Proline derived guanidine catalysts forge extensive H-bonded architectures: a solution and solid state study.

The preparation of a range of amino acid derived guanidine organocatalysts is reported together with their application to the Michael addition of 2-hydroxy-1,4-napthoquinone to β-nitrostyrene, achieving a maximum ee of 56%. Some insight into the mechanism was sought by using X-ray crystallography and a detailed study of the intra- and intermolecular hydrogen bonding is reported.

Elucidating cylindrospermopsin toxicity via synthetic analogues: An in vitro approach.

Cylindrospermopsin (CYN) is an alkaloid biosynthesized by selected cyanobacteria, the cyto- and genotoxic properties of which have been studied extensively by in vitro and in vivo experimental models. Various studies have separately established the role of uracil, guanidine and hydroxyl groups in CYN-induced toxicity. In the present study, we have prepared five synthetic analogues that all possess a uracil group but had variations in the other functionality found in CYN.

Mono- and ditopic hydroxamate ligands towards discrete and extended network architectures.

A family of mono- and ditopic hydroxamic acids has been employed in the synthesis and structural and physical characterisation of discrete (0D) and (1- and 2-D) extended network coordination complexes. Examples of the latter include the 1-D coordination polymer {[Zn(ii)(LH)]·2MeOH} (5; LH = 2-(methylamino)phenylhydroxamic acid) and the 2-D extended network {[Cu(ii)(LH)(HO)(NO)]·HO} (5; LH = 4-amino-2-(acetoxy)phenylhydroxamic acid). The 12-MC-4 metallacrown [Cu(ii)(LH)(MeOH)(NO)]·3HO·4MeOH (7) represents the first metal complex constructed using the novel ligand N-hydroxy-2-[(2-hydroxy-3-methoxybenzyl)amino]benzamide (LH).

Crowding out: ligand modifications and their structure directing effects on brucite-like {M(μ-OH)} (M = Co(ii), Ni(ii)) core growth within polymetallic cages.

Previous employment of the ligands 2-methoxy-6-[(methylimino)methyl]phenol (LH) and 2-methoxy-6-[(phenylimino)methyl]phenol (LH) has resulted in the self-assembly of pseudo metallocalix[6]arene complexes of general formulae: [M(μ-OH)(L)](NO) (M = Ni(ii), x = 1, y = 2 (1) and Co(ii/iii), x = 2, y = 3 (2)). Extrapolating upon this work, we report the coordination chemistry of ligands 2-methoxy-6-{[(2-methoxyphenyl)imino]methyl}phenol (LH), 2-[(benzylimino)methyl]-6-methoxyphenol (LH), 2-[(benzylamino)methyl]-6-methoxyphenol (LH) and 2-[(benzylamino)methyl]-4-bromo-6-methoxyphenol (LH), whose structures are modifications of ligands LH. These ligands are employed in the synthesis and characterisation of the dimetallic complex [Ni(ii)(L)(HO)](NO)·2HO·3MeOH (3); the monometallic complexes [Ni(ii)(L)] (4) and [Co(iii)(L)]·HO·MeOH (5a); and the tetranuclear pseudo metallocalix[4]arene complexes: [(NO)⊂Co(ii)(μ-OH)(L)(HO)](NO)·HO (6), [(NO)⊂Ni(ii)(μ-OH)(L)(HO)](NO)·HO (7) and [Ni(ii)(μ-OH)(L)(NO)]·MeCN (8).

Synthesis of Migrastatin Analogues as Inhibitors of Tumour Cell Migration: Exploring Structural Change in and on the Macrocyclic Ring.

Invited for the cover of this issue are Paul V. Murphy and co-workers at the National University of Ireland Galway (NUI Galway) and Warsaw University. The image depicts MGSTA-6 giving a stop signal to tumour cells that are on the move.

Synthesis of Migrastatin Analogues as Inhibitors of Tumour Cell Migration: Exploring Structural Change in and on the Macrocyclic Ring.

Migrastatin and isomigrastatin analogues have been synthesised in order to contribute to structure-activity studies on tumour cell migration inhibitors. These include macrocycles varying in ring size, functionality and alkene stereochemistry, as well as glucuronides. The synthesis work included application of the Saegusa-Ito reaction for regio- and stereoselective unsaturated macroketone formation, diastereoselective Brown allylation to generate 9-methylmigrastatin analogues and chelation-induced anomerisation to vary glucuronide configuration.

Molecular Pac-Man and Tacos: layered Cu(II) cages from ligands with high binding site concentrations.

