A study of the transport, extraction and co-ordination chemistry of a number of thiourea ligands with a series of transition and post-transition metal ions

[摘要] ENGLISH ABSTRACT: In this study, a number of mono- and di-substituted acyl(aroyl)thioureas were investigatedfor potential application as specific carriers (ionophores) for the transport and extraction ofAg(l) from a mixture of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(lI) ions. The experimentalarrangement for the transport experiments employed a liquid membrane set up involving a3-phase system - 2 aqueous phases (source and receiving phase) separated by achloroform membrane incorporating the ligand. Competitive metal ion transportexperiments were conducted using the liquid membrane set up. The aqueous source andreceiving phases were analyzed using Atomic Absorption Spectroscopy (AAS) and resultswere confirmed by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICPOES).The transport results show that the N,N-dialkyl-substituted-N'-acyl(aroyl) (HL)thioureas studied, with the exception of the N,N-di-(2-hydroxyethyl)-N'-benzoylthiourea(HL3) and N-piperidyl-N'-4-nitrobenzoylthiourea (HL9), were efficient and selective for Ag(I).HL9 was also selective for Ag(l) but not efficient. HL3 was selective for Cu(II). Under theexperimental conditions employed, 13% Cu(lI) was transported by HL3. Among the N,Ndialkyl-N'-aroylthioureas, maximum Ag(l) transport was obtained by using N,N-diethyl-N'-4-chlorobenzoylthiourea (HL5) and N,N-di-n-butyl-N'-benzoylthiourea (HL \ Under theexperimental conditions employed, the percentages of Ag(l) transported by HL5 and HL 1were 48% and 42% respectively.The transport selectivity and efficiency of 3,3,3' ,3'-tetraethyl-1 ,1'-isophthaloylbisthiourea(H2L12) and N,N-diethyl-N'-camphanoylthiourea (HL13)for Ag(l) were also studied. We wereparticularly interested, in comparing the Ag(l) transport and extraction efficiency of theseligands with that of the HL and H2L ligands. The experimental results reveal that, of all theligands we investigated in this study, HL 13 was the most efficient and selective carrier forAg(l) transport. The interesting result is that, depending on the ligand concentration used,HL 13 transported 71-81% of Ag(I).Competitive two-phase metal ion solvent extraction experiments were also performedunder conditions similar to the transport studies. The results show that by varying theligand concentration in the membrane phase, up to 100% Ag(l) can be selectively andefficiently extracted from the mixture of the seven metal ions. Finally, the N,N-di-(n)-butyl-N'-benzoylthiourea (HL1) ligand and its complex with Ag(l)were synthesized. Single crystals of the complex were grown for X-ray crystallography andthe crystal and molecular structure of the complex was determined. The crystal structureshowed that Ag(l) is bonded to the deprotonated ligand through the S,O atoms forminginteresting cluster [Ag (L - S, 0)] 4 in the solid state. This structure is monoclinic andcrystallizes in the space group P21!c with a = 17.805 (4) A, b = 21.759 (4) A, c =36.438 (7) A, f3= 96.34(3)°, Z = 8 and a final R-factor of 5.4%.

[发布机构] Stellenbosch University