Sequential Transformation Research Articles

Simultaneous and sequential transformations with nucleation at preferred sites

The advent of new materials may increase transformations that involve two or more product phases. This transformation involving two or more product phases may occur simultaneously or sequentially. It is well-known that heterogeneous nucleation has advantages over homogeneous nucleation. Several sites may become preferred because they favor heterogeneous nucleation. The interface of precipitates and the grain boundaries are one of the preferred locations for nucleation. We model simultaneous and sequential transformations nucleated at the preferred sites. This work employs both computer simulation and exact analytical solutions. Two product phases, 1 and 2, were considered. The product phase 1 nucleated at the matrix/particle interface and the product phase 2 nucleated at the grain boundaries. The analytical model showed an excellent agreement with simulation data. For each case, computer simulation obtained the microstructural evolution. We discussed the effect of nucleation at the preferred sites on the microstructure.

Facile synthesis of diverse hetero polyaromatic hydrocarbons (PAHs) via the styryl Diels–Alder reaction of conjugated diynes

The intramolecular styryl Diels–Alder reaction with conjugated diynes under thermally stable triazole-gold (TA–Au) catalytic conditions and the sequential transformation through alkyne activation to access various PAHs with high efficiency was reported for the first time.

Rapid construction of a polysubstituted “caged” oxa-bishomocubane framework from vinylidenecyclopropanes through a sequential dual catalysis of copper(i) and visible-light-induced photosensitization

A sequential dual catalytic transformation of vinylidenecyclopropanes for the rapid construction of polysubstituted “caged” oxa-bishomocubane products under mild conditions.

Light-driven sequential shape transformation of block copolymer particles through three-dimensional confined self-assembly.

Shape-controlled block copolymer (BCP) particles that respond to light stimulus have drawn great attention due to their promising applications in smart materials, yet polymeric particles with light-triggered controllable sequential shape transformation (SST) are still rarely reported. By confined co-assembly of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) and azo-containing light-responsive additives within emulsions, herein, we fabricated BCP particles with light-controlled SST behavior. Attributed to the quaternization of P2VP chains with bromoalkyl additives and the trans-cis isomerization of an azo group under UV light, the interfacial interactions between the BCPs and the surrounding aqueous phase are significantly varied; therefore, the particles exhibit three distinct phases in sequence: (1) elongation of ellipsoidal particles with increasing domain spacing; (2) shape transformation of elongated ellipsoidal particles into accordion-like particles; and (3) disassembly of polymer particles into small spheres. In addition, these particles with SST behavior can be used in light-controlled drug release at a high spatial-temporal resolution, demonstrating their potential in clinical settings and biomedicine.

The sequential structural transformation of a heptanuclear zinc cluster towards hierarchical porous carbon for supercapacitor applications.

The peripheral N/O chelating of Schiff base ligands, inner bridges, counterions, and metal centers gave rise to a brucite disk cluster [Zn7L6(OCH3)6](NO3)2 (Zn7, (HL = 2-methoxy-6-((methylimino)-methyl)phenolate)) which crystallized into hexagonal prismatic plates. The combination of crystallographic studies, in situ TG-MS, and other characterization techniques showed that with a fixed metal and ligand composition in the precursors, weak correlative interactions (e.g., electrostatic interactions) and shape matching between the cluster core and counterions determine the cluster packing modes in the crystals and affect their phase and morphological changes during pyrolysis. The tracking of the pyrolysis process showed that the peripheral ligands, inner bridge, and counterion decompose first, followed by the Zn7O6 core merging with cubic ZnO, which was then reduced by carbon and eventually evaporated, leaving behind a porous carbon structure. In this process, the solid material composition change was in the sequence {Zn7}-{Zn-O core@C}-{ZnO@C}-{Zn@C}-{C}, which was accompanied by a porosity change from micropores to hierarchical pores, and then to micropores again. The core structure and packing modes of Zn7 evolved into micropores and mesopores, respectively. Micro-mesoporous carbon Zn7-1000 featured a capacitance of 1797 F g-1 at 1 A g-1, where the BET specific surface area was 3119.18 m2 g-1, which, to the best of our knowledge, is the highest value reported for a porous carbon electrode. This work represents an important benchmark for the analysis of dynamic chemical processes involving coordination clusters at high temperatures, and it could lead to important applications in high-performance devices.

