Phosphorus Substitution Research Articles

ChemInform Abstract: Regioselective Alkylation Reactions of Enamines Derived from Phosphane Oxides — Synthesis of Phosphorus Substituted Enamino Esters, δ‐Amino‐phosphonates, Pyridone Derivatives and Pyrroles.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A modified oxidation procedure for ion-implanted silicon carbide devices annealed at low temperatures

There is recent evidence that the temperature at which implants in SiC are activated plays a determining role in the performance of some devices. One example is the dependence of the channel mobility of SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) on the annealing temperature needed to activate source and drain implants. Another example is the dependence of surface roughness on anneal temperature. In both cases, there are definite advantages in using low processing temperatures for implant activation anneals. This paper considers low-temperature ion implantation processing of SiC electronic materials, and modifications to the gate oxidation step for SiC MOSFETs that may be required by the use of low-temperature activation annealing. The term ‘low-temperature’ is used to indicate annealing temperatures well below 1500 °C which are typically used for donor implant activation in SiC. The substitution of phosphorus for nitrogen in the fabrication of MOSFETs, while enabling low-temperature activation annealing, leads to excessive gate leakage currents. The cause of oxide leakage is discussed speculatively in terms of excess carbon on the SiC prior to gate oxidation. These assumptions form the premise for SiC MOSFET experiments fabricated with phosphorus-implanted source and drain regions, and a modified oxidation procedure. MOSFETs built using phosphorus implants annealed at 1200 °C and the modified oxidation procedure exhibit I D/ I G current ratios greater than 10 4, and channel mobilities in excess of 10 cm 2/V s. The device yield is greater than 90%.

Regioselective Alkylation Reactions of Enamines Derived from Phosphane Oxides − Synthesis of Phosphorus Substituted Enamino Esters, δ-Amino-phosphonates, Pyridone Derivatives and Pyrroles

α-Substituted (2-iminoalkyl)phosphane oxides were obtained from the azaenolates of imines or enamines and alkyl halides. The functionalized imines or enamines thus obtained were used for the synthesis of δ-amino esters, δ-amino phosphonates and heterocycles such as 3,4-dihydropyridin-2-ones, 2-pyridones and pyrroles containing a phosphinyl substituent.

The influence of partial substitution of phosphorus by arsenic in monoclinic CsH2PO4. X-ray single crystal, vibrational and phase transitions in the mixed CsH2(PO4)0.72(AsO4)0.28

Partial substitution of P by As, leading to the solid solution CsH 2 (PO 4 ) 1− x (AsO 4 ) x , with x =0.28 (abbreviated as CDAP) has been shown. The structural characteristics of the crystals were analyzed by means of X-ray diffraction, which revealed that the new title compound is nearly isomorphous with the monoclinic phase of CsH 2 PO 4 (CDP). The structure was solved from 796 independent reflections with R 1 =0.0292 and Rw 2 =0.0702, refined with 59 parameters. The following results have been obtained: space group P2 1 , a =4.9250(4) Å, b =6.4370(3) Å, c =7.9280(6) Å, β =107.316(3)°, V =239.94(3) Å 3 , Z =2 and ρ cal =3.349 g cm −3 . The hydrogen bonds are clearly distinguished in the electron density maps which display distributions corresponding to order of protons. The shorter bond (2.452(4) Å), links the phosphate–arsenate groups into chains running along the b -axis and the longer bond (2.531(3) Å), crosslinks the chains to form (001) layers. The Raman and infrared spectra of CDAP recorded at room temperature in the frequency ranges 15–1200 cm −1 and 400–4000 cm −1 , respectively, confirm the presence of PO 3− 4 and AsO 3− 4 groups in the crystal. Differential scanning calorimetry traces show three phase transitions at 333, 449 and 490 K in this material, which are characterized by X-ray powder diffraction at high temperature. Graphic

Phosphorodithioates: synthesis and evaluation of new haptens for the generation of antibody acyl transferases

