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A range of morphologically distinct metallosupramolecular Cu(II) and Pd(II) complexes has been constructed, based on the tritopic ligand 1,1',1″-(benzene-1,3,5-triyl)tris(4,4-dimethylpentane-1,3-dione) (H). By control of the reaction conditions, it is possible to generate distinct coordination assemblies possessing either macrocyclic or polymeric structures and more importantly distinct activity in catalysis of the Suzuki-Miyaura cross-coupling.

The synthesis and crystal structures of a series of Ln(III) (Ln = Gd, Nd, Yb as well as Y) complexes of a bis-β-diketone ligand incorporating a 1,3-substituted phenyl ring between its two β-diketone domains (1,1′-(1,3-phenylene)bis(4,4-dimethylpentane-1,3-dione), H2L1) is reported. The crystal structures show the complexes are seven coordinate in the solid state with the general formula [Ln2L13(solvent)2]. The photophysical properties of the complexes were explored in both solution and the solid state, which show an increase in coordination number in solution.

Two of the most successful strategies for the preparation of three-dimensional coordination polymers and MOFs are reticular synthesis and pillaring. Here we present a new approach which combines aspects of both of these by employing a heterofunctional dicarboxylic and dipyridyl ligand, 2,5-di(pyridin-4-yl)terephthalic acid (H2L). The reaction of H2L with zinc(II) produces a non-interpenetrated 3D coordination polymer [ZnL(H2O)]n.

ion of a pyridine ligand from Weiss’ reagent ([PhI(Pyr)2]2+) using BF3-Et2O was found to activate Weiss’ reagent towards electrophilic aromatic substitution reactions. The activated species can be isolated when 4-DMAP is used as the pyridine ligand and was determined to be a [PhI(4-DMAP)]2+ in solution, and is associated with a triflate counterion in the solid state. The isolated cation was reactive in electrophilic aromatic substitution reactions towards mesitylene, xylene and toluene that Weiss’ reagent itself does not react with. If pyridine is used as the ligand the intermediate that results from abstraction cannot be isolated but is even more active, being observed to react with benzene.

An extended nitro-functionalised 1,2,4-triazole ligand has been used to induce considerable lattice distortion in a 2-D Hofmann framework material via competing supramolecular interactions. Single crystal X-ray diffraction analyses on [Fe3(N-cintrz)6(Pd(CN)4)3]·6H2O (N-cintrz: (E)-3-(2-nitrophenyl)acrylaldehyde) reveal a substantial deviation from a regular Hofmann structure, in particular as the intra- and inter-layer contacts are dominated by hydrogen-bonding interactions rather than the typical π-stacking arrays. Also, the 2-D Hofmann layers show an assortment of ligand conformations and local FeII coordination environments driven by the optimisation of competing supramolecular contacts. Temperature-dependent magnetic susceptibility measurements reveal a two-step spin crossover (SCO) transition. Variable temperature structural analyses show that the two crystallographically distinct FeII centres, which are arranged in stripes (2 : 1 ratio) within each Hofmann layer, undergo a cooperative HS ↔ HS/LS ↔ LS (HS = high spin, LS = low spin) transition without periodic spin-state ordering. The mismatch between crystallographic (2 : 1) and spin-state (1 : 1) periodicity at the HS : LS step provides key insight into the competition (frustration) between elastic interactions and crystallographically driven order.

In this study, a hydroxyl-rich Schiff base ligand, H4L, and its resulting complexes with ZnCl2, Zn(CH3COO)2 and Zn(ClO4)2 were explored. Interestingly, depending on the zinc salt and/or the crystallisation method, four unique structures were obtained. A synthesis with ZnCl2 gave 1, a mononuclear structure ((H3L)2Zn), while with Zn(CH3COO)2, a trinuclear system [(H3L)2Zn3(CH3COO)4], 2, was found. Interestingly two multinuclear architectures were observed with Zn(ClO4)2. Firstly, diethyl ether diffusion of a methanolic reaction mixture with minimal atmospheric air volume gave 3, a hexanuclear architecture of the type [(H2L)4(H3L)2Zn6](ClO4)2, while slow evaporation of a similar mixture gave 4, a nonanuclear architecture with the formula [(H2L)6Zn9(CO3)2](ClO4)2. Compound 4 unexpectedly fixed atmospheric CO2 as CO32−, incorporating it into the architecture. As expected, a diethyl ether diffusion with a larger volume of air (∼100 mL) of a similar methanolic reaction mixture gave a mixture of 3 and 4. In addition, bulk samples of all compounds were also investigated by PXRD, and results are in good agreement with the observed single crystal data. Furthermore, complexes 1–4 were characterised using FT-IR and simultaneous thermal analysis (STA), and additionally the photophysical properties of H4L and complexes 1–4 have also been explored.

A bis-β-diketone ligand incorporating a 3,5-substituted pyridine ring between its two β-diketone domains (1,1′-(pyridine-3,5-diyl)bis(4,4-dimethylpentane-1,3-dione), H2L1) and its interaction with three divalent cations (Cu2+, Zn2+ and Pd2+) is reported. Charge neutral dinuclear metallocycles of type [M2L12] were obtained in each case and their X-ray structures determined. [Pd2L12] incorporates two square-planar O4-coordinated metal centres. The zinc(II) and copper(II) complexes contain five-coordinate O4N1-metal centres in which the pyridyl nitrogen from adjacent [M2L12] metallocycles coordinates apically forming two-dimensional coordination polymers of type {[Zn2L12]n(dmf)n} and {[Cu2L12]n(dmf)n}. Desolvation of the coordination polymers led to loss of crystallinity.

Classical β-diketone ligands have been well demonstrated to exhibit a rich metal coordination chemistry yielding metal complexes displaying a variety of properties. The investigation of polydentate ligand derivatives containing more than one β-diketone domain, and in many instances also incorporating additional donor sites, have been demonstrated to react with a range of metal ion types to yield a wide range of metallo-supramolecular topologies. These include metallocyclic platforms, triangles, squares, cubes, helicates, tetrahedrons as well as other intricate structures that include a universal 3-ravel. In this report we cover the published literature in the area from 2008 with emphasis on the synthetic strategies employed as well as on the diverse structures of the metallo-supramolecular products obtained.

