Custom Coordination Environments for Lanthanoids: Tripodal Ligands Achieve Near-Perfect Octahedral Coordination for Two Dysprosium-Based Molecular Nanomagnets.

Controlling the coordination sphere of lanthanoid complexes is a challenging critical step toward controlling their relaxation properties. Here we present the synthesis of hexacoordinated dysprosium single-molecule magnets, where tripodal ligands achieve a near-perfect octahedral coordination. We perform a complete experimental and theoretical investigation of their magnetic properties, including a full single-crystal magnetic anisotropy analysis. The combination of electrostatic and crystal-field computational tools (SIMPRE and CONDON codes) allows us to explain the static behavior of these systems in detail.

Cyanide-bridged W(V)Mn(III) bimetallic chains composed of a blocked W hexacyanide precursor: geometry-related magnetic couplings and magnetostructural correlation.

Five one-dimensional bimetallic W(V)Mn(III) complexes 1-5, consisting of [W(CN)6(bpy)](-) anions and [Mn(Schiff base)](+) cations, were prepared. The central coordination geometry around each W atom is determined as a distorted dodecahedron (DD) for 1 and 2, and a distorted square antiprism (SAPR) for 3-5. Magnetic analyses demonstrate that compounds 1, 4, and 5 exhibit antiferromagnetic interactions between magnetic centers, which are different from the ferromagnetic couplings in 2 and 3. For the distorted DD geometry, the Mn-N(ax) (ax = axial) bond length increases when moving from 1 to 2, with the Mn-N(ax)-C(ax) angle remaining constant. The elongation of the bond length is responsible for the reduction in orbital overlap and consequent ferromagnetic coupling in 2. In comparison, for 3-5 with the distorted SAPR geometry, given that the Mn-N(ax) bond lengths are similar across all the samples, the increase in the Mn-N(ax)-C(ax) angles accounts for the enhanced magnetic strength. Notably, a correlation between structure and magnetic exchange coupling is established for the first time in W(V)Mn(III) bimetallic systems based on the [W(CN)6(bpy)](-) precursor.

Reversible crystal-to-amorphous structural conversion in the single end-on azide-bridged Co(II) complex: concomitant color and magnetic modulations.

Crystal clear: An end-on (EO) azide-bridged Co(II) layer (see scheme; 1) with coordinated water molecules, long spacer p-XBP4 ligands, and unbound azide anions was evacuated to generate a dehydrated sample of 2. A reversible crystal-to-amorphous structural transformation accompanied by color and magnetic changes takes place between 1 and 2 by using a desolvation-solvation protocol.

Submolecular Ligand Size and Spacing for Cell Adhesion.

Cell adhesion occurs when integrin recognizes and binds to Arg-Gly-Asp (RGD) ligands present in fibronectin. In this work, submolecular ligand size and spacing are tuned via template-mediated in situ growth of nanoparticles for dynamic macrophage modulation. To tune liganded gold nanoparticle (GNP) size and spacing from 3 to 20 nm, in situ localized assemblies of GNP arrays on nanomagnetite templates are engineered. 3 nm-spaced ligands stimulate the binding of integrin, which mediates macrophage-adhesion-assisted pro-regenerative polarization as compared to 20 nm-spaced ligands, which can be dynamically anchored to the substrate for stabilizing integrin binding and facilitating dynamic macrophage adhesion. Increasing the ligand size from 7 to 20 nm only slightly promotes macrophage adhesion, not observed with 13 nm-sized ligands. Increasing the ligand spacing from 3 to 17 nm significantly hinders macrophage adhesion that induces inflammatory polarization. Submolecular tuning of ligand spacing can dominantly modulate host macrophages.

Normal prion protein in Drosophila enhances the toxicity of pathogenic polyglutamine proteins and alters susceptibility to oxidative and autophagy signaling modulators.

