Influence of the organic layer thickness in (Metal-Assisted) secondary ion mass spectrometry using Ga+ and C 60 + projectiles

This article investigates the influence of the organic film thickness on the characteristic and molecular ion yields of polystyrene (PS), in combination with two different substrates (Si, Au) or gold condensation (MetA-SIMS), and for atomic (Ga⁺) and polyatomic (C ₆₀ ⁺ ) projectile bombardment. PS oligomer (m/z ～ 2000 Da) layers were prepared with various thicknesses ranging from 1 up to 45 nm on both substrates. Pristine samples on Si were also metallized by evaporating gold with three different thicknesses (0.5, 2, and 6 nm). Secondary ion mass spectrometry was performed using 12 keV atomic Ga⁺ and C ₆₀ ⁺ projectiles. The results show that upon Ga⁺ bombardment, the yield of the fingerprint fragment C₇H ₇ ⁺ increases as the PS coverage increases and reaches its maximum for a thickness that corresponds to a complete monolayer (～3.5 nm). Beyond the maximum, the yields decrease strongly and become constant for layers thicker than 12 nm. In contrast, upon C ₆₀ ⁺ bombardment, the C₇H ₇ ⁺ yields increase up to the monolayer coverage and they remain constant for higher thicknesses. A strong yield enhancement is confirmed upon Ga⁺ analysis of gold-metallized layers but yields decrease continuously with the gold coverage for C ₆₀ ⁺ bombardment. Upon Ga⁺ bombardment, the maximum PS fingerprint ion yields are obtained using a monolayer spin-coated on gold, whereas for C ₆₀ ⁺ , the best results are obtained with at least one monolayer, irrespective of the substrate and without any other treatment. The different behaviors are tentatively explained by arguments involving the different energy deposition mechanisms of both projectiles.     

Approaches to the quaternary stereocentre and to the heterocyclic core in diazonamide A using the Heck reaction and related coupling reactions

In model studies towards the quaternary centre at the heart of diazonamide A (early structure 2; revised structure 1), cyclisations of the alkene-substituted iodoaryls 4, 13, 18 and 23, under Heck reaction conditions, were shown to lead to the corresponding benzodihydrofuran 5, benzofuranone 14 and the oxindoles 19 and 24 respectively, in 50-80% yield. Further manipulation of the benzodihydrofuran 5 then led to the intermediates 30, 33 and 39, which make up parts of the oxazole-indole heterocyclic core in diazonamide A. Attempts to perform a corresponding 13-exo-trig Heck cyclisation from the precursor 46a, prepared from 44 and 45, leading to 47 were not successful. A similar outcome was obtained during attempts to effect Heck cyclisations from the ester 57 and the related ether 59. Treatment of the chromene-substituted iodoaryl 62 with Pd(OAc)2, PPh3 and Ag2CO3 led to the spirocycle 64 as a crystalline solid. X-Ray crystal structure analysis established that the quaternary centre in 64 had the same configuration as that present in diazonamide A (1).     

On the magnetic structure of Sr3Ir2O7: an x-ray resonant scattering study

This report presents azimuthal dependent and polarization dependent x-ray resonant magnetic scattering at the Ir L(3) edge for the bilayered iridate compound Sr(3)Ir(2)O(7). The two magnetic wave vectors, k1 = (1/2, 1/2, 0) and k2 = (1/2, -1/2, 0), result in domains of two symmetry-related G-type antiferromagnetic structures, denoted A and B, respectively. These domains are approximately 0.02 mm(2) and are independent of the thermal history. An understanding of this key aspect of the magnetism is necessary for an overall picture of the magnetic behaviour in this compound. The azimuthal and polarization dependence of the magnetic reflections, relating to both magnetic wavevectors, show that the Ir magnetic moments in the bilayer compound are oriented along the c axis. This contrasts with single layer Sr(2)IrO(4) where the moments are confined to the ab plane.     