This paper presents the synthesis of a tripodal ligand (H3L) via the Schiff base condensation of N,N-diethylsalicylaldehyde and tris(2-aminoethyl)amine. The neutral complexes of type [EuL], [GdL] and [DyL] were synthesized and characterized by FT-IR, SEM-EDS, PXRD, single crystal X-ray diffraction, CHN analysis and high resolution ESI-MS. X-ray crystallographic studies demonstrated that the heptadentate ligand incorporating a cavity pre-organized by hydrogen bonding binds the Ln(iii) ions to yield a face capped octahedral coordination geometry with three-fold symmetry. Photoluminescence studies show a typical Ln(iii) absorption character for the three complexes, with [EuL] demonstrating considerably stronger lanthanide-based luminescence peaks, and a Eu(iii) centered luminescence lifetime of 0.144 ± 0.01 ms. Temperature/field-dependent DC and temperature/frequency-dependent AC magnetic measurements carried out for the Dy(iii) complex indicated obvious magnetic anisotropy and suggested slow relaxation behaviour with considerable quantum tunnelling of the magnetization contribution.

A series of Fe(III) complexes of β-diketonate ligands, 1-(2-pyridyl)-3-(3-pyridyl)-1,3-propanedione (L1), 1-(2-pyridyl)-3-(2-pyridyl)-1,3-propanedione (L2), 1-(2-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L3), 1-(3-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L4), 1-(3-pyridyl)-3-(3-pyridyl)-1,3-propanedione (L5) and 1-(4-pyridyl)-3-(4-pyridyl)-1,3-propanedione (L6), viz. [Fe(L1)3] (1), [Fe(L2)3] (2), [Fe(L3)3] (3), [Fe(L4)3] (4), [Fe(L5)3] (5) and [Fe(L6)3] (6) have been structurally characterized. All but one complex (1) catalyzed the ring-opening polymerization (ROP) of e-caprolactone (e-CL) in near quantitative yield at 110 °C to give polymers with relatively narrow polydispersities (PDI). The comparison of in situ reaction and a reaction with preformed 1 indicated that the latter was a better catalyst, giving a higher molecular weight. Complex 2 catalyzed this reaction in a more modest yield reflecting its greater thermal stability, shorter Fe–O bonds and minimal distortion in fold angle among the isomeric complexes, suggesting that ligand dissociation is important for catalytic activity.

A large discrete face-capped tetranuclear iron(II) cage, [Fe4L4](BF4)8·n(solvent), was synthesised via metal-ion directed self-assembly. The cage is formed from a rigid tritopic ligand that incorporates chelating imidazole-imine functional groups. The cage displays temperature induced spin-crossover and LIESST effects and is amongst the largest iron(II) tetrahedral cages with such properties reported. The synthesis, structure and magnetic properties of this new metallo-cage are presented.

A series of five coordination compounds, namely, {[Co3(stp)2(bipy)(H2O)4]·2H2O}n, (1), {[Co3(stp)2(bipy)5(H2O)6]·4H2O}n, (2), [Co3(stp)2(bipy)4(H2O)10]·8H2O, (3), [Co(Hstp)2(Hbipy)2], (4) and {[Co(stp)2(H2O)2][Co(bipy)2(H2O)4]}·2Hbipy·2H2O, (5) have been synthesised hydrothermally, through the reaction of different molar ratios of 2-sulfoterephthalic acid monosodium salt, Na(H2stp), cobalt(II) nitrate hexahydrate and the N-donor ancillary co-ligand 4,4′-bipyridine (bipy). Due to the combination of the multiple potential coordination modes of the stp ligand and the bipy co-ligand, the products are structurally and topologically diverse with the connectivities of the materials dependent on the ratios of starting materials employed. Single-crystal X-ray diffraction studies show that compound 1 is a three-dimensional coordination polymer, compound 2 consists of infinite one-dimensional zig-zag chains, compound 3 is a discrete trinuclear complex, compound 4 is a discrete mononuclear complex and compound 5 is an ionic solid consisting of both cobalt containing cations and anions. Magnetic studies show that the Co(II) ions in 1 are strongly coupled, while 2, 3 and 5 show insignificant coupling due to larger metal–metal separations. Modelling required the introduction of zero field splitting parameters due to orbital angular momentum contributions in these cases.

Molecular switches have many potential applications in nanoscience and biomedicine. Transition metal complexes that can be switched from an inert, unreactive state to a catalytically active one by a simple change in conditions (e.g. pH shift) or by binding to a specific biomolecular target – so-called target-activated metal complexes (TAMCs) – hold particular allure as a means of harnessing the potent but at times indiscriminate reactivity of metal-based drugs. Towards this goal, we have prepared a series of ten structurally related ligands each of which bears a different pendant side-arm functional group off a common macrocyclic core. Copper(II) and nickel(II) complexes of these cyclam-based ‘molecular scorpionands’ have been prepared and characterised. X-ray crystal structures reveal a variety of binding modes between pendant side-arm and metal centre. Amine and triazole side-arms generally coordinate to the metal in the solid state via the pendant nitrogen atom, while carbonyl-containing side-arms (amide, urea, carbamate) and sulfonamide ligands either coordinate via their oxygen atoms, or do not coordinate to the metal. To investigate the switchability of side-arm coordination in solution, spectrophotometric pH titrations were carried out for all 20 metal complexes. Where pH changes trigger a change in the side-arm coordination and thence spectroscopic behaviour, pKa values have been calculated. Of the 20 complexes investigated, the majority undergo spectroscopic changes that are consistent with a switch in pendant coordination state at a specific pH. This ‘coordination switching’ is seen across a wide pH range with the different side-arm functionalities: four complexes (side-arm amines) have pKas at acidic pH (3.5–5), two (side-arm sulfonamides) around neutral pH (6–7.5), and six (side-arm amides, ureas and carbamates) at basic pH (10–13). Six complexes maintain their coordination state (bound or not bound) over the full pH range tested (2–13), while the remaining two undergo spectroscopic changes at high pH that are consistent with a change in protonation of a metal-bound water ligand. This ligand series represents a comprehensive model platform from which to build pH-switchable metal complexes for applications in nanoscience and biomedicine. We thank Emeritus Professor Leonard Lindoy (The University of Sydney) and Professor Marcel Maeder (The University of Newcastle) for helpful discussions. We thank the Australian Research Council (DP120104035) for funding, and The University of Sydney and Australian Government for financial support via an Australian Postgraduate Award to YHL. JKC acknowledges the support of the Australian Research Council.