To investigate the in vivo functions of normal prion protein (PrP) in Drosophila, we utilized characterized transgenic flies expressing ³(F)4-tagged mouse PrP (Mo-PrP³(F)4). The neurotoxicity of pathogenic Machado-Joseph Disease (MJD) glutamine (Q) 78 and 127Q proteins were enhanced by the co-expression of Mo-PrP³(F)4in the fly eyes, while the eyes of controls flies and flies expressing Mo-PrP³(F)4) alone or together with MJD-Q27 or 20Q proteins did not show any defect. Susceptibilities to H2O2, paraquat, and Dithiothreitol (DTT) were altered in Mo-PrP³(F)4 flies. In addition, Mo-PrP³(F)4 flies were significantly more susceptible to the perturbation of autophagy signaling by an autophagy inhibitor, 3-methyladenine (3-MA), and inducer, LiCl. Taken together, our data suggest that Mo-PrP³(F)4 may enhance the neurotoxicity of pathogenic Poly-Q proteins by perturbing oxidative and autophagy signaling.

Cyano-bridged pentanuclear and honeycomblike M(III)Cu(II) (M = Fe, Cr) bimetallic assemblies: structural variations modulated by side groups of macrocyclic ligands and magnetic properties.

Three two-dimensional (2D) layered M(III)-Cu(II) (M = Fe, Cr) bimetallic complexes and a discrete cluster were prepared using [M(CN)(6)](3-) and respective Cu macrocycles with methyl (1, 3) or ethyl (2, 4) side groups. The crystal structures can be described as aesthetic honeycomb-like M(2)Cu(3) neutral sheets (1, 3, 4) and a pentanuclear Fe(2)Cu(3) entity (2) with an isolated Cu(L2)(2+) moiety. The steric hindrance induced by the pendant groups renders the internal parameters of the Cu-N(ax) (where the "ax" subscript denotes axial) length and Cu-N(ax)-C(ax) angle to become elongated and acute. The magnetic data disclose that ferromagnetic couplings are transmitted between M(III) and Cu(II) ions through the CN links. For 4, particularly, there is a magnetically defined chain (J(c)) composed of dimers (J(d)) and trimers (J(t)), based on the structural considerations. The intramolecular magnetic coupling constants are J(d) = 3.73 cm(-1) and J(t) = 4.08 cm(-1), while the J(c) value corresponds to 0.17 cm(-1). From a magnetostructural point of view, it is reasoned that the Cu-N(ax) bond length is probably a determining factor of the strength of magnetic couplings in 4.

Cyanide-bridged W(V)Mn(III) single-chain magnet with isolated Mn(III) moieties exhibiting two types of relaxation dynamics.

A 5d-3d bimetallic compound was prepared by self-assembling [W(CN)(8)](3-) and the Mn(III) Schiff bases. This neutral complex consists of cyanide-linked W(V)Mn(III) anionic chains and isolated Mn(III) Schiff base cations. We demonstrate that two types of relaxation processes are involved in the system; the low-T dynamics may come from magnetic domain dynamics and the high-T relaxation stems from the anionic chain, revealing single-chain magnet character.

Microporous lanthanide-organic frameworks with open metal sites: unexpected sorption propensity and multifunctional properties.

Isostructural lanthanide-organic frameworks were prepared by a solvothermal reaction of the corresponding metal ions and the phosphine-oxide-based tricarboxylate ligand. The gravimetric gas uptake was unexpectedly increased when going from Nd(3+) to Gd(3+), which is associated with the enhanced surface areas and electrostatic interactions between exposed metal ions and gas molecules with quadrupole moments.

Cyanide-bridged Fe(III)-Mn(III) bimetallic systems assembled from the fac-Fe tricyanide and Mn Schiff bases: structures, magnetic properties, and density functional theory calculations.