The in situ formation and subsequent Cu(ii) ligation of the polydentate pro-ligands o-[(E)-(2-hydroxy-3-methoxyphenyl)methylideneamino]benzohydroxamic acid (L1H3), o-[(E)-(2-hydroxy-3-methoxy-5-bromophenyl)methylideneamino]benzohydroxamic acid (L2H3) and o-[(E)-(2-hydroxyphenyl)methylideneamino]benzohydroxamic acid (L3H3), leads to the self-assembly of the cages [Cu(ii)10(L1)4(2-aph)2(H2O)2](ClO4)4·5MeOH (), [Cu(ii)14(L1)8(MeOH)2.5(H2O)7.5](NO3)4·3MeOH·7H2O (), [Cu(ii)14(L2)8(MeOH)4(H2O)6](NO3)4·6H2O (), [Cu(ii)14(L3)8(MeOH)6(H2O)2](NO3)4·4MeOH·8H2O () and [Cu(ii)30O(OH)4(OMe)2(L1)16(MeOH)4(H2O)2](ClO4)4·2MeOH·30H2O ().

Homo- and heterometallic planes, chains and cubanes.

The synthesis, structural and magnetic characterisation of a family of homo- and heterometallic complexes constructed with the Schiff base ligands 2-iminomethyl-6-methoxy-phenol (L1H) and 2-imino-6-methoxy-phenol (L2H), are discussed. Members include the heterometallic tetranuclear complexes of general formula [Na2M2(X)2(L1)4(Y)2] (where M = Fe(III), X = (-)OMe, Y = NO3(-) (1) and M = Ni(II), X = N3(-) and Y = MeCN (2)), each possessing a butterfly-like topology. We also report the formation of the heterometallic molecular cage [Na3Ni2(L1)6](ClO4) (3) whose metallic skeleton describes a [rare] trigonal bipyramid, the homometallic 1-D coordination polymer [Mn(L1)2(Cl)]n (4), and the tetranuclear cubane clusters [Mn(III)3Mn(IV)(O)3(OEt)(OAc)3(L1)3] (5) and [Ni4(μ3-OMe)4(L2)4(MeOH)4] (6).

Synthetic, structural, spectroscopic and theoretical study of a Mn(III)-Cu(II) dimer containing a Jahn-Teller compressed Mn ion.

The heterobimetallic complex [Cu(II)Mn(III)(L)(2)(py)(4)](ClO(4))·EtOH (1) built using the pro-ligand 2,2'-biphenol (LH(2)), contains a rare example of a Jahn-Teller compressed Mn(III) centre. Dc magnetic susceptibility measurements on 1 reveal a strong antiferromagnetic exchange between the Cu(II) and Mn(III) ions mediated through the phenolate O-atoms (J = -33.4 cm(-1)), with magnetisation measurements at low temperatures and high fields suggesting significant anisotropy.

Ferromagnetic exchange in a twisted, oxime-bridged [Mn(III)2] dimer.

The dimeric complex [Mn(III)(2)(Naphth-sao)(2)(Naphth-saoH)(2)(MeOH)(2)]·4MeOH (1·4MeOH), acts as a simple model complex with which to examine the magneto-structural relationship in polymetallic, oxime-bridged Mn(III) complexes. Dc magnetic susceptibility studies reveal that ferromagnetic exchange is mediated through the heavily twisted Mn-O-N-Mn moiety (J = +1.24 cm(-1)) with magnetisation measurements at low temperatures and high fields suggesting significant anisotropy.

What controls the magnetic interaction in bis-μ-alkoxo Mn(III) dimers? A combined experimental and theoretical exploration.

The synthesis and magnetic characterisation of a series of bis-μ-alkoxide bridged Mn(III) dinuclear complexes of general formula [Mn(III)(2)(μ-OR)(2)(biphen)(2)(ROH)(x)(L)(y)] (where R = Me, Et; H(2) biphen = 2,2'-biphenol and L = terminally bonded N-donor ligand) is described, doubling the literature basis set for this type of complex. Building on these findings we have categorised all known μ-OR bridged Mn(III) dinuclear complexes into one of three classifications with respect to their molecular structures. We have then employed DFT and MO calculations to assess all potential magneto-structural correlations for this class of compound in order to identify the structural requirements for constructing ferromagnetic family members.

Investigating the solid state hosting abilities of homo- and hetero-valent [Co7] metallocalix[6]arenes.

