Oxygen Coordination Research Articles

Structural Transformation of Molten CaO–SiO<sub>2</sub>–Al<sub>2</sub>O<sub>3</sub>–Fe<i><sub>x</sub></i>O Slags during Secondary Refining of Steels

According to the variation of compositions during steel secondary refining process, the ice-quenched samples of CaO–SiO2–FexO–Al2O3 system were prepared, the structure were detected via the method of Raman spectroscopy, and the evolution of structural units were further analyzed. The results showed that, for the Fe3+ cation, two types of units of tetrahedral fourfold coordination ([FeO4]) and octahedral sixfold coordination ([FeO6]) coexisted in the molten slag, and the ratio of [FeO6]/[FeO4] increases with the decreasing ratio of CaO/(SiO2+Al2O3). For the Al3+ cations, four types of aluminum units of Q2Al, Q3Al, Q4Al coexisted in the molten slag and the lower polymerized units Q2Al transform into the higher polymerized Q3Al and Q4Al along with the ratio of Al/(Al+Si) increasing from 0.41 to 0.85. For the Si4+ cations, Q0Si, Q1Si and Q2Si are the main types of [SiO4]-tetrahedral units, the Ca2+ cations of oxygen coordination in [SiO4]-tetrahedral units are gradually replaced by Al3+, which just act as network modifier, with the increase of Al/(Si+Al) ratio. Accordingly, the degree of polymerization of molten slag presented in NBO/T increases with the process of secondary steelmaking.

Density of MgO–Al2O3–SiO2, MgO–CaO–SiO2 and MgO–CaO–Al2O3–SiO2 glasses and the structural role of MgO

Density and molar volume of MgO–Al2O3–SiO2, MgO–CaO–SiO2 and MgO–CaO–Al2O3–SiO2 glasses have been correlated with the structure by following the change in type and concentration of structural units with composition. It is assumed that for (MgO+CaO)≥Al2O3 all Al atoms form AlO4 tetrahedra. The type of modified units of SiO2 (Q3 and Q2) are determined by the ratio [(MgO+CaO)−Al2O3]/SiO2. In the case of (MgO+CaO)<Al2O3, there is a fraction of Al2O3 that forms units based on the AlO3/2 formula. The entire SiO2 content would be in the form of Q4 units. Any of the structural units has its own constant volume that is independent of the type of glass. The agreement between calculated and experimental density and molar volume strongly suggests that MgO has only a modifier role in the studied glasses. Formation of assumed MgO4, MgO5 and MgO6 polyhedra can be due to change in coordination of oxygen, rather being looked as structural units.

Structural Diversity of Nickel and Manganese Chloride Complexes with Pyridin-2-One.

Reactions of NiCl2·6H2O and pyridin-2-one (C5H5NO = Hhp) afforded novel molecular complexes, i.e., mononuclear [NiCl2(Hhp)4] (1), dinuclear [NiCl2(Hhp)(H2O)2]2.2Hhp (3) and [Ni2Cl4(Hhp)5]·2MeCN (4), and an ionic complex [Ni(Hhp)6]Cl2 (2). Single-crystal X-ray analyses revealed two modes of Hhp ligation in these complexes: a monodentate coordination of carbonyl oxygen in all of them and an additional µ2-oxygen bridging coordination in the dinuclear complex 4. Three bridging molecules of Hhp span two nickel(II) ions in 4 with a 2.9802 (5) Å separation of the metal ions. Complex 3 is a chlorido-bridged nickel dimer with a planar Ni2(µ-Cl)2 framework. Hydrogen bonds and parallel stacking arrangements of the Hhp molecules govern the connectivity patterns in the crystals, resulting in 1D structures in 1 and 5 or 2D in 3. A single manganese compound [MnCl2(Hhp)4] (5), isostructural to 1, was isolated under the similar conditions. This is in contrast to four nickel(II) chloride complexes with Hhp. Thermal analyses proved the stability of complexes 1 and 3 in argon up to 145 °C and 100 °C, respectively. The decomposition of 1 and 3 yielded nickel in argon and nickel(II) oxide in air at 800 °C.

