Turning on single-molecule magnet behavior in a linear {Mn3} compound.

The synthesis, structure, and magnetic properties are reported for a new manganese compound with a mixed-valent {Mn(3)} core arranged in a linear fashion. The previously reported complex 1, [Mn(IV)(3)(dpo)(6)]·2MeCN, where H(2)dpo is (E)-1-hydroxy-1,1-diphenylpropan-2-one oxime, served as a starting point for the isolation of a {Mn(3)} compound with an analogous core arrangement through the reaction of Mn(OAc)(2)·4H(2)O, H(3)oxol ((E)-2,5-dihydroxy-2,5-dimethylhexan-3-one oxime), and NaOH in MeOH and MeCN. By using these reaction conditions, compound 2, Na[Mn(IV)(2)Mn(III)(Hoxol)(6)](n)·MeOH·H(2)O, was successfully isolated revealing a central Mn(III) ion thereby introducing structural and magnetic anisotropy to the system. The structure of 2 reveals linear trinuclear Mn(IV)-Mn(III)-Mn(IV) units connected through Na(+) ions forming a linear one-dimensional coordination polymer. The Jahn-Teller axes of each trinuclear unit are aligned parallel within the same chain and form a 75° angle between the two symmetry related chains. Magnetic susceptibility measurements of 1 and 2 in the temperature range 1.9-300 K reveal that only the reduced compound, 2, is a single-molecule magnet (SMM) largely due to the anisotropy introduced by the Jahn-Teller distortions on the Mn(III) ions, which effectively induce this magnet behavior. Weak antiferromagnetic interactions along the chains through the Na(+) cations lead to a modulation of the intrinsic properties of the Mn(IV)-Mn(III)-Mn(IV) SMMs.

Disubstituted 1,8-diamidonaphthalene ligands as a flexible, responsive, and reactive framework for tantalum complexes.

Deprotonated N,N'-disubstituted 1,8-diaminonaphthalenes (R(2)DAN(2-); R = (CH(3))(2)CH, C(6)H(5), 3,5-Me(2)C(6)H(3)) were incorporated into Ta(V) complexes employing two methods. The direct proton transfer reaction of the parent amine, 1,8-(RNH)(2)C(10)H(6), with TaMe(3)Cl(2) led to elimination of methane and formation of TaCl(3)[1,8-(RN)(2)C(10)H(6)] (1, 2). Reaction of the dilithiated amido species, Li(2)R(2)DAN, with TaMe(3)Cl(2) or [Ta(NEt(2))(2)Cl(3) ] yielded TaMe(3)[1,8-(RN)(2)C(10)H(6)] (3, 4) and TaCl(NEt(2))(2)[1,8-(RN)(2)C(10)H(6)] (5, 6), respectively. X-ray structural studies of these complexes revealed the flexible coordination behavior of R(2)DAN(2-) by demonstrating that the ligand bonded to Ta with a coordination array dependent on the identity of the other ligands bonded to tantalum. Computational analysis of these complexes confirmed that the energetic components for binding of R(2)DAN(2-) to these TaX(3)(2+) fragments were dominated by the electronic features of the metal fragment. Chemical transformations of the bound ligand were evaluated by reaction of compounds 5 and 6 with LiNMe(2) and MeLi. Simple metathesis products Ta(NEt(2))(2)NMe(2)[1,8-((i)PrN)(2)C(10)H(6)] (R = (i)Pr 7, R = 3,5-Me(2)(C(6)H(3)) 8) were obtained from reactions with LiNMe(2). In contrast, when the R group of the DAN ligand was (i)Pr, reaction with MeLi ultimately led to activation of the isopropyl group and formation of the metallaziridine [kappa(3)-(Me(2)CN)((i)PrN)C(10)H(6)]Ta(NEt(2))(2) (9) species via the elimination of methane.

Capturing In+ monomers in a neutral weakly coordinating environment.

The application of a new bis(imino)pyridine ligand allowed the isolation and characterization of [{2,4-(t)Bu(2)C(6)H(3)N=CPh}(2)(NC(5)H(3))]In(+)(OTf)(-) as the first low-valent, main-group metal complex of this ligand scaffold. Structural analysis revealed a unique monomeric In(I) species with a surprisingly long metal-ligand bond. In conjunction with a density functional theory investigation, this complex is shown to display only nominal donor-acceptor interactions between the metal and the neutral ligand. The mixing of the occupied 5s metal orbital with the occupied ligand orbitals reduces the reactivity of the central atom and thus stabilizes this species. An In(III) species, [{2,4-(t)Bu(2)C(6)H(3)N=CPh}(2)(NC(5)H(3))]InCl(2)(+)InCl(4)(-) was also isolated and structurally characterized utilizing this ligand frame.

Linking high anisotropy Dy3 triangles to create a Dy6 single-molecule magnet.

A unique Dy(III)(6) complex is created by linking of two Dy(III)(3) triangles, in which intramolecular ferromagnetic interactions and single-molecule magnetic behaviour have been observed.

Salen-based [Zn2Ln3] complexes with fluorescence and single-molecule-magnet properties.