The synthesis of the extended dipyridyl ligand 4,4′-(2,5-dimethyl-1,4-phenylene)dipyridine (L) in an improved yield via the palladium catalysed Suzuki coupling of 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (1) and 1,4-dibromo-2,5-dimethylbenzene (2) is reported along with its use to form a two-dimensional coordination polymer [Co2L2(OAc)4(H2O)2]n. The coordination polymer consists of one-dimensional chains of octahedral cobalt ions bridged by acetate ligands which are connected to form two dimensional sheets with square lattice (sql) topology via the dipyridyl ligands (L). The structure contains small voids totalling ~6.6% of the unit cell volume. The crystal structures 1, L, L·2H2O, and L·2HNO3 are also reported.

The di-topic terpy/dpa hybrid ligand, 4′-{4-[bis(2-pyridyl)aminomethyl]phenyl}-2,2′:6′,2′′-terpyridine (L), incorporating both 2,2′:6′,2′′-terpyridine (terpy) and 2,2′-dipyridylamino domains has been synthesised. The metal complexes [CoLCl2], [ZnLCl2], [ZnL(CH3CO2)2], [Fe(L)2(PF6)2] and [Fe(L)(HL)](PF6)0.5(ClO4)2.5 have been isolated. X-ray structures of all five structures show that the respective metal ions preferentially bind to the terpy site of L, with the dpa site in the first four complexes remaining empty. In the fifth complex, which was isolated following the attempted reaction of silver perchlorate with [Fe(L)2(PF6)2], one dpa site is protonated. The crystal packing of all these species is dominated by extensive π-interactions. The 5-coordinate zinc(II) and cobalt(II) complexes are isostructural and exhibit a 3D network of interactions involving π-stacking as well as CH⋯Cl and CH⋯N hydrogen bonding. Similar interactions occur in the packing of [ZnL(CH3CO2)2] and [Fe(L)(HL)](PF6)0.5(ClO4)2.5 giving rise to 3D arrays. Reaction of palladium(II) with L yields a product of stoichiometry Pd2LCl4 for which the evidence suggests that palladium binds at both the terpy and dpa domains. Based on this result, addition of [Pd(CH3CN)2Cl2] to [Fe(L)2](PF6) in acetonitrile yielded a heterometallic complex in which the “free” dpa sites of [Fe(L)2](PF6) are now occupied by palladium ions to form a heterometallic product of type [FePd2(L)2Cl4](PF6)2·1.5CH3CN.

A rigid organic ligand, formed through the subcomponent self-assembly of p-toluidine and 6,6'-diformyl-3,3'-bipyridine, was employed in a systematic investigation into the synergistic and competing effects of metal and anion templation. A range of discrete and polymeric metal-organic complexes were formed, many of which represent structure types that have not previously been observed and whose formation would not be predicted on taking into account solely geometric considerations. These complex structures, capable of binding multiple guests within individual binding pockets, were characterized by NMR, ESI-MS, and single-crystal X-ray diffraction. The factors that stabilize individual complexes and lead to the formation of one over another are discussed.

A comparison of the interaction of Zn(II), Cd(II), Ag(I) and Pb(II) with a matrix of 18, 17-membered, dibenzo-substituted macrocyclic ligands (1–18) incorporating nitrogen, oxygen and/or sulfur heteroatom sites that share the same carbon backbone is reported. Potentiometric log K data for complexes of these metals with 5, 6, 8 and 9 incorporating unsymmetric arrangements of their donor sets were obtained and the results compared with previously determined stability data for the remaining symmetrical and unsymmetrical ligand complexes forming the above matrix. Structure–function relationships underlying the relative magnitudes of the respective log K values are discussed, with emphasis given to the influence of both the donor atom set and the donor atom sequence on the nature of the resulting complexes. The X-ray structures of [CdL(NO3)] (NO3)·CH3CH2OH (L = 4, SN4 donor set), [CdL(NO3)2]·CH3OH (L = 7, ON4 donor set), [AgL]PF6 (L = 4, SN4 donor set) and [AgL]PF6 (L = 9, OSN3 donor set) are presented along w...

Five new silver(I) coordination polymers of types [Ag2L1(NO3)2]n (1), [Ag2L2(NO3)2]n (2), [Ag2L3(NO3)2]n (3), [Ag2L4(NO3)2]n (4), and [AgL5(NO3)]n (5) have been synthesized, where L1–L5 are the Schiff base ligands formed from 2:1 condensation of acetylacetone with the symmetrical diamines H2N(CH2)nNH2, with n = 2 and 6 to give L1 and L2, 1,2-bis(2-aminophenoxy)ethane to give L3, 1,4-bis(2-aminophenoxy)butane to give L4, and 1,6-bis(4-aminophenoxy)butane to give L5. The single crystal X-ray structures of the Ag(I) complexes 1–5 have been determined. Both 1 and 2 adopt three-dimensional polymeric network structures, while 3–5 adopt two-dimensional-layered framework structures. In 1 and 2, the terminal O and γ-C atoms of two acacH-imine domains of the same ligand bind to different silver ions, while in each of 3–5 a γ-C from one or both acacH-imine domains binds to a silver ion, with the remaining coordination sites occupied by bridging monodentate or bidentate nitrato groups and/or a Schiff base ligand oxyg...

Employing N,N′-bis-(4-pyridinylmethylene)-1,5-naphthalenediamine (nbpy4) and iron(II) thiocyanate as building blocks, three coordination polymers, [Fe(NCS)2(nbpy4)(MeOH)2]n,1, [Fe(NCS)2(nbpy4)2]n·2nCHCl3·nH2O·2nEtOH, 2, and [Fe(NCS)2(nbpy4)(bpy)]n·2.5nDCM·0.75nH2O, 3, have been prepared. The three metal–organic materials were prepared by varying the solvent systems used and the inclusion of a second pyridine containing ligand (4,4′-bipyridine, bpy). Single crystal X-ray diffraction revealed 1 to be a one-dimensional structure with hydrogen bonding between adjacent chains and 2–3 to be two-dimension network solids with (4,4)-topologies.

