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Two morphologically different porous gold layered on Cu-oxide-based electrochemical sensors were developed for the selective detection of dopamine in the presence of uric acid, ascorbic acid or dextrose. The nanoparticles were prepared by layering Au onto either a cubic or octahedron-shaped Cu-oxide crystal via a galvanic reaction. These were characterized with scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopy. The porous structure of the gold over layer was clearly visible on the scanning electron microscopy image while the macro morphology was maintained. X-ray photoelectron spectroscopy confirmed the presence of metallic gold while both CuI (CuO) and CuII (Cu2O) were present in the samples. These two Au/Cu-oxide nanocomposites were used to modify glassy carbon electrodes and were tested for their dopamine sensing ability. Differential pulse voltammetry was used to investigate the selectivity towards dopamine in the presence of different interfering molecules uric acid, ascorbic acid and dextrose). From the differential pulse voltammetry, the lowest limit of detection was found to be 1.1 μM, with a sensitivity of 3.4 μA mM−1 mm−2 in the linear range of 10–250 μM for the porous gold layered covering the octahedron Cu-oxide-modified glassy carbon electrode. [ABSTRACT FROM AUTHOR]

Tungsten carbide-based nano-catalysts (Ni-WC, Co-WC and NiCo-WC) and molybdenum carbide-based nano-catalysts (Ni-MoC, Co-MoC and NiCo-MoC) were synthesised using a carbothermal reduction method. X-ray diffraction, scanning electron microscopy coupled with electron dispersive spectroscopy, x-ray photoelectron spectroscopy and cyclic voltammetry were used to evaluate the prepared electrocatalysts. The cyclic voltammetry results showed that Ni-WC coated electrode displayed the best hydrogen evolution reaction catalytic activity with the lowest overpotential of 1.421 V at a current density of 10 mA cm−2, and a Tafel slope of 135 mV dec−1 which is marginally lower than the benchmark Pt/C coated electrodes. Ni-MoC and Co-MoC coated electrocatalysts also produced current more effectively with a change in potential as compared to the Pt/C coated electrode. The durability test showed Co-WC, NiCo-WC and Ni-MoC coated electrodes to have high stability within a wide range of current densities. [ABSTRACT FROM AUTHOR]

The kinetics of dehydroxylation of South African kaolin revealed that both the inner and the surface hydroxyl groups disappear according to first order kinetics, however, the surface group disappeared faster than the inner groups, showing that diffusion control kinetics is also important. The temperature dependent transformations of the kaolin was measure by means of fractional conversion of the ratios between AlO6:AlO4 and Si-O-Al:Si-O-Si, which showed kobs values 0.0168 s-1 and 0.0089 s-1 for the transformation to the spinel phase and values of 0.0165 s-1 and 0.0156 s-1 for the transformation to mullite respectively. The pozzolanic activities of the kaolin calcined at different temperatures showed a maximum pozzolanic activity when the kaolin is calcined at 650°C and the pozzolanic activity for mullite is even less than for the uncalcined kaolin. XPS revealed that the atomic ratio between Si and Al did not change from kaolin to metakaolin (Si:Al = ca. 1.2) however the mullite showed a atomic ratio of Si:Al = 1.52, implying that some deallumination occurred during calcination at high temperatures.