A family of four isostructural complexes with a V-shaped pentanuclear [Zn(2)Ln(3)] core of general formula [Zn(2)Ln(3)(m-salen)(3)(N(3))(5)(OH)(2)] [Ln(III) = Tb(III) (1), Eu(III) (2), Ho(III) (3), Dy(III) (4); m-salen = N,N'-ethylenebis(3-methoxysalicylideneamine)] were isolated and structurally characterized. The fluorescence and magnetic measurements of the four compounds were investigated. Complex 1 exhibits strong fluorescence properties, while single-molecule-magnet behavior is seen in complex 4.

Two-dimensional networks of lanthanide cubane-shaped dumbbells.

The syntheses, structures, and magnetic properties are reported for three new lanthanide complexes, [Ln(III)(4)(mu(3)-OH)(2)(mu(3)-O)(2)(cpt)(6)(MeOH)(6)(H(2)O)](2) (Ln = Dy (1.15MeOH), Ho (2.14MeOH), and Tb (3.18MeOH)), based on 4-(4-carboxyphenyl)-1,2,4-triazole ligand (Hcpt). The three complexes were confirmed to be isomorphous by infrared spectroscopy and single-crystal X-ray diffraction. The crystal structure of 1 reveals that the eight-coordinate metal centers are organized in two cubane-shaped moieties composed of four Dy(III) ions each. All metal centers in the cubane core are bridged by two mu(3)-oxide and two mu(3)-hydroxide asymmetrical units. Moreover, each cubane is linked to its neighbor by two externally coordinating ligands, forming the dumbbell {Dy(III)(4)}(2) moiety. Electrostatic interactions between the ligands of the triazole-bridged dimers form an extended supramolecular two-dimensional arrangement analogous to a metal-organic framework with quadrilateral spaces occupied by ligands from axial sheets and by four solvent molecules. The magnetic properties of the three compounds have been investigated using dc and ac susceptibility measurements. For 1, the static and dynamic data corroborate the fact that the {Dy(III)(4)} cubane-shaped core exhibits slow relaxation of its magnetization below 5 K associated with a single-molecule magnet behavior.

A rare ligand bridged ferromagnetically coupled MnIV3 complex with a ground spin state of S = 9/2.

An exclusively chelating ligand bridged high-valent [MnIV3] complex has been synthesized, in which all Mn(IV) ions are ferromagnetically-coupled to exhibit an S(T) = 9/2 spin ground state.

Engineering silver(I) coordination networks through hydrogen bonding.

The silver(I) coordination networks [Ag2(mu-O2CCF3)2(mu-NN)2](infinity) exist as a polymer of macrocycles or a double-stranded polymer when NN = 1,2-C6H4[NHC(O)-4-C5H4N]2 or 1,2-C6H4[NHC(O)-3-C5H4N]2, respectively. Crystal engineering of the polymers is achieved through interchain hydrogen bonds.

Ring-opening polymerization of gold macrocycles and self-assembly of a coordination polymer through hydrogen-bonding.

The equilibrium between digold and tetragold rings and a ring-opened oligomer and polymer is established by NMR and ESI-MS studies in solution and by structure determinations in the solid state; the polymer containing amide-derivatized ligands undergoes self-assembly through hydrogen bonding to give an ordered network.

Novel Co-based metal-organic frameworks and their magnetic properties using asymmetrically binding 4-(4'-carboxyphenyl)-1,2,4-triazole.

Two novel Co-based metal-organic frameworks (MOFs) were synthesised and characterised using an asymmetrically binding ligand, 4-(4'-carboxyphenyl)-1,2,4 triazole (Hcpt). The isolated [Co3(II)(µ3-O)(OH)(cpt)3(H2O)2]n·xH2O·yDMF, Co-MOF1, exhibits a rhombohedral crystal structure (space group, P63/mc), with a trinuclear cobalt core that resembles the MIL88 series. This MOF shows paramagnetic behaviour down to 2 K with no saturation of magnetisation up to 7 T. This is presumably due to a geometrically frustrated triangular arrangement of Co spins. The two-dimensional complex, [Co(II)(cpt)(N3)]n, Co-MOF2, crystallises in a monoclinic crystal system (space group, C2/m). The magnetic measurements reveal metamagnetic behaviour for this complex with a critical field in the range of 700-1000 Oe.

Connecting single-ion magnets through ligand dimerisation.

A mononuclear as well as dinuclear Dy(III) complexes of general formula [Dy(hmb)(NO(3))(2)(DMF)(2)] (1) and [Dy(2)(hmt)(NO(3))(4)(DMF)(4)]·DMF (2), where Hhmb: (N'-(2-hydroxy-3-methoxybenzylidene)benzohydrazide and H(2)hmt: (N(1),N(4))-N'(1),N'(4)-bis(2-hydroxy-3-methoxybenzylidene)terephthalohydrazide were obtained using a synthetic strategy involving a polytopic Schiff base ligand. Single-crystal X-ray analysis reveals the Dy(III) ion is in a distorted pentagonal interpenetrating tetrahedral arrangement. The two symmetrical Dy(III) ions in complex 2 exhibit the same geometry and are well-isolated in the molecule by an hmt(2-) ligand. The direct current (dc) and alternating current (ac) magnetic measurements of the compounds were investigated. Complex 1 did not exhibit any ac signal whereas a frequency dependant signal was observed for 2 under zero dc field. When an optimum dc field was applied, clear frequency dependant signals were obtained for both complexes indicative of Single-Ion Magnet behaviour with relaxation barriers of U(eff) = 34 and 42 K for 1 and 2, respectively.

