OH Linkages Research Articles

Nucleophilic Nickel and Palladium Pincer Hydroxides: A Study of Their Reactions with Dimethyl Carbonate and Other Non‐Alkylating Organic Electrophiles

AbstractThe reactions of the pincer hydroxide complexes [(iPrPCP)M(OH)] (M=Ni, Pd) with dimethyl carbonate (DMC), and a set of organic electrophiles including benzaldehyde have been investigated in the context of our ongoing investigation on the synthesis of alkyl carbonates from CO2 and alcohols. The final outcome of such reactions is diverse, but for PhCHO and DMC the first step is a mechanistically similar addition of the [M]−OH linkage across the carbonyl functionality, that leads to unstable adducts. DMC is cleaved irreversibly by both Ni and Pd hydroxides, affording the corresponding methylcarbonates [(iPrPCP)MOCO2Me] and methanol, whereas PhCHO affords benzoate complexes [[(iPrPCP)MOCO2Ph]. The main kinetic and thermodynamic features of these reactions were reproduced satisfactorily by computational DFT models. The calculations throw light on the true causes of irreversibility of DMC cleavage by nucleophilic hydroxide complexes, which is the primary cause that prevents methanol carboxylation from being catalysed by the Ni or Pd pincers.

Synthesis and characterization of hetero-metal oxide nano-hybrid composite on pectin scaffold

Abstract Hetero-metal oxides play a vital role in the development of electrochemical sensors, energy storage devices etc., based on their electro-catalytic activity. To get better efficiency, agglomeration of the hetero-metal oxides has to be prevented. Moreover, the synergistic reinforcement of the properties of the metal oxides result in efficient shuttling of electrons at the hetero-metal oxide/liquid interface for sensing applications. In the current work a novel strategy is proposed which focuses on the growth of Copper oxide and Iron oxide nanoparticles on Pectin- a carbohydrate polymer scaffold. Copper oxide nano-particles and iron oxide nano-particles were synthesized by co-precipitation method. Both were ultrasonicated separately and were added to the acid extract of musk melon (Cucumis melo) peels, which is the source of pectin. The solution was heated and sonicated for 6 h and extracted with alcohol by solvent casting method. The blending of both metal oxides with pectin was uniform since the process occurs along with the formation of pectin. It was observed that the hetero-metal oxides disperse well in pectin with reduction in particle size where pectin acts as a scaffold by which the metal oxide nano-particles bind via the - OH linkage. The metal oxide nano-particles and hetero-metal oxide hybrid nanocomposite were characterized by SEM, EDX, UV–Visible, FT-IR, Raman, and XRD studies. The electrocatalytic activity was tested with cyclic voltammetric studies with potassium ferricyanide as the standard and it was observed that pectin scaffolded hetero-metal oxide composite has high electrocatalytic activity.

Aqueous Isolation of 17‐Nuclear Zr/Hf Oxide Clusters during the Hydrothermal Synthesis of ZrO2/HfO2

Novel 17-nuclear Zr/Hf oxide clusters ({Zr17 } and {Hf17 }) are isolated from aqueous systems. In the clusters, Zr/Hf ions are connected through μ3 -O, μ3 -OH, and μ2 -OH linkages into a pinwheel core which is wrapped with SO4 2- , HCOO- , and aqua ligands. Octahedral hexanuclear Zr/Hf oxide clusters ({Zr6 }oct and {Hf6 }oct ) are also isolated from the same hydrothermal system by decreasing the synthesis temperature. Structures, synthetic conditions, vibrational spectra, and ionic conductivity of the clusters are studied. Structural studies and synthesis inspection suggest that formation of {Zr6 }oct and {Zr17 } involves assembly of the same transferable building blocks, but the condensation degree and thermodynamic stability of the products increase with hydrothermal temperature. The role of {Zr6 }oct and {Zr17 } in the formation of ZrO2 nanocrystals are then discussed in the scenario of nonclassical nucleation theory. In addition, the Zr oxide clusters exhibit ionic conductivity owing to the mobility of protons. This study not only adds new members to the Zr/Hf oxide cluster family, but also establishes a connection from Zr4+ ions to ZrO2 in the hydrothermal preparation of zirconium oxide nanomaterials.