4,4′-biphenylene spaced lipophilic bis-β-diketone ligands of the type 4,4′-bis(RC(O)CH2C(O))C12H8 (R = Pr, Ph, hexyl, octyl, nonyl) have been prepared and used for the liquid–liquid extraction of d-block metal ions. These ligands are expected to interact with divalent metal ions to form charge-neutral trinuclear metallocycles of type [M3(L3)3(solvent)] as has been demonstrated with the previously reported derivative of H2L3 (R = tBu), the X-ray structure of which is reported. Liquid–liquid extraction studies were performed in a two-phase water/chloroform system employing a radiotracer technique for cobalt(II) and zinc(II). These experiments involved the systematic variation of ligand, metal and 4-ethylpyridine concentrations to probe the stoichiometries of the species extracted. Synergistic extraction was observed when 4-ethylpyridine was present with the ligand in the organic phase. Competitive extraction studies demonstrated the ligands are highly selective for copper(II) over cobalt(II), nickel(II), zinc(II) and cadmium(II).

The interaction of Cu(II) with three β-diketone ligands of type R1C(O)CH2C(O)R2 (where R1 = 2-, 3-, or 4-pyridyl and R2 = C6H5, respectively), HL1−HL3, along with the X-ray structures and the pKa values of each ligand, are reported. HL1 yields a dimeric complex of type [Cu(L1)2]2. In this structure, two deprotonated HL1 ligands coordinate in a trans planar fashion around each Cu(II) center, one oxygen from each CuL2 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 HL2 and HL3, 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 gener...

The synthesis of the new potentially pentadentate ligand, 2,2′-(2-methyl-2-(pyridin-2-yl)propane-1,3-diyl)bis(sulfanediyl)diethanamine (L 1 ), containing two thioether sulfurs, two –NH2 amines and a pyridyl nitrogen heteroatom is described. Reaction of L 1 with copper(II) chloride and addition of hexafluorophosphate anion has led to isolation of the mixed anion complex Cu2(L 1 )2Cl(PF6)3. The synthesis and X-ray structure of cobalt(III) species, [Co(L 1 )Cl](PF6)2, is also reported. In situ reaction of L 1 with copper(II) as a metal template in the presence of formaldehyde and the carbon acid nitroethane together with triethylamine (as base) led to macrocycle ring closure to yield [Cu(L 2 )Cl]PF6 (where L 2 = 6,13-dimethyl-6-nitro-13-(pyridin-2-yl)-1,11-dithia-4,8-diazacyclotetradecane) whose X-ray structure shows that the copper centre has a distorted square pyramidal coordination geometry being bound by both –NH2 nitrogens and both sulfurs of L 2 while the pyridyl nitrogen remains uncoordinated.

Interaction of copper(II) with the N-substituted bis(2-pyridylmethyl)amine derivatives, (R)-N1,N1-bis(pyridine-2-ylmethyl)butane-1,2-diamine (L1) and (R)-2-(bis(pyridin-2-ylmethyl)amino)butan-1-ol (L2), has led to isolation of optically active [Cu(L1)Cl]PF6 (1) and [Cu(L2)Cl]ClO4 (2), respectively. The X-ray structures of (1) and (2) show that the copper is bound to all four heteroatoms of the respective ligands as well as to a chlorine atom in a distorted square pyramidal arrangement in which the three nitrogens of L1 or L2 occupy three positions of each basal plane while the fourth position is occupied by the chloro ligand; apical sites in each case are filled by the amine donor from the NH2-substituted butane arm in L1 or the (protonated) alcohol oxygen of the 2-aminobutane-1-ol substituent in L2. To a first approximation the coordination geometry in 2 is distorted square pyramidal; however, the remaining (axial) site on each copper centre is involved in a long contact (2.96 A) with a bound chloro ligand from an adjacent complex which connects individual complex units in a zigzag 1-D polymeric chain, so that the coordination geometry could also be seen as pseudo-octahedral. A temperature-dependent magnetic study revealed the presence of ferromagnetic exchange coupling between copper centres in the chain reflecting the orthogonal structure between the chloro-bridged copper(II) ions; in contrast, and as expected, the discrete complex 1 is magnetically dilute.

A series of cationic, ditopic N-donor ligands based on 4,4'-bipyridine (4,4'-bipy), 3-aminopyrazine (apyz) and 2-aminopyrimidine (apym), each incorporating two positively-charged N-heterocycles linked by a conformationally-flexible spacer unit, have been synthesised and treated with palladium(II) or platinum(II) precursors [M(2,2'-bipy)(NO(3))(2)] (M = Pd(II) or Pt(II)) to form highly cationic metallocyclic species. Treatment of 1,6-bis(4,4'-bipyridinium)hexane nitrate with [M(2,2'-bipy)(NO(3))(2)] in aqueous solution, followed by the addition of KPF(6), resulted in the formation of the [2+2] species [M(2)(2,2'-bipy)(2){4,4'-bipy(CH(2))(6)4,4'-bipy}(2)](PF(6))(8). Treatment of [Pd(PhCN)(2)Cl(2)] with 1,3-bis(4,4'-bipyridinium)propane hexafluorophosphate in MeCN afforded [Pd(2)Cl(4){4,4'-bipy(CH(2))(3)4,4'-bipy}(2)](PF(6))(4). When the cationic apyz or apym ligands were used in aqueous solution, the analogous metallomacrocycles did not form. Instead, deprotonation of the exocyclic amino group occurred upon coordination of the ligand to afford a tetranuclear [4+2] species in the case of platinum(II), with Pt(II)...Pt(II) bonding supported by strong UV-vis absorption at lambda = 428 nm which was assigned to a metal-metal-to-ligand charge transfer (MMLCT) band. Thus, treatment of 1,6-bis(3-aminopyrazinium)hexane nitrate with [Pt(2,2'-bipy)(NO(3))(2)], followed by the addition of KPF(6), led to the formation of the red species [Pt(4)(2,2'-bipy)(4){apyz(CH(2))(6)apyz-2H}(2)](PF(6))(8). No related products could be identified with palladium(II), consistent with the low propensity for this metal ion to form strong Pd(II)...Pd(II) bonding interactions.