Observation of a Substitutional Location for VO(II) in Hexaaquazinc(diaquabismalonato)zincate in Different Crystals,in Addition to Interstitial: An Unusual Observation

Single-crystal electron paramagnetic resonance (EPR) studies of VO(II) doped in hexaaquazinc(diaquabismalonto)zincate have indicated interstitial location for vanadyl, which was a rare observation, considering the structure of the host lattice (K. Arun Prasath Lingam, S. Mithira and P. Sambasiva Rao, Appl. Magn. Reson. 38:295, 2010). However, substitutional location is noticed in a different crystal, in which interstitial resonances are almost absent. Generally, both types of resonances will be noticed in the same crystal. The spin Hamiltonian parameters calculated from the EPR spectra for substitutional location are: g _xx  = 1.981, g _yy  = 1.976, g _zz  = 1.941, A _xx  = 7.96 mT, A _yy  = 6.09 mT, and A _zz  = 17.83 mT. Crystal-field parameters, admixture and molecular orbital coefficients have been calculated from optical data, which reveal a moderately covalent metal–ligand bonding.     

The sublattice displacements and the elastic constants of A-15 compounds

The nature of the sublattice displacements in A-15 compounds has been discussed. Expressions have been derived for the elastic constants in terms of the force constants for these compounds. The numerical values of the force constants for Nb₃Sn have been evaluated.     

Synthesis and characterization of polyamides and poly(amide-imide)s derived from 2,2-bis(4-aminophenoxy) benzonitrile

A series of polyamides and poly(amide-imide)s were prepared by the direct poly-condensation of 2,2-bis(4-aminophenoxy) benzonitrile [4-APBN] with aromatic dicarboxylic acids and bis(carboxyphthalimide)s in N-methyl-2-pyrrolidone [NMP] with triphenyl phosphite and pyridine as condensing agents. The synthesis of 4-APBN involves a nucleophilic displacement reaction in dipolar aprotic solvent with the alkali metal salt of p-aminophenol and an activated aromatic dichloro compound. Bis(carboxyphthalimide)s were prepared by condensation of 4,4^′-diaminodiphenylsulfone, 3,3^′-diaminodiphenylsulfone, 4,4^′-diaminodiphenylether, 4,4^′-diaminodiphenylmethane, 3,3^′-diaminobenzophenone, and trimellitic anhydride at a 1:2 molar ratio. The inherent viscosities of the resulting polymers were found to be in the range of 0.31-0.93 dl/g and glass transition temperatures between 235 and 298 °C. All polymers were soluble in aprotic polar solvents such as dimethylsulfoxide and NMP. The results of thermogravimetry revealed that all the polymers showed no significant weight loss before 400 °C. Wide-angle X-ray diffractograms revealed that all polymers were found to be amorphous except for the polyamide derived from isophthalic acid and polyamide-imides derived from diaminodiphenylether and diaminobenzophenone based bis(carboxyphthalimide)s.     

Interaction of CO with Cu5OZr50 metallic glass surface

The adsorption of CO has been studied on the surface of a Cu₅₀Zr₅₀ metallic glass using X-ray and ultraviolet photoelectron spectroscopic techniques. CO dissociates on both these surfaces leading to the formation of graphitic and carbidic carbon species on the surface. However a reversal in intensity of the two species is observed on the metallic glass surface compared to that on the Zr metal surface. While Zr gets oxidised due to the oxygen produced as a result of the dissociation of CO, Cu remains unoxidised. Contribution No. 501 from the Solid State and Structural Chemistry Unit.     

Synthesis and spectral studies of [RuCl(CO)(L)(PPh3)(B)] (HL = 2'-hydroxychalcones and B = PPh3, pyridine or piperidine) and their catalytic and biological applications

The reactions of [RuHCl(CO)(PPh3)2(B)] (B = PPh3, pyridine or piperidine) and 2'-hydroxychalcones led to the formation of [RuCl(CO)(PPh3)(L)(B)] (L = chalconate). The new complexes have been characterized by analytical and spectral (IR, electronic, 1H NMR and 31P NMR) data. They have been assigned an octahedral structure. The complexes have been used as catalysts for the aerial oxidation of cinnamyl alcohol. Some of the complexes have been tested in vitro for growth inhibitory activity against the bacteria E. coli, S. typhi and Pseudomonas sp. and the fungi A. fumigatus.     

Synthesis and characterization of magnetoelectric polymer nanocomposites

Magnetoelectric polymer nanocomposite structures are synthesized using conducting polyaniline and nanosized BFO particles through in situ sol–gel polymerization. The effect of nanosized BFO in polyaniline matrix is studied. The SEM, XRD, VSM, FTIR, and UV–Vis studies were made to understand the morphology, crystalline structure, magnetic, and optical properties of PANI/BFO composites with various concentrations of nanofiller. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2418–2422, 2008