Urchin-like Cobalt Nanostructures For Catalytic Degradation Of Nitro Anilines

The undertaken study describes synthesis of urchin-like Cobalt nanostructures (Co NSs) in aqueous solution using gallic acid as both reductant and protecting agent for the catalytic degradation of 4-methyle-2-nitroaniline. UV-Visible (UV-Vis) spectroscopy was used as a primary tool to elaborately study and optimizes the necessary experimental condition for the developed synthetic protocol Fourier transform infrared (FTIR) spectroscopy showed the interaction between gallic acid and the surface of Co NSs via -OH linkages although Scanning electron microscopy (SEM) confirmed the formation of urchin shaped nanostructures with diameter in the range of 80-110 nm and length of tentacles between 1.0 - 1.8 µm. The as-synthesized Co NSs proved to be excellent heterogeneous catalyst for the 100 % reductive degradation of 4-methyle-2-nitroaniline in just 60 sec in presence of reductant (NaBH4) with reaction rate calculated to follow pseudo first order kinetic and rate constant of 0.055s -1 . Furthermore, Co NSs, showed excellent recyclability and were reused four times for the degradation of 4-methyle-2- nitroaniline with efficiency that displayed negligible catalytic poisoning. Copyright © 2016 VBRI Press.

Fluoride recovery using porous calcium silicate hydrates via spontaneous Ca2+ and OH− release

Abstract In the present study, porous calcium silicate hydrates (P-CSH) was prepared from CaO and soluble sodium silicate via a hydrothermal method and used for fluoride ions recovery. In comparison with the crystalline calcium silicate hydrates (C-CSH), P-CSH, which has large specific surface areas of 148.11 m2/g, a high Ca/Si molar ratio of 2.28 and low crystallinity, exhibited a high capacity for fluoride recovery from synthetic and practical electroplating wastewater. Fluoride recovery by P-CSH continued spontaneously at pH range of 6.4–7.4 without an extra pH adjustment. The fast Ca2+ dissolution rate of P-CSH was favorable for the fluoride precipitation with free Ca2+. Compared with the C-CSH, P-CSH exhibited massive Ca OH linkages, which enhanced the fluoride removal capacity by forming insoluble CaF2. Based on the analysis of the P-CSH samples before and after fluoride recovery by SEM, XRD, FTIR techniques, it was concluded that the surface Ca OH was active sites and the quantitative substitution of Ca OH groups by F− played a key role in F− ion exchange. The fluoride recovery efficiency of P-CSH is 79.6%. The present study demonstrated a good potential of P-CSH for the fluoride recovery.

Carbohydrate-surfactant interactions in aqueous and mixed organic solvents at various temperatures: Volumetric, compressibility and acoustical studies

Herein, we report the detailed volumetric, compressibility and acoustical studies of carbohydrate-surfactant interactions in aqueous and mixed organic solvents at various temperatures. The interactions between sugars (ribose, glucose, sucrose and raffinose) and sodium dodecyl sulfate (SDS, an anionic surfactant) were studied in aqueous solutions at various temperatures, i.e. 293.15, 303.15 and 313.15K using density and speed of sound measurements. Further, to clearly understand the sugar–surfactant interactions, various parameters such as molar volume (Vϕ), isentropic compressibility (κs) and apparent molar isentropic compressibility (κϕ,S) were calculated from the obtained data. The observed results revealed that different saccharides exhibit pronounced effect on micellization of SDS which might be due to the differences in number of –OH linkages. The increase in such linkages results in dominance of sugar–water interactions, thus favoring the micelle formation. Further, to support such conclusion, viscosity measurements (relative viscosity and viscous relaxation time) of SDS in aqueous solutions of sugars were also examined. The effect of different co-solvents viz. dimethyl sulfoxide (DMSO), methanol (MeOH) and dioxane on sugar-surfactant interactions has also been discussed and demonstrated in this paper.

Effect of fluoride doping for catalytic ozonation of low-temperature denitrification over cerium–titanium catalysts

Nanostructure cerium–titanium catalysts including fluoride (F−) doped ones were prepared by impregnation (Ce/TiO2 and Ce/F–TiO2) and co-precipitation (CeTi and CeTiF) method, and tested as ozonation catalysts for low-temperature NOX removal ranging from 40 to 180 °C. Interestingly, the doping of F− promotes the NOX removal for CeTi whereas inhibits the removal for Ce/TiO2. The NOX removal presents linear relationship with the concentration of hydroxyl radicals (OH). The surface –OH linked to Ce atoms as well as the H2O adsorption over Ce atoms play the important role in the generation of ·OH radicals. The doping of F− into CeTi improves the activation of Ce–OH linkage bonds and the adsorption of H2O over Ce atoms, thus increasing the concentration of OH radicals and catalytic activities. Although the doping of F− into Ce/TiO2 enhances the density of surface –OH, the ones linked to Ce atoms remain constant and the H2O adsorption over Ce atoms are declined, finally declining the catalytic activities.