The interaction of Cu(II), Fe(III) and Co(III) with 6,6,13-trimethyl-13-amino-1,4,8,11-tetraazacyclotetradecane (L 3 ) incorporating a pendent amine group has led to isolation of the new octahedral complexes [Cu(HL 3 )(ClO4)2]Cl·H2O (1), [Fe(L 3 )Cl](S2O6)·H2O (2), [Co(L 3 )Cl](ClO4)1.5Cl0.5·0.25H2O (3), [Co(HL 3 )Cl2](ClO4)2·H2O (4) and [Co(L 3 )Cl]2(S2O4)(ClO4)2 (5). In (1) the copper ion occupies the macrocyclic cavity of protonated (–NH3 +) L 3 which is present in its trans-III configuration; weakly bound ClO4 − ligands occupy the axial positions. The X-ray structure of (2) showed that Fe(III) occupies the N4-macrocyclic cavity of L 3 in a trans-III configuration, with the pendent amine group binding in an axial position. The remaining axial position is occupied by a Cl− ligand. Chromatography of the product obtained from the reaction of Na3[Co(CO3)3] with L 3 yielded three fractions. Fraction 1 yielded crystals (3) composed of three crystallographically independent species incorporating cations of type [Co(L 3 )Cl]2+ with very similar structures; in each case the macrocyclic ring nitrogens of L 3 are bound to the Co(III) in an asymmetric cis-fashion. Fraction 2 yielded the trans-III octahedral cationic complex (4) incorporating L 3 in its protonated form. The Co(III) complex (5) from fraction 3 shows a different coordination arrangement to the products from fractions 1 or 2. The macrocyclic ring coordinates in its trans-III form, but the axial sites in this case are occupied by the pendent-NH2 group and a Cl− ligand.

1,4- (H₂L¹) and 1,3-phenylene (H₂L²) linked bis-β-diketone ligands as well as corresponding metal complexes of composition M₃(L¹)₃B₆ and M₂(L²)₂B₂ with B = pyridine (Py) or 4-ethylpyridine (EtPy) have been synthesised. Extraction studies involving the systematic variation of the metal, bis-β-Bdiketone and 4-ethylpyridine concentrations have been performed for Co(Il) and Zn(II) in order to probe the solution stoichiometries of the extracted species. Significant synergistic effects were observed when EtPy was present along with the bis-β-diketone ligand in the organic (CHCI₃) phase. Competitive extraction studies (water/chloroform) demonstrated a clear uptake preference for Cu(II) over Co(II), Ni(II), Zn(Il) and Cd(II).

Interaction of copper(II) salts with 2,2′-dipyridylamine (1), N-cyclohexylmethyl-2,2′-dipyridylamine (2), di-2-pyridylaminomethylbenzene (3), 1,2-bis(di-2-pyridylaminomethyl)-benzene (4), 1,3-bis(di-2-pyridylaminomethyl)benzene (5), 1,4-bis(di-2-pyridylaminomethyl)benzene (6), 1,3,5-tris(di-2-pyridylaminomethyl)benzene (7) and 1,2,4,5-tetrakis(di-2-pyridylaminomethyl)benzene (8) has yielded the following complexes: [Cu(2)(μ-Cl)Cl]2, [Cu(3)(μ-Cl)Cl]2 · H2O, [Cu2(4)(NO3)4], [Cu2(5)(NO3)4] · 2CH3OH, [Cu2(6)(CH3OH)2(NO3)4], [Cu4(8)](NO3)4] · 4H2O while complexation of palladium(II) with 1, 4, 5 and 6 gave [Pd(1)2](PF6)2 · 2CH3OH, [Pd2(4)Cl4], [Pd2(4)(OAc)4], [Pd2(5)Cl4], [Pd2(6)Cl4] and [Pd2(6)(OAc)4] · CH2Cl2, respectively. X-ray structures of [Cu(2)(μ-Cl)Cl]2, [Cu(3)(μ-Cl)Cl]2 · 2C2H5OH, [Cu2(6)(CH3OH)2(NO3)4], [Pd(1)2](PF6)2 · 2CH3OH, [Pd2(4)(OAc)4] · 4H2O and [Pd2(6)(OAc)4] · 2CH2Cl2 are reported. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a diverse range of coordination geometries and lattice arrangements, with the structures of [Pd2(4)(OAc)4] · 4H2O and [Pd2(6)(OAc)4] · 2CH2Cl2, incorporating the isomeric ligands 4 and 6, showing some common features. Liquid–liquid (H2O/CHCl3) extraction experiments involving copper(II) and 1–3, 5, 7and 8 show that the degree of extraction depends markedly on the number of dpa-subunits (and concomitant lipophilicity) of the ligand employed with the tetrakis-dpa derivative 8 acting as the most efficient extractant of the six ligand systems investigated.

The solid state structures of [Ni(1)(2)][NO3](2) center dot 2MeOH center dot 2H(2)O, [Fe(1)(2)][ClO4](2) center dot 2MeOH center dot 0.5H(2)O, [Ru(1)(2)][PF6](2) and [Ru(1)(2)][PF6] [NO3] (1 = 4 `-(4-pyridyl)-2,2 `:6 `,2 ``-terpyridine) are presented and the structural variation observed for the M(1)(2)(2+) unit is discussed. Protonation of the pendant pyridine group in [Ru(1)(2)](2+) leads to the formation of a hydrogen-bonded, one-dimensional polymer [Ru(1)(H1)(n)](3n+) exemplifed by the solid-state structure of [Ru(1)(H1)Fe(NCS)(6) center dot 1.25H(2)O](n).

The synthesis of two new bifuctional ligand sytems incorporating two different “classical” coordination units connected by a bent (but flexible) thioether linkage is reported. The new systems are the β-diketone-pyridyl derivative, 3-(pyridin-4-ylthio)pentane-2,4-dione (L1), and its hydrazine condensation product, the pyridyl-pyrazole species 4-(3,5-dimethyl-1H-pyrazol-4-ylthio)pyridine (L2). Both systems were designed for use in metal−organic framework studies. With L1, four metal-containing products were crystallized, [Cu(L1−H)2]n (1), {[Cu(L1−H)2]·0.5H2O·CHCl3}n (2), {[Zn(L1−H)2]·2H2O}n (3), and [Zn(L1−H)2]·2MeOH}n (4); these display three different array types. Compound 1 incorporates 5-coordinate Cu(II) ions with square pyramidal stereochemistry. The β-diketonato groups from two ligands coordinate in the basal plane with the apical position occupied by a pyridyl nitrogen from a third ligand that bridges to an adjacent copper center. Propagation of this coordination motif produces a 1D chain. In 2, whi...

