Dinuclear Dysprosium Compounds: The Importance of Rigid Bridges.

We report the synthesis, structures and magnetic behaviour of two isostructural dinuclear Dy complexes where the metal ions of a previously reported monomeric building block are connected by a peroxide (O ) or a pair of fluoride (2×F) bridges. The nature of the bridge determines the distance between the metal ion dipoles leading to a dipolar coupling in the peroxido bridged compound of only ca. 70 % of that in the bis-fluorido bridged dimer.

An Effectively Uncoupled Gd Cluster Formed through Fixation of Atmospheric CO Showing Excellent Magnetocaloric Properties.

The [Gd(opch)(CO)(HO)]·4HO·10MeCN coordination cluster () crystallises in P1¯. The Gd core is held together by four bridging carbonates derived from atmospheric CO as well as the carboxyhydrazonyl oxygens of the 2-hydroxy-3-methoxybenzylidenepyrazine-2-carbohydrazide (Hopch) Schiff base ligands. The magnetic measurements show that the Gd ions are effectively uncoupled as seen from the low Weiss constant of 0.

A nested spin structure and single molecule magnet behaviour in an FeDy heterometallic cyclic coordination cluster.

The 20-nuclearity compound [FeDy(tea)(teaH)(NO)]·8MeCN (where teaH = triethanolamine) was synthesised and characterised through single crystal X-ray diffraction and magnetic measurements. The shape of the magnetic hysteresis in the microSQUID measurements was rationalised using the MAGELLAN program.

Fe-Gd Ferromagnetic Cyclic Coordination Cluster [FeGd(teaH)(N)(HO)] with Magnetic Anisotropy─Theory and Experiment.

The synthesis, structural, and magnetic characterization of [FeLn(teaH)(N)(HO)] (Ln = Gd and Y) and the previously reported isostructural Dy analogue are discussed. The commonly held belief that both Fe and Gd can be regarded as isotropic ions is shown to be an oversimplification. This conclusion is derived from the magnetic data for the Y analogue in terms of the zero-field splitting seen for Fe and from the fact that the magnetic data for the new Gd analogue can only be fit employing an additional anisotropy term for the Gd ions.

Synthesis of N-(2,4-dinitrophenyl) derivatives of D-ribosylamines; unexpected reaction and hydrolysis products.

Reaction of 2,3-O-isopropylidene-d-ribofuranosylamine with 2,4-dinitrofluorobenzene afforded the crystalline 2,3-O-isopropylidene-N-(2,4-dinitrophenyl)-β-d-ribofuranosylamine (3) and a 1:1 crystalline complex of 2,3-O-isopropylidene-N-(2,4-dinitrophenyl-α-d-ribofuranosylamine and 2,3-O-isopropylidene-β-d-ribofuranose; controlled acidic hydrolysis of 3 afforded N-(2,4-dinitrophenyl-α-d-ribopyranosylamine and not the expected β-d-furanosylamine derivative. The structures of the new compounds were confirmed by NMR spectroscopy and X-ray crystallography.

Breaking Symmetry Relaxes Structural and Magnetic Restraints, Suppressing QTM in Enantiopure Butterfly Fe Dy SMMs*.

The {Fe Dy } butterfly systems can show single molecule magnet (SMM) behaviour, the nature of which depends on details of the electronic structure, as previously demonstrated for the [Fe Dy (μ -OH) (Me-teaH) (O CPh) ] compound, where the [N,N-bis-(2-hydroxyethyl)-amino]-2-propanol (Me-teaH ) ligand is usually used in its racemic form. Here, we describe the consequences for the SMM properties by using enantiopure versions of this ligand and present the first homochiral 3d/4 f SMM, which could only be obtained for the S enantiomer of the ligand for [Fe Dy (μ -OH) (Me-teaH) (O CPh) ] since the R enantiomer underwent significant racemisation. To investigate this further, we prepared the [Fe Dy (μ -OH) (Me-teaH) (O CPh) (NO ) ] version, which could be obtained as the RS-, R- and S-compounds.

Terminal Ligand and Packing Effects on Slow Relaxation in an Isostructural Set of [Dy(H dapp)X ] Single Molecule Magnets*.

We report three structurally related single ion Dy compounds using the pentadentate ligand 2,6-bis((E)-1-(2-(pyridin-2-yl)-hydrazineylidene)ethyl)pyridine (H dapp) [Dy(H dapp)(NO ) ]NO (1), [Dy(H dapp)(OAc) ]Cl (2) and [Dy(H dapp)(NO ) ]Cl (NO ) (3). The (H dapp) occupies a helical twisted pentagonal equatorial arrangement with two anionic ligands in the axial positions. Further influence on the electronic and magnetic structure is provided by a closely associated counterion interacting with the central N-H group of the (H dapp).

