NP Ligand Research Articles

A Cobalt(II) Complex Bearing the Amine(imine)diphosphine PN(H)NP Ligand for Asymmetric Transfer Hydrogenation of Ketones

Novel chiral cobalt complex a containing amine(imine)diphosphine PN(H)NP ligand and complex b containing bis(amine)diphosphine PN(H)N(H)P ligand were synthesized. The structures of two complexes were characterized by X‐ray crystallography and high resolution mass spectrometry. The catalytic performances of cobalt complexes a and b for asymmetric transfer hydrogenation (ATH) of ketones under mild conditions were evaluated using 2‐propanolisopropanol as solvent and hydrogen source after being activated by 8 equivalents of base. Complex a showed a good reactivity for reduction of ketones, with a turnover number (TON) of up to 555, and a maximum enantiomeric excess (ee) value of up to 91 %. Complex b exhibited inertness for hydrogenation of ketones. Electronic structure studies on a and b were conducted to account for the function of ligands on the catalytic performances.

Anionic nanoparticle-lipid membrane interactions: the protonation of anionic ligands at the membrane surface reduces membrane disruption.

Monolayer-protected gold nanoparticles (Au NPs) are promising biomedical tools with applications in diagnosis and therapy, thanks to their biocompatibility and versatility. Here we show how the NP surface functionalization can drive the mechanism of interaction with lipid membranes. In particular, we show that the spontaneous protonation of anionic carboxylic groups on the NP surface can make the NP-membrane interaction faster and less disruptive.

Synthesis of PE Wax by Chromium Complexes Bearing NP Ligands

AbstractThree binuclear chromium complexes stabilized by 1,5,9,13‐tetra(phosphinoamine)cyclohexadecane ligand were synthesized and characterized. In combination with TMA‐depleted methylalumoxane/triethylaluminium (DMAO/TEA) as cocatalyst, they generate active catalytic systems for ethylene polymerization to form ultra low molecular weight polyethylene (PE) wax with moderate catalytic activity in methylcyclohexane (MeCy). The molecular weight of PE wax is ranging from 612 to 841 g/mol with a narrow polydispersity (PD=1.37‐1.80). The effects of polymerization parameters, such as solvent, temperature, catalyst concentration, the ratio of cocatalyst on the catalytic activity and properties of the PE wax were also investigated.

Design of Histone-Mimic Nanoparticles for DNA and RNA Compaction using Molecular Modeling

The design of nanoparticles that can induce specific structural transitions in nucleic acids is important for nanotechnology applications including gene delivery and nanoelectronics. It is known that in biological systems, the binding of cationic proteins induces structural changes in DNA or RNA, which can affect gene expression or cause the compaction of DNA into chromatin. The anionic backbone of the nucleic acids DNA and RNA allow for non-specific electrostatic interactions with cationic proteins, nanoparticles, or dendrimers. The interaction of nucleic acids and nanoparticles may be tuned through changes in nanoparticle size, charge, polarity, or shape. However, the factors that affect structural transitions are not fully understood. We performed atomistic molecular dynamics simulations of the binding of nucleic acids to monolayer-protected gold nanoparticles to elucidate structural changes that take place for nanoparticles and DNA upon binding. Results from these simulations were analyzed to determine modes of DNA and RNA bending with nanoparticles. Our simulations show that highly charged nanoparticles cause DNA to bend with little damage to the helix structure, similar to DNA in the nucleosome. Nanoparticle shape as well as charge is shown to affect the wrapping of nucleic acids with the nanoparticle. Low salt concentrations and high nanoparticle charge cause greater disruptions to DNA structure. We find that the roll parameter is the most important base-pair parameter for DNA bending. Requirements for bending differed significantly between DNA and dsRNA. The degree of DNA bending is controlled by the charge of the NPs, but ligand flexibility played a more significant role in dsRNA bending. We have shown that functionalized gold NPs can be designed to wrap and compact both RNA an DNAs with fine control of binding strength through NP charge and ligand chemistry.