Study on the Anodic Bonding Mechanism of Polymer Electrolyte and Aluminum Based on MEMS Sensor Package

In this paper, Polyethylene oxide (PEO) is used as the main material to prepare PEO–LiClO4, a polymer electrolyte packaging material. The complexation mechanism of PEO–LiClO4 was studied by fourier transform infrared (FT-IR) spectra. Finally, the bonding of PEO–LiClO4 with Al was completed by anodic bonding method. Secondly, the bonding mechanism of PEO–LiClO4 and Al was revealed by FT-IR and energy dispersive spectrum analysis. The results show that in a certain range, the more lithium salt content, the more Li+ number of ether oxygen coordination in the molecular chain of LiClO4 and PEO, the higher the degree of complexation; under the action of strong electrostatic field, the ion-coordination exchange of PEO–LiClO4 and Al at the bonding interface by ion diffusion is the direct reason for the two to achieve bonding.

Reaction Mechanism of the Isomerization of Monoterpene Epoxides with Fe3+ as Active Catalytic Specie: A Computational Approach.

The reaction mechanism of the isomerization of α and β-pinene epoxides with Fe species as catalysts was studied with density functional theory (DFT) calculations and an experimental methodology. β-pinene epoxide can be isomerized into myrtanal and myrtenol in four steps, while in the case of perillyl alcohol, two additional steps are necessary. On the other hand, high selectivity to myrtanal obtained experimentally can be explained by the number of steps and the kind of the hydrogen transference that is easier for this compound in comparison with myrtenol and perillyl alcohol. A thermodynamic analysis showed that transformation into myrtenol, myrtanal, and perillyl alcohol is spontaneous but transformation into myrtanal is the most favorable. In the case of α-pinene epoxide rearrangement, a mechanistic study was carried out toward the optimization of the possible intermediates. Synthesis of campholenic aldehyde and carveol from α-pinene epoxide was carried out through three steps after the coordination of oxygen to iron, showing that in contrast to carveol formation, campholenic aldehyde synthesis is spontaneous. Analysis of ∇2ρ, the total energy density (H = V + G), and the |V|/G ratio evaluated at the bond critical point of the Fe-O bond showed for both epoxides that such interaction is closed shell instead of covalent. Apparently, α-pinene epoxide can be isomerized faster that β-pinene epoxide with Fe3+, which is in agreement with previous experimental results. This is the first report where a reaction mechanism of isomerization of monoterpenes epoxides is studied based on very detailed experimental and computational methodologies.

Lattice oxygen activation in transition metal doped ceria

Density functional theory calculations were carried out to investigate the influence of doping transition metal (TM) ions into the ceria surface on the activation of surface lattice oxygen atoms. For this purpose, the structure and stability of the most stable (111) surface termination of CeO2 modified by TM ions was determined. Except for Zr and Pt dopants that preserve octahedral oxygen coordination, the TM dopants prefer a square-planar coordination when substituting the surface Ce ions. The surface construction from octahedral to square-planar is facile for all TM dopants, except for Pt (1.14 eV) and Zr (square-planar coordination unstable). Typically, the ionic radius of tetravalent TM cations is much smaller than that of Ce4+, resulting a significant tensile-strained lattice and explaining the lowered oxygen vacancy formation energy. Except for Zr, the square-planar structure is the preferred one when one oxygen vacancy is created. Thermodynamic analysis shows that TM-doped CeO2 surfaces contain oxygen defects under typical conditions of environmental catalysis. A case of practical importance is the facile lattice oxygen activation in Zr-doped CeO2(111), which benefits CO oxidation. The findings emphasize the origin of lattice oxygen activation and the preferred location of TM dopants in TM-ceria solid solution catalysts.

Influence of modifier cations on the local environment of aluminum in La2O3-Al2O3 and Y2O3-Al2O3 binary glasses.

The local environment of aluminum in xLa2O3-(100 -x)Al2O3 (LA) and yY2O3-(100 -y)Al2O3 (YA) glasses is investigated using 27Al MAS NMR and Raman scattering spectroscopy in the glass forming range, i.e., 27 ≤x≤ 50 and 26 ≤y≤ 37.5, respectively. The results suggest that four-fold Al ([4]Al) is predominant in both glasses, with a content of approximately 90% in LA glasses and 60% in YA glasses; the remaining percentages are made up of five- ([5]Al) and six-fold ([6]Al) Al. In LA glasses, the fraction of [4]Al increases slightly with an increase in the La2O3 content, whereas, in YA glasses, the distribution of Al species does not change. Raman scattering spectroscopy reveals that, in LA glasses, the amount of non-bridging oxygen increases with an increase in x; moreover, [5]Al and [6]Al both increase with a decrease in x for x≤ 40. Comparing with alkali earth aluminate glasses, we discuss the relationship between the fundamental structure of the AlO4 network and two parameters (the ratio of the number of oxygen atoms to that of Al and field strength).

