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ABSTRACT:A rare discrete mixed-valent heterometallic Fe(III)/Cu(II) cage, [Cu 6 Fe 8 L 8 ](ClO4)12·χsolvent (H 3 L = tris{[2-{(imidazole-4-yl)methylidene}amino]ethyl}amine), was designed and synthesized via metal-ion directed selfassembly with neutral tripodal metalloligands. The formation of this coordination cage was demonstrated by Xray crystallography, ESI mass spectrometry, FT-IR and UV-vis-NIR spectroscopy.The self-assembly of coordination cages has continued to receive considerable attention over the past decade, 1 because of their many potential applications in gas adsorption, 2 drug delivery, 3 catalysis, 4 magnetic materials, 5 host-guest phenomena 6 and synthetic membranes for ion channels. 7 Although a number of coordination cage types have been developed, the design and successful construction of these systems, particularly those with heteronuclear coordination motifs, still represents a significant challenge. 5d,5e,8 Three synthetic procedures have been successfully exploited for the construction of discrete heteronuclear coordination architectures: 1) exploitation of the inherent coordination properties between ligands and different metal ions for the metal-directed assembly of discrete metallosupramolecular architectures; 9 2) formation of discrete metallo-assemblies preorganised for binding a second metal ion, or ions, to yield discrete heterometallic architectures; 10 3) employing preformed metalloligands functionalised for use as building blocks reacting with additional metal ions and sometimes extra ligands. 2b,5c,5e,8b,11 In a recent review, 12 we discussed the employment of planar di-, tri-and oligonuclear platforms, including both homo-and heteronuclear systems, as structural elements for the formation of both discrete and polymeric metallosupramolecular assemblies. As part of our continuing efforts to prepare heterometallic coordination architectures, we reported the synthesis of predesigned hexanuclear Cu II /Ni II metallocycles featuring unprecedented six-node metallocoronand structural motifs 10b and the preparation of a discrete heteronuclear metallomacrocycle (Ag I 3 /Fe II ) by metalion directed self-assembly via a Fe II template. 10aHerein we report an extension of the above studies leading to the construction of a new discrete coordination heterometallic nanocage 1 [Cu 6 Fe 8 L 8 ] (ClO4)12·χsolvent (H 3 L = tris{[2-{(imidazole-4-yl)methylidene}amino]ethyl}amine) enclosing a void space of 277Å 3 . 13 Thus, we have employed a suitable metalloligand together with an additional metal ion (Cu II ) that was anticipated to favour structure-specific selfassembly. A key feature of our design was to employ short organic components that would bridge the different metal ions in a way that would give the potential for magnetic exchange between metal centers. In addition, we have employed a cooperative effect to build a robust metalloligand which can react with additional metal ions to yield a heterometallic cage. To this end we demonstrated that a heterometallic polyhedral cage can be ...

Neutral dimeric metallocyclic complexes of type [M 2 (L 1 ) 2 B n ] (where M = cobalt(II), nickel(II) and zinc(II), L 1 is the doubly deprotonated form of a 1,3-aryl linked bis-b-diketone ligand of type 1,3-bis(RC(O)CH 2 C(O))C 6 H 4 (R = Me, n-Pr, t-Bu) and B is pyridine (Py) or 4-ethylpyridine (EtPy)) have been synthesised, adding to similar complexes already reported for copper(II). New lipophilic ligand derivatives with R = octyl or nonyl were also prepared for use in solvent extraction experiments. Structural, electrochemical and solvent extraction investigations of selected metal complex systems from the above series are reported, with the X-ray ] has been examined. Oxidative processes for the complexes are dominantly irreversible, but several examples of quasireversible behaviour were observed and support the assignment of an anodic process, seen between +1.0 and +1.6 V, as a metal-centred oxidation. The reduction processes for the respective metal complexes are not simple, and irreversible in most cases. Solvent extraction studies (water/chloroform) involving variable concentrations of metal, bis-b-diketone and heterocyclic base have been performed for cobalt(II) and zinc(II) using a radiotracer technique to probe the stoichiometries of the extracted species in each case. Synergism was observed when 4-ethylpyridine was added to the bis-b-diketone ligand in the chloroform phase. Competitive extraction studies show a clear uptake preference for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).