Reaction of [(Tp)Fe(CN)(3)](-) [Tp = hydrotris(pyrazolyl)borate] with respective Mn(III) Schiff bases led to the formation of four dimeric molecules, [(Tp)Fe(CN)(3)][Mn(1-napen)(H(2)O)].MeCN.4H(2)O [1; 1-napen = N,N'-ethylenebis(2-hydroxy-1-naphthylideneiminato) dianion], [(Tp)Fe(CN)(3)][Mn(5-Clsalen)(H(2)O)] [2; 5-Clsalcy = N,N'-(trans-1,2-cyclohexanediylethylene)bis(5-chlorosalicylideneiminato) dianion], [(Tp)Fe(CN)(3)][Mn(2-acnapen)(MeOH)].MeOH [3; 2-acnapen = N,N'-ethylenebis(1-hydroxy-2-acetonaphthylideneiminato) dianion], [(Tp)Fe(CN)(3)][Mn(3-MeOsalen)(H(2)O)] [4; 3-MeOsalen = N,N'-ethylenebis(3-methoxysalicylideneiminato) dianion], and a one-dimensional (1D) zigzag chain [(Tp)Fe(CN)(3)][Mn(2-acnapen)].H(2)O (5). The dimers contain multiple intermolecular interactions such as hydrogen bonds, face-to-face pi-pi contacts, and edge-to-face CH-pi forces, raising molecular dimensions from one-dimensional (1D) up to three-dimensional (3D) arrays, whereas there are no pi-pi stacking interactions in the 1D chain compound. Magnetic measurements reveal that ferromagnetic couplings are obviously operative between Mn(III) and Fe(III) spin centers transmitted by CN bridges for 1-3 and 5, and antiferromagnetic interactions are however unexpectedly present in 4. On the basis of the proper spin Hamiltonians, magnetic exchange couplings are estimated to be in the span from 1.79 to 7.48 cm(-1) for the ferromagnetically coupled systems and -1.40 cm (-1) for the antiferromagnetic dimer. A slow magnetic relaxation is tangible in 5, which is in connection with isolated chains devoid of any intermolecular noncovalent interactions. Density Functional Theory (DFT) calculations and comparison of structural parameters suggest that the observed magnetic behaviors are mainly associated with the bending of the Mn-N[triple bond]C angle in the bridging pathway.

Octacyanometalate-based ferrimagnetic M(V)Mn(III) (M = Mo, W) bimetallic chain racemates with slow magnetic relaxations.

Cyanide-bridged M(V)-Mn(III) (M = Mo, W) bimetallic chain complexes with racemic spatial dispositions were constructed by self-assembling [M(CN)(8)](3-) precursors and Mn(III) Schiff bases. Antiferromagnetic couplings between spin centers within a chain result in a ferrimagnetic nature, and slow magnetic relaxations are observed as well.

ZnO nanowire field-effect transistors with floating gate nodes of Au nanoparticles.

The memory characteristics of top-gate single ZnO nanowire-based field-effect transistors (FETs) with floating gate nodes consisting of Au nanoparticles on top of the nanowire channels were investigated in this study. Au nanoparticles, synthesized by a thermal deposition of Au thin film and by a subsequent thermal annealing procedure, were embedded in between Al2O3 tunneling and control gate layers deposited on ZnO nanowire channels. For a representative single ZnO nanowire-based FET with floating gate nodes consisting of Au nanoparticles embedded between Al2O3 layers, its drain current versus gate voltage (I(DS)-V(DS)) characteristics for a double sweep in the gate voltage range from -4 to 4 V exhibit a clockwise hysteresis loop with a threshold voltage shift of deltaV(th) = 1.6 V, resulting from the tunneling of the charge carriers from the ZnO nanowire channel into the Au nanoparticles. In addition, the charge storage characteristic of threshold voltage shift with the elapsed time observed in this FET is also discussed in this paper.

Intermolecular contact-tuned magnetic nature in one-dimensional 3d-5d bimetallic systems: from a metamagnet to a single-chain magnet.

Assembling [W(CN) 6(bpy)] (-) and magnetic anisotropic Mn Schiff bases produced two Mn (III)(3d)-W (V)(5d) bimetallic chains. Modulation of the types and degrees of interchain pi-pi interactions in the one-dimensional coordination polymers leads to the variation of the magnetic behavior from a metamagnetic character to a single-chain magnet property.

A 60-Hz sinusoidal magnetic field induces apoptosis of prostate cancer cells through reactive oxygen species.

