and suggests that ATR-FTIR spectroscopy combined with computational analysis could potentially differentiate between chemical species that are retained simultaneously by the DGT device resin layer.
    • Bioactive (co)oligoesters with antioxidant properties – synthesis and structural characterization at the molecular level

      Maksymiak, Magdalena; Bałakier, Tomasz; Jurczak, Janusz; Adamus, Grazyna; Kowalczuk, Marek (Royal Society of Chemistry (RSC), 2016-06-10)
      A contemporary synthetic route, starting from the bioactive compound via the corresponding glycidyl ester and β-substituted β-lactone to (homo)- and (co)oligoesters with a bioactive moiety covalently linked as pendent groups along an oligomer backbone, was reported. The bioactive compounds were selected from antioxidants used in cosmetics. Two models of bioactive (homo)- and (co)oligoesters were synthesized via anionic ring-opening (co)oligomerization of p-methoxybenzoyloxymethylpropiolactone (p-AA-CH2-PL) initiated by p-anisic acid sodium salt. An analytical protocol was developed for a detailed structural characterization at the molecular level of these bioactive (co)oligoesters. The molecular level structure of the obtained bioactive (homo)- and (co)oligoesters was established by electrospray ionization tandem mass spectrometry (ESI-MS/MS) supported by 1H NMR analysis. Additionally, the results presented here are important for the analysis of designed biodegradable polymeric controlled-release systems of bioactive compounds with potential applications in cosmetology.
    • Characterisation of non-uniform functional surfaces: towards linking basic surface properties with electrocatalytic activity

      Maljusch, Artjom; Henry, John B; Tymoczko, Jakub; Bandarenka, Aliaksandr S; Schuhmann, Wolfgang (Royal Society of Chemistry (RSC), 2013-11-08)
      Functional materials, particularly heterogeneous catalysts, are often non-uniform at a microscopic level making their detailed characterisation extremely complex. This complexity inhibits the design and implementation of novel functional materials as such characterisation is a key to understanding interfaces for heterogeneous catalysis. We demonstrate that a combination of Scanning Kelvin Probe (SKP) and Scanning Electrochemical Microscopy (SECM) experiments made over the same sample surface using an integrated SKP–SECM system provides a powerful and robust tool to link basic surface properties with the observed electrocatalytic activity. As the SKP-response can be accurately assessed using modern quantum chemical approaches to benchmark analytical signals for different surface structures with varying compositions, application of an integrated SKP–SECM system can offer valuable insight into the origin of the observed electrocatalytic activity. As model objects, we used Pt(111)-like thin films modified with sub-monolayer and monolayer amounts of Cu atoms located at the electrode surface and in the sub-surface region. The exact position of the Cu atoms relative to the topmost Pt layer greatly affects basic surface properties and governs the electrocatalytic activity of the surface towards various reactions, i.e. the oxygen reduction reaction. SKP–SECM appeared to be a very sensitive tool to monitor those changes as a function of the spatial coordinates.
    • Cleaning the molecular machinery of cells via proteostasis, proteolysis and endocytosis selectively, effectively, and precisely: intracellular self-defense and cellular perturbations

      Kumar, Rajiv; Chhikara, Bhupender S; Gulia, Kiran; Chhillar, Mitrabasu; NIET, National Institute of Medical Science, India. chemistry_rajiv@hotmail.com. (Royal Society of Chemistry (RSC), 2020-11-02)
      Network coordinates of cellular processes (proteostasis, proteolysis, and endocytosis), and molecular chaperones are the key complements in the cell machinery and processes. Specifically, cellular pathways are responsible for the conformational maintenance, cellular concentration, interactions, protein synthesis, disposal of misfolded proteins, localization, folding, and degradation. The failure of cellular processes and pathways disturbs structural proteins and the nucleation of amyloids. These mishaps further initiate amyloid polymorphism, transmissibility, co-aggregation of pathogenic proteins in tissues and cells, prion strains, and mechanisms and pathways for toxicity. Consequently, these conditions favor and lead to the formation of elongated amyloid fibrils consisting of many-stranded β-sheets (N,N-terminus and C,C-terminus), and abnormal fibrous, extracellular, proteinaceous deposits. Finally, these β-sheets deposit, and cells fail to degrade them effectively. The essential torsion angles (φ, ψ, and ω) define the conformation of proteins and their architecture. Cells initiate several transformations and pathways during the regulation of protein homeostasis based on the requirements for the functioning of the cell, which are governed by ATP-dependent proteases. In this process, the kinetics of the molding/folding phenomenon is disturbed, and subsequently, it is dominated by cross-domain misfolding intermediates; however, simultaneously, it is opposed by small stretching forces, which naturally exist in the cell. The ubiquitin/proteasome system deals with damaged proteins, which are not refolded by the chaperone-type machinery. Ubiquitin-protein ligases (E3-Ub) participate in all the cellular activity initiated and governed by molecular chaperones to stabilize the cellular proteome and participate in the degradation phenomenon implemented for damaged proteins. Optical tweezers, a single-resolution based technique, disclose the folding pathway of linear chain proteins, which is how they convert themselves into a three-dimensional architecture. Further, DNA-protein conjugation analysis is performed to obtain folding energies as single-molecule kinetic and thermodynamic data.
    • Crowding out: ligand modifications and their structure directing effects on brucite-like {Mx(μ3-OH)y} (M = Co(ii), Ni(ii)) core growth within polymetallic cages

