Sequential Transformation Research Articles

3D hierarchical hollow microrod via in-situ growth 2D SnS nanoplates on MOF derived Co, N co-doped carbon rod for electrochemical sensing

Epinephrine (EP) is a catecholamine neurotransmitter produced from l-tyrosine (L-TY), which usually coexists with each other in biological fluids. Moreover, their abnormal concentrations are related to multiple diseases, so sensitive simultaneous determination of EP and l-TY is important. Herein, we delicately designed 3D SnS@Co,N-C hierarchical hollow microrod assembled from 2D SnS nanoplates vertically anchored on the MOF derived cobalt, nitrogen co-doped carbon rod (Co,N-C) as electrode materials using one-step hydrothermal method, followed by thermal annealing in N2, and accompanying sequential phase transformation (2D SnS2 nanoplates in-situ reduced to SnS phase). Obtained hierarchical hollow carbon microrod with beneficial heteroatom doped not only provided sufficient electroactive sites, but also increased the conductivity of the materials. As-fabricated strongly coupled 3D SnS@Co,N-C microrod displayed enhanced electrochemical performance, offering highly sensitive sensing responses toward biomolecules EP and L-TY. Differential pulse voltammetry (DPV) study indicated that the sensor offered wide linear ranges of 0.01–300.0 and 0.01–250.0 μmol/L, and low detection limits of 3.3 and 3.1 nmol/L for EP and L-TY respectively. The constructed sensor was successfully applied to monitor simultaneously EP and L-TY in milk, human urine and serum samples with high accuracy and reliability.

Method for identifying the triple transition (glass transition-dehydration-crystallization) of amorphous cellulose in cotton

Although having a full picture of the heat-induced alterations in the fine structure of cellulosic materials is essential for designing their thermal processing, there have been no reliable methods to identify thermal transition temperatures. This study shows that colorimetric, thermogravimetric, and thermal kinetic parameters were sensitive to the thermochemical and thermo-structural changes in cotton fiber at low temperatures. Among these parameters, the activation energy for the thermal decomposition, evolving two local maxima against the preheating temperature, identified sequential thermal transformations in amorphous cellulose: 1) glass transition at 160–180 °C (Tg), 2) cellulose dehydration at 200–220 °C, and 3) crystallization at 240–260 °C. These results indicated that results of the mechanical tests or other methods discussed in the literature, which have produced inconsistent and higher Tg values (200–240 °C) for cellulosic materials, might have been misled by the dehydration of amorphous cellulose.

Sheared free-surface flow over three-dimensional obstructions of finite amplitude

When shallow water flows over uneven bathymetry, the water surface is modulated. This type of problem has been revisited numerous times since it was first studied by Lord Kelvin in 1886. Our study analytically examines currents whose unperturbed velocity profile$U(z)$follows a power law $z^{q}$, flowing over a three-dimensional uneven bed. This particular form of $U$, which can model a miscellany of realistic flows, allows explicit analytical solutions. Arbitrary bed shapes can readily be imposed via Fourier’s theorem provided their steepness is moderate. Three-dimensional vorticity–bathymetry interaction effects are evident when the flow makes an oblique angle with a sinusoidally corrugated bed. Streamlines are found to twist and the fluid particle drift is redirected away from the direction of the unperturbed current. Furthermore, a perturbation technique is developed which satisfies the bottom boundary condition to arbitrary order also for large-amplitude obstructions which penetrate well into the current profile. This introduces higher-order harmonics of the bathymetry amplitude. States of resonance for first- and higher-order harmonics are readily calculated. Although the method is theoretically restricted to bathymetries of moderate inclination, a wide variety of steeper obstructions are satisfactorily represented by the method, even provoking occurrences of recirculation. All expressions are analytically explicit and sequential fast Fourier transformations ensure quick and easy computation for arbitrary three-dimensional bathymetries. A method for separating near and far fields ensures computational convergence under the appropriate radiation condition.

Sequential Transformation of Terminal Alkynes to 1,3-Dienes by a Cooperative Cobalt Pyridonate Catalyst

We describe the cobalt(II) catalyst 1 bearing a phosphinopyridonate ligand for sequential transformation of aryl terminal alkynes to (E,Z)-1,3-dienes with excellent stereoselectivity. By cooperativ...