An extension of the transition state analogue (TSA) hapten approach for the elicitation of catalytic antibodies for acyl-transfer reactions is described. It is based on the enlistment of phosphorodithioate 1 as a stable mimic of the putative tetrahedral intermediate (TI −) formed during the base-catalyzed hydrolysis of bisaryl carbonate 2. Six members of a library of 25 monoclonal antibodies elicited to 1 catalyze the hydrolysis of 2. The most efficient catalyst, 48F10, exhibits Michaelis-Menten kinetics [ K m(2)=686 μM, k cat(2)=2.7 min −1, k cat (2) k uncat (2) =3×10 4 ] and is one of the most active carbonate hydrolyzing antibodies yet reported. This report highlights the utility of haptens that incorporate substitution of the non-bridging phosphorus(V) oxygen atoms present in the more classical TSA approaches with sulfur, to elicit efficient catalysts for acyl-transfer processes.

High-resolution X-ray diffraction studies on growth interrupted heterointerfaces grown by metalorganic vapor-phase epitaxy

We have investigated the behavior of group V atoms at growth interrupted heterointerfaces in an InP/AsH 3-exposure/InP multilayer structure grown by metalorganic vapor-phase epitaxy, whose interfaces are exposed to AsH 3 gases, by means of high-resolution X-ray diffraction on an atomic scale and its simulation technique. It is found that primary factors for the incorporation of arsenic (As) atoms into InP layers consists of two modes, one is the incorporation into the grown layer due to the substitution of phosphorus (P) atoms by As atoms, and the other is that into the subsequently grown InP layer due to the incorporation from solid deposition of As atoms on the susceptor. In the processes, P atoms are substituted by As atoms not only in the monolayer of the surface but also in the internal layer. It is also found that the depth where the As atoms are incorporated critically depends on the exposure time of the InP surface to the AsH 3 ambiance. And As atoms which replace P atoms in the monolayer of the surface are easily evaporated in the PH 3 ambiance, but it is difficult to remove the incorporated As atoms inside the grown InP layer even by a long PH 3 purge time.

Phosphoran olivine from Pine Canyon, Piute Co., Utah

AbstractOlivines containing up to 6.1 wt.% P2O5 occur in association with apatite and an unnamed NaCaMg phosphate phase. Phosphoran olivine has been recorded only in pallasite meteorites and from one other terrestrial occurrence. The rarity of palpable phosphorus substitution for silicon may be related to the fact that in most terrestrial rocks, phosphorus is incorporated initially, and remains as, apatite; thus phosphorus excess in an undersilicated environment must be uncommon. However the highly capricious distribution of phosphorus in individual olivines from this and the meteoritic occurences suggests disequilibrium, and questions whether phosphoran olivine is ever stable relative to combinations of P-free olivine and phosphate/phosphide minerals.

P 2-induced [formula omitted] exchange on GaAs during gas-source molecular beam epitaxy growth interruptions

P As exchange behavior on GaAs under a P 2 flux in a gas-source molecular beam epitaxy (GSMBE) system has been studied by reflection high-energy electron diffraction (RHEED), high-resolution double-crystal X-ray rocking curves (DCXRC) and cross-sectional scanning tunneling microscopy (STM). We found that the exposure of GaAs to a P 2 flux results in severe substitution of As atoms by P atoms at the normal temperature for growing GaAs ( T s = 570°C). When T s < 500°C, a streaky RHEED pattern can be maintained even during P 2 flux exposure of over 10 min. DCXRC of a 25-period P 2-exposed GaAs structure grown at 550°C show a set of satellite peaks, indicating formation of a periodic structure. Approximately an average of 0.45 monolayer of phosphorus is incorporated at each interface via As P exchange. High-resolution cross-sectional STM images reveal non-uniform (both laterally and vertically) interfacial layers of width as large as 10 monolayers. For the sample grown at 450°C, no clear satellite peaks are present. STM images of the sample exhibit much thinner interlayers, consistent with a lower level of phosphorus substitution.

