Biomedical subjects
Publications and source records attributed to Paul G Plieger.
The strength and selectivity of anion-binding by metal salt extractants have been assessed by defining the pH-dependence of anion uptake into a water-immiscible solution of the "metal-only" complexes; high Cl-/SO4(2-) selectivity of transport has been developed.
Zinc metal reduction of the cobalt(III) complex [Co(1,4-bcc)](+) (1,4-bcc = 1,4-bis-carboxymethylcyclam) produces the corresponding cobalt(II) complex which crystallises as the coordination polymer {[Co(1,4-bcc)]ZnCl(2)}(n). A method has been developed for removal of the cobalt(III) ion from [Co(1,4-bcc)](+) and isolation of the free ligand as its hydrochloride salt, H(2)(1,4-bcc).4HCl. This has been used for the preparation of new metal complexes, and the syntheses and characterisation of the copper(ii), nickel(ii), zinc(ii) and chromium(iii) complexes containing the 1,4-bcc ligand are described. X-Ray crystal structures of {[Co(1,4-bcc)]ZnCl(2)}(n).2.5H(2)O, {[Cu(1,4-bcc)]CuCl(2)}(n).0.25MeOH.H(2)O and [Cu(1,4-bcc)H]ClO(4) show the complexes to have the trans(O) geometry of the 1,4-bcc ligand, while the structure of [Cr(1,4-bcc)H(0.5)](ClO(4))(1.5).EtOH exhibits the cis(O) configuration.
The ligand 4,5-dicarboxyimidazole (H(2)DCI) and its methyl derivative 1-methyl-4,5-dicarboxyimidazole (H(2)MDCI) have been shown to bind to Be(II) forming a zwitterionic species that has been structurally characterized. A new dicarboxyimidazole-based polymer has been prepared and its Be-binding properties have been studied using NMR ((1)H and (9)Be) and fluorescence spectroscopy; it represents a rare example of beryllium binding to a polymer. Models of the mononuclear and polymeric Be(II)-binding sites have been studied using density functional theory (DFT), and the (9)Be NMR chemical shifts of these model materials have been calculated for the purpose of direct comparison to experimentally observed values. Differences in the binding modes of the mononuclear and polymeric species are discussed.
The structures of a series of beryllium containing complexes have been optimized at the B3LYP/6-31G(d) level and their (9)Be magnetic shielding values have been determined using B3LYP/6-311G+g(2d,p) and the gauge-including atomic orbital (GIAO) method. The calculated chemical shifts are in excellent agreement with experimental values. The performance of a variety of NMR methods (SGO, IGAIM, CSGT) were also examined but were found to be inferior to the GIAO method at the chosen level of theory employed. The theoretical method has been utilized to predict the beryllium chemical shifts of structurally characterized complexes for which no measured (9)Be NMR spectrum exists, and to investigate a literature complex with an unusual (9)Be NMR chemical shift. A new standard for beryllium NMR in nonaqueous solvents has been suggested.
A bis(pyridine-armed) acyclic Schiff base ligand L1 has been synthesised from 3,6-diformylpyridazine and two equivalents of 2-(2-aminoethyl)pyridine. Reduction of this ligand using NaBH(4) resulted in the formation of the amine analogue L2. Complexes of the form [M(2)L1(mu-X)]Y(2)ClO(4)[where: M = Cu(II), X = OH(-) and Y = ClO(4)(-) 1, Cl(-) 2, Br(-) 3 or I(-) 4; M = Co(II), X = OH(-) and Y = ClO(4)(-) 5; M = Ni(II), X = SCN(-) 6 or X = N(3)(-) 7 and Y = ClO(4)(-)], and [Cu(2)L2(mu-OH)](ClO(4))(3) 8 were prepared and characterised. The complexes 1 and 5-7 have been characterised by single-crystal X-ray diffraction. The acyclic L1 ligand provides three nitrogen donor atoms per metal centre, including a pyridazine bridge between the metal centres, and the anion X also bridges the two metal centres. As required, coordinating solvent molecules or additional anions make up the remainder of the coordination sphere. The two copper centres of 1 are very strongly antiferromagnetically coupled (2J=-1146 cm(-1))via the pyridazine and hydroxide ion bridges, whereas the competing antiferromagnetic pyridazine bridging pathway and ferromagnetic 1,1-bridging azide pathway resulted in the observation of weak antiferromagnetic exchange in the dinickel(II) complex 7 (2J=-14 cm(-1)). Electrochemical examination of L1, L2 and complexes 1 and 5-8 revealed multiple redox processes. These have been tentatively assigned to a mixture of metal centred and ligand centred redox processes on the basis of cyclic voltammetry and coulometry results and comparisons with literature examples.
A new series of meso-substituted diaryl free-base and metalloporphyrins have been prepared. Each arene has been substituted with both a methyl group in the ortho position and a formyl group in the meta position. Rotation of the arene units is prevented at room temperature due to the steric restrictions imposed by the flanking methyl groups at the porphyrin beta-pyrrolic positions on the methyl groups at the ortho position on the meso-substituted arene unit. This allowed the alpha alpha and alpha beta atropisomers of this porphyrin to be separated and characterised. X-Ray crystallographic determination of the structure of the free-base porphyrin revealed a very flat porphyrin core. Metallation resulted in the isolation and characterisation of the nickel, zinc and copper derivatives. The assignments of the alpha alpha and alpha beta isomers are confirmed by X-ray crystallographic determination of the structures of the Cu(II) analogues. The copper alpha alpha structure exhibits a very twisted porphyrin core, the copper alpha beta structure is also distorted, but to a lesser degree. The activation energy for rotation has been calculated for each of the 2H, Ni and Zn derivatives. The energy required to rotate the arene ring increases in the order Ni < Zn approximately 2H. No significant difference in the free energy of rotation was observed between experiments carried out with the alpha alpha and small alpha beta isomers.
10,25-Di-tert-alkyl-14,21-dimethyl-3,6,14,21-tetraazatricyclo[21.3.1.18,12]octacosa-1(27),2,6,8,10,12(28),23,25-octaene-27,28-diol macrocycles form Ni(II) and Cu(II) complexes in which the metal cation and the sulfate anion are bound in separated sites in a zwitterionic form of the ligand. The nonyl-substituted macrocycle shows a higher affinity for SO(4)(2-) and a lower binding strength for Cu(2+) than open chain analogues, the pH-dependences for which fall in ranges which allow loading of CuSO(4) at pH approximately 4 and easy stripping to recycle the ligand. X-Ray structure determinations of the Cu(II) and Ni(II) sulfate complexes of the tert-butyl substituted ligand suggest that the de-tuning of M(2+)-binding results from a distortion from planarity of the "salen" N(2)O(2)(2-) donor set imposed by the incorporation of the hexamethylene strap in the ligand and reveal that the sulfate is bound as a hydrate in a 2:2:2:2, ligand-M(2+)-SO(4)(2-)-H(2)O, assembly.
Structure analysis of the title compound, C(9)H(6)BrNO, has established that bromination of an 8-hydroxyquinoline derivative occurred in the 7-position. Intermolecular and weak intramolecular O-H.N hydrogen bonds are present, the former causing the molecules to pack as hydrogen-bonded dimers in the solid state.
The pH-dependence of simultaneous metal- and sulfate-loading of simple salen derivatives demonstrates the feasibility of their application as extractants for recovery of base metals from the leaching of sulfidic ores. The efficacy of the ligands depends on the templating of the sulfate binding site by the attendant metal ion.