PURPOSE: To explore the effects of power frequency magnetic fields (MF) on cell growth in prostate cancer, DU145, PC3, and LNCaP cells were examined in vitro. MATERIALS AND METHODS: The cells were exposed to various intensities and durations of 60-Hz sinusoidal MF in combination with various serum concentrations in the media. To analyze MF effects on cell growth, cell counting, trypan blue exclusion assay, Western blot analysis, flow cytometry, enzyme-linked immunosorbent assay (ELISA), semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), fluorescence microscopy, and spectrofluorometry were used. RESULTS: MF exposure induced significant cell growth inhibition and apoptosis in an intensity- and time-dependent manner, in which cell cycle arrest, cleaved Caspase-3, and reactive oxygen species (ROS) increased. Pretreatment with a Caspase-3 inhibitor or antioxidant, N-acetyl-L-cysteine (NAC), significantly attenuated MF-induced cell growth inhibition and cell death. Media replacement experiments failed to show any notable change in the MF effects. CONCLUSIONS: These results demonstrate 60-Hz sinusoidal MF-activated cell growth inhibition of prostate cancer in vitro. Apoptosis together with cell cycle arrest were the dominant causes of the MF-elicited cell growth inhibition, mediated by MF-induced ROS. These results suggest that a possibility of using 60-Hz MF in radiation therapy of prostate cancer could usefully be investigated.

Reversible crystal-to-amorphous structural transformations and magnetic variations in single end-on azide-bridged MII (M = Mn, Ni) coordination polymers.

MII (M = Mn, Ni) coordination frameworks, singly linked by end-on azide ligands, were prepared by employing the long, flexible spacer ligand, p-XBP4. These two-dimensional layer structures underwent reversible crystal-to-amorphous phase transformations during the hydration-dehydration process. Moreover, the magnetic nature changes from antiferromagnetic to ferromagnetic coupling when moving from Mn to Ni.

Tuning of chain chirality by interchain stacking forces and the structure-property relationship in coordination systems constructed by meridional FeIII cyanide and MnIII Schiff bases.

We synthesized six Fe(iii)-Mn(iii) bimetallic compounds by self-assembling the newly developed mer-Fe cyanide PPh4[Fe(Clqpa)(CN)3]·H2O (1) and PPh4[Fe(Brqpa)(CN)3]·H2O (2) with Mn Schiff base Mn(5-Xsalen)+ cations. These compounds include [Fe(Xqpa)(CN)3][Mn(5-Ysalen)]·pMeOH·qH2O [qpaH2 = N-(quinolin-8-yl)picolinamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = Cl, Y = H (3); X = Cl, Y = Br (4); X = Br, Y = H (5); X = Br, Y = F (6); X = Br, Y = Cl (7); X = Br, Y = Br (8)]. When precursor 1 was used, compounds 3 and 4 were isolated to give a dinuclear entity and a linear chain structure, respectively. The reaction of precursor 2 with the Schiff bases afforded four linear Fe(iii)-Mn(iii) chain complexes. Chain chirality with P- and M-helicity emerges in 4, 7, and 8, while 5 exhibits chain helicity opposite to the previous chain complexes and 6 presents no chain helicity. Such a structural feature is heavily dependent on the interchain π-π contacts and the Fe precursor bridging unit. Chiral induction from a local ethylenediamine link of Y-salen is propagated over the chain via noncovalent π-π interactions. All the bimetallic compounds show antiferromagnetic interactions transmitted by the cyanide linkage. A field-induced metamagnetic transition is involved in 4, 7, and 8, while a field-induced two-step transition is evident in 6. From a magnetostructural viewpoint, the coupling constant is primarily governed by the Mn-Nax-Cax angle (ax = axial) in the bimetallic chain complexes composed of mer-Fe(iii) tricyanides, although the torsion angle plays a role.

Evaluation of the accuracy of dose delivery for IMRT based on transit dosimetry.