Enhancement of Seeding and Electroless Cu Plating on TaN Barrier Layers: The Role of Plasma Functionalized Self-Assembled Monolayers

Self-assembled monolayers (SAMs) are extensively used in microelectronic copper metallization primarily as seed-trapping layers, diffusion barriers, or pore-sealants for porous dielectric materials. However, direct electroless copper plating of nitride barrier layers assisted by a seed-trapping SAM is rarely examined. Therefore, this work uses TaN, a standard barrier material for Cu metallization, as a model substrate to develop a new seeding (catalyst formation) process for electroless copper plating, involving substrate pretreatments from piranha etching (hydroxylation), octadecyltrichlorosilane SAM (OTS-SAM) deposition and subsequent functionalization. Catalytic particles upon adsorption onto piranha-treated (reference) TaN layers via Ta−OH linkages tend to agglomerate to give a limited density of 8 × 1013 m−2. In contrast, those adsorbed on piranha-treated TaN layers with a plasma-functionalized OTS-SAM over-coating are free from agglomeration and remain an average size of only 3 nm, along with an elevated density of 1 × 1015 m−2. X-ray photoelectron spectroscopy, together with transmission electron microscopy, clearly identifies the thin-film materials deposited and functional groups induced by each of the pretreatments, allowing the mechanism of seeding enhancement to be clarified. Finally, the enhancement of seeding to benefit electroless copper plating will be demonstrated.

Pigment Yellow 101 analogs from 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde – Synthesis and characterization

Pigment Yellow 101 analogs have been synthesized from 3-(1,3-benzothiazol-2-yl)-2-hydroxynaphthalene-1-carbaldehyde by combining with different aromatic diamines. Out of the four synthesized aldazines two show pigment properties and remaining show properties like dyes. Existence of excited state intramolecular proton transfer process between phenolic –OH and azomethine linkage (N–) has been computationally ascertained. Two pigment analogs showed solid state fluorescent which were compared with commercially available Pigment Yellow 101. For dyes analogs, effects of solvent polarity on photophysical properties such as absorption, emission have been studied. Density functional theory and time dependent density functional theory computations have been used to investigate structural parameters and understanding photophysical properties of synthesized analogs. All these aldazines show good thermal stability.

PENGARUH RASIO MOLAR SUBSTRAT DAN KONSENTRASI KATALIS PADA PEMBUATAN DECYL POLIGLIKOSIDA DARI D-GLUKOSA DAN DEKANOL

There are two methods to produce alkyl polyglucoside (APG) which are direct method and indirect method. In this research, APG synthesize with direct method that involves by directly reacting d-glucose with decanol with molar ratio variation of d-glucose:decanol are 1:10; 2:10; 4:10 and 6:10 (mol GL/mol C10) and HCl concentration as catalyst variation are 0,5; 1; 1,5 dan 2 (% based on weight of d-glucose) in 3 hours with temperature reaction is 95 0C. Next process is neutralizing with strong base (NaOH) until pH value is about 8-10 then the aqueous solutions are distillated with vacuum distillation. This research analyze density, yield and wavelength. Decyl polyglycoside synthetic optimum results best density value is 1,05 gr/mL in molar ratio of d-glucose:decanol 2:10 (mol GL/mol C10) and catalyst concentration 0,5%. Best yield in molar ratio of d-glucose:decanol 2:10 (mol GL/mol C10) and catalyst consentration 1,5% (% based on weight of d-glucose) with yield value is 84,09 %. Wavelength analysis of ether and OH linkage with Fourier Transform Infrared (FT-IR) spectroscopy detected ether (COC) linkage at wavenumber 1032,33 cm-1 and OH groups detected at wavenumber 3365,21 cm-1.