A family of homo-valent [Co(II)(7)(OH)(6)(L(1))(6)](NO(3))(2) (1), [(MeOH)(2) is a subset of Co(II)(7)(OH)(6)(L(1))(6)](NO(3))(2) (2) (where L(1)H = 2-iminomethyl-6-methoxyphenol) and hetero-valent [(NO(3))(2) is a subset of Co(III)Co(II)(6)(OH)(6)(L(2))(6)](NO(3))·3MeCN (4) (where L(2)H = 2-iminophenyl-6-methoxyphenol) complexes possess metallic skeletons describing planar hexagonal discs. Their organic exteriors form double-bowl shaped topologies, and coupled with their 3-D connectivity, this results in the formation of molecular cavities in the solid state. These confined spaces are shown to behave as host units in the solid state for guests including solvent molecules and charge balancing counter anions.

Twisted molecular magnets.

The use of derivatised salicylaldoximes in manganese chemistry has led to the synthesis of a family of approximately fifty hexanuclear ([Mn(III)(6)]) and thirty trinuclear ([Mn(III)(3)]) Single-Molecule Magnets (SMMs). Deliberate, targeted structural distortion of the metallic core afforded family members with increasingly puckered configurations, leading to a switch in the pairwise magnetic exchange from antiferromagnetic to ferromagnetic. Examination of both the structural and magnetic data revealed a semi-quantitative magneto-structural correlation, from which the factors governing the magnetic properties could be extracted and used for predicting the properties of new family members and even more complicated structures containing analogous building blocks.

Accidentally on purpose: construction of a ferromagnetic, oxime-based [Mn(III)2] dimer.

The serendipitous self-assembly of the complex [Mn(III)(2)Zn(II)(2)(Ph-sao)(2)(Ph-saoH)(4)(hmp)(2)] (1),whose magnetic core consists solely of two symmetry equivalent Mn(iii) ions linked by two symmetry equivalent -N-O- moieties, provides a relatively simple model complex with which to study the magneto-structural relationship in oxime-bridged Mn(III) cluster compounds. Dc magnetic susceptibility measurements reveal ferromagnetic (J = +2.2 cm(-1)) exchange resulting in an S = 4 ground state.

A family of double-bowl pseudo metallocalix[6]arene discs.

We report the synthesis and magnetic characterisation of a series of planar [M₇] (M= Ni(II), Zn(II)) disc complexes [Ni₇(OH)₆(L₁)₆](NO₃)₂ (1), [Ni₇(OH)₆(L₁)₆](NO₃)₂·2MeOH (2), [Ni₇(OH)₆(L₁)₆](NO₃)₂·3MeNO₂ (3), [Ni₇(OH)₆(L₂)₆](NO₃)₂·2MeCN (4), [Zn₇(OH)₆(L₁)₆](NO₃)₂·2MeOH·H₂O (5) and [Zn₇(OH)₆(L₁)₆](NO₃)₂·3MeNO₂ (6) (where HL₁ = 2-iminomethyl-6-methoxy-phenol, HL₂ = 2-iminomethyl-4-bromo-6-methoxy-phenol). Each member exhibits a double-bowl pseudo metallocalix[6]arene topology whereby the individual [M₇] units form molecular host cavities which are able to accommodate various guest molecules (MeCN, MeNO₂ and MeOH). Magnetic susceptibility measurements carried out on complexes 1 and 4 indicate weak exchange between the Ni(II) centres.

Two heptacopper(II) disk complexes with a [Cu(7)(μ(3)-OH)(4)(μ-OR)(2)](8+) core.

The reaction of CuX(2) (X(-) ≠ F(-)) salts with 1 equiv of 3-pyridyl-5-tert-butylpyrazole (HL) in basic methanol yields blue solids, from which disk complexes of the type [Cu(7)(μ(3)-OH)(4)(μ-OR)(2)(μ-L)(6)](2+) and/or the cubane [Cu(4)(μ(3)-OH)(4)(HL)(4)](4+) can be isolated by recrystallization under the appropriate conditions. Two of the disk complexes have been prepared in crystalline form: [Cu(7)(μ(3)-OH)(4)(μ-OCH(2)CF(3))(2)(μ-L)(6)][BF(4)](2) (2) and [Cu(7)(μ(3)-OH)(4)(μ-OCH(3))(2)(μ-L)(6)]Cl(2)·xCH(2)Cl(2) (3·xCH(2)Cl(2)). The molecular structures of both compounds as solvated crystals can be described as [Cu⊂Cu(6)(μ-OH)(4)(μ-OR)(2)(μ-L)(6)](2+) (R = CH(2)CF(3) or CH(3)) adducts.