Nuclear magnetic resonance measurements confirm that, as expected, the mer isomer of tris(β-diketonato) cobalt(III) complexes is more stable (mer isomers are more stable because they are less affected by steric hindrance and they have lower dipoles). An excess of the mer isomer or only the mer isomer is experimentally observed. The existence of both fac and mer isomers is predicted by density functional theory calculations. At room temperature, the nuclear magnetic resonance peaks of phenyl-containing mer complexes are broad due to the intermediate rotation of bulky phenyl groups resulting in only the average orientation of the non-equivalent protons in the mer complexes. However, upon heating to 55°C (thus speeding up the rotation) or cooling to −50°C (slowing down the rotation), this broad peak is resolved into three sets of carbon peaks appearing in the 13C NMR spectrum, as well as splitting of the ¹H NMR peaks for the non-equivalent protons in the mer isomer. In solid-state 13C NMR the aromatic rings do not rotate, resulting in the splitting of all the 13C NMR peaks. Two sets of well-defined peaks are observed for the fluorine-containing compound [Co(CF3COCHCOCPh)3] in both the 13C and 19F NMR spectra, indicating that both the fac and mer isomers are present with a ratio of fac:mer = 0.1:1. The X-ray photoelectron spectroscopy measured binding energy of the Co 2p3/2 photoelectron lines are influenced by the subtle electronic (electron-donating or electron-withdrawing) properties of the R groups on the β-diketonato ligands. Various relationships are established between the binding energy of Co 2p3/2 and several physical and density functional theory–calculated properties, confirming good electronic communication (the measurable electronic effect that a molecular fragment has on the physical properties of another molecular fragment in the molecule) of the substituent groups through the pseudo aromatic system of the β-diketonato backbones to the metal. [ABSTRACT FROM AUTHOR]

Several morphologically different Cu-oxide nanocrystals (cube, exposing only the (100) facets; elongated octahedron, exposing only the (111) facets; normal octahedron, exposing only the (111) facets; rounded octahedron, exposing only the (111) facets; truncated edge cube, exposing the (100), (110), and (111) facets) have been prepared. Mixed oxidation state facets were obtained, with the X-ray Photoelectron Spectroscopy revealing that both CuI and CuII are present in the samples. The % CuI and CuII vary for the different morphologies. Morphologies exposing the (111) facet showed the highest % CuI present, with the morphologies exposing the (100) facet showing the least amount of CuI. The glassy carbon electrode's surface was modified with these Cu-oxide nanocrystals and their sensing performance for glucose detection was investigated. The limits of detection (LOD) observed for all the Cu-oxide nanocrystal electrodes were < 2 µM. Electrodes modified with Cu-oxide nanocrystals exposing the (111) facets and having more CuI present in the sample resulted in better glucose detection limits. [ABSTRACT FROM AUTHOR]

Truncated cubic Cu-oxide nanocrystals with edge lengths of ca. 600 nm were prepared employing the low-cost copper (II) chloride as the precursor. XRD revealed that the truncated cubic Cu-oxide nanocrystals are present in both the CuI and Cu0 state. XPS characterisation gives insight into the amount of each state present in the as-prepared, oxidised, reduced and recovered catalyst species. The catalytic activity of the truncated cubic Cu-oxide nanocrystals was tested for the reduction of nitrophenols using NaBH4. After one catalytic cycle of the reduction of 4-nitrophenol, the activity almost halved. The SEM images revealed that the recovered catalyst showed some disfigurement of the structure, and XPS confirmed the reduction of the CuI to metallic Cu0. [ABSTRACT FROM AUTHOR]

p-Cresol as additive to the Grubbs second generation catalyst (GII) allows the cross-metathesis of acrylates with prop-1-en-1-ylbenzenes under conditions that only give the prop-1-en-1-ylbenzene self-metathesis product in the absence of cresol. NMR and IR spectroscopy, MALDI-TOF MS and XPS supported the formation of a ruthenium benzylidene with hydrogen bonds between p-cresol and the chloride ligands of GII. XPS furthermore confirmed p-cresol to increase the binding energies of the GII Ru 3d5/2, 3d3/2, 3p3/2 and 3p1/2 photoelectron lines, whereas 1H NMR spectroscopy indicated the carbene carbon and hydrogen to be shielded. It is thus postulated that p-cresol allows for more facile interaction between electron-deficient compounds and the ruthenium benzylidene by decreasing the electron density on the metal center and increasing the electron density on the carbene. [ABSTRACT FROM AUTHOR]