Management of Innovations in Public Administration: Strategies to Prevent the Participation of Financial Intermediaries in Shadow Operations

This article summarizes the arguments and counterarguments within the scientific discussion on improving public administration tools in the context of implementing innovative mechanisms for combating shadow financial transactions. The main purpose of this research is to formalize innovative strategies to counter the shadow withdrawal of capital with the participation of financial intermediaries. The systematization of scientific sources and approaches to solving the problem of the de-shadow economy proved that a characteristic feature of the functioning of the shadow market is the active participation of financial intermediaries in shadow operations. The information base is data from the World Bank and the Organization for Economic Cooperation and Development, the Group for the Development of Financial Measures to Combat Money Laundering, Transparency International, and the World Economic Forum. The period of the study is 2003-2021. The EU countries, Ukraine, Moldova, and Montenegro, as candidate countries for EU membership, were selected as the object of the study. This study applied the methods of bibliometric analysis to generalize the existing scientific work on the investigated issue, analysis of changes in the number of search changes on the problems of shadowing the economy, and clustering regions by the number of search queries on the shadow economy. Intellectual data analysis methods (one-dimensional branching CART and agglomeration methods) were used for clustering countries depending on the nature of the policy of countering the shadowing of the economy. Based on the results of the bibliometric analysis, theories describing the shadow economy, in particular: innovation theory, the theory of centralization, and institutional theory, were summarized. The article presents the results of cluster analysis, which proved the practicality of selecting three clusters of countries: cluster 1 – Cyprus, Czech Republic, Denmark, Finland, Greece, Ireland, Italy, Luxembourg, and Portugal; cluster 2 – Bulgaria, Croatia, Estonia, France, Malta, Netherlands, Spain, Sweden, Belgium, Greece, Austria, Hungary, and Slovak Republic, Slovenia; cluster 3 – Lithuania, Latvia, Romania, Poland, Moldova, Montenegro, and Ukraine. The study empirically confirmed and theoretically proved that the entire set of innovative scenarios for implementing economic de-shadowing policy could be divided into three types (evolutionary scenario, sequential transformation scenario, and forced scenario). The above scenarios depend on the speed of change in the indicators of developing the shadow economic sector and their sensitivity to the implemented measures.

Efficient synthesis of a novel euchromatic histone methyl transferase 2 (G9a) inhibitor

An efficient synthetic route was set up to prepare in good scale M-108, a novel bicycle derivative recently identified as a potent and selective G9a inhibitor, potentially useful as anti-fibroadipogenic agent. In particular, a facile three-steps sequential transformation of a substituted cis-cinnamate ethyl ester intermediate allowed to obtain the corresponding cyclopropyl nitrile derivative in high yield, which was smoothly transformed into the title racemate and then resolved by chiral HPLC.

Synthesis of New Statin Derivatives

AbstractHerein we report the synthesis of the new statin derivative MC609 in 80 % overall yield by sequential transformation of simvastatin including dehydration, and Michael addition of N‐benzyl hydroxylamine followed by cyclization. The preparation of nitronestatins MC649 and MC645 is also described from (2S,4R)‐4‐((tert‐butyldimethylsilyl)oxy)‐6‐oxotetrahydro‐2H‐pyran‐2‐carbaldehyde by reaction with N‐benzyl hydroxylamine, and N‐hydroxylamine followed by reduction with sodium cyanoborohydride and coupling with commercially available 2‐chloro‐6‐methylquinoline‐3‐carbaldehyde, in 77 % and 24 % overall yield, respectively.