Structure, reactivity and mechanical properties of water ultra-confined in the ordered crystal: A case study of jennite

Jennite is an important structural prototype of C–S–H gel that is the major component of the cement hydrate. The structure, dynamics and mechanical properties of jennite were investigated by reactive force field molecular dynamics simulation. Water molecules, confined between the neighboring calcium silicate sheets, dissociate and form the Si–OH bonds with the oxygen atoms in the bridging silicate tetrahedron, which is consistent with the strong signal of Si–OH linkage from NMR testing (Cong and Kirkpatrick, 1996) [1]. Dynamically, the high diffusion rate and the dissociation reaction of water molecules reduce the stability in the interlayer region. Additionally, uniaxial tensile testing, applied to the jennite structure in the x, y and z direction, exhibited the an-isotropic nature of the layered crystal. While Si–O bonds, acting in a skeleton role, contribute to the mechanical behavior in the y direction, the unstable H-bonds connectivity weakens the tensile strength and stiffness in the z direction. More importantly, the reactive force field accompanied together both the mechanical response and chemical response during the large tensile deformation process. On the one hand, the silicate chains de-polymerize to enhance the loading resistance and on the other hand, water molecules, attacking the Si–O and Ca–O bonds, dissociate into hydroxyls, which are detrimental to the cohesive force development.

Synthesis of a benzoxazine with precisely two phenolic OH linkages and the properties of its high‐performance copolymers

ABSTRACTA phenolic OH‐containing benzoxazine (F‐ap), which cannot be directly synthesized from the condensation of bisphenol F, aminophenol, and formaldehyde by traditional procedures, has been successfully prepared in our alternative synthetic approach. F‐ap was prepared by three steps including (a) condensation of 4‐aminophenol and 5,5'‐methylenebis(2‐hydroxybenzaldehyde) (1), (b) reduction of the resulting imine linkage by sodium borohydride, and (c) ring closure condensation by formaldehyde. The key starting material, (1), was prepared from 2‐hydroxybenzaldehyde and s‐trioxane in the presence of sulfuric acid. F‐ap is structurally similar to bis(3,4‐dihydro‐2H‐3‐phenyl‐1,3‐benzoxazinyl)methane (F‐a, a commercial benzoxazine based on bisphenol F/aniline/formaldehyde) except for two phenolic OHs. The phenolic OHs can provide reaction sites with epoxy and 1,1'‐(methylenedi‐p‐phenylene)bismaleimide (BMI). The structure–property relationships between the thermosets of F‐ap/epoxy, F‐a/epoxy, F‐ap/BMI, and F‐a/BMI were discussed. Experimental data showed that thermosets based on F‐ap/epoxy and F‐ap/BMI provided much better thermal properties than those based on F‐a/epoxy and F‐a/BMI. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2686–2694

Eu3+ assisted structural collapse of GaOOH nanorods: Probed through EXAFS and vibrational techniques

Layered structure of highly crystalline orthorhombic GaOOH nanorods undergo significant lattice distortions leading to amorphisation even when very small amounts of Eu3+ ions (1at.% or more) are present during its synthesis. Local short range order around Ga3+ is unaffected by the structural collapse, even though the lattice disorder increases with increase in Eu3+ content in the lattice, as confirmed from the EXAFS studies. Incorporation of Eu3+ ions at the interlayer spacing of GaOOH lattice and its reaction with structure stabilizing OH linkages in the lattice is responsible for the collapse of the structure leading to amorphisation.

Hydrogen bond connectivity in jennite from ab initio simulations

The protonation scheme and the hydrogen bond connectivity in the structure of jennite were investigated by ab initio molecular dynamics simulations. The calculated statistics of hydrogen bonds at ambient conditions is consistent with the protonation scheme proposed by Bonaccorsi et al. (2004) based on the bond valence theory. The protons in the system are associated with the 2Ca–OH linkage and H 2O molecules. The dangling Si–O bond on the bridging tetrahedra is de-protonated. The proton dynamics revealed in the molecular dynamic simulations explains the apparent discrepancies in the NMR and X-ray diffraction studies of jennite.

Structural Investigations of Alkali Silicate Gels

Investigation of a series of synthetic alkali silicate gels and gels produced by the alkali silica reaction (ASR) in field concrete using 29Si NMR spectroscopy, X‐ray diffraction, and bulk chemical analysis shows that local structures of the synthetic and field gels are quite similar. The most abundant Si sites for the field and synthetic gels with similar compositions have Q3 polymerization, and the number of non‐bridging oxygens per Si is similar for these samples. These samples also yield a basal X‐ray diffraction peak near 8–12 Å, suggesting that the structure is dominated by sheet‐like units, consistent with the dominant Q3 polymerization. Calculations based on the relative site abundances of the sites observed by 29Si NMR and the bulk chemical compositions indicate that there is insufficient alkali to charge‐balance all the non‐bridging oxygens and that there is a significant concentration of Si–OH linkages. The results provide strong support for the basic structural concepts of the so‐called kanemite model for ASR gel proposed by Wieker and coworkers, although the overall gel structure is likely to be more complex.

