Triangular Metal Research Articles

Finite Element Analysis of Lossless Propagation in Surface Plasmon Polariton Waveguides With Nanoscale Spot-Sizes

We present simulation results on the propagation characteristics of active plasmonic waveguides at 1.55 mum wavelength based on semiconductors as the active gain media. Three waveguide structures were investigated: metal rib, metal-semiconductor-metal (MSM), and triangular metal groove. In all three structures, we observed strong plasmon mode confinement with nanoscale spot-sizes and corresponding simulated gain values compatible with existing semiconductor technology. We show the effect of systematic modification of waveguide geometry on the required gain for achieving lossless propagation in all the three plasmonic waveguide structures. We demonstrate that lossless propagation with subwavelength spot sizes well below the diffraction limit of light can be obtained by controlling the geometrical parameters of the proposed waveguides.

Dimensional Accuracy of an Epoxy Die Material Using Different Polymerization Methods

Shrinkage of resinous die materials during setting reaction limits their acceptance, even though these materials show several advantages compared to stone die materials with respect to strength, abrasion resistance, and detail reproduction. The purpose of this study was to determine if retarding the setting reaction during polymerization and altering the base-to-catalyst ratio, as suggested by previous studies, can be recommended for resinous die materials to reduce the inaccuracy in transferring the spatial position of teeth or implants from the oral cavity to the master cast. A Blue Star Type E epoxy resin die material was tested. A reference triangular metal master die was fabricated. Forty medium-consistency polyether impressions of this model were made. Four groups (S, M, N, P) were compared, and ten dies were fabricated for each group. In the S group, the epoxy resin die material was manipulated according to the manufacturer's instructions; in the other three groups, the epoxy resin die material was manipulated by retarding the setting reaction and by modifying the epoxy resin base/activator ratio. One-way ANOVA revealed significant differences between the four groups of the epoxy resin die material (p < 0.0001). Tukey's multiple comparisons test (p < 0.05) revealed that none of the resin groups was similar to the metal master die for each of the tested dimensions (A, B, and C). For the specific dimension C, however, the P group was statistically closer to the metal master die than the S group. The epoxy resin die material tested in this research did not improve its dimensional accuracy following retarding polymerization or modifying the epoxy resin base/activator ratio. The epoxy resin material exhibited higher contraction variability across all tested groups. This shrinkage can significantly affect the dimension of the master cast.

Glycal–ruthenium carbonyl clusters: Syntheses, characterization, and anticancer activity

Four new chiral ruthenium carbonyl cluster complexes Ru 3(μ-H) 2(CO) 9(L-2H) ( 1), Ru 3(μ-H) 2(CO) 7(L-2H)(dppm) ( 2) , Ru 3(μ-H) 2(CO) 7(L-2H)(PPh 3) 2 ( 3) , Ru 3(μ-H) 2(CO) 7(L-2H)(dppe) ( 4) containing a dehydrogenated form (L-2H) of 3,4,6-tri- O-benzyl- d-galactal (L) as a chiral ligand have been prepared and characterized. The anticancer activity of five compounds 1–4 and Ru 3(μ-H) 2(CO) 9(L-2H) 5 (L = tribenzyl glucal) against six types of human cancer cell lines was studied and compared to cisplatin. Compound 1 was chosen to produce more detailed growth curves based on overall highest activity profile. The structure of compound 2 was established by a single-crystal X-ray diffraction analysis. The structure based on triangular metal framework contains a bridging dehydrogenated tribenzyl galactal ligand bonded in a parallel μ 3-η 2-bonding mode and a bridging dppm ligand. Variable-temperature NMR studies show that the two hydride ligands in compounds 1 and 2 are dynamically active on the NMR time scale at room temperature.