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Synthesis of the 2,2 -dipyridylamine derivatives di-2-pyridylaminomethylbenzene 1, 1,2-bis(di-2-pyridylaminomethyl)benzene 2, 1,3-bis(di-2-pyridylaminomethyl)benzene 3, 2,6-bis(di-2-pyridylaminomethyl)pyridine 4, 1,4-bis(di-2-pyridylaminomethyl)benzene 5, and 1,3,5-tris(di-2-pyridylaminomethyl)benzene 6 are reported together with the single-crystal X-ray structures of 2, 3, and 5. Reaction of individual salts of the type AgX (where X = NO 3 − , PF 6 − , ClO 4 − , or BF 4 − ) with the above ligands has led to the isolation of thirteen Ag(I) complexes, nine of which have also been characterised by X-ray diffraction. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a range of coordination arrangements. A series of liquid-liquid (H 2 O/CHCl 3 ) extraction experiments of Ag(I) with varying concentrations of 1-6 in the organic phase have been undertaken, with the counter ion in the aqueous phase being respectively picrate, perchlorate and nitrate. In general, extraction efficiencies for a given ionophore followed the Hofmeister order of picrate > perchlorate > nitrate; in each case the tris-dpa derivative 6 acting as the most efficient extractant of the six systems investigated. Competitive seven-metal bulk membrane transport experiments (H 2 O/CHCl 3 /H 2 O) employing the above ligands as the ionophore in the organic phase and equimolar concentrations of Co(II), Ni(II), Zn(II), Cu(II), Cd(II), Pb(II) and Ag(I) in the aqueous source phase were also undertaken, with transport occurring against a pH gradient. Under the conditions employed 1 and 5 yielded negligible transport of any of the metals present in the source phase while sole transport selectivity for Ag(I) was observed for 2-4 and 6.

The interaction of Cu(II) with the following secondary N-substituted derivatives of di(2-picolyl)amine () are reported: N-cyclohexylmethyl-di(2-picolyl)amine (), N-benzyl-di(2-picolyl)amine (), N-(4-pyridylmethyl)-di(2-picolyl)amine (), N-(4-carboxymethylbenzyl)-di(2-picolyl)amine (), N-(9-anthracen-8-ylmethyl)-di(2-picolyl)amine (), 1,3-bis[di(2-picolyl)aminomethyl]benzene (), 1,4-bis[di(2-picolyl)aminomethyl]benzene () and 2,4,6-tris[di(2-picolyl)amino]triazine (). The solid complexes [Cu()(micro-Cl)](2)(PF(6))(2), [Cu()(micro-Cl)](2)(PF(6))(2).0.5CH(2)Cl(2), Cu()(ClO(4))(2), Cu()(2)(ClO(4))(2), [Cu()(ClO(4))(2)(H(2)O)].0.5H(2)O, Cu(2)()(ClO(4))(4), [Cu(2)()(Cl)(4)] and [Cu(2)(+H)(micro-OCH(3))(2)(H(2)O)](ClO(4))(3).C(4)H(10)O were isolated and X-ray structures of [Cu()(micro-Cl)](2)(PF(6))(2), [Cu()(micro-Cl)](2)(PF(6))(2).0.5CH(2)Cl(2,) [Cu()(2)(ClO(4))(2)(H(2)O)].0.5H(2)O, [Cu(2)()Cl(4)] and [Cu(2)(+H)(micro-OCH(3))(2)(H(2)O)](ClO(4))(3).C(4)H(10)O were obtained. The series is characterised by a varied range of coordination geometries and lattice architectures which in the case of [Cu()(ClO(4))(2)(H(2)O)].0.5H(2)O includes a chain-like structure formed by unusual intermolecular pi-interactions between metal bound perchlorate anions and the aromatic rings of adjacent anthracenyl groups. Variable temperature magnetic susceptibility measurements have been performed for [Cu()(micro-Cl)](2)(PF(6))(2) and [Cu()(micro-Cl)](2)(PF(6))(2).0.5H(2)O over the range 2-300 K. Both compounds show Curie-Weiss behaviour, with the data indicating weak antiferromagnetic interaction between the pairs of copper ions in each complex. Liquid-liquid (H(2)O/CHCl(3)) extraction experiments involving and as extractants showed that, relative to the parent (unsubstituted) dipic ligand , substitution at the secondary amine site in each case resulted in an increase in extraction efficiency towards Cu(II) (as its perchlorate salt); at least in part, this increase may be attributed to the enhanced lipophilicities of the N-substituted derivatives.

The interaction of Cu(II) with three β-diketone ligands of type R 1 C(O)CH 2 C(O)R 2 (where R 1 = 2-, 3-, or 4-pyridyl and R 2 = C 6 H 5 , respectively), HL 1 -HL 3 , along with the X-ray structures and the pK a values of each ligand, are reported. HL 1 yields a dimeric complex of type [Cu(L 1 ) 2 ] 2 . In this structure, two deprotonated HL 1 ligands coordinate in a trans planar fashion around each Cu(II) center, one oxygen from each CuL 2 unit bridges to an axial site of the second complex unit such that both Cu(II) centers attain equivalent five-coordinate square pyramidal geometries. The two-substituted pyridyl groups in this complex do not coordinate, perhaps reflecting steric factors associated with the closeness of the pyridyl nitrogen to the attached (conjugated) β-diketonato backbone of each ligand. The remaining two Cu(II) species, derived from HL 2 and HL 3 , are both coordination polymers of type [Cu(L) 2 ] n in which the terminal pyridine group of each ligand is intermolecularly linked to an adjacent copper center to generate the respective infinite structures. HL 2 was also demonstrated to form a fibrous metallogel when reacted with CuCl 2 in an acetonitrile/water mixture under defined conditions.

Bis-pyridylimine ligands with different linking elements are capable of forming unique hexanuclear circular Cu(II) meso-helicates; the self-assembly is controlled by coordination of sulfate ions to the metal centres.