The effect of substituting phosphorus for a ring carbon atom in the valence isomers cyclobutene, bicyclobutane, and 1,3‐butadiene. a quantum‐chemical investigation

AbstractCyclobutene, bicyclobutane, and 1,3‐butadiene are valence isomers within the concept of the Woodward‐Hoffman rules. According to thermochemical considerations and in agreement with energy optimized quantum‐chemical calculations at the ab initio RHF and MP2/6‐31G(d,p) levels bicyclobutane is the least and 1,3‐butadiene the most stable valence isomer. Phosphorus substitution exerts a considerable effect on the relative stabilities of the various valence isomers. Bicyclobutanes containing phosphorus atoms in the bridgehead positions are considerably more stable than the other phosphorus‐substituted valence isomers. This conclusion was confirmed by an analysis of the natural bond populations.

Integrated approach to the point-non point-pollution abatement in urban drainage

An area in Switzerland of 260 km2 with 230 000 inhabitants was analysed for the feasibility of combined sewage overflow (CSO) tanks to reduce the pollution in receiving waters during rain events. The case study demonstrates the consideration of the point and of the non point pollution with respect to choice and application of water pollution control measures in urban drainage. For example, measures which reduce pollutant sources (e.g. substitution of phosphorus in detergents) or reduce surface runoff (e.g. dispersed retention or infiltration of rainfall runoff) are more efficient than a strategy of uniform and area wide application of CSO tanks. The new Swiss guideline for Integrated Urban Drainage Master Planning (IUDMP) introduces a radical changes in the scope and in the procedures of planning process. This guideline defines the urban drainage system as one single system, consisting of urban area, soil and ground water system, drainage network, waste water treatment plant and receiving waters. The consideration of comprehensive urban drainage system allows the choice of site-specific and problem-related measures.

Integrated approach to the point-non point-pollution abatement in urban drainage

An area in Switzerland of 260 km2 with 230 000 inhabitants was analysed for the feasibility of combined sewage overflow (CSO) tanks to reduce the pollution in receiving waters during rain events. The case study demonstrates the consideration of the point and of the non point pollution with respect to choice and application of water pollution control measures in urban drainage. For example, measures which reduce pollutant sources (e.g. substitution of phosphorus in detergents) or reduce surface runoff (e.g. dispersed retention or infiltration of rainfall runoff) are more efficient than a strategy of uniform and area wide application of CSO tanks. The new Swiss guideline for Integrated Urban Drainage Master Planning (IUDMP) introduces a radical changes in the scope and in the procedures of planning process. This guideline defines the urban drainage system as one single system, consististing of urban area, soil and ground water system, drainage network, waste water treatment plant and receiving waters. The consideration of comprehensive urban drainage system allows the choice of site-specific and problem-related measures.

Synthesis and Photochemical Properties of the Orthogonal Porphyrin Triad Composed of Free-Base and Phosphorus(V) Porphyrins

Abstract A novel triad molecule composed of three porphyrins was synthesized by the use of the axial substitution of phosphorus(V) porphyrin. Photochemical properties of the triad suggest that the photoinduced electron transfer was accomplished.

ChemInform Abstract: Phosphorus Substituted “CN2” Groups: Building Blocks in Heterocyclic Chemistry

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The Synthesis of the Molecular Sieve Cloverite in the Presence of Heteroatoms

Various cloverite samples containing a series of heteroatoms have been synthesized at optimized HF : Ga2O3 ratios and characterized by XRD, adsorption measurements, infrared and ESR spectroscopy. The results show that the pure cloverite structure is only formed in the presence of Ti, Si, Zn, and Mg ions. However, no real evidence can be given for an isomorphous substitution of phosphorus or gallium by the heteroatoms. Conditions for the storage of detemplated cloverite samples are given, which avoid amorphization under the influence of moisture.

Simulation of the electronic and vibrational structure of hydrogenated amorphous silicon using cluster models

AbstractA set of simple models of hydrogenated amorphous silicon (a‐Si:H) consisting of hypothetical silane molecules with diamond or similar lattices was studied by the semiempirical AM1 method. Densities of states and infrared spectra were calculated for the silane molecules and similar molecules with dangling bonds disorder, and with boron or phosphorus substitution to simulate doping. Some examples are presented, and a comparison is made with experimental properties of a‐Si:H. It is proposed to use these models in a study of the Staebler–Wronski photodegradation of a‐Si:H and other aspects of amorphous silicon technology. © John Wiley &amp; Sons, Inc.