Numerical and experimental investigation of wedge tip radius effect on wedge plasmons

We report numerical analysis and experimental observation of strongly localized plasmons guided by triangular metal wedges and pay special attention to the effect of smooth (nonzero radius) tips. Dispersion, dissipation, and field structure of such wedge plasmons are analyzed using the compact two-dimensional finite-difference time-domain algorithm. Experimental observation is conducted by the end-fire excitation and near-field scanning optical microscope detection of the predicted plasmons on 40° silver nanowedges with the wedge tip radii of 20, 85, and 125 nm that were fabricated by the focused-ion beam method. The effect of smoothing wedge tips is shown to be similar to that of increasing wedge angle. Increasing wedge angle or wedge tip radius results in increasing propagation distance at the same time as decreasing field localization (decreasing wave number). Quantitative differences between the theoretical and experimental propagation distances are suggested to be due to a contribution of scattered bulk and surface waves near the excitation region as well as the addition of losses due to surface roughness. The theoretical and measured propagation distances are several plasmon wavelengths and are useful for a range of nano-optical applications.

Triangular metal wedges for subwavelength plasmon-polariton guiding at telecom wavelengths

We report on subwavelength plasmon-polariton guiding by triangular metal wedges at telecom wavelengths. A high-quality fabrication procedure for making gold wedge waveguides, which is also mass-production compatible offering large-scale parallel fabrication of plasmonic components, is developed. Using scanning near-field optical imaging at the wavelengths in the range of 1.43-1.52 microm, we demonstrate low-loss (propagation length approximately 120 microm) and well-confined (mode width congruent with 1.3 microm) wedge plasmon-polariton guiding along triangular 6-microm-high and 70.5 degree-angle gold wedges. Experimental observations are consistent with numerical simulations performed with the multiple multipole and finite difference time domain methods.

Probing Defect Sites on TiO2 with [Re3(CO)12H3]: Spectroscopic Characterization of the Surface Species

Samples of the anatase phase of titania were treated under vacuum to create Ti(3+) surface-defect sites and surface O(-) and O(2) (-) species (indicated by electron paramagnetic resonance (EPR) spectra), accompanied by the disappearance of bridging surface OH groups and the formation of terminal Ti(3+)-OH groups (indicated by IR spectra). EPR spectra showed that the probe molecule [Re(3)(CO)(12)H(3)] reacted preferentially with the Ti(3+) sites, forming Ti(4+) sites with OH groups as the [Re(3)(CO)(12)H(3)] was adsorbed. Extended X-ray absorption fine structure (EXAFS) spectra showed that these clusters were deprotonated upon adsorption, with the triangular metal frame remaining intact; EPR spectra demonstrated the simultaneous removal of surface O(-) and O(2) (-) species. The data determined by the three complementary techniques form the basis of a schematic representation of the surface chemistry. According to this picture, during evacuation at 773 K, defect sites are formed on hydroxylated titania as a bridging OH group is removed, forming two neighboring Ti(3+) sites, or, when a Ti(4+)-O bond is cleaved, forming a Ti(3+) site and an O(-) species, with the Ti(4+)-OH group being converted into a Ti(3+)-OH group. When the probe molecule [Re(3)(CO)(12)H(3)] is adsorbed on a titania surface with Ti(3+) defect sites, it reacts preferentially with these sites, becoming deprotonated, removing most of the oxygen radicals, and healing the defect sites.

Nanofocusing of light energy by ridged metal heterostructures

With regard to thin Ag and Al films of the same thickness, the phase velocity of surface plasmon polaritons (SPPs) on the Ag surface is smaller than that on the Al surface. We have designed a ridged metal heterostructure (RMH) for nanofocusing of light energy. Finite difference time domain simulations reveal that the RMHs constructed with both the Ag and Al films can result in giant local field enhancement, instead of around the sharp corners, as the triangular metal nanocrystals constructed with a homogeneous metal material do, in the middle part of the structures. Further assembly of the RMHs can construct interesting nanoantennas and array probes, implying potential applications of the RMHs in nanophotonics and biophotonics.

Neutron Powder Diffraction with natSm: Crystal Structures and Magnetism of a Binary Samarium Deuteride and a Ternary Samarium Magnesium Deuteride.