Synthesis and Cytotoxicity of A-Azepanodammaradiene

Sequential transformations of dipterocarpol (oximation, first-order Beckmann rearrangement, dehydration, isomerization) synthesized the new dammarane-type triterpenoid A-azepanodammara-20(21),24(25)-diene. Its cytotoxicity was studied in vitro against 60 cell lines of 9 human tumor types. The cytotoxicity against all cancer cell types increased significantly as compared to native dipterocarpol if an azepane fragment was introduced into ring A (percent inhibition from 15.72% to 82.08%). Detailed cytotoxicity studies confirmed the activity against a broad spectrum of human tumor cell lines with a mean (MID) log LC50 of 5.57.

Modular Arene Difunctionalization of Unactivated C-O and C-H Bonds by Sequential Chromium-Catalyzed Transformations.

Sequential transformations of unactivated C-O and C-H bonds under chromium catalysis are described. The use of a N-benzyl-substituted imino group as an auxiliary combined with chromium(II) chloride as a precatalyst and 2,3-dichlorobutane as an oxidant allows the arene C-O and C-H bonds to sequentially couple to arylmagnesium reagents to incorporate two identical or different aryl groups into the ortho positions of benzaldehydes.

Sequential Symmetry-Breaking Intercolumnar Transformations of a Conjugated Rod Molecule with a Flexible Coil

In this paper, we report distinct symmetry-breaking phase transitions in molecules based on oligo-para-phenylene rods and a poly(ethylene oxide) coil depending on the length of the aromatic rod block The observed phase transitions were characterized by differential scanning calorimetry (DSC) and X-ray scattering methods. Compound 1 with a tetra-para-phenylene rod exhibited a symmetry breaking intercolumnar transition from p2gg to p6mm symmetry. This phase transition was accompanied by an endothermic peak in the DSC profile (first-order transition), suggesting an in-plane twist of the ribbon-like rod domain. On the other hand, 2 with a longer penta-para-phenylene rod exhibited sequential symmetry breaking intercolumnar transitions from c2mm to p2gg to p6mm symmetry. In contrast with 1, the phase transitions were accompanied by no enthalpy change. Therefore, the ribbon-like rod domains were not segmented due to increased inter-rod interactions of the longer aromatic rods. The phase transitions of 2 are attributed to increased thermal motions of the coils, which vary the orientational angle of the aromatic columns in the lattice.

Mustard Gold of the Gaching Ore Deposit (Maletoyvayam Ore Field, Kamchatka, Russia)

The Gaching high-sulfidation (HS) epithermal Au–Ag deposits, part of the Maletoyvayam ore field, which is located in the volcanic belts of the Kamchatka Peninsula (Russia). The main ore components are native gold, tellurides, selenides, and sulphoselenotellurides of Au and oxidation products of Au-tellurides. This study examines the different types of native gold in this ore deposit and the mechanisms and sequential transformation of calaverite (AuTe2) into mustard gold. The primary high fineness gold (964‰–978‰) intergrown with maletoyvayamite Au3Te6Se4 and other unnamed phases (AuSe, Au(Te,Se)) differ from the secondary (mustard) gold in terms of fineness (1000‰) and texture. Primary gold is homogeneous, whereas mustard is spongy. Two types of mustard gold were identified: a) Mixtures of Fe-Sb(Te,Se,S) oxides and fine gold particles, which formed during the hypogenic transformation stage of calaverite due to the impact of hydrothermal fluids, and b) spotted and colloform gold consisting of aggregates of gold particles in a goethite/hydrogoethite matrix. This formed during the hypergenic transformation stage. Selenides and sulphoselenotellurides of gold did not undergo oxidation. Pseudomorphic replacement of calaverite by Au-Sb(Te,Se,S,As) oxides was also observed.

Sequential structural transformations via pseudohalide-anion exchange reactions in Cu(II) supramolecular complexes

We report here the first example of sequential post-synthetic structural transformations via pseudohalide anion exchanges. Assembly of a rigid angular ligand 3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole (L240) with CuBr2 results in a 1D crystalline material {[Cu(L240)(Br)2](DMF)(H2O)}n (1). Immersing the green microcrystalline sample of 1 into an aqua solution of NaN(CN)2 (Na(dca)), the partly exchanged blue species {[Cu(L240)(dca)Br](H2O)}n (2) is obtained after ca. a week. Then, the fully exchanged green [Cu(L240)(dca)2]n (3) occurs after about ten days and 2 gradually disappears. Further immersing 1 or 3 into the solution of NaN3, a new deep green material defined as [Cu(L240)(N3)2]2 (4) can be obtained. These structural transformations can be ascribed to the solvent-mediated structural transformation, accompanied the change of crystallinity, shape, size, and color. Notably, 2–4 cannot be synthesized by direct assembly of L240 and Cu salts with those pseudohalide (dca– or N3–).