Unsaturated germanium and phosphorus compounds: reactions of germaphosphenes with .alpha.-ethylene aldehydes and ketones

Germaphosphenes MeS2Ge=PR (R: 2,4,6-triisopropylphenyl (Is), 1; 2,4,6-tri-tert-butylphenyl (Ar), 2) react with a-ethylene aldehydes and ketones to give [2 + 2] and [2 + 4] cycloadditions (for aldehydes) and [2 + 4] cycloadditions and 1,2-additions (for ketones). Four- and six-membered ring derivatives can be easily differentiated by P-31 NMR chemical shifts which are, respectively, +36 to +89 ppm and -33 to -77 ppm. 5a', obtained from 2 and crotonaldehyde, has been structurally characterized by X-ray diffraction: the six-membered ring (germaoxaphosphorinene) conformation is a sofa form, with large folding along the Ge-C axis. A NMR study at various temperatures for 3a, 3a', and 5a' displays dynamic phenomenon including phosphorus and ring inversion. The low DELTAG* values (respectively 18.2,13.7, and 13.2 kcal/mol) seem mainly due to substitution of phosphorus by the electropositive germanium and particularly to large steric effects; the 2,4,6-tri-tert-butylphenyl group lowers the inversion barrier by 5 kcal/mol when compared with the 2,4,6-triisopropylphenyl group.

Structural Study of Lead Orthophosphovanadates: Role of the Electron Lone Pairs in the Phase Transitions

A structural investigation of the lead orthophosphovanadate compounds Pb3P2xV2(1-x)O8 has been performed using neutron and X-ray powder diffraction. Results obtained by a Rietveld analysis are presented and compared with previous data on "pure" lead vanadate (x = 0) and lead phosphate (x = 1). The influence of the substitution of phosphorus for vanadium on the mechanism of the phase transitions of lead vanadate and lead phosphate is analyzed. For a given concentration x, a decrease of the distance between the layers of lead atoms is observed when the temperature diminishes. In the vanadium- and phosphorus-rich compounds a critical value is reached where the lone pairs of the lead atoms repel each other as well as the proximate oxygen atoms: this induces a phase transition from the high temperature phase. For the other compounds (middle part of the phase diagram) a critical value is not reached and the high temperature phase remains stable down to 5 K. The possibility of a monoclinic local order inside the high temperature rhombohedral phase is also pointed out.

Phosphorus in Strained Ring Systems

Abstract The effect of phosphorus substitution on the properties of strained cyclic systems is evaluated by means of quantum chemical caaculations at an ab initio calculations at SCF and MCSCF level. Main emphasizes is directed to an investigation of bonding in the series of phosphacyclobutadienes (in comparison to azacyclobutadienes), cyclophosphenes and phosphacylopropenes.

Schottky Contacts Formed on Phosphidized InGaAs

ABSTRACTThe surface of InGaAs (In 53 %) lattice-matched to InP has been phosphidized using phosphine plasma. X-ray photoelectron spectroscopy analysis indicates that substitution of phosphorus for arsenic and deposition of phosphorus layer occur due to phosphidization. Formation of indium and arsenic oxides is suppressed at the phosphidized surface of InGaAs, while phosphorus oxide is observed. Tunneling metal-insulator-semiconductor type Schottky contacts are formed on phosphidized InGaAs by evaporating various metals such as Au, Cu, Ti and Al. An effective barrier height as high as 0.7 eV is evaluated from the room temperature current-voltage characteristic for Au/InGaAs Schottky contacts. The true barrier height estimated from the Richardson plot varies depending on the metal work function.

ION Exchange Characterisation of Modified Zeolite

Isomorphous substitution of phosphorus into a natural zeolite affords the possibility to change the overall framework charge from negative to positive. The substances so created should be used for purification of waste waters. The work describes the preparation of phosphated zeolite, their characterisation and examples of their anion exchange of NO3 on observed in deionized water, drinking water and in the solution containing varying amounts of nitrate.