Oxygen Vacancy Mediated Stabilization of Cubic Phase at Room Temperature and Resistive Switching Effect in Sm‐ and Dy‐Doped HfO2 Thin Film

Recently, binary transition metal oxide‐based resistive random access memory (RRAM) has been attracted for future nonvolatile data storage devices. Herein, the structural evolution and resistive switching behavior of pristine and Sm‐ or Dy‐doped hafnium oxide (HfO2) films of ≈60 nm deposited on p++‐Si (100) substrates through electron‐beam evaporation technique are systematically investigated. Although it is reported that 12 at% of Sm or 11 at% of Dy doped in HfO2 nanoparticles stabilize the high‐temperature cubic phase at RT, herein, the stabilization of cubic phase after doping at most half of these dopant concentration is demonstrated. Furthermore, these films exhibit the bipolar switching behavior distinctive to RRAM device. Interestingly, the resistive switching characteristics are found to be of forming‐free nature. To understand the switching behavior, different conduction models such as the Ohmic and Poole–Frenkel emission are used. The monoclinic to cubic phase transformation and resistive switching phenomenon are discussed in terms of the abundant formation of oxygen vacancies producing eightfold oxygen coordination to Sm3+ or Dy3+ ion evidenced from photoluminescence and X‐ray photoelectron spectroscopy. The resistive switching mechanism through the formation of conducting filaments is pictorially illustrated in HfO2‐based RRAM.

Different magneto-optical response of magnetic sublattices as a function of temperature in ferrimagnetic bismuth iron garnet films

In this paper we investigate the magneto-optical (MO) and magnetic properties of bismuth iron garnet $\mathrm{B}{\mathrm{i}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$ thin films over a wide range of photon energies (1.6--3.5 eV) and temperatures (5--740 K). Depending on the photon energy range, the Faraday rotation (${\mathrm{\ensuremath{\Theta}}}_{F}$) and ellipticity (${\ensuremath{\varepsilon}}_{F}$) vary nonmonotonously with temperature. This behavior cannot be explained by a magnetization variation that can only decrease with increasing temperature. ${\mathrm{\ensuremath{\Theta}}}_{F}$ and ${\ensuremath{\varepsilon}}_{F}$ spectra have therefore been analyzed using a model based on two optical transitions of a diamagnetic nature, representing the tetrahedral and octahedral iron sites. Thus, the contribution of each magnetic sublattice has been extracted from the global macroscopic MO response and investigated as a function of temperature. The magnetic properties of octahedral and tetrahedral sublattices depend differently on temperature, suggesting a different anisotropy due to oxygen coordination. We have demonstrated that this relatively simple macroscopic measurement with a subsequent analysis can grant access to the information on the properties at a microscopic level. These results can advance the fundamental understanding of MO properties in multisublattice magnetic materials.

The crystal structure and magnetic properties of the new phosphate-vanadates Sr2.4-xCo2.6+xP3VO15, x=0.00, 0.02 and 0.04

The study of the phase composition of the SrCo2(VO4)2 – SrCo2(PO4)2 system showed that it belongs to pseudo binary equilibria. The new phosphate-vanadates Sr2.4-xCo2.6+xP3VO15, x ​= ​0–0.04, was found to crystallize in the Sr2.36Mg2.64P4O15 structural type. The crystal structure of the Sr2.4-хCo2.6+xP3VO15 (x ​= ​0.00, 0.02 and 0.04) consists of three types of tetrahedra, Co(1)O4, P/V(1)O4 and P(2)O4, one octahedron, Sr/Co(2)O6, and ten-fold oxygen coordination around Sr(1) ions. There are two types of chains directed along c-axis, consisting of edge-sharing octahedra, Sr/Co(2)O6, and corner-sharing tetrahedra, Co(1)O4, respectively. These chains are connected through P/V(1)O4, that form P/V(1)2O7 pyro-groups, and single P(2)O4 groups. Magnetic susceptibility of Sr2.4-хCo2.6+xP3VO15 (x ​= ​0.00, 0.02, 0.04) measured in the temperature range from 2 to 300 ​K is found to be determined by linear chains of tetrahedrally surrounded cobalt and by paramagnetic octahedral cobalt ions.