Three copper(II) complexes derived from 2-(hydroxymethyl)pyridine (LH) have been synthesised and a comparative X-ray investigation of their respective crystal structures undertaken. In the absence of added base, LH reacts with copper(II) chloride or nitrate to yield the five-coordinate [Cu(LH)2Cl]Cl and six-coordinate [Cu(LH)2(NO3)2] species. In the chloro complex the coordination geometry is distorted trigonal bipyramidal, with the pyridyl nitrogens occupying the axial position and two hydroxyl oxygens from the bidentate ligands together with a chloro group occupying the equatorial sites. The structure of the nitrate species, published previously, has been reinvestigated at low temperature in order to specify the weak interactions in the crystal; it contains two molecules of bidentate LH bound trans in the equatorial plane while monodentate nitrato ligands occupy the axial sites. In each of these complexes the hydroxyl protons act as hydrogen bond donors, interacting with the non-coordinated chloride anion in [Cu(LH)2Cl]Cl and the coordinated nitrato groups in [Cu(LH)2(NO3)2] to form bridged, hydrogen-bonded, copper(II)-organic arrays in each case; offset face-to-face π-stacking in the latter produces a two dimensional structure. Further weak CH⋯Cl, CH⋯O interactions stabilise both arrangements. The X-ray structure of the complex [Cu(L)2] · 4H2O containing the deprotonated ligand is also described. The presence of the latter results in the above hydrogen bonding arrangements being ‘switched off’ and instead a new two-dimensional network involving bridging tetrameric water clusters hydrogen bound to adjacent ligand hydroxo groups to give extended sheets is generated; offset face-to-face π-stacking occurs between sheets to yield a three dimensional array.

The use of a highly efficient reductive amination procedure for the postsynthetic end-capping of metal-templated helicate and tetrahedral supramolecular structures bearing terminal aldehyde groups is reported. Metal template formation of a [Fe2L3](4+) dinuclear helicate and two [Fe4L6](8+) tetrahedra (where L is a linear ligand incorporating two bipyridine domains separated by one or two 1,4-(2,5-dimethoxyaryl) linkers and terminated by salicylaldehyde functions is described. Postassembly reaction of each of these "open" di- and tetranuclear species with excess ammonium acetate (as a source of ammonia) and sodium cyanoborohydride results in a remarkable reaction sequence whereby the three aldehyde groups terminating each end of the helicate, or each of the four vertices of the respective tetrahedra, react with ammonia then undergo successive reductive amination to yield corresponding fully tertiary-amine capped cryptate and tetrahedral covalent cages.

We have developed six dihydroxidoplatinum(IV) compounds with cytotoxic potential. Each derived from active platinum(II) species, these complexes consist of a heterocyclic ligand (HL) and ancillary ligand (AL) in the form [Pt(HL)(AL)(OH)2](2+), where HL is a methyl-functionalised variant of 1,10-phenanthroline and AL is the S,S or R,R isomer of 1,2-diaminocyclohexane. NMR characterisation and X-ray diffraction studies clearly confirmed the coordination geometry of the octahedral platinum(IV) complexes. The self-stacking of these complexes was determined using pulsed gradient stimulated echo nuclear magnetic resonance. The self-association behaviour of square planar platinum(II) complexes is largely dependent on concentration, whereas platinum(IV) complexes do not aggregate under the same conditions, possibly due to the presence of axial ligands. The cytotoxicity of the most active complex, exhibited in several cell lines, has been retained in the platinum(IV) form.

A series of novel indolyl-imine ligand precursors have been synthesized. In particular, bidentate, tridentate, and potentially tetradentate ligands were prepared, each containing both indolyl sp2-N and imine sp2-N donors. A series of neutral rhodium(I) and iridium(I) complexes of these ligands were synthesized, including monometallic and bimetallic complexes. The X-ray structures of three of the monometallic complexes with bidentate indolyl-imine ligands were determined. In each complex, the metal center was in a square planar conformation, as expected for Rh(I) and Ir(I) complexes. The fiveand six-membered metallocycles formed on complexation of the metal with the ligands were all planar, and the aromaticity of the ligands was maintained. The Rh(I) complex with the tridentate indolyl ligand (L) reacted at room temperature with CH2Cl2 to form the Rh(III) chloromethyl complex [Rh(L)(CO)-(CH2Cl)(Cl)] via oxidative addition of the C-Cl bond of CH2Cl2. The Rh/Ir(I) indolyl-imine complexes are efficient catalysts for the intramolecular cyclization of 4-pentynoic acid to form c-methylene-c-butyrolactone. A dinuclear Rh(I) complex was the most active catalyst, demonstrating a significant degree of bimetallic cooperativity.

The title compound, [Co(C6H15NO3)2](CH3CO2)2, contains two triethanolamine ligands bound to a Co2+ metal centre, which lies on a crystallographic inversion site such that the asymmetric unit contains half of the cation and one acetate anion. The triethanolamine ligands coordinate via each axial N and two of the three O atoms, while the third arm of the ligand is pendant with the hydroxyl group pointing away from the metal centre. The acetate anions are hydrogen bonded to the coordinated hydroxyl groups and also to the free arm, forming a two-dimensional sheet-like motif.

A mixed valent heterometallic Cu(II)/Na(I) coordination polymer (1) is generated by the reaction of a Schiff base ligand, (6,6'-(1E,1'E)-(2-hydroxypropane-1,3-diyl)bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(2-methoxyphenol)) with copper(II) acetate and sodium perchlorate. In addition to the presence of alcohol oxygen-sodium coordination bonds, the single crystal X-ray structure reveals that the 1D coordination polymer is stabilised by the formation of phenyl-sodium η2-bonds, face-to-face π-π contacts and Cu-π interactions.

