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The binding and extraction of Ag(i) by tripodal Schiff-base ligands incorporating different aromatic podand arms are reported. These ligands have been synthesized by condensation of tris(2-aminoethyl)amine with benzaldehyde (1), 4-phenylbenzaldehyde (2), 2- (3) and 4-pyridinecarbaldehyde (4). The structures of 1and of four Ag(i) complexes [Ag(1)]ClO4, [Ag(2)]ClO4, [Ag3(3)2](ClO4)3and {[Ag3(4)2](ClO4)3}nhave been determined by single crystal X-ray diffraction. The structure of 1shows intramolecular C–Hπ (aromatic) interactions between phenyl rings, while bonding of Ag(i) viaAg–N interactions within the ionophore pocket is confirmed. In [Ag(1)]ClO4, and [Ag(2)]ClO4additional long-range Ag–H interactions are observed, while π–π stacking occurs in the polynuclear species [Ag3(3)2](ClO4)3and {[Ag3(4)2](ClO4)3}n. Potentiometric titration, liquid–liquid extraction and 1H NMR spectroscopic studies were performed to probe the nature of the silver complexes in solution. Potentiometric studies confirm increasing complex stability with Ag(i) in the order 2< 4< 1< 3, and enhanced Ag(i) extraction efficiency was observed with both increasing lipophilicity of the ionophore and the presence of additional donor groups. 1H NMR spectroscopic studies were employed to probe the solution complexation behaviour of 1–4towards Ag(i) and these confirm the formation of primarily 1 : 1 Ag : L complexes in solution. [ABSTRACT FROM AUTHOR]

Uncharged complexes, formulated as trimeric metallocycles of type [M3(L1)3(Py)6] (where M = cobalt(ii), nickel(ii) and zinc(ii) and L1 is the doubly deprotonated form of a 1,4-phenylene linked bis-β-diketone ligand of type 1,4-bis(RC(O)CH2C(O))C6H4 (R = t-Bu)) have been synthesised, adding to related, previously reported complexes of these metals with L1 (R = Ph) and copper(ii) with L1 (R = Me, Et, Pr, t-Bu, Ph). New lipophilic ligand derivatives with R = hexyl, octyl or nonyl were also prepared for use in solvent extraction experiments. The X-ray structures of H2L1 (R = t-Bu) and of its trinuclear (triangular) nickel(ii) complex [Ni3(L1)3(Py)6]·3.5Py (R = t-Bu) are also presented. Electrochemical studies of H2L1, [Co3(L1)3(Py)6], [Ni3(L1)3(Py)6], [Cu3(L1)3], [Zn3(L1)3(Py)6] and [Fe4(L1)6] (all with R = t-Bu) show that oxidative processes for the complexes are predominantly irreversible, but several examples of quasireversible behaviour also occur and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as involving metal-centred oxidations. The reduction behaviour for the respective metal complexes is not simple, being irreversible in most cases. Solvent extraction studies (water/chloroform) involving the systematic variation of the metal, bis-β-diketone and heterocyclic base concentrations have been performed for cobalt(ii) and zinc(ii) using a radiotracer technique in order to probe the stoichiometries of the respective extracted species. Significant extraction synergism was observed when 4-ethylpyridine was also present with the bis-β-diketone ligand in the chloroform phase. Competitive extraction studies demonstrated a clear uptake preference for copper(ii) over cobalt(ii), nickel(ii), zinc(ii) and cadmium(ii). [ABSTRACT FROM AUTHOR]

The synthesis and crystal structure of a new 34-membered N6O4-donor macrocycle 2 is reported. Solvent extraction experiments (water/chloroform) indicated that 2 acts as an efficient extractant towards silver(i) and zinc(ii) at pH values beyond 6 while the extraction of iodide and chromate occurs below this pH. A competitive metal extraction experiment at pH 7.2 in which the perchlorate salts of cobalt(ii), nickel(ii), copper(ii), zinc(ii) and cadmium(ii) were present together in the aqueous phase led to the following order of increasing extraction efficiency: cobalt(ii) < nickel(ii) < zinc(ii) < copper(ii) ∼ cadmium(ii). A substantial synergistic enhancement of zinc(ii) salt extraction was observed for a dual-host extraction system using the macrocycle 2 as cation binder and the tripodal thiourea ligand 3 as anion receptor; in particular, a notable extraction of zinc(ii) sulfate was obtained. [ABSTRACT FROM AUTHOR]

Uptake of a tetrafluoroborate anion into the centre of a dicopper bis-salicylaldoxime complex causes a major contraction of the cavity and an increase in helicity. [ABSTRACT FROM AUTHOR]

A new metallo-capsule has been synthesised that consists of three copper(ii) ions and two molecules of a tris-deprotonated tripodal ligand in which three 2,4-pentanedione groups are linked via their γ-carbons through thioether spacers to the 1,3,5-positions of a triazine core. [ABSTRACT FROM AUTHOR]