Crystal Structure,Characterization, and Luminescence Properties of Mn4+-Doped K3Nb2O4F5

In this paper, we present the high-pressure/high-temperature synthesis and characterization of the potassium fluoridooxidoniobate K₃Nb₂O₄F₅. Single-crystal analysis revealed that the phase crystallizes in the trigonal space group m (hR18) with a=5.799(2), c=21.371(4) Å, V=622.4(4) ų and Z=3 at T=299 K exhibiting a structure type closely related to that of Ba₂RbFe₂F₉. The assignment of the anion positions to oxygen and fluorine is based on crystallographic data and BLBS/CHARDI calculations. Further characterization via EDX spectroscopy was carried out, corroborating the ratio of K to Nb. Doping of the title compound with Mn⁴⁺ was achieved in a secondary step using a ball-mill, resulting in a red phosphor material, which was additionally analyzed by luminescence spectroscopy. The emission maximum is located at λ_max=630 nm.     

Cationic ester-containing gemini surfactants: determination of aggregation numbers by time-resolved fluorescence quenching

The micellar aggregation number of a series of ester-containing gemini surfactants has been determined with steady state and with time-resolved fluorescence quenching. The latter method gave values of aggregation number about twice those obtained with the former method. It was found that the length of the spacer was the most important factor affecting the aggregation number. The length and the nature of the surfactant alkyl chains were of less importance in spite of the fact that the length of the alkyl chains strongly affects the solution properties of the unimers.     

5,5'-Azoxytetrazolates - a new nitrogen-rich dianion and its comparison to 5,5'-azotetrazolate

A modification of the synthesis of sodium 5,5'-azotetrazolate pentahydrate, described by Thiele in 1898, yields the unknown and unexpected corresponding 5N-oxido derivative sodium 5,5'-azoxybistetrazolate pentahydrate (Na(2)zTO·5H(2)O, ). Purification was achieved by recrystallization based on the better solubility of Na(2)zTO·5H(2)O in water. Different nitrogen-rich salts, such as the diammonium (), the dihydroxylammonium (), the bis-diaminoguanidinium (), the bis-triaminoguanidinium () and the diaminouronium salt (), have been prepared using metathesis reactions starting from barium 5,5'-azoxybistetrazolate pentahydrate () and ammonium, hydroxylammonium, diaminoguanidinium or diaminouronium sulfate and triaminoguanidinium chloride, respectively. The nitrogen rich azoxy-derivatives were characterized using NMR, IR and Raman spectroscopy, mass spectrometry and elemental analysis. Additionally the solid state structures of , , and were determined by single crystal X-ray diffraction. The heats of formation of and and their corresponding azo-tetrazolate derivatives were calculated by the atomization method based on CBS-4M enthalpies. With these values and the crystal densities, several detonation parameters such as the detonation velocity, detonation pressure and specific impulse were calculated (EXPLO5) and compared. The sensitivities towards shock (BAM drophammer), friction (BAM friction tester) and electrostatic discharge of the described compounds were determined.     

Novel access to carbodiphosphoranes in the coordination sphere of group 10 metals: template synthesis and protonation of PCP pincer carbodiphosphorane complexes of C(dppm)2