Large-Size Superlattices Synthesized by Sequential Sulfur Substitution-Induced Transformation of Metastable MoTe2

We demonstrate a general protocol that uses a metastable phase as a template, followed by chalcogen substitution and phase transformation to obtain superlattices, or single crystals, of layered transition metal dichalcogenides (TMDs). In particular, the single-crystalline 2H-MoTe2 thin film, with the available wafer-scale synthesis, is selected as the template to study the chalcogen substitution mechanism. Analogous to the initiation polymerization process, a Te vacancy-initiated and S diffusion-mediated mechanism is proposed to describe the sequential substitution: the complete sulfurization of the top and bottom MoTe2 layers at the first stage, followed by the alloying process in the middle layers and finally the full conversion of the flake into MoS2. The substitution in each layer starts from the vacancy and expands to the nearby region catalyzed by the strain field, whereas the sulfurization sequence in the multilayer system is mediated by the cross-layer S diffusion process. This is confirmed by the cross-sectional observation of the intermediate state by scanning transmission electron microscopy and density functional theory studies. This unique mechanism enables us to fabricate the sub-centimeter scale, composition-tunable, and symmetric MoS2/MoTe2(1–x)S2x/MoS2 superlattices. Our work presents a new tool for the large-scale synthesis of TMD-based heterostructures toward industrial applications.

Spectral analysis method of electrophysical non-destructive testing data

A computational method for spectral analysis of the electrophysical test results based on sequential mathematical algorithm transformations using a discrete linear response function has been developed. The procedure for constructing spectral functions has a certain order and is aimed at obtaining adequate results of the experimental sample approximation in the frequency domain. It is shown that use of the low-frequency FIR filter function as part of the convolution, together with the fast Fourier transform, gives accurate results for structural inhomogeneities localization in welded joints.

Transforming CO2 into Methanol with N-Heterocyclic Carbene-Stabilized Coinage Metal Hydrides Immobilized in a Metal-Organic Framework UiO-68.

By synergizing the advantages of homogeneous and heterogeneous catalysis, single-site heterogeneous catalysis represents a highly promising opportunity for many catalytic processes. Particularly, the unprecedented designability and versatility of metal-organic frameworks (MOFs) promote them as salient platforms for designing single-site catalytic materials by introducing isolated, well-defined active sites into the frameworks. Herein, we design new MOF-supported single-site catalysts for CO2 hydrogenation to methanol (CH3OH), a reaction of great significance in CO2 valorization. Specifically, N-heterocyclic carbene (NHC), a class of excellent modifiers and anchors, is used to anchor coinage metal hydrides M(I)-H (M = Cu, Ag, and Au) onto the organic linker of UiO-68. The strong metal-ligand interactions between NHC and M(I)-H verify the robustness and feasibility of our design strategy. On the tailor-made catalysts, a three-stage sequential transformation is proposed for CH3OH synthesis with HCOOH and HCHO as the transit intermediates. A density functional theory-based comparative study suggests that UiO-68 decorated with NHC-Cu(I)-H performs best for CO2 hydrogenation to HCOOH. This is further rationalized by three linear relationships for the Gibbs energy barrier of CO2 hydrogenation to HCOO intermediate, the first with the NBO charge of the hydride in NHC-M(I)-H, the second with the electronegativity of M, and the third with the gap between the lowest unoccupied molecular orbital of CO2 and the highest occupied molecular orbital of the catalyst. It is confirmed that the high efficiency of MOF-supported NHC-Cu(I)-H for CO2 transformation to CH3OH is via the proposed three-stage mechanism, and in each stage, the step involving heterolytic dissociation of H2 together with product generation is the most energy-intensive. The rate-limiting step in the entire mechanism is identified to be H2 dissociation accompanying with simultaneous HCHO and H2O formation. Altogether, the tailor-made UiO-68 decorated with NHC-Cu(I)-H features well-defined active sites, enables precise manipulation of reaction paths, and demonstrates excellent reactivity for CO2 hydrogenation to CH3OH. It is also predicted to surpass a recently reported MOF-808 catalyst consisting of neighboring Zn2+-O-Zr4+ sites. The designed MOFs as well as the proposed strategy here establish a new paradigm and can be extended to other hydrogenation reactions.