Structural Indicator to Characterize the Crystal-Field Splitting of Ce3+ in Garnets

The structure–property relationship is a hot research topic in both chemistry and material science. A structural descriptor has significant applications in machine learning and high-throughput screening for rapid estimations of material properties. In this work, we report a simple structural indicator to characterize the crystal-field splitting of Ce3+ ions in the garnet structure. The indicator is the interplanar distance of the octahedron, which is calculated as 2/√3 | x + y + z | · L, where L stands for the cell parameter and (x, y, z) are the oxygen coordinates in a specific form. The indicator value is correlated to the crystal-field splitting of Ce3+ in the lanthanide aluminum/gallium garnets and is able to reproduce the reverse garnet effect. By inspecting the polyhedral competition effect in the garnet structure, this indicator is found to be correlated to the tetragonal distortion of the dodecahedron, which determines the crystal-field splitting.

Origin of the mixed alkali effect in silicate glass

Silicate glasses have evolved from basic structural materials to enabling materials for advanced applications. In this article, we unravel the origin of the mixed alkali effect for alkali silicate 22.7R2O–77.3SiO2 glasses (R = Na and/or K) by identifying the variation in the alkali ion location around the non-bridging oxygen atoms. To do so, we constructed a state-of-the art structural model, which reproduces both diffraction and NMR data with a particular focus on the behavior of the alkali ions. A novel topological analysis using persistent homology found that sodium-potassium silicate glass shows a significant reduction in large cavities as a result of the mixed alkali effect. Furthermore, a highly correlated pair arrangement between sodium and potassium ions around non-bridging oxygen atoms was identified. The potassium ions can be trapped in K–O polyhedra due to the increased bridging oxygen coordination; therefore, the correlated pair arrangement is likely the intrinsic origin of the mixed alkali effect.

Effect of B-site substitution on structural, magnetic and optical properties of Ho2Ti2O7 pyrochlore oxide

Ho2Ti2O7 is a prominent quantum material, known for its exotic spin ice state, where structural and electronic properties are coupled. We report the systematic examination of the effects of Fe substitution at the non-magnetic Ti site (x = 0, 0.05, 0.075, 0.1, 0.125 and 0.15) in Ho2Ti2O7 on the structural, optical and magnetic properties. It is found that the optical properties of polycrystalline Ho2Ti2-xFexO7-δ (x = 0, 0.05, 0.075, 0.1, 0.125 and 0.15) can be tuned through partial substitution of the trivalent Fe3+ ion for the tetravalent Ti4+ ion. This Fe substitution not only creates charge-compensating oxygen vacancies but also modifies the optical band gap. A systematic structural, X-ray photoelectron spectroscopy, magnetic and optical analysis reveals that above a critical content of x = 0.1, a possible reduction in the oxygen coordination number (octahedral to tetrahedral) occurs, which appears in the form of high spin to low spin crossover for a fraction of the substituted Fe3+ ions. These results provide a new route to tune the optical band gap and absorption coefficient of Ho2Ti2O7 for magneto-optical applications.

Chemical Mimics of Aspartate-Directed Proteases: Predictive and Strictly Specific Hydrolysis of a Globular Protein at Asp-X Sequence Promoted by Polyoxometalate Complexes Rationalized by a Combined Experimental and Theoretical Approach.

