David K Henderson

Publications (9)45.39 Total impact

• Article: Structural, magnetic, and electronic properties of phenolic oxime complexes of Cu and Ni.

  Alexander M Whyte, Benjamin Roach, David K Henderson, Peter A Tasker, Michio M Matsushita, Kunio Awaga, Fraser J White, Patricia Richardson, Neil Robertson
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  ABSTRACT: Square planar complexes of the type Ni(L(1))(2), Ni(L(2))(2), Cu(L(1))(2), and Cu(L(2))(2), where L(1)H = 2-hydroxy-5-t-octylacetophenone oxime and L(2)H = 2-hydroxy-5-n-propylacetophenone oxime, have been prepared and characterized by single-crystal X-ray diffraction, cyclic voltammetry, UV/vis spectroscopy, field-effect-transistor measurements, density functional theory (DFT) and time-dependent DFT (TDDFT) calculations, and, in the case of the paramagnetic species, electron paramagnetic resonance (EPR) and magnetic susceptibility. Variation of alkyl groups on the ligand from t-octyl to n-propyl enabled electronic isolation of the complexes in the crystal structures of M(L(1))(2) contrasting with π-stacking interactions for M(L(2))(2) (M = Ni, Cu). This was evidenced by a one-dimensional antiferromagnetic chain for Cu(L(2))(2) but ideal paramagnetic behavior for Cu(L(1))(2) down to 1.8 K. Despite isostructural single crystal structures for M(L(2))(2), thin-film X-ray diffraction and scanning electron microscopy (SEM) revealed different morphologies depending on the metal and the deposition method (vapor or solution). The Cu complexes displayed limited electronic interaction between the central metal and the delocalized ligands, with more mixing in the case of Ni(II), as shown by electrochemistry and UV/vis spectroscopy. The complexes M(L(2))(2) showed poor charge transport in a field-effect transistor (FET) device despite the ability to form π-stacking structures, and this provides design insights for metal complexes to be used in conductive thin-film devices.
  Inorganic Chemistry 11/2011; 50(24):12867-76. · 4.60 Impact Factor
• Article: Using the outer coordination sphere to tune the strength of metal extractants.

  Ross S Forgan, Benjamin D Roach, Peter A Wood, Fraser J White, John Campbell, David K Henderson, Eduardo Kamenetzky, Fiona E McAllister, Simon Parsons, Elna Pidcock, Patricia Richardson, Ronald M Swart, Peter A Tasker
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  ABSTRACT: A series of 3-substituted salicylaldoximes has been used to demonstrate the importance of outer-sphere interactions on the efficacy of solvent extractants that are used to produce approximately one-quarter of the world's copper. The distribution coefficient for extraction of copper by 5-tert-butyl-3-X-salicylaldoximes (X = H, Me, (t)Bu, NO(2), Cl, Br, OMe) varies by more than two orders of magnitude. X-ray structure determinations of preorganized free ligand dimers (10 new structures are reported) indicate that substituents with a hydrogen-bond acceptor atom attached to the 3-carbon atom, ortho to the phenolic oxygen, buttress the intermolecular hydrogen bond from the oximic proton. Density functional theory calculations demonstrate that this hydrogen-bond buttressing is maintained in copper(II) complexes and contributes significantly to their relative stabilities in energy-minimized gas-phase structures. A remarkable correlation between the order of the calculated enthalpies of formation of the copper complexes in the gas phase and the observed strength of the ligands as copper solvent extractants is ascribed to the low solvation energies of species in the water-immiscible phase and/or the similarities of the solvation enthalpies of the preorganized ligand dimers and their copper(II) complexes.
  Inorganic Chemistry 05/2011; 50(10):4515-22. · 4.60 Impact Factor
• Article: Cation and anion selectivity of zwitterionic salicylaldoxime metal salt extractants.

  Ross S Forgan, James E Davidson, Francesca P A Fabbiani, Stuart G Galbraith, David K Henderson, Stephen A Moggach, Simon Parsons, Peter A Tasker, Fraser J White
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  ABSTRACT: 3-Dialkylaminomethyl substituted salicylaldoximes are efficient metal salt extractants, and, in contrast to related "salen"-based reagents, are sufficiently stable to acid hydrolysis to allow commercial application in base metal recovery. Crystal structures show that metal salts are bound by a zwitterionic form of the reagents, with copper(II) nitrate, tetrafluoroborate and trifluoroacetate forming [Cu()(2)X(2)] assemblies in a tritopic arrangement with a trans-disposition of the anions outwith the coordination sphere. Copper(II) chloride, bromide and zinc(II) chloride form 1:1 assemblies, [Cu()X(2)], with the halides in the inner coordination sphere of the metal, leading to high chloride selectivity and very good mass transport efficiencies of CuCl(2). Introduction of the anion-binding sites into the salicylaldoxime extractants changes their cation selectivities; the ligands co-extract small amounts of Fe(III) along with Cu(II) from mixed metal aqueous feed solutions, an issue which will need to be addressed prior to industrial application.
  Dalton Transactions 02/2010; 39(7):1763-70. · 3.84 Impact Factor
• Source

  Available from: ed.ac.uk

  Article: Polyacidic multiloading metal extractants.