We demonstrate a general method for the construction of M8L4 tubular complexes via subcomponent self-assembly, starting from Cu(I) or Ag(I) precursors together with suitable elongated tetraamine and 2-formylpyridine subcomponents. The tubular architectures were often observed as equilibrium mixtures of diastereomers having two different point symmetries (D2d or D2 ⇄ D4) in solution. The equilibria between diastereomers were influenced through variation in ligand length, substituents, metal ion identity, counteranion, and temperature. In the presence of dicyanoaurate(I) and Au(I), the D4-symmetric hosts were able to bind linear Au(Au(CN)2)2(-) (with two different configurations) as the best-fitting guest. Substitution of dicyanoargentate(I) for dicyanoaurate(I) resulted in the formation of Ag(Au(CN)2)2(-) as the optimal guest through transmetalation. Density functional theory was employed to elucidate the host-guest chemistries of the tubes.

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 2 and 3 incorporating dimethoxy-substituted 1,4-phenylene and tetramethoxy-substituted 4,4'-biphenylene bridges between pairs of 2,2'-bipyridyl groups has been carried out via double-Suzuki coupling reactions between 5-bromo-5'-methyl-2'-bipyridine and the appropriate di-pinacol-diboronic esters using microwave heating. Reaction of 2 and 3 with selected Fe(II) or Ni(II) salts yields a mixture of both [M(2)L(3)](4+) triple helicates and [M(4)L(6)](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 [Ni(2)(2)(3)](PF(6))(4), [(PF(6)) ⊂ Fe(4)(2)(6)](PF(6))(7), [Fe(4)(3)(6)](PF(6))(8) and [Ni(4)(3)(6)](PF(6))(8) have been determined, while the structure of the parent Fe(II) cage in the series, [(PF(6)) ⊂ Fe(4)(1)(6)](PF(6))(7), was reported previously. The internal volumes of the Fe(II) tetrahedral cages have been calculated and increase from 102 Å(3) for [Fe(4)(1)(6)](8+) to 227 Å(3) for [Fe(4)(2)(6)](8+) to 417 Å(3) for [Fe(4)(3)(6)](8+) and to an impressive 839 Å(3) for [Ni(4)(3)(6)](8+). The corresponding void volume in the triple helicate [Ni(2)(2)(3)](4+) is 29 Å(3).

An unusual discrete heteronuclear metallomacrocycle was designed and synthesized via metal-ion-directed self-assembly by an iron(II) template. The formation of this metallomacrocycle was demonstrated by X-ray crystallography, electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, and NMR spectroscopy.

Crowning glory: The assembly of CuII or CuII and NiII and a new 1,4-aryl-linked bis(triketonato) ligand designed to adopt a bent configuration leads to unusual Cu6-nNinL3 (n=0, 3) metallacycles that feature unique hexanuclear metallacoronand structural motifs. In the case of the hexanuclear CuII species, strong antiferromagnetic interactions exist between proximate pairs of metal ions in each structure.

Publisher Summary This chapter discusses the synthesis and properties of metal-containing molecular architectures incorporating β-diketonate motifs. The chapter focuses on the systems in which the use of designed metal-ion-directed assembly is employed for constructing new supramolecular entities. The simplest β-diketone ligand is 2,4-pentanedione (acetylacetone, acacH). β-diketones such as acacH show a tendency to form neutral complexes—with the geometry adopted normally reflecting the preferred geometry of the metal ion involved. In the case of cobalt(II), tetrahedral complexes can also result if a bulky β-diketonate ion is used. The ability to form higher coordinate species can be tuned through variation of the terminal R groups on the β-diketone. Reflecting the available relative orientations of the β-diketonate groups in each ligand type, a range of both dinuclear (rectangular) and trinuclear (triangular) “platform-like” products are isolated and characterized. In the lanthanum-containing complex, the lanthanum(III) ion is eleven coordinate being bound by the six “internal” oxygens from the β-diketonate groups, the three pyridyl nitrogens, a tetrahydrofuran group, and a water molecule.

The interaction of the diastereopure N,N'-bis(acetylacetone)cyclohexanediimine ligands, L(1)(1R,2R), L(2)(1S,2S), and their 1:1 mixture, with Zn(II) chloride has been investigated. Four new coordination polymers, [ZnL(1)Cl2 x H2O]n (1), [ZnL(2)Cl2 x H2O]n (2), [ZnL(2)Cl2]n (3), and [Zn6(L(2))6Cl12 x 2 H2O]n (4), each consisting of an infinite single helical chain displaying different pitches and/or handedness have been isolated. The complexed Schiff base ligands are present in their deprotonated enol forms, and the nitrogen atoms, which do not coordinate, are protonated because of proton transfer from the adjacent enol oxygen (coupled with concomitant N-H...O bond formation); each bound ligand is thus pseudo-zwitterionic. The respective zinc centers are bound to two chloro ligands and two oxygen donors from acacH-imine units belonging to different N,N'-bis(acetylacetone)cyclohexanediimine ligands such that the coordination at each zinc is distorted tetrahedral. Compounds 1 and 2, prepared from enantiopure L(1) and L(2), respectively, are enantiomers with similar structures, with the helical pitch in each being 17.0 A. Overall, the structure of 3 may be described as a one-dimensional helical chain with a pitch of 17.3 A, with each period corresponding to two L(2) ligands and two metal centers. The structure of [(Zn6L(2)6Cl12) x 2 H2O]n (4) contains six Zn(II) centers connected via six L(2) ligands to form a "bowed" helical repeat unit, with the pitch of the helix corresponding to 43.5 A. Supramolecular (intra- and intermolecular) aspects of all these unusual polymeric structures are discussed. Finally, the synthesis and characterization of an unprecedented six zinc-node discrete supramolecular assembly, [Zn6(L(1))3(L(2))3Cl12] (5), incorporating a 78-membered metallacycle, is also reported.

Uncharged complexes, formulated as trimeric metallocycles of type [M3(L(1))3(Py)6] (where M = cobalt(II), nickel(II) and zinc(II) and L(1) is the doubly deprotonated form of a 1,4-phenylene linked bis-beta-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 L(1) (R = Ph) and copper(ii) with L(1) (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 H2L(1) (R = t-Bu) and of its trinuclear (triangular) nickel(II) complex [Ni3(L(1))3(Py)6].3.5Py (R = t-Bu) are also presented. Electrochemical studies of H2L(1), [Co3(L(1))3(Py)6], [Ni3(L(1))3(Py)6], [Cu3(L(1))3], [Zn3(L(1))3(Py)6] and [Fe4(L(1))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-beta-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-beta-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).