Theoretical assessment of TD-DFT applied to a ferrocene-based complex

We present a theoretical study of the electronic absorption spectrum of the 2-ferrocenyl-1,8-naphthyridine (FcNP) complex using the time-dependent density functional theory (TD-DFT) approach. The calculations were carried out at the DFT/LANL2DZ(Fe)/6-31++G(d) level of theory with nine DFT functionals of the type GGA (PBE, B97D), HGGA (B3LYP, PBE0), HMGGA (M05, M06) and range-separated (wB97XD, CAM-B3LYP, LC-wPBE) in the condensed phase (CH2Cl2). The experimental spectrum for FcNP presents three electronic absorption bands (A, B, C) in the UV region and one band (D) in the visible region. We found that there is no unique functional that reproduces the entire electronic spectrum. GGA and LC-wPBE functionals predict large errors (up to 0.57eV) for the UV bands. On the contrary, HGGA (PBE0), HMGGA (M05, M06) and range-separated (wB97XD, CAM-B3LYP) functionals give small errors for these bands, 0.18, 0.12 and 0.25eV, respectively. Band D is well described by all the functionals with errors up to 0.26eV, except by the M05 and M06 functionals, which fail in this region with significant errors (0.52 and 0.56eV). The analysis of the excitation energies shows that the PBE0, wB97XD and CAM-B3LYP functionals predict the best agreement with the experimental data. The two stronger bands (A, B) in the UV region are assigned to a ligand–ligand charge transfer (L-LCT) that involves the cyclopentadienyl rings (Cp) and the naphthyridine fragment (NP), and then associated with π→π∗ electronic transitions. The two weaker bands (C, D) are assigned to a charge transfer from ligand (Cp) to metal (Fe)-ligand (NP) (L-MLCT) which is mainly addressed through the dxy and dz2 atomic orbitals, respectively. No charge transfer is observed between metal and NP ligand. It was shown that the theoretical methods used for understanding the electronic absorption properties of FcNP were adequate because the results showed an excellent agreement with experimental ones.

Gold Nanoparticle Monolayers from Sequential Interfacial Ligand Exchange and Migration in a Three-Phase System.

Using a three-phase system, centimeter-scale monolayer gold nanoparticle (Au NP) films have been prepared that have long-range order and hydrophobic ligands. The system contains an interface between an aqueous phase containing Au NPs and an oil phase containing one of various types of amine ligands, and a water/air interface. As the Au NPs diffuse to the water/oil interface, ligand exchange takes place which temporarily traps them at the water/oil interface. The ligand-exchanged particles then spontaneously migrate to the air/water interface, where they self-assemble, forming a monolayer under certain conditions. The spontaneous formation of the NP film at the air/water interface was due to the minimization of the system Helmholtz free energy. However, the extent of surface functionalization was dictated by kinetics. This decouples interfacial ligand exchange from interfacial self-assembly, while maintaining the simplicity of a single system. The interparticle center-to-center distance was dictated by the amine ligand length. The Au NP monolayers exhibit tunable surface plasma resonance and excellent spatial homogeneity, which is useful for surface-enhanced Raman scattering. The “air/water/oil” self-assembly method developed here not only benefits the fundamental understanding of NP ligand conformations, but is also applicable to the manufacture of plasmonic nanoparticle devices with precisely designed optical properties.

Censored at the Nanoscale.

Censored at the Nanoscale.

Electronic influences of bridging and chelating diimine ligand coordination in formamidinate-bridged Rh2(II,II) dimers

Two new formamidinate-bridged Rh2II,II complexes, cis-[Rh2II,II(μ-DTolF)2(μ-np)2]2+ (3; DTolF=N,N′-di-p-tolylformamidinate; np=1,8-naphthyridine) and cis-[Rh2II,II(μ-DTolF)2(κ2-dap)2]2+ (4; dap=1,12-diazaperylene), were synthesized from cis-[Rh2II,II(μ-DTolF)2(CH3CN)6](BF4)2 (1), and their properties were compared to those of cis-[Rh2II,II(μ-DTolF)2(phen)2](BF4)2 (2). Density functional theory (DFT) and electrochemical analyses support the description of the highest occupied molecular orbitals (HOMOs) of 3 and 4 as possessing contributions from the metals and formamidinate bridging ligands, with Rh2/form character, and lowest unoccupied molecular orbitals (LUMOs) localized on the respective diimine ligand np and dap π∗ orbitals. Both 3 and 4 display strong, low energy Rh2/form→diimine(π∗) metal/ligand-to-ligand charger transfer (1ML–LCT) transitions with maxima at 566nm (ε=3600M−1cm−1) for 3 and at 630nm (ε=2900M−1cm−1) for 4 in CH3CN. Time dependent-DFT (TD-DFT) calculations support these assignments. The ability of both the bridging np and chelating dap diimine ligands to produce strong absorption of these Rh2II,II complexes throughout the visible region is potentially useful for the development of new photocatalysts for H2 production and photochemotherapeutics.