A novel high-spin tridecanuclear Ni(II) cluster with an azido-bridged core exhibiting disk-like topology.

A high-spin tridecanuclear Ni(II) cluster, [Ni(II)(13)(N(3))(18)(dpo)(4)(Hdpo)(2)(H(2)hpo)(4)(H(2)O)(MeOH)] [Ni(II)(13)(N(3))(18)(dpo)(4)(Hdpo)(2)(H(2)hpo)(4)(H(2)O)(2)] (1) (Hdpo = 1-(dimethylamino)propan-2-one oxime and H(2)hpo = 1-(hydroxyamino)propan-2-one oxime) with a purely azido-bridged core, is reported with dominant ferromagnetic coupling between Ni(II) ions. The latter molecule exhibits a unique planar core topology with the largest N(3)(-):Ni(II) ratio reported to date.

Fluorescent dialdehyde ligand for the encapsulation of dinuclear luminescent lanthanide complexes.

Five dinuclear lanthanide complexes [Ln(III)(2)(hpd)(6)].solvent, Ln(III) = Eu(III) (1.2MeCN), Gd(III) (2.2MeCN), Tb(III) (3.MeCN.MeOH), Dy(III) (4.2MeCN), Ho(III) (5.2MeCN) and Hhpd (2-Hydroxyisophthaldehyde) were synthesised and structurally and magnetically characterised. X-Ray structural analysis shows all complexes are isostructural and crystallise in the triclinic P1 space group. The dinuclear complexes are composed of eight-coordinate lanthanide ions linked by two phenoxide bridges from two hpd(-) ligands. Complex 1 exhibits characteristic fluorescence in the visible region.

Synthesis, characterisation and computational studies on a novel one-dimensional arrangement of Schiff-base Mn3 single-molecule magnet.

The syntheses, structures and magnetic properties are reported for three new manganese complexes containing the Schiff-base ((2-hydroxy-3-methoxyphenyl)methylene)isonicotinohydrazine (H(2)hmi) ligand. Complex [Mn(II)(H(2)hmi)(2)(MeOH)(2)Cl(2)] (1) was obtained from the reaction of H(2)hmi with MnCl(2) in a MeOH-MeCN mixture. Addition of triethylamine to the previous reaction mixture followed by diethyl ether diffusion yielded a dinuclear manganese [Mn(III)(2)(hmi)(2)(OMe)(2)](infinity).2MeCN.2OEt(2) (2) compound. Upon increasing the MnCl(2)/H(2)hmi ratio, the mixed valence complex [Mn(III)(2)Mn(II)(hmi)(2)(OMe)(2)Cl(2)](infinity).MeOH (3) was obtained. Dc and ac magnetic measurements were carried out on all three samples. The ac susceptibility and field dependence of the magnetisation measurements confirmed that complex 3 exhibits a single-molecule magnet behaviour with an effective energy barrier of 8.1 K and an Arrhenius pre-exponential factor of 3 x 10(-9) s.

Combining oximes with azides to create a novel 1-D [NaCo(III)(2)] system: synthesis, structure and solid-state NMR.

The synthesis and structure of a novel complex with the formula [NaCo(III)(2)(dmo)(2)(mu-N(3))(3)(N(3))(2)](infinity), , are reported. Complex was synthesized from the reaction of 1-(dimethylamino)propan-2-one oxime (Hdmo), CoCl(2).6H(2)O, and NaN(3) in MeOH. It crystallizes in the monoclinic space group C2/c. The molecular structure consists of one Na(I) and two Co(III) ions bridged by two oxime ligands, two end-to-end azide and three end-on azide anions. The units are linked, forming a 1-D chain. This complex was characterized by UV-Vis spectroscopy where the data confirm the presence of low-spin Co(III) ions. Solid-state (23)Na NMR experiments indicate the presence of one magnetically unique site in the repeating unit, that sample purity in the bulk powdered form is high, and that it possesses microcrystalline order. Solid-state (59)Co NMR experiments at ultra-high field (B(0) = 21.1 T) are in agreement with the structure obtained through X-ray crystallography where the Co(III) ions are coordinated to five nitrogen atoms as well as an oxygen atom.

Atom efficient cyclotrimerization of dimethylcyanamide catalyzed by aluminium amide: a combined experimental and theoretical investigation.

A novel method for the cyclotrimerization of dimethylcyanamide to form hexamethylmelamine has been developed using an aluminium amide catalyst; detailed DFT modelling of the catalytic cycle supports a triple insertion, nucleophilic ring closure, deinsertion mechanism.