Highly efficient water‐soluble visible light photoinitiators

The monoacylphosphineoxide (MAPO) salts Na‐TPO and Li‐TPO and the bisacylphosphineoxide (BAPO) salts BAPO‐ONa and BAPO‐OLi define an important and in the latter case a new class of water‐soluble photoinitiators (PIs) for radical polymerization. These compounds showed excellent water‐solubility of at least 29 g/L for Na‐TPO and up to 60 g/L for BAPO‐ONa in deionized water, thus exceeding the solubility of the state of the art PI for water‐based systems Irgacure 2959 ( I2959 ) 6‐ to 12‐fold. However, biocompatibility, storage stability, and reactivity were equally important to replace the state of the art compounds. Concerning these properties, the MAPO and BAPO salts were at least in the same range (biocompatibility, stability) or showed even better results (reactivity) and had the additional advantage of visible light initiation. Na‐TPO and Li‐TPO achieved double bond conversions of an aqueous solution of N‐acryloylmorpholine over 97% with broad band irradiation (320–500 nm), Li‐TPO showed additionally very good biocompatibility (LC₅₀ = 3.1 mmol/L) and BAPO‐OLi showed highest reactivity with visible light irradiation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 473–479     

Bent Phosphaallenes With “Hidden” Lone Pairs as Ligands

Phosphaheteroallenes R−P=C=L, with L = N-heterocyclic carbenes (NHCs), can be viewed to a certain extent as phosphaisonitriles stabilized with NHCs, R−P=C:←L. The suitability of these molecules as ligands for coinage-metal ions was investigated and coordination through the central carbon center was observed in most cases. A combination of experiments, spectroscopic methods, and DFT calculations indicates the presence of a hidden electron pair at the carbon center of R−P=C:←L. Remarkably, this lone pair also inserts intramolecularly in C−H bonds showing the carbene-type reactivity which is expected for phosphaisonitriles.     

The Single Server Queue with Mixing Dependencies

Methodology and Computing in Applied Probability - We study a single server queue, where a certain type of dependence is introduced between the service times, or between the inter-arrival times, or...     

Transference Numbers in the H2O + NaCl + MgCl2 System at T = 298.15 K,Determined in a Five-Compartment Hittorf Cell

The concentration range of transference number measurements with the Hittorf cell has been extended up to a total concentration of c _T = 3.4 mol·dm^?3 for the H₂O + NaCl + MgCl₂ ternary system at (298.15 ± 0.05) °C. This was achieved with a redesigned Hittorf cell, by dividing each of the anodic/cathodic compartments into two subcompartments: one with a low concentration of H₂O + NaCl for the electrode reaction and another one in contact with the middle compartment with the ternary solution to be measured. Measurements of the transference numbers were also made for the corresponding H₂O + NaCl and H₂O + MgCl₂ binary systems. The experimental details and the results are described.     

DARSTELLUNG UND NMR-SPEKTROSKOPISCHE UNTERSUCHUNGEN DER 2-FLUOR-2,2-DIPHENYL-2,3-DIHYDRO-1,3,2λ5-BENZOXAZAPHOSPHOLE

Abstract

Pentakoordinierte Phosphorverbindungen vom Typ der 2.3-Dihydro-1.3.2-benzoxazaphosphole entstehen bei der Umsetzung von 2-Amino-phenolen oder N-Äthyl-2-hydroxy-anilinen mit Diphenyl-trifluorphosphoran unter Verwendung von Triäthylamin als Fluorwasserstoff-Akzeptor. Die Synthese einer großen Anzahl verschieden substituierter Spezies zeigt die Allgemeingültigkeit dieses Verfahrens. Die isolierbaren Substanzen werden durch NMR-Spektren (¹H, ³¹P, ¹⁹F) und die üblichen analytischen Methoden charakterisiert. Die Markierung einer Verbindung mit ¹⁵N trägt wesentlich zur Struktursicherung bei. Bei den 3-H-2-Fluor-2.2-diphenyl-1.3.2-benzoxazaphospholen wurde ein bemerkenswerter Zusammenhang zwischen P–F-Kopplungskonstante und dem F-shift aufgefunden, der eine lineare Korrelation dieser beiden Größen erkennen läßt.

Pentacoordinated phosphorus compounds of the type of 2,3-dihydro-1,3,2-benzoxazaphospholes originate from reaction of 2-aminophenol or N-ethyl-2-hydroxyaniline with diphenyl-trifluorophosphorane using triethylamine as an HF-acceptor. The described synthesis of a great number of differently substituted species indicates the wide field of application. The substances are characterized by nmr spectroscopy (¹H, ³¹P, ¹⁹F) and the usual analytical methods. By marking one compound with ¹⁵N the structure assignment is proved. Remarkably, the compounds of the type 3-H-2-fluoro-2,2-diphenyl-1,3,2-benzoxazaphospholes exhibit a nearly linear correlation between the P–F-coupling constants and the F-chemical shift.     

Facile Phenylphosphinidene Transfer Reactions from Carbene–Phosphinidene Zinc Complexes

Phosphinidenes [R-P] are convenient P₁ building blocks for the synthesis of a plethora of organophosphorus compounds. Thus far, transition-metal-complexed phosphinidenes have been used for their singlet ground-state reactivity to promote selective addition and insertion reactions. One disadvantage of this approach is that after transfer of the P₁ moiety to the substrate, a challenging demetallation step is required to provide the free phosphine. We report a simple method that enables the Lewis acid promoted transfer of phenylphosphinidene, [PhP], from NHC=PPh adducts (NHC=N-heterocyclic carbene) to various substrates to produce directly uncoordinated phosphorus heterocycles that are difficult to obtain otherwise.     

Non-universal shear viscosity from Einstein gravity

A very famous result of gauge/gravity duality is the universality of the ratio of shear viscosity to entropy density in every field theory holographically dual to classical, two-derivative (Einstein) gravity. We present a way to obtain deviation from this universality by breaking the rotational symmetry spontaneously. In anisotropic fluids additional shear modes exist and their corresponding shear viscosities may be non-universal. We confirm this by explicitly calculating the shear viscosities in a transversely isotropic background, a p-wave superfluid, and study its critical behavior. This is a first decisive step towards further applications of gauge/gravity duality to physical systems.     

Phosphaketenes as Building Blocks for the Synthesis of Triphospha Heterocycles

Unsaturated phosphorus compounds, such as phosphaalkenes and phosphaalkynes, show a versatile reactivity in cycloadditions. Although phosphaketenes (R?P?C?O) have been known for three decades, their chemistry has remained limited. Herein, we show that heteroatom‐substituted phosphaketenes, R₃E?P?C?O (E=Si, Sn), are building blocks for silyl‐ and stannyl‐substituted five‐membered heterocycles containing three phosphorous atoms. The structure of the heterocyclic anion depends on the nature of the tetrel atom involved. Although the silyl analogue [P₃C₂(OSiR₃)₂]^? is an aromatic 1,2,4‐triphospholide, the stannyl compound [P(CO)₂(PSnR₃)₂]^? is a 1,2,4‐triphosphacyclopenta‐3,5‐dionate with a delocalized OCPCO fragment. Because of their anionic character, these compounds can easily be used as building blocks, for example, in the preparation of a silyl‐functionalized hexaphosphaferrocene or the parent 1,2,4‐triphosphacyclopenta‐3,5‐dionate [P(CO)₂(PH)₂]^?. NMR spectroscopic investigations and computations have shown that the heterocycle‐formation reactions presented herein are remarkably complex.