      Slater-Parry, ME; Durrant, JP; Howells, JM; Pitak, MB; Horton, PN; Klooster, WT; Coles, SJ; O'Connor, HM; Brechin, EK; Barra, AL; et al. (Royal Society of Chemistry (RSC), 2018-12-20)
      © The Royal Society of Chemistry. Previous employment of the ligands 2-methoxy-6-[(methylimino)methyl]phenol (L 1 H) and 2-methoxy-6-[(phenylimino)methyl]phenol (L 2 H) has resulted in the self-assembly of pseudo metallocalix[6]arene complexes of general formulae: [M 7 (μ 3 -OH) 6 (L x ) 6 ](NO 3 ) y (M = Ni(ii), x = 1, y = 2 (1) and Co(ii/iii), x = 2, y = 3 (2)). Extrapolating upon this work, we report the coordination chemistry of ligands 2-methoxy-6-{[(2-methoxyphenyl)imino]methyl}phenol (L 3 H), 2-[(benzylimino)methyl]-6-methoxyphenol (L 4 H), 2-[(benzylamino)methyl]-6-methoxyphenol (L 5 H) and 2-[(benzylamino)methyl]-4-bromo-6-methoxyphenol (L 6 H), whose structures are modifications of ligands L 1-2 H. These ligands are employed in the synthesis and characterisation of the dimetallic complex [Ni(ii) 2 (L 3 ) 3 (H 2 O)](NO 3 )·2H 2 O·3MeOH (3); the monometallic complexes [Ni(ii)(L 4 ) 2 ] (4) and [Co(iii)(L 4 ) 3 ]·H 2 O·MeOH (5a); and the tetranuclear pseudo metallocalix[4]arene complexes: [(NO 3 )⊂Co(ii) 4 (μ 3 -OH) 2 (L 5 ) 4 (H 2 O) 2 ](NO 3 )·H 2 O (6), [(NO 3 )⊂Ni(ii) 4 (μ 3 -OH) 2 (L 5 ) 4 (H 2 O) 2 ](NO 3 )·H 2 O (7) and [Ni(ii) 4 (μ 3 -OH) 2 (L 6 ) 4 (NO 3 ) 2 ]·MeCN (8). The tetrametallic 'butterfly' core topologies in 6-8 are discussed with respect to their structural and topological relationship with their heptanuclear [M 7 ] (M = Co(ii), Ni(ii)) pseudo metallocalix[6]arene ancestors (1 and 2).
    • High nuclearity Ni(ii) cages from hydroxamate ligands

      McDonald, C; Sanz, S; Brechin, EK; Singh, MK; Rajaraman, G; Gaynor, D; Jones, LF (Royal Society of Chemistry (RSC), 2014-08-13)
      The synthesis, structural and magnetic characterisation of a family of Ni(ii) cages built from hydroxamate ligands is presented. Two pentanuclear 12-MCNi(ii)-4 metallacrowns [Ni5(L1) 4(MeOH)4](ClO4)2·2MeOH (1) and [Ni5(L1)4(py)5](ClO 4)2·H2O (2) (where L1H 2 = 2-(dimethylamino)phenylhydroxamic acid) share analogous, near-planar {Ni5(L1)4}2+ cores, but differ in the number and nature of the ligands located at the axial Ni(ii) sites; the addition of pyridine converting square planar Ni(ii) ions to square-based pyramidal and octahedral Ni(ii) ions, introducing extra paramagnetic metal centres which 'switch on' additional magnetic superexchange pathways. Subtle variations in the reaction scheme used to produce complexes 1 and 2 result in both a change of topology and an increase in nuclearity, through isolation of the hepta- and nonametallic complexes [Ni7(L 1H)8(L1)2(H2O) 6](SO4)·15H2O (3), [Ni 9(μ-H2O)2(L2)6(L 2H)4(H2O)2](SO4) ·29H2O (4) and [Ni9(μ-H2O) 2(L2)6(L2H)4(H 2O)2](ClO4)2·2MeOH· 18H2O (5) (where L2H2 = 2-(amino) phenylhydroxamic acid). Complementary dc magnetic susceptibility studies and DFT analysis indicate dominant antiferromagnetic exchange interactions in 1, 2, 4 and 5, but competing ferro- and antiferromagnetic exchange in 3. © the Partner Organisations 2014.
    • Molecular pac-man and tacos: layered cu(ii) cages from ligands with high binding site concentrations