Ultrathin supercapacitor electrodes with high volumetric capacitance and stability using direct covalent-bonding between pseudocapacitive nanoparticles and conducting materials

We introduce high-performance ultrathin supercapacitor electrodes obtained through the direct covalent-bonding layer-by-layer (LbL) assembly (or ligand-exchange LbL assembly) of amine-functionalized multiwalled carbon nanotubes (CNTs) and transition metal oxide nanoparticles (TMO NPs). The main characteristic of our approach is that the internal interfacial resistance of the electrodes can be minimized through the direct covalent-bonding adsorption of densely packed, high-quality TMO NPs onto CNTs without the aid of nonactive binders or insulating NP ligands, and the resulting volumetric capacitance and cycling stability of the electrodes can be significantly enhanced. For this study, well-defined oleic acid-stabilized pseudocapacitive metal oxide nanoparticles (i.e., OA–Fe3O4 and OA–MnO NPs) prepared in toluene were densely adsorbed onto the CNT layer due to the high affinity between the surface of the TMO NPs and the NH2 moieties of the CNTs. The (CNT/OA–Fe3O4 NP)20 multilayer electrode exhibited a high volumetric capacitance of 248±15Fcm−3 (128±7Fg−1) at 5mVs−1 despite the intrinsically low specific capacitance of the Fe3O4 NPs. Additionally, these film electrodes exhibited high performance stability, maintaining 99.2% of their initial capacitance after 1000 cycles. Furthermore, upon the insertion of OA–MnO NPs with high crystallinity and a high theoretical pseudocapacitance value within multilayers instead of OA–Fe3O4 NPs, the formed electrodes (i.e., (CNT/OA–MnO NP)20 multilayers) exhibited a higher volumetric capacitance of 305±10Fcm−3 (183±5Fg−1) (at a scan rate of 5mVs−1) than other conventional ultrathin supercapacitor electrodes, including manganese oxide or iron oxide NPs.

Synthesis and oxidation of d6 tungsten pincer complexes: a complete series of tungsten(ii) hydridocarbonyl and halocarbonyl pincer complexes

Reaction of the neutral P(H)NP ligand [HN(SiMe(2)CH(2)PPh(2))(2)] with tungsten hexacarbonyl resulted in coordination of P(H)NP through both phosphorus donor atoms to form the tungsten complex [W(P(HN)P)(CO)(4)] (1). Reaction of P(H)NP with tris(acetonitrile)tricarbonyl tungsten gave both facial and meridional tridentate isomers [W(P(H)NP)(CO)(3)] (2-fac and 3-mer). These three d(6) tungsten complexes could be interconverted under appropriate conditions. The thermodynamically favored isomer 3 was protonated to form seven-coordinate [W(P(H)NP)(CO)(3)H][BF(4)] (4). A related series of cationic tungsten(II) halide complexes was synthesized, [W(P(H)NP)(CO)(3)X](+) (6, X = I; 7, X = Br; 8, X = Cl; 9, X = F), by various routes. All of the tungsten(II) complexes underwent deprotonation at the amine site of the P(H)NP ligand when triethylamine was added, resulting in neutral seven-coordinate complexes. Variable temperature (1)H, (31)P{(1)H}, and (13)C{(1)H} NMR spectroscopy showed fluxional behavior for all the seven-coordinate complexes reported here. Analysis of IR and NMR spectroscopic data showed trends through the series of coordinated halides. Crystal structures of tetracarbonyl 1, meridional tricarbonyl 3, and cationic hydride 4 were determined to confirm the coordination mode of the P(H)NP ligand.