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Assemblies of Two New Metal−Organic Frameworks Constructed from Cd(II) with 2,2‘-Bipyrimidine and Cyclic Oxocarbon Dianions CnOn2- (n = 4, 5)

Two extended networks of Cd(II) with 2,2‘-bipyrimidine (bpym) and cyclic oxocarbon dianions CnOn2- (n = 4, 5) with formulas [Cd(C4O4)(bpym)0.5(H2O)] (1) and [Cd(C5O5)(bpym)0.5(H2O)] (2) have been synthesized and characterized by single-crystal X-ray diffraction studies. Structural determination reveals that, in compounds 1, each Cd center lies in a seven-coordinate environment bonded to two bpym nitrogen atoms and five oxygen donors from four squarate and one water molecules. The squarate acts as a bridging ligand with two different binding modes, a tetramonodentate (μ4) and a bis-bridging (μ4) coordination mode, linking the Cd(II) ions to form a two-dimensional (2D) metal−squarate layer. Adjacent layers are then mutually linked via bridges of bis-bidentate bpym ligands constructing a three-dimensional (3D) triangular metal−organic framework (MOF). In compound 2, each Cd center lies in an eight-coordinate environment bonded to two bpym nitrogen atoms and six oxygen donors from three croconate ligands and ...

P–C and C–H bond cleavages of dppm in the thermal reaction of [Ru 3(CO) 10(μ-dppm)] with benzothiophene: X-ray structures of [Ru 6(μ-CO)(CO) 13{μ 4-PhP(C 6H 4)PPh}(μ 6-C)] and [Ru 4(CO) 9(μ 3-η 2-PhPCH 2PPh 2)(μ 4-η 6:η 1:η 1-C 6H 4)(μ-H)

The thermal reaction of [Ru 3(CO) 10(μ-dppm)] ( 1) with benzothiophene in refluxing toluene gives a complex mixture of products. These include the known compounds [Ru 2(CO) 6{μ-CH 2PPh(C 6H 4)PPh}] ( 2), [Ru 2(CO) 6{μ-C 6H 4PPh(CH 2)PPh}] ( 3), [Ru 3(CO) 9{μ 3-η 3-(Ph)PCH 2P(Ph)C 6H 4}] ( 4) and [Ru 3(CO) 10{μ-η 2-PPh(CH 2)(C 6H 4)PPh}] ( 6), as well as the new clusters [Ru 6(μ-CO)(CO) 13{μ 3-η 2-PhP(C 6H 4)PPh}(μ 6-C)] ( 5) and [Ru 4(CO) 9(μ 3-η 2-PhPCH 2PPh 2)(μ 4-η 6:η 1:η 1-C 6H 4)(μ-H)] ( 7). The solid-state molecular structures of 5 and 7 were confirmed by single crystal X-ray analyses. Compound 5 consists of interesting example of a hexaruthenium interstitial carbido cluster having a tetradentate diphosphine ligand derived from the activation of P–C and C–H bonds of the dppm ligand in 1. The tetranuclear compound 7 consists of a unique example of a non-planar spiked triangular metal fragment of ruthenium [Ru(1), Ru(2) and Ru(3)] unit with Ru(4) being bonded to Ru(1). The μ 4-η 1:η 6:η 1-benzyne ligand in this compound represents a previously uncharacterized bonding mode for benzyne. Compounds 5 and 7 do not contain any benzothiophene-derived ligand. The reaction of 4 with benzothiophene gives 2, 3, 5 and 6. Thermolysis of 1 in refluxing toluene gives 2, 3 and 4; none of 5 and 7 is detected in reaction mixture.

Neutron Powder Diffraction with natSm: Crystal Structures and Magnetism of a Binary Samarium Deuteride and a Ternary Samarium Magnesium Deuteride