Synthesis and Structure of a Novel Lithium Gallosiloxane Containing a Ga4Si4O8 Macrocycle Analogous to the S8R Building Unit of Zeolites

The reaction of LiGaMe4 with diphenysilanediol in THF at 50 °C leads to the formation of the title gallosiloxane Li2(Li(THF)2)2[Ph2SiO2GaMe2]2[Ph2SiO2GaMe(OH)]2·2THF (1), which is made up of a central tetraanionic Ga4Si4O8 16-membered macrocyclic core. The cavity that is created by this tetraanionic gallosiloxane ring and also the presence of two Ga−OH groups pointing toward the center of the macrocyclic ring facilitate the entrapment of two lithium cations in the core through two Li−O(siloxide) and two Li−OH(Ga) linkages. The other two lithium ions are located at the periphery and are bound to the gallosiloxane ring through the Li−O(Si) linkages. Compound 1 represents the first organic-soluble molecular model compound for the S8R secondary building unit of several gallo- and aluminosilicates.

Asphaltene adsorption on kaolinite characterized by infrared and X-ray absorption spectroscopies

The petroleum industry has observed that the trapping of oils in sedimentary rock is largely correlated to the presence of kaolinite clays in the rock's intergranular space. Using X-ray absorption and Fourier transform infrared (FTIR) spectroscopies, we studied at the microscopic level the adsorption process of asphaltenes in the presence and absence of water. We show that oil modifies the local environment of aluminum in this material and, more precisely, the Al–OH linkage. Finally, we show evidence that the process involved is different when the adsorption is performed with or without water.

3-(4-Methoxyphenoxy)-1,2-benzisothiazole 1,1-Dioxide: its Relation to Mechanistic Behaviour in Catalytic Transfer Hydrogenolysis

Conjugation of oxygen with an aromatic ring, as in a phenol, gives a C—O bond length of about 1.35 Å, whereas the C—O bond length in an aliphatic alcohol is about 1.45 Å. A saccharyl ether derivative of a phenol changes the phenolic C—O bond length to 1.42 Å and makes the bond chemically more susceptible to catalytic ipso replacement of the aromatic C—OH linkage by C—H. The present study of the title compound, C14H11NO4S, was carried out in order to examine specifically the effect of saccharyl ether formation on the C—O bond length of a phenol.

29Si and 17O NMR investigation of the structure of some crystalline calcium silicate hydrates

Abstract This paper presents the results of a systematic investigation of the structure of 17O-enriched, hydrothermally synthesized 1.1-nm tobermorite, 1.4-nm tobermorite, jennite, calciochondrodite, xonotlite, and hillebrandite, using 29Si magic angle spinning (MAS) NMR, 1H-29Si cross-polarization magic angle spinning (CPMAS) NMR, and 17O MAS NMR. The 17O and most of the 1H-29Si CPMAS results are the first reported for these phases. Six types of oxygen sites were observed in tobermorite and jennite, including both SiOH CaOH linkages. The structure of 1.4-nm tobermorite is similar to that of 1.1-nm tobermorite with about 26% of the Ca2+′s in the interlayers. The results support the proposed jennite structure in which silicate chains and rows of OH− groups alternately occur along the CaO layers [1]. Jennite contains long, single silicate chains similar to those in 1.4-nm tobermorite, with SiOH sites primarily occurring on bridging tetrahedra, and there seems to be no interlayer Ca2+′s. Although the Si sites in xonotlite and calciochondrodite cross-polarize well, neither contains SiOH linkages.

Vapor Phase Vibrational Spectra for Re(2)O(7) and the Infrared Spectrum of Gaseous HReO(4). Molecular Shapes of Mn(2)O(7), Tc(2)O(7), and Re(2)O(7).

The Raman and infrared spectra of gas phase Re(2)O(7) are reported. The experimental vibrational spectra of molecular Tc(2)O(7) and Re(2)O(7) are compared with calculated spectra. The results of these studies agree with a nonlinear M-O-M bridge for Tc(2)O(7) and Re(2)O(7). For infrared intensity calculations, the point charge approximation is used, while for the Raman calculations a combination of bond and atom polarizabilities is adopted. Pure Re(2)O(7) was prepared from rhenium wire, but attempts to prepare it from rhenium powder and oxygen always led to infrared spectra showing serious contamination from a species containing an -OH linkage. Detailed experiments identified this molecule as HReO(4), a unique transition metal analogue of the perhalic acids, and a partial infrared spectrum of this molecule is reported.