Integrated soluble polymer and mesoporous silica as a double–type support to immobilize tertiary amine–Ru/diamine–bifunctionality for aza–addition/reduction cascade reaction

Exploiting advantages of a double–type support to create an active site–isolated heterobifunctional catalyst is beneficial to an efficiently sequential organic transformation. Herein, an integrated soluble polymer and mesoporous silica as a double–type support to immobilize the tertiary amine–Ru/diamine–bifunctionality for the construction of an active site–isolated catalyst is developed, where the tertiary amine–functionality is tethered in the outer soluble polymer and chiral ruthenium/diamine–functionality is anchored within the inner mesoporous silica. Electron microscopy images, together with analyses of solid–state NMR spectra, disclose that catalyst possesses the uniformly distributive morphology with well–defined single–site ruthenium/diamine active centers. As envisaged, the heterobifunctional catalyst performs a highly efficient aza–Michael addition/asymmetric transfer hydrogenation enantioselective cascade reaction, where the outer tertiary amine–functionality enables a high reactivity to afford β–secondary amino ketones via an aza–Michael addition reaction of enones and amines, and the inner chiral ruthenium/diamine–functionality guarantees a high enantioselectivity to chiral γ–secondary amino alcohols via an asymmetric transfer hydrogenation of β–secondary amino ketones. Furthermore, this catalyst can also be recovered easily and recycled for six runs, showing a practical preparation of aryl–substituted γ–secondary amino alcohols.

Improving the Efficiency of the Multireference Driven Similarity Renormalization Group via Sequential Transformation, Density Fitting, and the Noninteracting Virtual Orbital Approximation.

This study examines several techniques to improve the efficiency of the linearized multireference driven similarity renormalization group truncated to one- and two-body operators [MR-LDSRG(2)]. We propose a sequential MR-LDSRG(2) [sq-MR-LDSRG(2)] scheme, in which one-body substitutions are folded exactly into the Hamiltonian. This new approach is combined with density fitting (DF) to reduce the storage cost of two-electron integrals. To further avoid storage of large four-index intermediates, we propose a noninteracting virtual orbital (NIVO) approximation of the Baker-Campbell-Hausdorff series that neglects commutators terms with three and four virtual indices. The NIVO approximation reduces the computational prefactor of the MR-LDSRG(2), bringing it closer to that of coupled cluster with singles and doubles (CCSD). We test the effect of the DF and NIVO approximations on the MR-LDSRG(2) and sq-MR-LDSRG(2) methods by computing properties of eight diatomic molecules. The diatomic constants obtained by DF-sq-MR-LDSRG(2)+NIVO are found to be as accurate as those from the original MR-LDSRG(2) and coupled cluster theory with singles, doubles, and perturbative triples. Finally, we demonstrate that the DF-sq-MR-LDSRG(2)+NIVO scheme can be applied to chemical systems with more than 550 basis functions by computing the automerization energy of cyclobutadiene with a quintuple-ζ basis set. The predicted automerization energy is found to be similar to the value computed with Mukherjee's state-specific multireference coupled cluster theory with singles and doubles.

Sustainable and rapid production of biofuel γ-valerolactone from biomass-derived levulinate enabled by a fluoride-ionic liquid

ABSTRACT γ-Valerolactone (GVL) is a versatile biomass-derived molecule for both value-added chemicals and biofuels, which is typically prepared from levulinates over metal particles or oxides in the presence of hydrogen, formic acid or alcohol. Herein, we reported a rapid and mild approach for cascade hydrogenation-cyclization of ethyl levulinate (EL) to GVL in the presence of readily available ionic liquid tetrabutylammonium fluoride ([TBA]F) and polymethylhydrosiloxane (PMHS) as catalyst and hydrogen source, respectively. After reacting at room temperature for 30 min, a high GVL yield of 85% with TOF value of 52 h−1 could be obtained over 3 mol% [TBA]F. In addition to optimizing reaction parameters, the catalytic mechanism was also elucidated for the one-pot sequential transformation of EL to GVL.