Assisted Self-Assembly to Target Heterometallic Mn-Nd and Mn-Sm SMMs: Synthesis and Magnetic Characterisation of [Mn Ln (O) (OH) (mdea) (piv) (NO ) ] (Ln=Nd, Sm, Eu, Gd)*.

In an assisted self-assembly approach starting from the [Mn O (piv) (4-Me-py) (pivH) ] cluster a family of Mn-Ln compounds (Ln=Pr-Yb) was synthesised. The reaction of [Mn O (piv) (4-Me-py) (pivH) ] (1) with N-methyldiethanolamine (mdeaH ) and Ln(NO )  ⋅ 6H O in MeCN generally yields two main structure types: for Ln=Tb-Yb a previously reported Mn Ln motif is obtained, whereas for Ln=Pr-Eu a series of Mn Ln clusters is obtained. Within this series the Gd analogue represents a special case because it shows both structural types as well as a third Mn Ln inverse butterfly motif.

Cyan-Emitting Cu(I) Complexes and Their Luminescent Metallopolymers.

Copper complexes have shown great versatility and a wide application range across the natural and life sciences, with a particular promise as organic light-emitting diodes. In this work, four novel heteroleptic Cu(I) complexes were designed in order to allow their integration in advanced materials such as metallopolymers. We herein present the synthesis and the electrochemical and photophysical characterisation of these Cu(I) complexes, in combination with ab initio calculations.

A multifunctional use of bis(methylene)bis(5-bromo-2-hydroxyl salicyloylhydrazone): from metal sensing to ambient catalysis of A3 coupling reactions.

The potential use of bis(methylene)bis(5-bromo-2-hydroxylsalicyloylhydrazone) as a multifunctional fluorescence sensor for Cu, Ni, Co and Fe ions was investigated. The optical behaviour shows an increase in an absorption band at 408 nm which can be ascribed to the d-d transition (UV-vis) of the metal ions and a concomitant decrease in fluorescence intensity at 507 nm. The crystallographic analysis shows the binding site of the sensor to two Cu ions and confirms the stoichiometry of 1 : 2 (ligand to metal) which is in good agreement with a Job plot analysis.

Synthesis, Characterization, Electrochemistry, Photoluminescence and Magnetic Properties of a Dinuclear Erbium(III)-Containing Monolacunary Dawson-Type Tungstophosphate: [{Er(HO)(CHCOO)(PWO)}].

Reaction of the trilacunary Wells-Dawson anion {α-PWO} with Er ion in a 1 M LiOAc/HOAc buffer (pH 4.8) solution produces a dinuclear erbium(III) substituted sandwich-type structure [{Er(HO)(CHCOO)(PWO)}] (). The isolated compound was structurally characterized using single crystal and powder X-ray diffraction, FTIR spectroscopy, mass spectrometry and thermogravimetric analysis.

The Influence of Halide Substituents on the Structural and Magnetic Properties of FeDy Rings.

We report the synthesis and magnetic properties of three new nine-membered Fe(III)-Dy(III) cyclic coordination clusters (CCCs), with a core motif of [FeDy(μ-OMe)(vanox)(X-benz)] where the benzoate ligands are substituted in the para-position with X = F (), Cl (), Br (). Single crystal X-ray diffraction structure analyses show that for the smaller fluorine or chlorine substituents the resulting structures exhibit an isostructural FeDy core, whilst the 4-bromobenzoate ligand leads to structural distortions which affect the dynamic magnetic behavior. The magnetic susceptibility and magnetization of - were investigated and show similar behavior in the dc (direct current) magnetic data.

Di- and Tri-nuclear V and Cr Complexes of Dipyridyltriazoles: Ligand Rearrangements, Mixed Valency and Ferromagnetic Coupling.

The first dinuclear and trinuclear chromium(III) and dinuclear vanadium(III) complexes of --substituted-3,5-di(2-pyridyl)-1,2,4-triazole () ligands have been prepared by solvothermal complexations under inert atmospheres, and characterized. The reactions of Cr and V with ( = amino) resulted in deamination of the ligand and yielded the dinuclear doubly-triazolate bridged complexes [ ( )Cl] () and [ ( )Cl] (). In the case of the Cr complex this bridging results in a rare example of ferromagnetic coupling for a dinuclear Cr compound.

The First Use of a ReX Synthon to Modulate Fe Spin Crossover via Supramolecular Halogen⋅⋅⋅Halogen Interactions.

We have added the {Re X } (X=Br, Cl) synthon to a pocket-based ligand to provide supramolecular design using halogen⋅⋅⋅halogen interactions within an Fe system that has the potential to undergo spin crossover (SCO). By removing the solvent from the crystal lattice, we "switch on" halogen⋅⋅⋅halogen interactions between neighboring molecules, providing a supramolecular cooperative pathway for SCO. Furthermore, changes to the halogen-based interaction allow us to modify the temperature and nature of the SCO event.

Exploring the Vibrational Side of Spin-Phonon Coupling in Single-Molecule Magnets via Dy Nuclear Resonance Vibrational Spectroscopy.

Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) using the Mössbauer isotope Dy has been employed for the first time to study the vibrational properties of a single-molecule magnet (SMM) incorporating Dy , namely [Dy(Cy PO) (H O) ]Br ⋅2 (Cy PO)⋅2 H O ⋅2 EtOH. The experimental partial phonon density of states (pDOS), which includes all vibrational modes involving a displacement of the Dy ion, was reproduced by means of simulations using density functional theory (DFT), enabling the assignment of all intramolecular vibrational modes. This study proves that Dy NRVS is a powerful experimental tool with significant potential to help to clarify the role of phonons in SMMs.

Syntheses, Crystal Structure, Electrocatalytic, and Magnetic Properties of the Monolanthanide-Containing Germanotungstates [Ln(HO) GeWO] (Ln = Dy, Er, = 4,3).

Two monolanthanide-containing polyanions based on monolacunary Keggin germanotungstates [Ln(HO) GeWO] (Ln = Dy, Er, = 4,3) have been synthesized in simple one-pot synthetic procedure and compositionally characterized in solid state by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis. Electronic absorption and emission spectra of the title compounds in solution were also studied. The [Dy(HO)GeWO] Keggin POM exhibits a slow relaxation of magnetization.

Multimodeling Approach to Ferromagnetic Spin-Wave Excitations in the High-Spin Cluster MnSr Observed by Inelastic Neutron Scattering.

The magnetism of the mixed-valence high-spin cluster [MnSrO(N)Cl(MedhmpH)(MeCN)]Cl () exhibiting intramolecular ferromagnetic interactions was studied using inelastic neutron scattering (INS), and reliable values for the exchange coupling constants were determined based on the quality of simultaneous fits to the INS and magnetic data. The challenge of the huge size of the Hilbert space (3 375 000) and many exchange coupling constants (7 assuming a symmetry) generally encountered in large spin clusters was resolved as follows: (a) The results of the restricted Hilbert space ferromagnetic cluster spin wave theory were compared to the experimental spectroscopic data. The observed INS transitions were thus assigned to spin wave excitations in a bounded ferromagnetic spin cluster and moreover could be visualized in a straightforward way based on this theory.

Tetranuclear Cu(ii)-chiral complexes: synthesis, characterization and biological activity.

Tetranuclear chiral Cu(ii)-Schiff-base complexes S-1 and R-1, were synthesised using enantiomerically pure ()-(HvanPheol) and ()-(HvanPheol) ligands respectively in the ratio of 1 : 1 of Cu(NO) to (/)-(HvanPheol) in MeOH at room temperature. A pair of polynuclear chiral Cu(ii)-cluster complexes were characterized using single-crystal X-ray diffraction, elemental analysis, infrared and CD spectroscopy. The results revealed the importance of these chiral ligands encouraging the arrangement of copper metal in non-centrosymmetric polar packing.

Synthesis, structure and electrochemical characterization of an isopolytungstate (WO) held by Mn anchors within a superlacunary crown heteropolyanion {PW}.

An isopolyanion {WO} within an archetypal {PW} heteropolyanion assembly [(PWO)(WO)KLiMnNa(HO)Cl] (MnW-PW) has been synthesized by the reaction of the cyclic superlacunary anion [HPWO] and Mn(ClO)·6HO in 1 M LiCl solution medium at pH 8. The isolated compound has been characterized by single-crystal X-ray crystallography, powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy, elemental analysis and thermogravimetric analysis. Electrochemical studies were also performed on MnW-PW, which confirmed the presence of Mn centres bonded to the tungstic framework.

Mechanism of magnetisation relaxation in {MIII2DyIII2} (M = Cr, Mn, Fe, Al) "Butterfly" complexes: how important are the transition metal ions here?

We describe the synthesis, characterisation and magnetic studies of four tetranuclear, isostructural "butterfly" heterometallic complexes: [MIII2LnIII2(μ-OH)(-Me-PhCO)(L)] (HL = 2,2'-((pyridin-2-ylmethyl)azanediyl)bis(ethan-1-ol), M = Cr, Ln = Dy (), Y (), M = Mn, Ln = Dy (), Y ()), which extend our previous study on the analogous {FeDy}, {FeY} and {AlDy} compounds. We also present data on the yttrium diluted {AlDy}: {AlDyY}. Compounds dc and ac magnetic susceptibility data reveal single-molecule magnet (SMM) behaviour for complex {MnDy}, in the absence of an external magnetic field, with an anisotropy barrier of 19.

Single Crystal Investigations Unravel the Magnetic Anisotropy of the "Square-In Square" CrDy SMM Coordination Cluster.

In the search for new single molecule magnets (SMM), i.e., molecular systems that can retain their magnetization without the need to apply an external magnetic field, a successful strategy is to associate 3 and 4 ions to form molecular coordination clusters.