Binary SmH(3) (trigonal, a=656.7(3), c=680.1(3) pm, P$\bar 3$c1, Z=6), ternary SmMg2H7 (tetragonal, a=626.47(6), c=937.2(2) pm, P4(1)2(1)2, Z=4) and the corresponding deuterides SmD3 (a=653.9(1)m, c=676.7(2) pm) and SmMg2D7 (a=624.10(1), c=934.81(2) pm) have been prepared by hydrogenation (deuteration) of elemental samarium and the Laves phase SmMg2, respectively, and investigated by X-ray and neutron powder diffraction and SQUID and vibration magnetometry. The problem of the enormous neutron absorption of the natural isotopic mixture (natSm) is circumvented by carefully choosing the neutron wavelength (approximately 50 pm) and the use of double-walled cylindrical sample holders and a high-intensity neutron diffractometer (D4c at ILL). SmD3 crystallises with a tysonite-type structure and has three independently ordered deuterium atom sites with trigonal-planar, trigonal-pyramidal and tetrahedral metal environments and Sm--D bond lengths in the range 220(1)-258(1) pm (average: 235 pm). SmMg2D7 is a new deuteride that crystallises with an LaMg2D7-type structure. It displays four fully occupied deuterium sites having triangular and tetrahedral metal environments and Sm--D bond lengths in the range 227.6(5)-246.8(8) pm (average: 239 pm). These are the first samarium-deuterium bond lengths to be reported. Both deuterides are paramagnetic down to 2 K (SmD3: mueff=0.63(1) muB, thetap approximately -4 K; SmMg2D7: mueff=0.57(2) muB, thetap approximately -4 K). Their crystal structures and chemical and physical properties suggest mainly ionic bonding according to the limiting ionic formulae Sm3+(H-)3 and Sm3+(Mg2+)2(H-)7.

Universality in one-dimensional orbital wave ordering in spinel and related compounds: an experimental perspective

Recent state-of-the-art crystallographic investigations of transition metal spinel compounds have revealed that the d-orbital charge carriers undergo ordering transitions with the formation of local ‘molecular bonding’ units such as dimers in MgTi2O4, octomers in CuIr2S4, and heptamers in AlV2O4. Herein, we provide a unifying scheme involving one-dimensional (1D) orbital wave (OW) ordering applicable to all of these spinels. The relative phase of the orbitals in the chains is shown to be crucial to the formation of different local units, and thus both the amplitude and phase of the OW play important roles. Examination of Horibe et al's (2006 Phys. Rev. Lett.96 086406) structure for AlV2O4 serves as the vehicle for developing the general behaviour for such orbital wave ordering. Ordered AlV2O4 will be seen to organize into three equivalent chains in 2D Kagome planes coupled so as to form units of three dimer bonds. Three additional equivalent chains manifest a more complex tetramerization with three different charge states and two different bonding schemes. The OW ordering scheme developed is extended to other spinel and related compounds with local triangular transition metal coordination and partial filling of the t2g-d orbitals.

En Route to the Formation of High-Efficiency, Osmium(II)-Based Phosphorescent Materials

Triosmium cluster complexes [Os3(CO)8(fppz)2] (2a) and [Os3(CO)8(fptz)2] (2b) bearing two 2-pyridyl azolate ligands were synthesized in an attempt to establish the reaction mechanism that gives rise to the blue-emitting phosphorescent complexes [Os(CO)2(fppz)2] (1a) and [Os(CO)2(fptz)2] (1b) [(fppz)H = 3-(trifluoromethyl)-5-(2-pyridyl)pyrazole; (fptz)H = 3-(trifluoromethyl)-5-(2-pyridyl)triazole]. X-ray structural analysis of 2b showed an open triangular metal framework incorporating multisite-coordinated 2-pyridyltriazolate ligands. Treatment of 2 with the respective 2-pyridylazolate ligand led to the formation of blue-emitting complex 1b, confirming their intermediacy, while the reaction of 2b with phosphine ligand PPh2Me afforded two hitherto novel hydride complexes 3 and 4, for which the reversible interconversion was clearly established at higher temperatures (> 180 degrees C). The single-crystal X-ray diffraction analyses of 3 and 4 confirmed their monometallic and isomeric nature, together with the coordination of two phosphine ligands located in the trans-disposition and one CO and one hydride located opposite to the pyridyl triazolate chelate. Subtle differences in photophysical properties were examined for isomers 3 and 4 on the basis of steady state absorption and emission, the relaxation dynamics, and temperature-dependent luminescent studies. The results, in combination with time-dependent density function theory (TDDFT) calculations, provide fundamental insights into the future design and preparation of highly efficient phosphorescent emitters.