Substitution of the Dimethylamino Group in Gramines and One-Pot Cyclization to Tetrahydro-β-carbolines Using a Triazine-Based Activating Agent

A new method for the substitution of 3-[(dimethylamino)methyl]indoles (gramines) with malonate-based nucleophiles was developed using 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) as the activating agent for the dimethylamino group. The reaction was completed in 1.5-6 h at room temperature in the presence of a tert-amine base and lithium salt. CDMT afforded superior results to methyl iodide, a common activating agent for the dimethylamino group in Mannich bases, particularly in the reactions of 1-substituted gramines. The reactivity of the possible intermediates, bis(indol-3-ylmethyl)dimethylammonium salts, was examined to obtain mechanistic insights on the reaction. This substitution method with CDMT enabled the sequential transformation of gramines: substitution with ( N-alkylidene)aminomalonates followed by the Pictet-Spengler reaction under acidic conditions afforded 1,2,3,4-tetrahydro-β-carboline derivatives in one pot.

Thermolysis of [Pd(NH3)4]Cl2–(NH4)2Cr2O7 Mixtures in an Inert Atmosphere

Sequential thermal transformations of a 3[Pd(NH3)4]Cl2–2(NH4)2Cr2O7 mixture (Pd : Cr molar ratio, 3 : 4) are studied via thermal analysis and mass spectrometry in an argon atmosphere and the temperature range of 50 to 550°C. XRD and elemental analysis show that the solid product obtained after thermolysis of the mixture under the selected conditions is a Pd1 − xCrx palladium-based solid solution that is isostructural to Pd (cell parameter a = 3.8921(5) A) and the Cr2O3 oxide phase. A model of the solid-phase transformations in the mixture in an argon atmosphere is proposed that includes the formation of palladium and chromium metallic phases.

A modular Golden Gate toolkit for Yarrowia lipolytica synthetic biology.

SummaryThe oleaginous yeast Yarrowia lipolytica is an established host for the bio‐based production of valuable compounds and an organism for which many genetic tools have been developed. However, to properly engineer Y. lipolytica and take full advantage of its potential, we need efficient, versatile, standardized and modular cloning tools. Here, we present a new modular Golden Gate toolkit for the one‐step assembly of three transcription units that includes a selective marker and sequences for genome integration. Perfectly suited to a combinatorial approach, it contains nine different validated promoters, including inducible promoters, which allows expression to be fine‐tuned. Moreover, this toolbox incorporates six different markers (three auxotrophic markers, two antibiotic‐resistance markers and one metabolic marker), which allows the fast sequential construction and transformation of multiple elements. In total, the toolbox contains 64 bricks, and it has been validated and characterized using three different fluorescent reporter proteins. Additionally, it was successfully used to assemble and integrate a three‐gene pathway allowing xylose utilization by Y. lipolytica. This toolbox provides a powerful new tool for rapidly engineering Y. lipolytica strains and is available to the community through Addgene.

Structural Transformations in the Thermal Dehydration of [Cu2(bpa)(btec)(H2O)4]n Coordination Polymer.

Reactions between pyridinic ligands such as 1,2-bis(4-pyridyl)ethane (bpa) and transition metal cations are a very widespread technique to produce extended coordination polymers such as Metal-Organic Frameworks. In combination with a second ligand these systems could present different topologies and behaviors. In this context, the use of 1,2,4,5-benzenetetracarboxylic acid (H4btec) gave us a novel 2D compound, [Cu2(bpa)(btec)(H2O)4]n (1), which was prepared by microwave-assisted synthesis and structurally characterized by means of single crystal X-ray diffraction. Its thermal behavior was analyzed through thermogravimetric analysis and variable temperature powder X-ray diffraction, concluding that thermal stability is influenced by the coordination water molecules, allowing two sequential thermochromic phase transformations to take place. These transformations were monitored by electronic paramagnetic resonance spectroscopy and magnetic susceptibility measurements. In addition, the crystal structure of the anhydrous compound [Cu2(bpa)(btec)]n (1.ah) was determined. Finally, a topological study was carried out for the bpa ligand considering all the structures deposited in the Cambridge Structural Databased. More than 1000 structures were analyzed and classified into 17 different topologies, according to the role of the ligand.

(Invited) Β-SnSb for Sodium Ion Battery Anodes: Phase Transformations Responsible for Enhanced Cycling Stability Revealed By in Situ TEM

The alloy β-SnSb is known to be a highly stable anode for sodium ion batteries during cycling, but its sodiation−desodiation alloying reactions are poorly understood. Combining in situ TEM with electroanalytical methods, we demonstrate that β-SnSb forms Na3Sb and Na15Sn4 in sequence upon sodiation and re-forms as β- SnSb upon desodiation. The negative enthalpy of mixing for Sn and Sb is sufficient to cause sequentially deposited bilayers of Sn/Sb to transform into β-SnSb, resulting in comparable cycling stability. The good cycling stability of β-SnSb results from the complex two-phase amorphous−nanocrystalline microstructure in the partially charged− discharged states, as well as the intrinsic mechanical toughness of the β phase. Per the in situ TEM results, the sequential phase transformation shows minimal fracturing of the β-SnSb, indicating facile buffering of stresses. Extensively cycled specimens eventually show crystalline Sn phase segregation, which may be the source of the ultimate capacity fade in the alloy and bilayers.