The authors have developed and evaluated a new method that uses transit dose in the treatment room in verification of dose delivery to patients. Five intensity modulated radiotherapy (IMRT) plans were selected from actual cancer patients, and transit dose was measured using MapCHECK 2 and an anthropomorphic phantom. The criteria used as a verification tool for the dose delivery to the patient were gamma-index-based dose comparison between the computed dose and measured dose. When the doses were delivered to an anthropomorphic phantom normally, the average passing rate was 95.2% based on a gamma index analysis. This feasibility study suggested that transit dose-based quality assurance can provide information about the accuracy of an inhomogeneity correction algorithm and patient positioning during treatment, allowing its use as a verification tool for actual dose delivery to patients in the treatment room.

Dehydration-triggered magnetic phase conversion in the porous Cu(II)Mn(III) metal-organic framework.

Dehydration of the three-dimensional Cu(II)-Mn(III) coordination network undergoes a dramatic magnetic phase transformation from a paramagnetic state to a long-range magnetic ordered phase with glassy behavior. The gas adsorption behavior and re-entrant spin glass character are uniquely apparent in the dehydrated sample.

Syntheses, structures, and magnetic properties of cyano- and phenoxide-bridged Fe(III)-Mn(III) tetrameric assemblies formed by blocked fac-Fe tricyanide with aliphatic rings.

Three tetranuclear clusters [(Tp(Me,mt3))Fe(CN)3Mn(L)]2 (1, L = 5-Clacphmen; 2, L = 5-Clsalen; 3, L = 5-MeOsalen; Tp(Me,mt3) = hydrotris(3-methyl-4,5-propylene-5-methylpyrazol-1-yl)borate) were prepared by assembling the fac-Fe tricyanide with the corresponding Mn Schiff bases. The assembled molecules are linked by cyanide and phenoxide bridges. Weak π-π contacts between molecules are evident in these clusters. Compounds 1-3 exhibit slow relaxation of the magnetization. The phenoxide linkers mediate ferromagnetic coupling between the Mn centers, which is ascribed to the long axial Mn-O* length. The overall magnetic exchange coupling nature of the Fe-C≡N-Mn route is accounted for by the important structural parameters of bridging pathways such as Mn-N(cyano) length, Mn-N(cyano)-C(cyano) angle, and C(eq)-Fe···Mn-N(eq) (eq = equatorial) torsion angle.

Reversible structural transformation and selective gas adsorption in a unique aqua-bridged Mn(II) metal-organic framework.

An aqua-bridged Mn metal-organic framework was prepared, and a dramatic structural transformation occurs upon solvent exchange-resolvation and desolvation-resolvation processes. The desolvated phase, formed by removing the aqua bridges, exhibits selective CO(2) uptake over N(2), H(2), and CH(4). Further, antiferromagnetic couplings are also found between Mn spins in the secondary building units.

Synthesis, structures and magnetic characterizations of isostructural tetranuclear Ln4 clusters (Ln = Dy, Ho, and Eu).

Isostructural tetranuclear clusters [Ln4(salen)6]·xH2O [Ln = Dy, 1·5.5H2O; Ho, 2·4.6H2O; Eu, 3·5.2H2O; salen = N,N'-ethylenebis(salicylideneiminato)dianion] were prepared by self-assembling the corresponding lanthanide ions and a quadridentate Schiff base. Interestingly, the Ln ions are surrounded by the N- and O-donors of the Schiff bases, leading to seven- and eight-coordinate environments. The heptacoordinated Ln centers adopt a distorted capped trigonal prism, while the octacoordinated Ln atoms are in a dodecahedral disposition. The Dy complex exhibits slow magnetic relaxation, characteristic of a single-molecule magnet. Two relaxation modes in the Dy system are evident when H(dc) = 1.4 kG is applied, which is attributable to the existence of the dissimilar coordination geometries around Dy. In comparison, the Ho and Eu analogues were magnetically inspected, displaying no typical slow magnetic relaxation. These findings elucidate that the metal component in the system plays a central role in the occurrence of the magnetization relaxation process. The pronounced long-range order may contribute to intrachain exchange couplings and through-space dipolar interactions between adjacent chains.