(Invited) The Liquid Sunlight Alliance Solar Fuels Hub

Artificial photosynthesis, the solar-driven conversion of feedstock components including water, carbon dioxide and nitrogen into fuels, chemicals and materials, has the potential to generate products needed by society using renewable resources. In this talk we will describe a new research program established in October 2020 that is focused on accelerating the science advances needed to enable sunlight to synthesize the complex molecules that comprise liquid fuels. This ambitious goal is being addressed by tailoring the properties of coupled chemical microenvironments to enable sequential catalytic transformations, and using co-design as a new paradigm to design systems that have the durability, selectivity and efficiency required for operation under real-world conditions. Examples of progress by the team will be presented.

1,2-Dibutoxyethane-Promoted Oxidative Cleavage of Olefins into Carboxylic Acids Using O2 Under Clean Conditions.

Herein, we report the first example of an effective and green approach for the oxidative cleavage of olefins to carboxylic acids using a 1,2-dibutoxyethane/O2 system under clean conditions. This novel oxidation system also has excellent functional-group tolerance and is applicable for large-scale synthesis. The target products were prepared in good to excellent yields by a one-pot sequential transformation without an external initiator, catalyst, and additive.

Sequential Diimination, Staudinger [2 + 2] Ketene-Imine Cycloaddition, and Ring-Closing Metathesis (RCM) Reactions: In Route to Bis(4-spiro-fused-β-lactams)-Based Macrocycles.

Based on sequential organic transformations, that is, diimine formation, Staudinger [2 + 2] ketene-imine cycloaddition, and ring-closing metathesis (RCM) reactions, the synthesis with full structural identification including NMR and HRMS spectral data along with single X-ray diffraction analysis (for anti 7b, anti 8b, syn 9a, and anti 9b) of the first syn/anti bis-4-spiro-β-lactams-based azacrown ethers (7a,b-9a,b) is reported.

Hippocampal Representations of Event Structure and Temporal Context during Episodic Temporal Order Memory.

The hippocampus plays an important role in representing spatial locations and sequences and in transforming representations. How these representational structures and operations support memory for the temporal order of random items is still poorly understood. We addressed this question by leveraging the method of loci, a powerful mnemonic strategy for temporal order memory that particularly recruits hippocampus-dependent computations of spatial locations and associations. Applying representational similarity analysis to functional magnetic resonance imaging activation patterns revealed that hippocampal subfields contained representations of multiple features of sequence structure, including spatial locations, location distance, and sequence boundaries, as well as episodic-like temporal context. Critically, the hippocampal CA1 exhibited spatial transformation of representational patterns, showing lower pattern similarity for items in same locations than closely matched different locations during retrieval, whereas the CA23DG exhibited sequential transformation of representational patterns, showing lower pattern similarity for items in near locations than in far locations during encoding. These transformations enabled the encoding of multiple items in the same location and disambiguation of adjacent items. Our results suggest that the hippocampus can flexibly reconfigure multiplexed event structure representations to support accurate temporal order memory.

An efficient manganese-oxidizing fungus Cladosporium halotolerans strain XM01: Mn(II) oxidization and Cd adsorption behavior

The applications of biogenic Mn oxides (BMOs) formed by Mn-oxidizing fungus in decontaminating heavy metals have attracted increasing attention. In this study, an efficient Mn-oxidizing fungus was isolated from soil and identified as Cladosporium halotolerans strain XM01. The Mn(II) adsorption and oxidation activities of this strain were investigated, showing significantly high removal and oxidation rates of soluble Mn(II) of 99.9% and 88.2%, respectively. Dynamic analysis of the Mn(II) removal process demonstrated the oxidation process of Mn(II) to Mn(III) was the rate-limiting step in the Mn(II) metabolic process. The XRD and SAED characterization showed that more layers were orderly accumulated along the c-axis with the formation of fungal BMOs, which might lead to the decrease in its specific surface area. The adsorption of Cd(II) by the formed BMOs was investigated and compared with two typical abiotic Mn oxides, indicating that the adsorption capacity decreased with the following order: immature BMO, mature BMO, δ-MnO2, acid birnessite, while the fixation capacity decreased in the order of acid birnessite, mature BMO, δ-MnO2, immature BMO. The inverse correlation between the capacity of Cd(II) adsorption and fixation of immature and mature BMOs was probably attributed to the increase in the layer stacking of BMOs. This result indicates an interesting phenomenon of high reservation of Cd(II) resulting from sequential transformation from strong adsorption to strong fixation with the formation of BMOs. This study offers considerable insights into fungal Mn oxidation mechanisms and provides theoretical guidance for fungal BMOs in heavy metals bioremediation.