Sequential mineral transformation during underground coal gasification with the presence of coal partings

Underground coal gasification (UCG) can be adopted to convert unminable coal resources into synthesis gas for use in the production of electricity, fuels, and chemicals. UCG is a promising technology with many health, safety, and environmental advantages over conventional mining techniques. It is of great scientific significance to study the mineral transformation and identify the typical minerals in certain process conditions, because it may help to ensure the stable operation of the gasification processes and improve the utilization efficiency of coal seams. The presence of coal partings has an important impact on mineral transformation. In this paper, the UCG process has been subdivided into pyrolysis, reduction, and oxidation stages, and the progressive coal conversion products were prepared. Ulanqab lignite was used as the test coal. The minerals in the coal transformation products were identified by X-ray diffraction (XRD) and scanning electron microscopy coupled with an energy-dispersive spectrometer (SEM-EDS). The thermodynamic equilibrium simulation software, FactSage 7.2, was used to calculate the relevant phase diagram to assist in understanding the mineral transformations. The experimental results indicate that the different iron-bearing minerals occur in raw coal and non-coal partings which are nontronite (Na0.3Fe2Si4O10(OH)2.4H2O) and glauconite (K (Fe, Al)2(Si, Al)4O10(OH)2) respectively. Pyrrhotite is the main iron-bearing mineral in the pyrolysis products. In the reduction stage, the relative content of Al2O3 is increased due to the presence of non-coal partings, which reacts with FeO to produce hercynite (FeAl2O4) at a temperature above 1100 °C. When the temperature increases to 1300 °C, hercynite is converted to the thermodynamically-stable cordierite (Fe2Al4Si5O18). In the oxidation stage, mullite (Al6Si2O13) is produced when the oxidation temperature reaching 1300 °C, which could be used to reflect the underground reaction conditions in the coal seam. The phase diagram of (SiO2)6.2Al2O3-CaO-Fe2O3 proves that mullite and anorthite (CaAl2Si2O8) are the dominant minerals when the mole fraction of (SiO2)6.2Al2O3 is above 0.7. In addition, the ash melting point rises with an increase of Si and Al content in the presence of non-coal partings.

Mining Small Routine Clinical Data: A Population Pharmacokinetic Model and Optimal Sampling Times of Capecitabine and its Metabolites.

The present study was performed to demonstrate that small amounts of routine clinical data allow to generate valuable knowledge. Concretely, the aims of this research were to build a joint population pharmacokinetic model for capecitabine and three of its metabolites (5-DFUR, 5-FU and 5-FUH2) and to determine optimal sampling times for therapeutic drug monitoring. We used data of 7 treatment cycles of capecitabine in patients with metastatic colorectal cancer. The population pharmacokinetic model was built as a multicompartmental model using NONMEM and was internally validated by visual predictive check. Optimal sampling times were estimated using PFIM 4.0 following D-optimality criterion. The final model was a multicompartmental model which represented the sequential transformations from capecitabine to its metabolites 5-DFUR, 5-FU and 5-FUH2 and was correctly validated. The optimal sampling times were 0.546, 0.892, 1.562, 4.736 and 8 hours after the administration of the drug. For its correct implementation in clinical practice, the values were rounded to 0.5, 1, 1.5, 5 and 8 hours after the administration of the drug. Capecitabine, 5-DFUR, 5-FU and 5-FUH2 can be correctly described by the joint multicompartmental model presented in this work. The aforementioned times are optimal to maximize the information of samples. Useful knowledge can be obtained for clinical practice from small databases.

Diastereoselective Synthesis of CF3-Substituted Spiroisochromans by [1,5]-Hydride Shift/Cyclization/Intramolecular Friedel-Crafts Reaction Sequence.

Developed herein is a diastereoselective synthesis of CF3-substituted spiroisochromans via C(sp3)-H bond functionalization involving sequential transformations ([1,5]-hydride shift/cyclization/elimination of MeOH/intramolecular Friedel-Crafts reaction).