Competitive transport, extraction and coordination chemistry of a number of ligands with selected transition and post-transition metal ions

[摘要] The competitive transport, extraction, and coordination chemistry for a series of N-(thio)phosphorylated (thio)amide and N-(thio)phosphorylated (thio)urea ligands wereinvestigated with the seven transition and post-transition metal ions Co(II), Ni(II),Cu(II), Zn(II), Ag(I), Cd(II) and Pb(II). Three N-benzylated derivatives of 1,4,7,10-tetraazacyclododecane (cyclen) were synthesized and a similar study carried out withthe same metal ions and the deprotonated precursors. The ligands were all potentialspecific carriers (ionophores) in the organic phase. The seven metal ions had equalconcentrations in the source phase.The experimental arrangement for the transport studies employed a set-up involvingthree phases: a source phase and a receiving phase (both aqueous), separated by achloroform membrane (organic phase). Competitive metal ion solvent extractioninvolved two phases: an aqueous phase and an organic phase. Similar conditionswere used in transport and extraction studies. The metal ion concentrations in theaqueous phases were analyzed by atomic absorption spectroscopy (AAS).The transport results of deprotonated N-(thio)phosphorylated (thio)amides and N-(thio)phosphoryated (thio)ureas showed that PhC(S)NPO(OPri)2 (L1),BrPhC(S)NPO-(OPri)2 (L11) and PriNHC(S)NPO(OPri)2 (L16) transported Ag(I) intothe receiving phase. Under these experimental conditions, L1 had the highest Ag(I)transport efficiency, at 36.3%, while L11 only transported one metal ion, viz. Ag(I).With NH2C(S)NP(S)(OPri)2 (L4), 94.6% of Ag(I) remained in the membrane phase.Thus L4 appeared to have the highest formation constant with Ag(I). A small amountof Cu(II) was also transported by L1, NH2C(S)NP(O)(OPri)2 (L9), L16 andButNHC(S)-NPO(OPri)2 (L20). L20 had the highest selectivity for Cu(II).Results of competitive metal ion extraction studies revealed that most ligandsextracted up to 100% Ag(I), except L1 and morpholine substituted ligands (L7, L17) .The formation constant of L1 effects a subtle balance between metal uptake andmetal loss into and out of the respective membrane phase. HL7 and HL17 had lowsolubility in chloroform. L4 extracted the highest percentage of Cu(II) (49%).Two neutral ligands, PhCONHPO(OPri)2 (1) and BrPhCONHPO(OPri)2 (2) wereisolated and their molecular structure determined. They had monoclinic unit cells in the space groups C2/c and P21/n, respectively. An unprecedented octanuclear[Ag(I)(L4-S,N)]8 (3) complex was also crystallized. The extended structure showedthree different cavities alternating with two unique 16-membered rings, creating anovel AgS2N2 cage. Two polynuclear Cu(I) chelates with deprotonated L4 and L6(tBuNHC(S)NP(S)(OPri)2) were isolated by the same crystallization method. Thecomplex [Cu(I)(L4–S,S)]9 (4) consisted of a hexagonal-prismatic hexamer, whichexhibited an unusual and unprecedented supramolecular 'honeycomb packing. Thetrinuclear [Cu(I)(L6–S,S)]3 (5) consisted of a 6-membered Cu3S3 ring attached to ahydroxy tetrahydrofuran molecule.Di-, tri- and tetra-benzyl-1,4,7,10-tetraazacyclododecane (cyclen) was synthesized,and characterized. None of these compounds was effective in metal transport underthese experimental conditions. Nevertheless, Tetra-benzyl cyclen showed thehighest extraction efficiency for Ag(I), at 100%, and the highest selectivity for Ag(I)extraction, compared to Cu(II).An intermediate of dibenzyl cyclen compound dibenzylated dioxocyclen (6) wascrystallized and found a host THF molecule in the lattice. The crystal and molecularstructure confirmed the cis-configuration. The X-ray structure of the Cu(II) complexwith dibenzylated cyclen (7) was determined for the first time. It was found to havean ideal square pyramidal coordination geometry around the central metal ion.A serendipitous organic compound of isopropylammonium(isopropylamino)-oxoacetate mono-hydrate (8) was crystallized. The crystal was held together byinter-molecular hydrogen bonds, which lead to two-dimensional layers withhydrophobic interactions.

[发布机构] Stellenbosch University