Adiabatic nano-focusing of plasmons by sharp metallic wedges

In this paper, we demonstrate the possibility of efficient adiabatic nano-focusing of plasmons by a sharp triangular metal wedge. The geometrical optics approach and the approximation of continuous electrodynamics are used for the analysis. In particular, it is demonstrated that both the phase and group velocities of an incident anti-symmetric (with respect to the magnetic field) plasmon tend to zero at the tip of the wedge, and the plasmon adiabatically slows down, eventually dissipating in the metal. Typically, the amplitude of the plasmon significantly increases near the wedge tip, but this increase is finite even in the absence of dissipation in the metal. The dependence of the local field enhancement near the tip on structural parameters, dissipation in the metal, angle of incidence, etc., is analyzed in this paper. It is also shown that an anti-symmetric film plasmon can effectively be guided by a triangular metal wedge, forming a wedge plasmon mode that is localized near the tip of the wedge and propagates along this tip. A new existence condition for these localized wedge plasmons is derived and discussed.

Vapor-phase synthesis of 1,2-dihydro-2,2,4-trimethylquinolines from anilines and acetone over group 5–7 metal halide clusters as catalysts

Reaction of aniline with acetone to form 1,2-dihydro-2,2,4-trimethylquinoline ( 1) was studied in a gas-phase reaction over halide clusters as solid acid catalysts. After activation of a niobium halide cluster, [(Nb 6Cl 12)Cl 2(H 2O) 4]·4H 2O ( 2), which has an octahedral metal framework, at an elevated temperature in a hydrogen stream for 1 h, reaction was initiated by introduction of stoichiometric amounts of aniline and acetone at the activation temperature. The catalysis to yield 1 became evident above 200 °C. Both the catalytic activity of 2 and the selectivity for 1 increased with increasing temperature, having a local maximum at 300 °C. The selectivity for 1 was 76% with 34% conversion at 450 °C. Reactions of o-, m-, and p-toluidines with acetone also produced the corresponding quinolines. The chloride clusters of tantalum with the same metal framework and rhenium with a triangular metal framework also catalyzed the condensation. Thus, a halide cluster can be a substitute for liquid acid, particularly at high temperatures.

Synthesis of [{Os 3(CO) 10(μ 2-H)} 2{μ 2,μ 2-NC 6H 4C 6H 4N}] and [{Os 3(CO) 9(μ 2-H)PPh 3} 2{μ 2,μ 2-NC 6H 4C 6H 4N}]: Carbon–carbon bond formation promoted by organorhodium species

Synthesis and characterization of linked cluster [{Os 3(CO) 10(μ 2-H)} 2{μ 2,μ 2-NC 6H 4C 6H 4N}] ( 1) from the reaction of [Os 3Rh(μ-H) 3(CO) 12] with aniline in the presence of an excess amount of 4-vinyl phenol in refluxing heptane is reported. A similar reaction with [Os 3(CO) 10(NCMe) 2] as starting material gave a known compound, [Os 3(CO) 10(μ 2-H)(μ 2-HNC 6H 5)] ( 2). The treatment of complexes 1 and 2 with Wilkinson’s catalyst in refluxing heptane respectively, yielded [{Os 3(CO) 9(μ 2-H)PPh 3} 2{μ 2,μ 2-NC 6H 4C 6H 4N}] ( 3). An interesting and unexpected C–C coupling of phenyl-amido ligands was observed in complexes 1 and 3, which is believed to be catalysed by the organometallic rhodium species. The newly synthesized compounds 1 and 3 were fully characterized by IR, 1H NMR spectroscopy, mass spectroscopy, elemental analysis, and X-ray crystallography. Both structures 1 and 3 comprise two triangles of osmium atoms. The two triangular osmium metal cores are linked by a bi-amido ligand via the two nitrogen atoms N(1) and N(1)* and N(1) and N(2), at their equatorial sites. The electronic absorption spectra of complexes 1, 2, and 3 display both low energy absorption, dπ (Os) → π* (amido) metal-to-ligand charge-transfer (MLCT) transition, and π → π* intra-ligand electronic transitions of the amido and bi-amido ligands.