Air-Stable Pd(R-allyl)LCl (L= Q-Phos, P(t-Bu)3, etc.) Systems for C–C/N Couplings: Insight into the Structure–Activity Relationship and Catalyst Activation Pathway

A series of Pd(R-allyl)LCl complexes [R = H, 1-Me, 1-Ph, 1-gem-Me(2), 2-Me; L = Q-Phos, P(t-Bu)(3), P(t-Bu)(2)(p-NMe(2)C(6)H(4)), P(t-Bu)(2)Np] have been synthesized and evaluated in the Buchwald-Hartwig aminations in detail, in addition to the preliminary studies on Suzuki coupling and α-arylation reactions. Pd(crotyl)Q-PhosCl (9) was found to be a superior catalyst to the other Q-Phos-based catalysts, and the reported in situ systems, in model coupling reactions involving 4-bromoanisole substrate with either N-methylaniline or 4-tert-butylbenzeneboronic acid. Precatalyst 9 also performed better than the catalysts bearing P(t-Bu)(2)(p-NMe(2)C(6)H(4)) ligand; however, it is comparable to the new crotyl catalysts bearing P(t-Bu)(3) or P(t-Bu)(2)Np ligands. In α-arylation of a biologically important model substrate, 1-tetralone, Pd(allyl)P(t-Bu)(2)(p-NMe(2)C(6)H(4))Cl (15) was found to be the best catalyst. The reason for the relatively higher activity of the crotyl complexes in comparison to the allyl derivatives in C-N bond formation reactions was investigated using X-ray crystallography in conjunction with NMR spectroscopic studies.

Metal Nanoparticle−Block Copolymer Composite Assembly and Disassembly

Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules.

Effect of Axial Coordination on the Electronic Structure and Biological Activity of Dirhodium(II,II) Complexes

The reactivities toward biomolecules of a series of three dirhodium(II,II) complexes that possess an increasing number of accessible axial coordination sites are compared. In cis-[Rh2(OAc)2(np)2]2+ (1; np=1,8-naphthyridine) both axial sites are available for coordination, whereas for cis-[Rh2(OAc)2(np)(pynp)]2+ (2; pynp=2-(2-pyridyl)1,8-naphthyridine) and cis-[Rh2(OAc)2(pynp)2]2+ (3) the bridging pynp ligand blocks one and two of the axial coordination sites in the complexes, respectively. The electronic absorption spectra of the complexes are consistent with strong metal-to-ligand charge transfer transitions at low energy and ligand-centered peaks localized on the np and/or pynp ligands in the UV and near-UV regions. Time-dependent density functional theory calculations were used to aid in the assignments. The three complexes exhibit metal-centered oxidations and reductions, localized on the aromatic ligands. The ability of the complexes to stabilize duplex DNA and to inhibit transcription in vitro is greatly affected by the availability of an open axial coordination site. The present work shows that open axial coordination sites on the dirhodium complexes are necessary for biological activity.

Ligand Cleavage Put into Reverse: PC Bond Breaking and Remaking in an Alkylphosphane Iron Complex

Complex formation between FeX(2)6 H(2)O (X=BF(4) or ClO(4)) and the pyridine-derived tetrapodal tetraphosphane C(5)H(3)N[CMe(CH(2)PMe(2))(2)](2) (1) in methanol proceeds with solvent-induced cleavage of one PMe(2) group. Depending on the reaction temperature and the nature of the counterion, iron(II) is coordinated, in distorted square-pyramidal fashion, by the anionic remainder of the chelating ligand, C(5)H(3)N[CMe(CH(2)PMe(2))(2)][CMe(CH(2)PMe(2))(CH(2) (-))] (NP(3)C(-) donor set: X=BF(4), -50 degrees C: 2; X=ClO(4), RT: 4) or its protonated form C(5)H(3)N[CMe(CH(2)PMe(2))(2)][CMe(CH(2)PMe(2))(CH(3))], in which the methyl group is in agostic interaction with the metal centre (X=BF(4), RT: 3; X=ClO(4), +50 degrees C: 5). A monodentate phosphinite ligand Me(2)POMe, formed from the cleaved PMe(2) group and methanol, completes the coordination octahedron in both cases. Working in CD(3)OD (X=BF(4), RT) gives the deuterium-substituted analogue of 3, with ligands L(CH(2)D) (L=residual chelating ligand) and Me(2)POCD(3). A mechanism for the observed phosphorus-carbon bond cleavage is suggested. Complex 2, when isolated at -50 degrees C, is stable in the solid state even at room temperature. The reaction of 2 in methanol with carbon monoxide (10.5 bar) at elevated temperature forms, in addition to as yet unidentified side products, the carbonyl complex [(1)Fe(CO)](BF(4))(2) (7), in which the previous P--C bond cleavage has been reversed, reforming the original tetrapodal pentadentate NP(4) ligand 1. All compounds have been fully characterised, including X-ray structure analyses in most cases.