      McDonald, C; Williams, DW; Comar, P; Coles, SJ; Keene, TD; Pitak, MB; Brechin, EK; Jones, LF; School of Chemistry, NUI Galway, University Road, Galway, Ireland. (Royal Society of Chemistry (RSC), 2015-06-24)
      © The Royal Society of Chemistry 2015. The in situ formation and subsequent Cu(ii) ligation of the polydentate pro-ligands o-[(E)-(2-hydroxy-3-methoxyphenyl)methylideneamino]benzohydroxamic acid (L1H3), o-[(E)-(2-hydroxy-3-methoxy-5-bromophenyl)methylideneamino]benzohydroxamic acid (L2H3) and o-[(E)-(2-hydroxyphenyl)methylideneamino]benzohydroxamic acid (L3H3), leads to the self-assembly of the cages [Cu(ii)10(L1)4(2-aph)2(H2O)2](ClO4)4·5MeOH (1), [Cu(ii)14(L1)8(MeOH)2.5(H2O)7.5](NO3)4·3MeOH·7H2O (2), [Cu(ii)14(L2)8(MeOH)4(H2O)6](NO3)4·6H2O (3), [Cu(ii)14(L3)8(MeOH)6(H2O)2](NO3)4·4MeOH·8H2O (4) and [Cu(ii)30O(OH)4(OMe)2(L1)16(MeOH)4(H2O)2](ClO4)4·2MeOH·30H2O (5). Each member comprises a highly unusual topology derived from off-set, stacked, near planar layers of polynuclear subunits connected through long Cu(ii)-O contacts. The exact topology observed is dependent on the specific reaction conditions and methodologies employed. Dc magnetic susceptibility studies on 1, 2, 4 and 5 reveals strong antiferromagnetic exchange between the Cu(ii) centres in all siblings. We also present the 1D coordination polymer {[Cu(ii)(L4)]·H2O}n (6) comprising the pseudo macrocyclic ligand [[2-[(E)-(2-hydroxy-3-methoxy-phenyl)methyleneamino]benzoyl]amino]ethanimidate (L4H2), which is formed upon the incorporation of an MeCN unit at the hydroxamate group of precursor ligand L1H3.
    • Mono- and ditopic hydroxamate ligands towards discrete and extended network architectures

      Fugu, MB; Ellaby, RJ; O'Connor, HM; Pitak, MB; Klooster, W; Horton, PN; Coles, SJ; Al-Mashhadani, MH; Perepichka, IF; Brechin, EK; et al. (Royal Society of Chemistry (RSC), 2019-06-04)
      © 2019 The Royal Society of Chemistry. A family of mono- and ditopic hydroxamic acids has been employed in the synthesis and structural and physical characterisation of discrete (0D) and (1- and 2-D) extended network coordination complexes. Examples of the latter include the 1-D coordination polymer {[Zn(ii)(L3H)2]·2MeOH}n (5; L3H2 = 2-(methylamino)phenylhydroxamic acid) and the 2-D extended network {[Cu(ii)(L2H)(H2O)(NO3)]·H2O}n (5; L2H2 = 4-amino-2-(acetoxy)phenylhydroxamic acid). The 12-MC-4 metallacrown [Cu(ii)5(L4H)4(MeOH)2(NO3)2]·3H2O·4MeOH (7) represents the first metal complex constructed using the novel ligand N-hydroxy-2-[(2-hydroxy-3-methoxybenzyl)amino]benzamide (L4H3). Variable temperature magnetic susceptibility studies confirm strong antiferromagnetic exchange between the Cu(ii) centres in 7. Coordination polymer 5 shows photoluminescence in the blue region (λPL ∼ 421-450 nm) with a bathochromic shift of the emission (∼15-30 nm) from solution to the solid state.
    • Potential linkages between mineral magnetic measurements and urban roadside soil pollution (part 2)