Creating efficient and residue-directed artificial proteases is a challenging task due to the extreme inertness of the peptide bond, combined with the difficulty of achieving specific interactions between the catalysts and the protein side chains. Herein we report strictly site-selective hydrolysis of a multi-subunit globular protein, hemoglobin (Hb) from bovine blood, by a range of ZrIV -substituted polyoxometalates (Zr-POMs) in mildly acidic and physiological pH solutions. Among 570 peptide bonds in Hb, selective cleavage was observed at only eleven sites, each occurring at Asp-X peptide bonds located in the positive patches on the protein surface. The molecular origins of the observed Asp-X selectivity were rationalized by means of molecular docking, DFT-based binding, and mechanistic studies on model peptides. The proposed mechanism of hydrolysis involves coordination of the amide oxygen to ZrIV followed by a direct nucleophilic attack of the side chain carboxylate group on the C-terminal amide carbon atom with formation of a cyclic anhydride, which is further hydrolyzed to give the reaction products. The activation energy for the cleavage of the structurally related Glu-X sequence compared to Asp-X was calculated to be higher by 1.4 kcal mol-1 , which corresponds to a difference of about one order of magnitude in the rates of hydrolysis. The higher activation energy is attributed to the higher strain present in the six-membered ring of glutaric anhydride (Glu-X), as compared to the five-membered ring of the succinic anhydride (Asp-X) intermediate. Similarly, the cleavage at X-Asp and X-Glu bonds are predicted to be kinetically less likely as the corresponding activation energies were 6 kcal mol-1 higher, explaining the experimentally observed selectivity. The synergy between the negatively charged polyoxometalate cluster, which binds at positive patches on protein surfaces, and selective activation of Asp-X peptide bonds located in these regions by ZrIV ions, results in a novel class of artificial proteases with aspartate-directed reactivity, which is very rare among naturally occurring proteases.

Synthesis and Characterization of Sodium-Iron Antimonate Na2FeSbO5: One-Dimensional Antiferromagnetic Chain Compound with a Spin-Glass Ground State.

A new oxide, sodium-iron antimonate, Na2FeSbO5, was synthesized and structurally characterized, and its static and dynamic magnetic properties were comprehensively studied both experimentally by dc and ac magnetic susceptibility, magnetization, specific heat, electron spin resonance (ESR) and Mössbauer measurements, and theoretically by density functional calculations. The resulting single-crystal structure (a = 15.6991(9) Å; b = 5.3323 (4) Å; c = 10.8875(6) Å; S.G. Pbna) consists of edge-shared SbO6 octahedral chains, which alternate with vertex-linked, magnetically active FeO4 tetrahedral chains. The 57Fe Mössbauer spectra confirmed the presence of high-spin Fe3+ (3d5) ions in a distorted tetrahedral oxygen coordination. The magnetic susceptibility and specific heat data show the absence of a long-range magnetic ordering in Na2FeSbO5 down to 2 K, but ac magnetic susceptibility unambigously demonstrates spin-glass-type behavior with a unique two-step freezing at Tf1 ≈ 80 K and Tf2 ≈ 35 K. Magnetic hyperfine splitting of 57Fe Mössbauer spectra was observed below T* ≈ 104 K (Tf1 < T*). The spectra just below T* (Tf1 < T < T*) exhibit a relaxation behavior caused by critical spin fluctuations, indicating the existence of short-range correlations. The stochastic model of ionic spin relaxation was used to account for the shape of the Mössbauer spectra below the freezing temperature. A complex slow dynamics is further supported by ESR data revealing two different absorption modes presumably related to ordered and disordered segments of spin chains. The data imply a spin-cluster ground state for Na2FeSbO5.

Silicon-containing diorganotin complexes with salicylaldehyde thiosemicarbazone and their anticancer activity

Eight novel silicon-containing diorganotin complexes with salicylaldehyde thiosemicarbazone were synthesized. They were characterized by $$^{1}\hbox {H NMR}$$ , $$^{13}\hbox {C NMR}$$ , IR spectra, elemental analysis and X-ray single-crystal diffraction. Spectroscopic and X-rays studies indicated that the thiosemicarbazone Schiff base and tin atom were coordinated as a parallel five- and six-membered heterocyclic structure. In addition, the bioassay of the synthesized complexes was performed and the results show that the silicon-containing diorganotin complexes with salicylaldehyde thiosemicarbazone have good anticancer activity on human breast cancer cells. Eight silicon-containing organotin complexes containing salicylaldehyde thiosemicarbazone derivatives were synthesized. The Sn atom in the complexes were penta-coordinated in a distorted trigonal bipyramidal configuration, forming a five- and six-membered chelate ring through the coordination of oxygen, nitrogen, sulfur atoms. All the complexes showed significant anticancer activity, especially complex 3cb and 3ab.