Abstract: A series of metal hexacyanometallate nanoparticles KxMy[M′(CN)6]z·qH2O, with M=M′=Co (1) or Fe (2), M=Co and M′=Fe (3) and M=Fe and M′=Co (4) were prepared by either co-precipitation or reverse micro-emulsion. These nanoparticles were characterised by ATR FTIR, TEM and XPS, which revealed the presence of CoII/III and/or FeII/III within the compounds. The average binding energies found for the Co 2p3/2 photoelectron lines for CoII and CoIII were ca. 781.7 and 782.9 eV respectively, while the binding energies for FeII and FeIII of the Fe 2p3/2 photoelectron lines were located at 709.5 and 711.4 eV. TEM reveal the particle size ranged between 180 and 520 nm. The eight different compounds’ catalytic activity were tested for the solvent-free oxidation of benzyl alcohol using hydrogen peroxide as the oxidant. The progression of the reaction was monitored using ATR FTIR, by following the appearance of the carbonyl stretching frequency of the oxidation products, which showed the formation of not only benzyl aldehyde but also benzyl benzoate, which is the condensation product of benzyl alcohol and benzoic acid (another oxidation product). The TOF of the catalytic oxidation reaction was correlated with the mean particle diameter, % occurrence of CoII/III and/or FeII/III, total metal electronegativity and the degree of covalence of the Co- and Fe-ligand bond.Graphical Abstract: [ABSTRACT FROM AUTHOR]

A series of ferrocenyl-functionalized β-diketonato manganese(III) complexes, [Mn(FcCOCHCOR)3] with R = CF3, CH3, Ph (phenyl) and Fc (ferrocenyl) was subjected to a systematic XPS study of the Mn 2p3/2 and Fe 2p3/2 core-level photoelectron lines and their satellite structures. A charge-transfer process from the β-diketonato ligand to the Mn(III) metal center is responsible for the prominent shake-up satellite peaks of the Mn 2p photoelectron lines and the shake-down satellite peaks of the Fe 2p photoelectron lines. Multiplet splitting simulations of the photoelectron lines of the Mn(III) center of [Mn(FcCOCHCOR)3] resemble the calculated Mn 2p3/2 envelope of Mn3+ ions well, indicating the Mn(III) centers are in the high spin state. XPS spectra of complexes with unsymmetrical β-diketonato ligands (i.e., R not Fc) were described with two sets of multiplet splitting peaks representing fac and the more stable mer isomers respectively. Stronger electron-donating ligands stabilize fac more than mer isomers. The sum of group electronegativities, ΣχR, of the β-diketonato pendant side groups influences the binding energies of the multiplet splitting and charge transfer peaks in both Mn and Fe 2p3/2 photoelectron lines, the ratio of satellite to main peak intensities, and the degree of covalence of the Mn-O bond. [ABSTRACT FROM AUTHOR]

A rhodium(I) dicarbonyl on HY zeolite prepared from [Rh(CH 3 COCHCOCH 3 )(CO) 2 ] were charaterised by Attenuated Total Reflectance Fourier Transformed Infrared (ATR FTIR) and X-ray Photoelectron Spectroscopy (XPS). The ATR FTIR spectra of the anchored rhodium complex showed that [Rh(CH 3 COCHCOCH 3 )(CO) 2 ] reacted with the HY zeolite by loosing the [CH 3 COCHCOCH 3 ] − ligand to form Rh(CO) 2 /HY zeolite and [CH 3 COCHCOCH 3 ]/HY zeolite. The sharpness of the v (CO) bands measured by the ATR FTIR showed that the rhodium(I) dicarbonyl complex are distributed fairly uniform over the zeolite support. This heterogeneous catalyst was monitored for the oxidative addition of methyl iodide in the liquid phase, followed by reductive elimination of acetyl iodide upon treatment with CO gas. These reactions were monitored by following the carbonyl stretching frequencies from ATR FTIR measurements and the change in binding energy of the Rh 3d 5/2 photoelectron line as measured by XPS, observed rate constants determined were mutually consistent with each other. [ABSTRACT FROM AUTHOR]