      Crosby, C.J.; Fullen, Michael A.; Booth, C.A.; CBE Loughborough University LE11 3TU, United Kingdom. c.j.crosby@lboro.ac.uk. (Royal Society of Chemistry (RSC), 2014-01-15)
      Use of mineral magnetic concentration parameters (χLF, χARM and SIRM) as a potential pollution proxy for soil samples collected from Wolverhampton (UK) is explored. Comparison of soil-related analytical data by correlation analyses between each magnetic parameter and individual geochemical classes (i.e. Fe, Pb, Ni, Zn, Cd), are reported. χLF, χARM and SIRM parameters reveal significant (p < 0.001 n = 60), strong (r = 0.632-0.797), associations with Fe, Cu, Zn and Pb. Inter-geochemical correlations suggest anthropogenic influences, which is supported by low χFD% measurements that infer an influence of multi-domain mineralogy are indicative of anthropogenic combustion processes. Results indicate mineral magnetic measurements could potentially be used as a geochemical indicator for soils in certain environments and/or specific settings that are appropriate for monitoring techniques. The mineral magnetic technique offers a simple, reliable, rapid, sensitive, inexpensive and non-destructive approach that could be a valuable pollution proxy for soil contamination studies. © 2014 The Royal Society of Chemistry.
    • Proline derived guanidine catalysts forge extensive H-bonded architectures: a solution and solid state study

      Al-Taie, Zahraa S; Anetts, Simon R; Christensen, Jeppe; Coles, Simon J; Horton, Peter N; Evans, Daniel M; Jones, Leigh F; de Kleijne, Frank FJ; Ledbetter, Shaun M; Mehdar, Yassin TH; et al. (Royal Society of Chemistry (RSC), 2020-06-11)
      The preparation of a range of amino acid derived guanidine organocatalysts is reported together with their application to the Michael addition of 2-hydroxy-1,4-napthoquinone to b-nitrostyrene, achieving a maximum ee of 56%. Some insight into the mechanism was sought by using X-ray crystallography and a detailed study of the intra- and intermolecular hydrogen bonding is reported.
    • Solvothermal synthesis of discrete cages and extended networks comprising {Cr(iii)3O(O2CR)3(oxime)3}2− (R = H, CH3, C(CH3)3, C14H9) building blocks

      Houton, E; Comar, P; Pitak, MB; Coles, SJ; Ryder, AG; Piligkos, S; Brechin, EK; Jones, LF (Royal Society of Chemistry (RSC), 2016-07-28)
      © 2016 The Royal Society of Chemistry. The synthesis, structural and magnetic characterisation of a family of related Cr(iii) cages are reported. Each member comprises {Cr(iii)3O(O2CR1)3(R2-sao)3}2- (R1 = H, CH3, C(CH3)3, C14H9; R2 = Me, Ph, tBu, C10H8) triangles linked by Na+ cations, resulting in either the discrete complexes [H3O][NEt4]2[NaCr(iii)6O2(O2C-C14H9)6(Naphth-sao)6] (1) and [Na4Cr(iii)6O2(O2CC(CH3)3)6(3,5-di-tBu-sao)6(MeCN)6] (3); or the extended networks [H3O]2[Na2Cr(iii)6O2(O2CH)6(Ph-sao)6(MeCN)2(H2O)2]n·4MeCN (2); [H3O][Na3Cr(iii)6O2(O2CCH3)6(Me-sao)6(MeCN)]n (4) and [Na2Cr(iii)3O(O2CCH3)3(Me-sao)3(H2O)6]n·3MeCN (5). Magnetic susceptibility data obtained for 2 and 4 reveal weak antiferromagnetic exchange between the Cr(iii) ions in the triangles.
    • Synthesis of triazole-linked morpholino oligonucleotides via Cu<sup>I</sup> catalysed cycloaddition

      Palframan, MJ; Alharthy, RD; Powalowska, PK; Hayes, CJ; School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK. chris.hayes@nottingham.ac.uk. (Royal Society of Chemistry (RSC), 2016-02-16)
      © The Royal Society of Chemistry 2016. Triazole-linked morpholino (TLMO) oligonucleic acids were synthesised using the CuI catalysed (3 + 2) azide-alkyne cycloaddition (CuAAC) reaction. The modified DNA analogues were incorporated into 13-mer sequences via solid phase synthesis. UV melting experiments showed that the TLMO modification gives higher Tm values than the corresponding TLDNA modification.
    • The verticillenes. Pivotal intermediates in the biosynthesis of the taxanes and the phomactins

      Palframan, MJ; Pattenden, G; School of Chemistry, The University of Nottingham, University Park, Nottingham, NG7 2RD, UK. gp@nottingham.ac.uk. (Royal Society of Chemistry (RSC), 2018-07-06)
      © 2019 The Royal Society of Chemistry. Covering: up to May 2018 The verticillene family of 6,12-membered ring-fused diterpenes are found in plants, liverworts, corals and insects. Carbocations derived from verticillene hydrocarbons are central intermediates in the biosynthesis of the taxane and the phomactin families of polycyclic natural products. This perspective delineates these unique biosynthetic interrelationships, which are reinforced by recent biomimetic synthesis investigations, alongside quantum chemical calculations and targeted engineering studies of the taxadiene synthase (TXS) cascade.