Zinc complexes of anionic NPPN and NP(S)PN ligands and rearrangement to the isomeric NPNP and NP(S)NP ligands in mercury complexes

The lithium (imido)diphosphineimide Li(Et2O)[DippNPhP-P((n)Bu)PhNDipp] (1) (Dipp = 2,6-(i)Pr2C6H3) undergoes simple metathesis reactions with equimolar amounts of zinc halides, ZnCl2 and (t)BuZnBr, to give the respective N,N'-chelated complexes {Zn(micro-Cl)[DippNPhP-P((n)Bu)PhNDipp]}2 (2) and (t)BuZn[NDippPhP-P((n)Bu)PhNDipp] (3). In contrast, the reaction of two equivalents of complex 1 with HgCl2 affords the rearranged bis(imidodiphosphinoamine) complex, Hg[PhP([double bond, length as m-dash]NDipp)(micro-NDipp)P((n)Bu)Ph]2 (4), where the ligand acts as a P-centered anion. The (imido)diphosphineimide backbone of remains intact on oxidation with elemental sulfur to afford the lithium (imido)diphosphineimine sulfide complex, Li(Et2O)[DippNPhP(S)-P((n)Bu)PhNDipp] (6). Reactions of 6 with group 12 metal halides show similar behaviour to those of complex 1. The N,N' chelated metathesis products RZn[DippNPhP(S)-P((n)Bu)PhNDipp] (7, R = Cl; 8, R = (t)Bu) are obtained on reaction with ZnCl2 and (t)BuZnBr, respectively. Isomerization of the ligand backbone occurs on reaction of 6 with HgCl2 to form the homoleptic P,S-chelated mercury complex Hg[Ph(S)P(=NDipp)(micro-NDipp)P((n)Bu)Ph]2 (9). Complexes 2, 3, 4, 6, 8 and 9 have been characterized by X-ray crystallography.

Quest for Second-Harmonic-Generation-Active Coordination Polymers: Synthesis and Properties of Silver(I) Pyrimidinolates

In the search for coordination compounds showing significant second harmonic generation (SHG) activity, reaction of Ag(I) ions with the 4-hydroxypyrimidine (4-Hpymo) and 5-nitro-2-hydroxypyrimidine (HNP) ligands generated four crystalline 1D polymers, Ag(4-pymo)·nH2O (n = 2.5, 0), Ag(NP)(NH3), and Ag(NP), the latter two crystallizing in acentric space groups. Their synthesis, complete characterization, and structural determination, by conventional single-crystal and laboratory X-ray powder diffraction methods, are presented and discussed in the frame of diazaaromatic-ligand- and metal-containing species. XRPD has also allowed the detection of the polyhydrated, elusive Ag(4-pymo)·nH2O (n = 2, 3) species. Powders of Ag(NP) have shown an SHG activity close to that of standard urea. By applying the geometrical model proposed by Zyss, it is shown that the NP ligand is a highly promising chromophore, the oxo and nitro functionalities cooperatively promoting a high hyperpolarizability.

Three-dimensional Structures of the Fab Fragment of Murine N1G9 Antibody from the Primary Immune Response and of its Complex with (4-Hydroxy-3-Nitrophenyl)acetate

The three-dimensional structures of the Fab fragment, in its unliganded and liganded crystals, of mouse anti-(4-hydroxy-3-nitrophenyl)acetate (NP) antibody N1G9 have been determined by the molecular replacement method. The unliganded and NP-liganded structures were refined at 2.4 Å resolution to crystallographic R-factors of 0.194 and 0.196, respectively. Antibody N1G9 bears |lclambd| light chains, and is one of the primary immune response antibodies. Fab N1G9 exhibits an elbow angle of 197° in both structures. This large angle is ascribed to the V L–C Linterface formed by |lclambd|- chain residues. A hydrophobic pocket surrounded by the complementarity- determining regions except L2 is identified as a hapten-binding site. Be- tween the liganded and unliganded structures, root-mean-square (r.m.s.) positional deviations are 0.42 Å for the main-chain atoms, and 0.74 Å for all the protein atoms. The major structural differences between these structures are localized in the hapten-binding site, and yield an r.m.s. deviation of 1.03 Å for the side-chain atoms. The soaked NP ligand is in van der Waals contact with the aromatic side-chains of Tyr32L and Trp91L of the light chain, and Trp33H and Tyr97H of the heavy chain, and is hydrogen-bonded to the side-chains of Trp96L, His35H, Arg50H, Tyr95H, and Ser100aH. The side-chain of Lys58H is salt-bridged to the NP hydroxyl group. The side-chains of Arg50H, Trp33H, and Tyr97H are shifted toward the NP carboxyl group. The side-chain of Trp33H, whose replacement to Leu increases affinity by tenfold, is sandwiched between the Arg50H and Tyr97H side-chains, and is in cramped contact both with the ligand and with these side-chains. Affinity increases in the maturation of the anti-NP antibodies are ascribable to conformational relief of these cramped contacts through the replacement of Trp33H or through suitable structural alterations in the H3 region.