Raman and EXAFS study of neodymium and praseodymium included alumino-germanate glass

Germanate glass has been synthesised keeping Al2O3 fixed at 10 mol% with Neodymium oxide and Praseodymium oxide varying from 5 mol% to 10 mol%. The effect of the rare-earth inclusion on the structure of the host matrix was examined by several techniques. Extended x-ray Absorption Fine Structure showed tetrahedral coordination of oxygen around Ge for all the glasses and gave the oxygen coordinations around Nd and Pr to be 8.7 and 8.9 respectively which is in contrast to the often quoted octahedral coordination for these ions. Raman spectroscopic studies have shown the Qn linkages of the GeO4 tetrahedra in these glasses as predominantly Q2 and Q3. The distribution of relative fractions of these linkages shows the Pr containing glass as having a few Q° and maximum Q2 connectivities while for the Nd and Nd-Pr containing glasses, these distributions peak for the Q3 connected linkages. These observations lead to the view that the Pr containing glass has a less well connected network than the Nd containing glasses. The presence of Pr in these glasses results in a decrease in electronic band gap energy and an increase in the electronic polarizability.

Characterization of Natural Rubber/Polyethylene Oxide (NR/PEO) Block Copolymer-Metal Ion Chelates

Two shot solution polymerized natural rubber/polyethylene oxide (NR/PEO) block copolymers are used as chelating exchanger for the metal ions Mn(II) and Fe(II). The polymer - metal ion chelates are prepared via solution batch adsorption method and are subjected to various characterisation techniques. Adsorption studies shows 96 and 63 % complexation for Mn(II) and Fe(III) ions, respectively. The 72 helical conformation of PEO and metal-etheric oxygen coordination are confirmed by FT-IR spectroscopy. The XRD results revealed the complete miscibility of metal ions and semi-crystalline nature of samples. The EDX analysis confirmed the presence of metal ions in the polymer chelates. Surface morphology is also studied using SEM and TEM techniques.

Influence of vanadium doping on the structural and electric properties of Sr0.5Ca0.5Mn1–xVxO3–δ

The solid solution Sr0.5Ca0.5Mn1–xVxO3–δ (0 ≤ x ≤ 0.125) has been obtained via a citrate-nitrate synthesis route. Powder X-ray diffraction (XRD) data for x = 0, 0.025 and 0.05 reveal the formation of perovskite-type orthorhombic structure with Pbnm space group (SG). Further increase of the vanadium content results in the appearance of the tetragonal crystal structure (SG I4/mcm) so that the composition of x = 0.075 is formed by the orthorhombic and tetragonal phase constituents in the 1:3 vol ratio. The single-phase sample at x = 0.1 is characterized by tetragonal symmetry of its unit cell. The comparison between the calculated (XRD) and pycnometric density values is indicative of 6-fold oxygen coordination of vanadium dopants. High-temperature electrical conductivity (σ) and Seebeck coefficient (S) measurements give evidence to the presence of electronic charge carriers that can be associated with Mn3+ cations appearing in response to vanadium doping. The largest thermoelectric power factor S2σ = 1.5 µW·K−2·cm−1 is attained in the two-phase composition x = 0.075 at 450 °C.

Cp2Mo(OH)(OH2)]+‐Catalyzed Hydrolysis of Mono‐ and Difunctional Ethers: Theoretical Understanding of Their Divergent Reactivity

The reaction mechanism of [Cp2Mo(OH)(OH2)]+‐catalyzed hydrolysis of ethyl vinyl, divinyl, and diethyl ethers was theoretically investigated. The reaction pathway evolving through the coordination of the ether oxygen to Mo is notably disfavored, as experimentally suggested. This is the only operative coordination mode for diethyl ether and explains why this monofunctional ether is not hydrolyzed by molybdocenes. However, difunctional ethers containing a functionality susceptible to activation like the vinyl group present an alternative reaction pathway proceeding through the coordination of the vinyl terminal carbon to Mo with accessible rate‐determining Gibbs energy barriers of 29.3 kcal/mol (divinyl ether) and 22.2 kcal/mol (ethyl vinyl ether). In these cases, the catalyst withdraws electron density from the unsaturated bonds and prepares the group for an easy OH‐nucleophilic attack. This explains the molybdocene‐catalyzed hydrolysis of ethyl vinyl ether experimentally observed and, more interestingly, reveals what the crucial role of the functional groups linked to the ether oxygen really is in the viability of these reactive processes.