Twisting, bending, stretching: strategies for making ferromagnetic [Mn(III)3] triangles.

The synthesis and characterisation of a large family of trimetallic [Mn(III)(3)] Single-Molecule Magnets is presented. The complexes reported can be divided into three categories with general formulae (type 1) [Mn(III)(3)O(R-sao)(3)(X)(sol)(3-4)] (where R = H, Me, (t)Bu; X = (-)O(2)CR (R = H, Me, Ph etc); sol = py and/or H(2)O), (type 2) [Mn(III)(3)O(R-sao)(3)(X)(sol)(3-5)] (where R = Me, Et, Ph, (t)Bu; X = (-)O(2)CR (R = H, Me, Ph etc); sol = MeOH, EtOH and/or H(2)O), and (type 3) [Mn(III)(3)O(R-sao)(3)(sol)(3)(XO(4))] (where R = H, Et, Ph, naphth; sol = py, MeOH, beta-pic, Et-py, (t)Bu-py; X = Cl, Re). We show that deliberate structural distortions of the molecule can be used to tune the observed magnetic properties.

Magnetism in metal-organic capsules.

Nickel and cobalt seamed metal-organic capsules have been isolated and studied using structural, magnetic and computational approaches. Antiferromagnetic exchange in the Ni capsule results from coordination environments enforced by the capsule framework.

A F-bridged Mn(II) molecular square.

We report on a tetranuclear Mn(ii) complex possessing a F-bridged molecular square topology directed by 1,10-phenanthroline ligands.

Ferromagnetic Ni(II) discs.

A family of planar disc-like hexa-, octa- and decametallic Ni(II) complexes exhibit dominant ferromagnetic exchange. The deca- and octametallic clusters [Ni(II) (10)(tmp)(2)(N(3))(8)(acac)(6)(MeOH)(6)] (1, H(3)tmp=1,1,1-tris(hydroxymethyl)propane; acac=acetylacetonate) and [Ni(II) (8)(thme)(2)(O(2)CPh)(4)(Cl)(6)(MeCN)(6)(H(2)O)(2)] (2, H(3)thme=1,1,1-tris(hydroxymethyl)ethane) represent rare examples of Ni(II)-based single-molecule magnets, and [Ni(II) (10)] (1) possesses the largest barrier to magnetisation reversal of any Ni(II) single-molecule magnet to date.

Attempting to understand (and control) the relationship between structure and magnetism in an extended family of Mn(6) single-molecule magnets.

The synthesis and characterisation of a large family of hexametallic [Mn(III)(6)] Single-Molecule Magnets of general formula [Mn(III)(6)O(2)(R-sao)(6)(X)(2)(sol)(4-6)] (where R = H, Me, Et; X = (-)O(2)CR' (R' = H, Me, Ph etc) or Hal(-); sol = EtOH, MeOH and/or H(2)O) are presented. We show how deliberate structural distortions of the [Mn(3)O] trinuclear moieties within the [Mn(6)] complexes are used to tune their magnetic properties. These findings highlight a qualitative magneto-structural correlation whereby the type (anti- or ferromagnetic) of each Mn(2) pairwise magnetic exchange is dominated by the magnitude of each individual Mn-N-O-Mn torsion angle.

Constructing clusters with enhanced magnetic properties by assembling and distorting Mn3 building blocks.

The reaction of Mn(ClO4)(2).6H2O with Naphth-saoH2 (Naphth-saoH2=2-hydroxy-1-napthaldoxime) in pyridine (py) forms the complex [MnIII3O(Naphth-sao)3(py)3](ClO4).0.

1D chains of Mn6 single-molecule magnets.

Use of the dicarboxylates iso-phthalate and succinate in the preparation of [Mn(6)] SMMs links the hexametallic units into 1D chains.

A cobalt metallacrown anion host with guest-dependent redox activity.

Two bowl-shaped cavities, each having three OH(-) hydrogen-bond donors at its base, are present in double-cone-shaped metallacrown anion host [Co(6)(mu-OH)(6)(mu-L)(6)](m+) (1(m+); HL=3{5}-(pyrid-2-yl)-5{3}-(tert-butyl)pyrazole). Depending on its affinity for the anions present, it can be isolated in its Co(III) (3)Co(II) (3) (m=3; e.g.

Enhancing SMM properties via axial distortion of Mn(III)3 clusters.

Replacement of carboxylate and solvent with facially capping tripodal ligands enhances the single-molecule magnet (SMM) properties of [Mn(III)3] triangles.