Thermodynamics of homogeneous hydrogenation: Part V. Hydrogenation of cyclohexene catalyzed by Rh(I) complexes of the bidentate (NP) ligand, (2-(diphenylphosphino)ethyl)benzylamine

The oxidative addition of H 2 to the Rh(I) complexes of the bidentate NP ligand, (2-(diphenylphosphino)ethyl)benzylamine, viz. [Rh(NP)(Cl)(CO)] 1, ▪ 2, [Rh(NP) 2Cl] 3 proceeds at 30 °C and l atm H 2 m 7:3 benzene-ethanol solvent with the formation of the thermodynamically stable cis dihydrides [Rh(NP)(Cl)(CO)(H) 2] 1a, 1b, ▪ 2a, 2b and [Rh(NP) 2(H) 2Cl] 3a, 3b characterized by their hydride NMR in situ. The homogeneous hydrogenation of cyclohexene catalyzed by complexes 1 – 3 was investigated in the temperature range 10 – 40 °C at 0.6 – 1 atm of H 2 partial pressure. Thermodynamic parameters for the formation of the Rh(III) dihydrido complexes of 1 – 3 and the corresponding monoolefin complexes of Rh(I) were computed. The activation parameters corresponding to the rate constant k for the homogeneous hydrogenation of cyclohexene were also calculated. The catalytic activity of the complexes decreases in the order 2 > 3 ⪢ 1. Except complex 1, the catalytic activity of the bidentate complexes of Rh(I) 2 and 3 is higher than those of RhCl(diphos) 4 (diphos = Ph 2PCH 2CH 2PPh 2) and RhCl(NP 2) 5 (NP 2 = H-N(CH 2CH 2-PPh 2) 2). This is because the stabilities of the hydrides of 2 and 3 are lower than those of 4 and 5.

Radiotracer studies on ion-selective electrode membranes containing metal complexes of a nonylphenoxypoly(ethyleneoxy)ethanol in poly(vinyl chloride) matrices

Radiotracer studies with 133Ba, 45Ca and 36Cl are reported for PVC matrix membranes containing 2-nitrophenyl phenyl ether and the tetraphenylborate of a barium (or calcium) complex with a nonylphenoxypoly(ethyleneoxy)ethanol (NP), Antarox CO880. The results show that there is very limited permeation of radioactive barium and calcium ions through the membrane systems. However, the continued uptake (with time) of radioactive barium ions by the membranes (the uptake of calcium ion is less) suggests that in relation to selective electrode response the stabilization of ions by the NP ligand within the membrane is important in addition to the simple availability of membrane pathways for primary-ion transport through the membrane. Permselectivity to counter-ions is indicated by the non-permeation of radioactive chloride ions.

Covalency of neptunium(IV) tris(cyclopentadienyl) compounds from Moessbauer spectra

Isomer shifts measured from the /sup 237/Np Moessbauer spectra of NpCp/sub 3/OR (R = alkyl), NpCp/sub 3/R, and NpCpAr (Ar = aryl) are used as a measure of the covalency in Np(IV) ligand bonding. The isomer shifts in NpCp/sub 3/-n-Bu and NpCp/sub 3/C/sub 6/H/sub 4/C/sub 2/H/sub 5/ show a strong sigma character for the Np-n-Bu and Np-C/sub 6/H/sub 4/C/sub 2/H/sub 5/ bonds. The sigma character of Np-OR bonding is definite but less pronounced. The comparatively low covalency in the bonding of NpCp/sub 4/ is ascribed to longer Np-C bonds in NpCp/sub 4/ than in NpCp/sub 3//sup +/ compounds. The /sup 237/Np isomer shift in Np(MeCp)Cl/sub 3/ . 2THF indicates that the MeCp ligand is sigma-bonded in this compound.