Reaction of [Mn3(OAc)6O•3H2O]+ (1) with ferrocenyl β-diketones of the type FcCOCH2COR with R = CF3 (2a) and CH3 (2b), Ph = C6H5 (2c), and Fc = FeII(η5-C5H4)(η5-C5H5) (2d) yielded a series of ferrocene-functionalized β-diketonato manganese(III) complexes 3a-3d, respectively, of general formula [Mn(FcCOCHCOR)3]. The mixed-ligand β-diketonato complex [Mn(FcCOCHCOFc)2(FcCOCHCOCH3)] (4) was obtained by reacting mixtures of diketones 2b and 2d with 1. A single-crystal X-ray structure determination of 3b (Z = 2, triclinic, space group P1̅) highlighted a weak axial elongating Jahn-Teller effect and a high degree of bond conjugation. An X-ray photoelectron spectroscopic study, by virtue of linear relationships between group electronegativities of ligand R groups, χR, or ∑χR, and binding energies of both the Fe 2p3/2 and Mn 2p3/2 photoelectron lines, confirmed communication between molecular fragments of 2a-2d as well as 3a-3d. This unprecedented observation allows prediction of binding energies from known β-diketonato side group χR values. [ABSTRACT FROM AUTHOR]

Ruthenocene-containing β-diketones, RcCOCH2COR with Rc = ruthenocenyl and R = C10F21 (1), CF3 (2), C6F5 (3), C10H21 (4), CH3 (5) and C6H5 (6), were synthesised by Claisen condensation of the appropriate methyl ester with acetylruthenocene, and their spectroscopic, electrochemical and thermal properties were compared. A new synthetic route utilising 1,2,3-benzotriazol-1-ylethanone (9) or 1,2,3-benzotriazol-1-yl(ruthenocenyl)methanone (10) as a reactant, rather than the conventional esters, was found to be more efficient for β-diketone synthesis. The apparent acid dissociation constants, pKa′, of the new ruthenocene-containing β-diketones are 7.14(4) (1, R = C10F21), 9.92(3) (3, R = C6F5) and 10.06(2) (4, R = C10H21). Peak anodic potentials of the ruthenocenyl group of 1–6, pKa′ values and the FTIR ν(C=O) stretching frequencies of the precursor esters, RCOOCH3, correlated linearly with the Gordy scale group electronegativity, χR, of the C10F21 (χC10F21 = 3.04), C6F5 (χC6F5 = 2.46), C10H21 (χC10H21 = 2.43) and other R-groups. An electrochemical study in the non-interacting solvent and electrolyte system CH2Cl2/0.1 mol dm−3 [N(nBu4)][B(C6F5)4] revealed electrochemically irreversible one-electron transfer Rc/Rc+ couples in the potential range 650 ＜ Epa ＜ 1110 mV. Strikingly, reduction of the unstable monomeric 17 electron species, [Rc+(C5H5)(C5H4COCH2COR)], was clearly observed for all β-diketones possessing fluorinated R-groups, even at slow (100 mV s−1) scan rates. The enol isomer of the fluorinated β-diketones had ＞90% abundance under the conditions of study and the first order rate constant of enol to keto conversion varied between 220 and 50 000 s−1 depending on solvent (CDCl3 or CD3CN) and R-groups. Thermal analysis (DSC) of 1 and 4 showed no liquid crystalline mesophase behaviour but definite polymorphism was observed. β-diketones 1 and 4 exist as low temperature polymorphs below 42 °C or 12 °C respectively. The high temperature polymorphs converted to isotropic liquids at 83 °C (compound 1) or 52 °C (compound 4). [ABSTRACT FROM AUTHOR]

Nano γ-alumina-supported transition metal-based mono- (Pd 0/γ-Al2O3 or Co111/γ-Al2O3) and bimetallic catalysts (Pd0 Co111 /γ-Al2O3), were prepared by wet impregnation, oxidation and in situ reduction of the palladium. The palladium(II) acetate [Pd113 (OOCCH3)6], cobalt(II) acetate [Co11 (OOCCH3)2]•4H2O and palladium, cobalt bridging tetraacetate [Pd11 Co11 (OOCCH3)4]•H2O•2CH3COOH, were used as catalyst precursors to prepare a 7.4 % mol catalyst/support loading. The oxidation states of these activated catalysts were studied by XPS. These catalysts were evaluated for hydrogenation of cinnamaldehyde in a biphasic reaction under 3 MPa of hydrogen at 80°C. The Pd0/-Al2O3 selectively catalyzed the hydrogenation of C=C bond in cinnamaldehyde to form phenylpropanol (100%). In contrast, catalysiswith Pd0 Co111/γ-Al2O3 hydrogenated both C=C and C=O bonds consecutively, forming 65 % phenylpropanal and 35 % phenylpropanol with TOF = 47.2 h-1 . No reaction occurred when Co111/γ-Al2O3 was used. [ABSTRACT FROM AUTHOR]

