Search

In the present study the interaction of Fe(ii) and Ni(ii) with the related expanded quaterpyridines, 1,2-, 1,3- and 1,4-bis-(5′-methyl-[2,2′]bipyridinyl-5-ylmethoxy)benzene ligands (4–6respectively), incorporating flexible, bis-aryl/methylene ether linkages in the bridges between the dipyridyl domains, was shown to predominantly result in the assembly of [M2L3]4+complexes; although with 4and 6there was also evidence for the (minor) formation of the corresponding [M4L6]8+species. Overall, this result contrasts with the behaviour of the essentially rigid ‘parent’ quaterpyridine 1for which only tetrahedral [M4L6]8+cage species were observed when reacted with various Fe(ii) salts. It also contrasts with that observed for 2and 3incorporating essentially rigid substituted phenylene and biphenylene bridges between the dipyridyl domains where reaction with Fe(ii) and Ni(ii) yielded both [M2L3]4+and [M4L6]8+complex types, but in this case it was the latter species that was assigned as the thermodynamically favoured product type. The X-ray structures of the triple helicate complexes [H2O⊂Ni2(4)3](PF6)4·THF·2.2H2O, [Ni2(6)3](PF6)4·1.95MeCN·1.2THF·1.8H2O, and the very unusual triple helicate PF6−inclusion complex, [(PF6)⊂Ni2(5)3](PF6)3·1.75MeCN·5.25THF·0.25H2O are reported. [ABSTRACT FROM AUTHOR]

As an extension of prior studies involving the linear quaterpyridine ligand, 5,5′′′-dimethyl-2,2′:5′,5′′:2′′,2′′′-quaterpyridine 1, the synthesis of the related expanded quaterpyridine derivatives 2and 3incorporating dimethoxy-substituted 1,4-phenylene and tetramethoxy-substituted 4,4′-biphenylene bridges between pairs of 2,2′-bipyridyl groups has been carried out viadouble-Suzuki coupling reactions between 5-bromo-5′-methyl-2′-bipyridine and the appropriate di-pinacol-diboronic esters using microwave heating. Reaction of 2and 3with selected Fe(ii) or Ni(ii) salts yields a mixture of both [M2L3]4+triple helicates and [M4L6]8+tetrahedra, in particular cases the ratio of the products formed was shown to be dependent on the reaction conditions; the respective products are all sufficiently inert to allow their chromatographic separation and isolation. Longer reaction times and higher concentrations were found to favour tetrahedron formation. The X-ray structures of solvated [Ni2(2)3](PF6)4, [(PF6) ⊂ Fe4(2)6](PF6)7, [Fe4(3)6](PF6)8and [Ni4(3)6](PF6)8have been determined, while the structure of the parent Fe(ii) cage in the series, [(PF6) ⊂ Fe4(1)6](PF6)7, was reported previously. The internal volumes of the Fe(ii) tetrahedral cages have been calculated and increase from 102 Å3for [Fe4(1)6]8+to 227 Å3for [Fe4(2)6]8+to 417 Å3for [Fe4(3)6]8+and to an impressive 839 Å3for [Ni4(3)6]8+. The corresponding void volume in the triple helicate [Ni2(2)3]4+is 29 Å3. [ABSTRACT FROM AUTHOR]

Diastereopure (1R,2R)-N,N′-bis(acetylacetone)cyclohexanedi-imine L1and its corresponding (1R,2R)L1/(1S,2S)L2enantiomeric mixture react with AgNO3to yield the unusual coordination polymer [Ag2(L1)(L2)(NO3)2]n(1) and the unique trimetallic discrete species {[Ag3(L1)3(μ3-O,O,O-NO3)(H2O)3]2(NO3)}(NO3)3·8.5H2O (2) which incorporates a symmetrical μ3-bridging nitrato group that gives rise to a C3-symmetric triskelion motif; both species also feature γ-carbon η1aryl-like coordination of neutral bridging acetylacetone-imine units to the respective Ag(I) centres. [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]

A series of platinum(ii) complexes of the type [Pt(NN)(pyB)2](NO3)2 (NN = bipy, phen; pyB = 3- or 4-pyridineboronic acid) were successfully prepared and fully characterised by 1D- and 2D-multinuclear NMR spectroscopy and ESI-MS. Using VT 1H NMR spectroscopy, rotational isomers for [Pt(NN)(3-pyB)2](NO3)2 were identified and the free energies of activation for rotation of 3-pyB about the Pt–N bond were determined to be ΔG‡310 = 69.2 ± 0.1 kJ mol−1 and ΔG‡305 = 66.0 ± 0.1 kJ mol−1 for [Pt(bipy)(3-pyB)2](NO3)2 and [Pt(phen)(3-pyB)2](NO3)2, respectively. The 3- and 4-pyB ligands readily deboronate in boiling H2O to afford [Pt(NN)(py)2](NO3)2; the structure of [Pt(phen)(py)2]2+ (as its PF6− salt) was confirmed by X-ray crystallography. Preliminary thermal denaturation studies revealed only minimal interactions between [Pt(NN)(pyB)2](NO3)2 and calf-thymus DNA and is attributed to hydroxylation of the boronic acid groups at pH 7.4 to afford the corresponding zwitterionic boronate species. This was confirmed by means of variable pH 1H and 11B{1H} NMR spectroscopy. [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]