In 3Ir 3B, In 3Rh 3B and In 5Ir 9B 4, the first indium platinum metal borides

The first indium platinum metal borides have been synthesized and structurally characterized by single crystal X-ray diffraction data. In 3Ir 3B and In 3Rh 3B are isotypic. They crystallize with the hexagonal space group P 6 ¯ 2 m and Z = 1 . The lattice constants are a = 6 8 5.7 8 ( 1 ) pm , c = 2 8 7.3 0 ( 1 ) pm for In 3Ir 3B and a = 6 7 8.4 7 ( 3 ) pm , c = 2 8 8.6 1 ( 6 ) pm for In 3Rh 3B. The structure which is derived from the Fe 2P type is characterized by columns of boron centered triangular platinum metal prisms inserted in a three-dimensional indium matrix. The indium atoms are on split positions. In 5Ir 9B 4 (hexagonal, space group P 6 ¯ 2 m , a = 5 5 9.0 ( 2 ) pm , c = 1 0 3 2.6 ( 3 ) pm , Z = 1 ) crystallizes with a structure derived from the CeCo 3B 2 type. The structure can be interpreted as a layer as well as a channel structure. In part the indium atoms are arranged at the vertices of a honeycomb net (Schlaefli symbol 6 3) separating slabs consisting of double layers of triangular Ir 6B prisms, and in part they form a linear chain in a hexagonal channel formed by iridium prisms and indium atoms of the honeycomb lattice.

Theoretical and experimental investigation of strongly localized plasmons on triangular metal wedges for subwavelength waveguiding

We report numerical analysis and experimental observation of strongly localized plasmons guided by a triangular metal wedge. Dispersion and dissipation of such wedge plasmons are analyzed using the finite-difference time-domain algorithm. Experimental observation is conducted by the end-fire excitation and near-field detection of the predicted plasmons on a 40° silver nanowedge. Good agreement with the theoretically predicted propagation distances is demonstrated. Differences between the theoretical and experimental field distribution are explained by insufficient resolution of the near-field optical probe.

Reactivity of the Unsaturated Triosmium Cluster Os3(CO)8(μ3-η2-Ph2PCH2P(Ph)C6H4)(μ-H) with Benzothiophene: Activation of a P−C Bond in Diphosphine and a C−H Bond in Benzothiophene

Treatment of the electronically unsaturated cluster Os3(CO)8(μ3-η2-Ph2PCH2P(Ph)C6H4)(μ-H) (1) with benzothiophene in refluxing m-xylene afforded Os3(CO)7(μ-PPh2)(μ-PMePh)(μ3-η2-C6H4) (2), Os3(CO)7(μ3-η2-PPh(C6H4)CH2PPh)(μ3-η3-SC8H5)(μ-H) (3), and Os3(CO)8(μ-CO)(μ3-η2-PPh(C6H4)CH2PPh) (4). Thermolysis of 1 in refluxing toluene for 35 h afforded only 4, whereas in refluxing m-xylene it gave both 4 and 2. Compound 4 can also be obtained from the thermolysis of Os3(CO)9(μ3-η2-PPh(C6H4)CH2PPh2)(μ-H) (5) in refluxing toluene. All the complexes have been structurally characterized. Compound 3 contains a unique example of a μ3-η2 benzothienyl ligand coordinated through the sulfur atom and the C−C double bond of the five-membered ring in a σ,π vinyl fashion. This coordination mode results in the rupture of one osmium−osmium bond, whereas the basic triangular metal framework is retained in the case of 2 and 4, which are derived from the activation of P−C and C−H bonds of 1 and do not contain any benzothiophene-derived ligand.

First triangular carboxylate cluster with the Fe(II)Fe(II)Fe(II) metal core

First iron(II) carboxylate cluster with the triangular metal core K[Fe3(μ3-OH)(OOCCMe3)6(HOOCCMe3)3] (I) has been isolated from the reaction between FeSO4·7H2O and KOOCCMe3 in the presence of the excess of pivalic acid in MeCN. The X-ray data and magnetic study show the complex molecular unit to be constructed of the Fe(II) atoms.