Sequential transformation study of minerals during underground coal gasification: Promising to indirectly reflect the actual reaction condition

AbstractThe mineralogical characteristics of underground coal gasification (UCG) residuals are closely related to the gasification conditions. The study of the mineral composition and transformation of ash and slag under different gasification conditions has important scientific significance for understanding the real gasification conditions, improving the utilization efficiency of coal, and identifying and controlling the environmental impact. In this paper, the sequential transformation of minerals under different temperature and atmosphere are studied by X‐ray diffraction (XRD) and FactSage software, and the elemental composition of the surface of the UCG ash and slag is characterized by SEM‐EDX. The results show that the main minerals in the semicoke are quartz (SiO2), illite (K1.5Al4(Si6.5Al1.5)O20(OH)4), and sanidine (KAlSi3O8). In the 900–1300°C reduction, ash, quartz, sanidine, hercynite (FeAl2O4), anorthite (CaAl2Si2O8), and mullite (Al6Si2O13) are the main minerals. The minerals in the oxidation residuals (1100–1500°C) are quartz, anorthite, hematite (Fe2O3), hercynite, cordierite (Fe2Al4Si5O18), and cristobalite. The reaction temperature has a significant effect on the changes in mineralogy. The reaction temperature is low during the pyrolysis process, and most changes involve only structural changes. With the reaction temperature increases, a series of reactions occur between different minerals. The reaction atmosphere also has a significant effect on the mineralogy. The research on the transformation of minerals in UCG residues can indirectly reflect the actual process of UCG, which can provide suggestions for the stable operation of the UCG process.

Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe\u2013Mn\u2013Al\u2013Ni Shape Memory Alloys

In situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

Synthesis of [1,4]Thiazino[4,3-a]indol-10-one Derivatives through Radical Anti Aza-Michael Addition of 2′-Aminochalcones

An efficient method for the synthesis of [1,4]thiazino[4,3-a]indole derivatives using sodium chlorodifluoroacetate (ClCF2CO2Na) and elemental sulfur as the difluoromethylthiolating reagent system has been developed. Three-component reactions of 2'-aminochalcones, sulfur, and ClCF2CO2Na under basic conditions using TEMPO as the oxidant afforded [1,4]thiazino[4,3-a]indol-10-ones containing a difluoromethyl thioether moiety in good yields. Four bonds including one C-N, two C-S, and one C-C bonds are selectively formed in the sequential transformation process.

An Expedite Synthesis of Some Angularly Fused Novel ‘U’‐Shaped Tetracyclic Furophenanthraquinones Simulating ABCD Rings of Isotanshinone‐II

AbstractAn expedite general synthesis of three angularly fused furophenantharquinones is described from 1‐(2‐furyl)‐naphthalen‐2‐carbaldehyde derivatives. 1‐(2‐furyl)‐naphthalen‐2‐carbaldehyde derivatives on sequential functional group transformation of the −CHO group afforded 2‐[1‐(2‐furyl])‐naphthalen‐2‐acetic acid derivatives in reasonably overall good yields. Cyclization of the carboxylic acids lead to the formation of furophenanthrenol derivatives. The phenolic intermediates were oxidized with Fremy's salt to furnish the condensed furophenanthraquinone derivatives in excellent yields. The synthesized compounds simulate the ABCD core nucleus of the naturally occurring isotanshinone‐II isolated from Salvia glutinosa.