In a novel template synthesis of carbodiphosphoranes (CDPs), the phosphine functionalized CDP ligand C(dppm)(2) (dppm = Ph(2)PCH(2)PPh(2)) is formed in the coordination sphere of group 10 metals from CS(2) and 4 equivalents of dppm. The products are the PCP pincer complexes [M(Cl)(C(dppm)(2)-κ3P,C,P)]Cl (M = Ni, Pd, Pt) and 2 equivalents of dppmS. The compound C(dppm)(2), which is composed of a divalent carbon atom and two dppm subunits, represents a new PCP-type pincer ligand with the formally neutral carbon Lewis base of the CDP functionality as the central carbon. Treatment of [M(Cl)(C(dppm)(2)-κ3P,C,P)]Cl (M = Pd, Pt) with hydrochloric acid results in protonation at the CDP carbon atom and the formation of the PCP pincer complexes [M(Cl)(CH(dppm)(2)-κ3P,C,P)]Cl(2) (M = Pd, Pt). The PCP pincer ligand [CH(dppm)(2)](+) involves a formally cationic central carbon donor. The reaction of [Ni(Cl)(C(dppm)(2)-κ3P,C,P)]Cl with HCl leads to the extrusion of NiCl(2) and formation of the diprotonated CDP compound [CH(2)(dppm)(2)]Cl(2), from which the monoprotonated conjugate base [CH(dppm)(2)]Cl is obtained upon addition of bases, such as NH(3). The crystal structures of [M(Cl)(C(dppm)(2)-κ3P,C,P)]Cl (M = Ni, Pd, Pt), [Ni(Cl)(C(dppm)(2)-κ3P,C,P)](2)[NiCl(4)], [M(Cl)(CH(dppm)(2)-κ3P,C,P)]Cl(2) (M = Pd, Pt) as well as [CH(2)(dppm)(2)]Cl(2) and [CH(dppm)(2)]Cl are presented. A comparison of the solid state structures reveals interesting features, e.g. infinite supramolecular networks mediated by C-H···Cl hydrogen bond interactions and an unexpected loss of molecular symmetry upon protonation in the complexes [M(CH(dppm)(2)-κ3P,C,P)(Cl)]Cl(2) (M = Pd, Pt) as a result of the flexible ligand backbone. Additionally the new compounds were characterized comprehensively in solution by multinuclear (31)P, (13)C and (1)H NMR spectroscopy: Several spectroscopic parameters show a striking variability in particular regarding the carbodiphosphorane functionality. Furthermore the compound [Ni(Cl)(C(dppm)(2)-κ3P,C,P)]Cl was examined by cyclic voltammetry (CV) and could be shown to display quasi-reversible oxidative as well as reductive behaviour.     

Evidence for stratification of deuterium-tritium fuel in inertial confinement fusion implosions

Measurements of the D(d,p)T (dd) and T(t,2n)(4)He (tt) reaction yields have been compared with those of the D(t,n)(4)He (dt) reaction yield, using deuterium-tritium gas-filled inertial confinement fusion capsule implosions. In these experiments, carried out on the OMEGA laser, absolute spectral measurements of dd protons and tt neutrons were obtained. From these measurements, it was concluded that the dd yield is anomalously low and the tt yield is anomalously high relative to the dt yield, an observation that we conjecture to be caused by a stratification of the fuel in the implosion core. This effect may be present in ignition experiments planned on the National Ignition Facility.     

Hydrogen Bonding in the Crystal Structures of New Imidazolium Triflimide Protic Ionic Liquids

Abstract  The synthesis and crystal structures of 1,3-diamino-2-methylimidazolium bis(trifluoromethylsulfonyl)imide (1), 1,3-dihydroxy-2-methylimidazolium bis(trifluoromethylsulfonyl)imide (2) and 1-(2-(diethylammonio)ethyl)-3-methylimidazolium bis(bis(trifluoromethylsulfonyl)imide) (4) are reported. The salts 1, 2 and 4 have melting points below 100 °C, the intermediate 1-(2-(diethylamino)ethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (3) is liquid at room temperature. Compound 1 is monoclinic, space group P2₁/n with a = 8.4979(4) ?, b = 12.2803(6) ?, c = 13.9400(7) ?, β = 93.086(4)°, and Z = 4. Compound 2 is monoclinic, space group P2₁/c with a = 7.6165(2) ?, b = 20.5323(8) ?, c = 9.7654(3) ?, β = 111.046(2)°, and Z = 4. Compound 4 is triclinic, space group with a = 8.5313(4) ?, b = 9.2157(4) ?, c = 20.5812(8) ?, α = 84.668(2)°, β = 83.738(2)°, γ = 63.096(2)°, and Z = 2. The ions in 1 build a network of N–H···O hydrogen bonds, in 2 they are linked to chains by O–H···N and bifurcated O–H···O hydrogen bonds, whereas in 4 they form pairs by N–H···O contacts. The triflimide anions adopt transoid conformations. Index Abstract  Short interionic contacts, conformational flexibility, and disorder phenomena were identified in the crystal structures of three new, low-melting, protic imidazolium triflimides.