The bimetallic paddlewheel catalyst precursor, [PdIICoII(μ-OOCCH3)4] H2O·2CH3COOH (1), prepared from[Pd3(μ-OOCCH3)6] and [Co(OOCCH3)2], was used as a single source precursor to prepare,after binding to a surface-hydroxylated silicon wafer and oxidation,the bimetallic oxides of PdIVCoIII/SiO2catalyst supported on a model planar (i.e., two-dimensional) siliconwafer. This catalyst catalyzes the aerobic oxidation of alcohols toits corresponding carbonyl compounds. The bimetallic tetracarboxylatocatalyst precursor was bonded to the surface-hydroxylated siliconwafer by spin-coating and also by grafting. X-ray photoelectron spectroscopy(XPS) revealed that one of the four μ-acetato bridging ligandswas substituted by Si–O fragments in a covalent bond formationprocess during grafting of 1onto the wafer. In contrast,during the spin-coating process, all four acetato ligands remainedintact during fixation on the silicon surface. Upon oxidation andworkup, the grafted sample’s Pd:Co ratio remained unchanged(1.0:1.3), whereas the spin-coated sample’s Pd content decreasedwith respect to Co content. XPS determined binding energies were interpretedto imply that after oxidation in an oxygen/argon mixture of the graftedsample both PdIIand CoIIwere oxidized to producePdO2(337.5 eV) and CoIII2O3(781.1 eV) which most probably interacts with the silicon surfacevia PdIV–O–Si and CoIII–O–Sibonds. Solvent free aerobic oxidation of octadecanol to its correspondingcarbonyl compound was achieved on this oxidized PdIVCoIII/SiO2model catalyst using molecular oxygen asoxidant under solvent-free conditions. The use of the single sourcecatalyst precursor, 1, resulted in a PdIVCoIII/SiO2catalyst with superior catalytic activitytoward the oxidation of octadecanol over a catalyst prepared froma physical mixture of the separate reactant compounds tripalladium(II)hexaacetate and cobalt(II) diacetate. [ABSTRACT FROM AUTHOR]

The metathesis of 1-hexene and (E)-anethole in the presence of Grubbs 2nd generation catalyst was monitored by in situ 1H NMR spectroscopy at different temperatures (15 °C, 25 °C, and 45 °C) and anethole mol fractions (XAnethole ≈ 0.17, 0.29, 0.5, 0.71, 0.83). Time traces confirmed the instantaneous formation of (E)-1-(4-methoxyphenyl)-1-hexene, the cross-metathesis product. A maximum concentration of (E)-1-(4-methoxyphenyl)-1-hexene is reached fairly fast (the time depending on the reaction conditions), and this is followed by a decrease in the concentration of (E)-1-(4-methoxyphenyl)-1-hexene due to secondary metathesis. The maximum concentration of (E)-1-(4-methoxyphenyl)-1-hexene was more dependent on the XAnethole than the temperature. The highest TOF (3.46 min−1) was obtained for the reaction where XAnethole was 0.16 at 45 °C. The highest concentration of the cross-metathesis product was however achieved after 6 min with an anethole mol fraction of 0.84 at 25 °C. A preliminary kinetic study indicated that the secondary metathesis reaction followed first order kinetics. [ABSTRACT FROM AUTHOR]