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-beta-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 structures of [Co(2)(L(1))(2)(Py)(4)] x 2.25CHCl(3) x 0.5H(2)O (R=Pr), [Co(2)(L(1))(2)(EtPy)(4)] (R=t-Bu), [Ni(2)(L(1))(2)(EtPy)(4)] (R=t-Bu), [Zn(2)(L(1))(2)(EtPy)(2)] (R=Me) and [Zn(2)(L(1))(2)(EtPy)(4)] (R=t-Bu) being presented. The electrochemistry of H(2)L(1) (R=t-Bu) and of [Fe(2)(L(1))(3)], [Co(2)(L(1))(2)(Py)(4)], [Ni(2)(L(1))(2)(Py)(4)], [Cu(2)(L(1))(2)] and [Zn(2)(L(1))(2)(Py)(2)] 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-beta-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-beta-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).

Four previously documented ligand design strategies for achieving Ag(I) discrimination have been applied to the design of a new N-benzylated N2S3-donor macrocycle; the latter shows high selectivity for Ag(I) over Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) in log K and bulk membrane transport studies.

A range of 1,3-aryl linked, bis-beta-diketone derivatives (LH2) has been employed to synthesise neutral bis(ligand), dinuclear complexes incorporating square-planar copper(II) and tris(ligand) dinuclear helical derivatives containing octahedral iron(III). The 1H NMR spectra of the free ligands contain singlet peaks at ca. 16.2 ppm, indicative of enolic protons, confirming that the (bis) enol tautomer is present in solution. An X-ray structure of a ligand from the series incorporating tert-butyl terminal substituents confirms that the same tautomer persists in the solid and that the relative orientation of the bis-beta-diketone fragments is such that the coordination vectors lie at approximately 120 degrees to each other. The planar, dinuclear copper complexes form 1 : 2 adducts with pyridine and 4-(dimethylamino)pyridine, confirmed by X-ray structures, that incorporate five-coordinate metal centres. Based on this behaviour, the prospect of linking copper centres in the dinuclear complexes using the difunctional heterocyclic bases, 4,4'-bipyridine, 4,4'-trans-azopyridine and pyrazine as co-ligands has been probed. However, 4,4'-bipyridine was observed to coordinate through only one of its heterocyclic nitrogen atoms in the solid state to form a 1 : 2 ([Cu2(L)2]: 4,4'-bipyridine) adduct, analogous to the structures obtained with the above mono-functional nitrogen bases. Nevertheless, an X-ray structure determination shows that the related difunctional base, 4,4'-trans-azopyridine, coordinates in a bridging fashion via both its heterocyclic nitrogen atoms on alternate sides of each planar [Cu2(L)2] unit to produce an infinite one dimensional metallo chain. In contrast, with pyrazine, a new neutral, discrete assembly of type [Cu4(L)4(pyrazine)2] is formed. The X-ray structure shows that two planar dinuclear complexes are linked by two pyrazine molecules in a sandwich arrangement such that the coordination environment of each copper ion is approximately square pyramidal with the overall tetranuclear structure thus taking the form of a 'dimer of dimers'.

Two tripodal ligands, each derived from 1,1,1-tris(hydroxymethyl)ethane and terminated respectively by 4-pyridyl (L1) and 2-pyridyl groups (L2), have been synthesised. Competitive seven-metal extraction studies (H2O/CHCl3) incorporating equal concentrations of cobalt(ii), nickel(ii), copper(ii), zinc(ii), silver(i), cadmium(ii), and lead(ii) in the aqueous phase and L1 or L2 in the organic phase showed selective extraction of silver(i) in each case. A parallel solvent extraction experiment involving a related tripodal tris-pyridyl ligand (L3) based on a 1,3,5-substituted aryl ring scaffold and incorporating thioether sulfurs in each tripod arm also showed extraction selectivity for silver(i); extraction efficiencies towards this metal ion fall in the order L3 > L1 > L2. Physical data are in accord with L1 forming a capsule-like complex of type [Ag3L12]3+ in which silver ions link pairs of pyridyl groups from different ligands. In contrast, L2 yields a complex of type [Ag2L2(NO)3]n whose X-ray structure showed it to be a two-dimensional coordination polymer in which the three pyridyl donors of each L2 coordinate to three silver(i) centres, two of which are crystallographically distinct, with the centres also bonded to bidentate and/or bridging bidentate nitrato groups.

In the title compound, (C(24)H(20)As)(2)[Co(2)(C(6)H(6)NO(6))(2)(OH)(2)]·8H(2)O, the Co(III) atom in the binuclear centrosymmetric anion is octa-hedrally surrounded by one N atom and three O atoms of the tetra-dentate nitrilo-triacetate ligand and two μ-hydroxide ligands. The crystal packing is controlled by C-H⋯O and O-H⋯O hydrogen-bonding inter-actions. The crystal employed in this study proved to be a two-component twin around (01).

A discrete octanuclear high-spin FeII cage [Fe8L12](BF4)16·n(solvent) was synthesised via metal ion-directed self-assembly. The cage formation is facilitated by incorporating a relatively flexible ditopic ligand with chelating pyrazolyl–pyridine functional units. The synthesis, structure, and magnetic properties of this metallo-cage are presented.

In the title complex, [Cu(C13H11N2O)(N3)], the Cu(II) cation is four-coordinated by an N2O donor set of the tridentate Schiff base ligand and by the terminal N atom of the azide anion, forming a slightly distorted square-planar configuration.

Di- and trinuclear CuII complexes [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O incorporating the isomeric Schiff base ligands 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L1) and 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L2), each incorporating two separated α-diimine coordination domains, have been synthesised and their X-ray crystal structures and variable temperature magnetic properties determined. The X-ray crystal structure of [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O shows that each CuII centre is bound to two nitrogen atoms from L1, two from a bipyridine ligand, and a chloride anion. Intramolecular π-stacking interactions are present between the central phenyl ring of L1 and both rings of each bipyridine ligand. The structure of [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O shows an unusual trinuclear circular helicate arrangement with approximate C3-symmetry. A chloride anion is encapsulated in the structure being bound by six non-classical hydrogen bond interactions. Variable temperature magnetic susceptibility measurements indicated the presence of weak antiferromagnetic behaviour for [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and weak ferromagnetic behaviour for [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O.