  Ross J Gordon, John Campbell, David K Henderson, Dorothy C R Henry, Ronald M Swart, Peter A Tasker, Fraser J White, Jenny L Wood, Lesley J Yellowlees
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  ABSTRACT: Novel polynucleating, di- and tri-acidic ligands have been designed to increase the molar and mass transport efficiencies for the recovery of base metals by solvent extraction.
  Chemical Communications 11/2008; · 6.17 Impact Factor
• Source

  Available from: ed.ac.uk

  Article: Transport of metal salts by zwitterionic ligands; simple but highly efficient salicylaldoxime extractants.

  Ross S Forgan, James E Davidson, Stuart G Galbraith, David K Henderson, Simon Parsons, Peter A Tasker, Fraser J White
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  ABSTRACT: Attaching dialkylaminomethyl arms to commercial phenolic oxime copper extractants yields reagents which transport base metal salts very efficiently by forming neutral 1:1 or 1:2 complexes with zwitterionic forms of the ligands.
  Chemical Communications 10/2008; · 6.17 Impact Factor
• Article: Supramolecular chemistry in metal recovery; H-bond buttressing to tune extractant strength.

  Ross S Forgan, Peter A Wood, John Campbell, David K Henderson, Fiona E McAllister, Simon Parsons, Elna Pidcock, Ronald M Swart, Peter A Tasker
  Chemical Communications 01/2008; · 6.17 Impact Factor
• Article: The binding of phosphonic acids at aluminium oxide surfaces and correlation with passivation of aluminium flake.

  Rachel J Cooper, Philip J Camp, David K Henderson, Paul A Lovatt, David A Nation, Stuart Richards, Peter A Tasker
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  ABSTRACT: Measurements of adsorption isotherms of a series of thirteen mono- and di-phosphonic acids have shown that these bind strongly to the surface of high surface area aluminium trihydroxide. The incorporation of such phosphonates into a suspension of aluminium flake in an aqueous medium, modelling the continuous phase of a water-based paint, greatly suppresses the evolution of hydrogen. Whilst strong binding of the phosphonate to aluminium oxides is an essential criterion for good passivation, other factors such as the hydrophobicity of the ligand are also important in suppressing hydrogen-evolution.
  Dalton Transactions 05/2007; · 3.84 Impact Factor
• Article: The assembly of rotaxane-like dye/cyclodextrin/surface complexes on aluminium trihydroxide or goethite.

  Rachel J Cooper, Philip J Camp, Ross J Gordon, David K Henderson, Dorothy C R Henry, Hamish McNab, Sonali S De Silva, Daniel Tackley, Peter A Tasker, Paul Wight
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  ABSTRACT: Simple azo-dyes carrying phosphonic acid and arsonic acid substituents such as 4-(4-hydroxyphenyl azo)phenylphosphonic acid (5) and 4-(4-hydroxyphenylazo)phenylarsonic acid (6) bind more strongly to high surface area oxides such as aluminium trihydroxide and goethite than their carboxylic and sulfonic acid analogues and the phosphonate-functionalized dyes have been shown to have greater humidity fastness when printed onto commercial alumina-coated papers. Adsorption isotherm measurements provide evidence for the formation of ternary dye/cyclodextrin/surface complexes. Dyes which form such ternary complexes show higher light fastness when printed onto alumina coated papers in an ink formulation containing alpha-cyclodextrin.
  Dalton Transactions 07/2006; · 3.84 Impact Factor
• Article: Attachment of phosphonate-functionalised azo-dyes to oxide surfaces to give enhanced light and wet fastness.

  Sonali S De Silva, Philip J Camp, David K Henderson, Dorothy C R Henry, Hamish McNab, Peter A Tasker, Paul Wight
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  ABSTRACT: Phosphonate-functionalised dyes have been shown to bind strongly to aluminium oxides and to form stable 1:1 complexes with cyclodextrins at the surface.
  Chemical Communications 08/2003; · 6.17 Impact Factor