The general synthetic strategy towards water-soluble biodegradable drug carriers and the properties that they must have are discussed. The syntheses of water-soluble biodegradable copolymers of lysine and aspartic acid as potential drug-delivering devices, having amine-functionalised side chains are then described. Covalent anchoring of carboxylic acid derivatives of the antineoplastic ferrocene and photodynamically active phthalocyanine moieties to the amine-containing drug carrier copolymers under mild coupling conditions has been achieved utilising the coupling reagent O-benzotriazolyl-N,N,N′,N′-tetramethyluronium hexafluorophosphate to promote formation of the biodegradable amide bond. Even though the parent antineoplastic ferrocene and phthalocyanine derivatives are themselves insoluble in water at pH < 7, the new carrier-drug conjugates that were obtained are well water-soluble. [ABSTRACT FROM AUTHOR]

Palladium-based heterometallic complexes are important because of their interesting physical properties and excellent catalytic activity. In this study, four monometallic trinuclear palladium long chain carboxylates and four palladium-based bimetallic bridging tetracarboxylate complexes were synthesised. These complexes were characterised by different techniques, including DSC, TGA-MS, X-Ray diffraction and IR spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: A comparative investigation of seven ferrocene-containing chalcones (Fc–CO–CH;C6H4R, with R=OCH3, CH3, Ph, t Bu, H, Br and CF3) has been performed based on their electrochemical and spectroscopical behavior as well as with DFT calculations. These compounds were prepared by Claisen-Schmidt condensation of acetylferrocene and the appropriate benzaldehyde derivative. All compounds exhibited reversible chemical and electrochemical behavior, as confirmed by ΔE =83−93mV and i pc/i pa =0.93−1.00. The formal reduction potential E°′ for the compounds ranged between 231.0 and 261.5mV versus FcH/FcH+ as an internal standard. The UV–Vis spectra of all ferrocene-containing chalcones showed the characteristic peaks for aromatic systems at ±380nm and a peak in the visible region at ±490nm, which is attributed to the ferrocene moiety. FTIR of all the ferrocene-containing chalcones showed a characteristic CO stretching peak at ±1650cm−1. DFT calculated HOMO energies and ionization potentials correlate well with experimentally measured E°′ values. [Copyright &y& Elsevier]

Graphical abstract The electrochemical behavior of the Fc/Fc+ of ferrocenyl-terpyridine coordination metal complexes is related to the charge transfer and binding energy of the Fe 2p photoelectron lines as measured by XPS, giving insight into the electronic properties of the complexes. Highlights • Preparation of coordinated ferrocenyl-terpyridine complexes. • Electrochemical study of the coordinated ferrocenyl-terpyridine complexes. • X-ray photoelectron spectroscopy of ferrocenyl-terpyridine coordination complexes. • The intensity of satellite structures in XPS indicated the amount of charge transferred. • Single crystal structure of [Rh(Fctpy) 2 ][PF 6 ] 3. Abstract A series of 4′-ferrocenyl-2,2′:6′,2′'-terpyridine coordination metal complexes, [M(Fctpy) 2 ][PF 6 ] x with M = Co (2), Fe (3), and Rh (4) and x = 2 (for 2 and 3) or 3 (for 4), was subjected to an electrochemical and X-ray photoelectron spectroscopic study. The formal reduction potential of the Fc/Fc+ couple of the ferrocenyl-moiety (FeII) is related to the Allred Rochow electronegativities of the different coordinated metals, as well as with binding energies of the Fe 2p 3/2 photoelectron lines (as measured by XPS). The binding energy position of the main Fe 2p 3/2 photoelectron line, spin–orbit splitting between the main and satellite structure (charge transfer band) of the Fe 2p 3/2 photoelectron line as well as the intensity ratio between the of the main and satellite structure of the Fe 2p 3/2 photoelectron line (I ratio , this gives the relative amount of charge being transferred) gave insight in the electronic structure of these ferrocenyl-terpyridine coordination metal complexes, 2 – 4. A single crystal X-ray structure determination of 4 highlighted the disorder of the PF 6 counter anions as well as double occupancy of the central metal atom of Rh (in 4) with Fe, the Fe:Rh ratio is 0.14:0.85. [ABSTRACT FROM AUTHOR]