DFT Study on the Mechanisms and Selectivities in Rh (III)-Catalyzed [5 + 1] Annulation of 2-Alkenylanilides and 2-Alkylphenols with Allenyl Acetates.

The mechanisms and regio-, chemo-, and stereoselectivity were theoretically investigated in the Rh(III)-catalyzed [5 + 1] annulation of 2-alkenylanilides and 2-alkylphenols with allenyl acetates. Two different reactants, 2-alkenylanilides and 2-alkylphenols, were selected as model systems in the density functional theory calculations. The obtained theoretical results show that both these reactants exhibit similar steps, namely, (1) N-H/O-H deprotonation and C-H activation, (2) allenyl acetate migratory insertion, (3) ß-oxygen elimination, (4) intramolecular nucleophilic addition of the nitrogen/oxygen-rhodium bond resulting in [5 + 1]-annulation, and (5) protonation with the formation of the desired product and regeneration of the Rh(III) catalyst. The theoretical evidence suggests that the selectivity is determined at the step of allenyl acetate's migratory insertion. Moreover, the regioselectivity is driven by electronic effects, while the interaction energies (C-H···π and C-H···O interactions) play a more imperative role in controlling the stereoselectivity. The obtained theoretical results not only well rationalize the experimental observations but also provide important mechanistic insights for related types of [5 + 1]-annulation reactions.

Fabrication of Cellulose Filters Incorporating Metal-Organic Frameworks for Efficient Nicotine Adsorption from Cigarette Smoke.

To prevent negative effects of smoking, there is constant research on the development of various types of sustainable filter materials, capable of removing toxic compounds present in cigarette smoke. Because of the extraordinary porosity and adsorption properties, metal-organic frameworks (MOFs) represent promising adsorbents for volatile toxic molecules such as nicotine. This study reports new hybrid materials wherein six types of common MOFs of different porosity and particle size are incorporated into sustainable cellulose fiber from bamboo pulp, resulting in a series of cellulose filter samples abbreviated as MOF@CF. The obtained hybrid cellulose filters were fully characterized and investigated in nicotine adsorption from cigarette smoke, using a specially designed experimental setup. The results revealed that the UiO-66@CF material features the best mechanical performance, facile recyclability, and excellent nicotine adsorption efficiency that attains 90% with relative standard deviations lower than 8.80%. This phenomenon may be caused by the large pore size, open metal sites, and high loading of UiO-66 in cellulose filters. Additionally, the high adsorption capacity showed almost 85% removal of nicotine after the third adsorption cycle. The DFT calculation methods allowed further investigation of the nicotine adsorption mechanism, showing that the energy difference between HOMO and LUMO for UiO-66 was the closest to that of nicotine, which further proves the adsorption ability of nicotine by this material. Owing to the flexibility, recyclability, and excellent adsorption performance, the prepared hybrid MOF@CF materials may find prospective applications in nicotine adsorption from cigarette smoke.

Theoretical Analysis of a Three-Component Reaction between Two Diazo Compounds and a Hydroxylamine Derivative: Mechanism, Enantioselectivity, and Effect of Cooperative Catalysis.

The mechanism, enantioselectivity, and effect of chiral phosphoric acid (CPA) cocatalyst were investigated by the density functional theory (DFT) for the three-component asymmetric aminohydroxylation between two diazo compounds and a hydroxylamine derivative. This type of cascade process is cooperatively catalyzed by Rh2(OAc)4 and CPA. The obtained results clearly indicate that the first step of the global reaction involves a nucleophilic attack at the nitrogen center of N-hydroxyaniline by rhodium-carbene intermediates producing imines. Subsequently, an enolate intermediate was recognized as the key species generated from the second diazo compound and the leaving benzyl alcohol (BnOH) fragment of the first step and in the presence of the same dirhodium catalyst. Then, the reaction is terminated by the asymmetric Mannich-type addition, delivering the aminohydroxylation products of an S-R conformation with the assistance of chiral phosphoric acid. The distortion/interaction analysis shows that the relative distortions of CPA and the enol play a vital role in the energy ordering of the stereocontrolling transition states (TSs). Furthermore, the influence of different substituents in CPA was fully rationalized by distortion/interaction analysis. This study opens up novel synthetic possibilities and improves the reaction predictability when exploring the related types of cooperatively catalyzed organic transformations.

DFT Rationalization of Gold(I)-Catalyzed Couplings between Alkynyl Thioether and Nitrenoid Derivatives: Mechanism, Selectivity Patterns, and Effects of Substituents.

The present work focuses on a theoretical investigation of mechanistic features, chemoselectivity, regioselectivity, and effect of substituents in the gold-catalyzed reactions of alkynyl thioethers and isoxazoles. The DFT calculations reveal that the nucleophilic attack of isoxazole to a ß-position of catalyst-bound ynamide forms a vinyl intermediate. This undergoes cleavage of the N-O isoxazole bond and isomerizes to form an α-imino α'-sulfenyl gold carbene complex with stabilization of the Au-S interaction. For 3,5-dimethylisoxazole, the reaction follows a formal [3 + 2] cycloaddition pathway and a 1,3-H migration to give the pyrrole products. Replacement of 3,5-dimethylisoxazole by 3,5-dimethyl-4-phenylisoxazole leads to the formation of deacylative annulation products and desulfenylated 3-acylated pyrroles. Reactions with 4-methyl-3,5-diphenylisoxazoles induce the formation of N-acylated pyrroles and desulfenylated 3-acylated pyrroles. For the minor pathway, the α-addition and 1,2-S migration result in sulfur-substituted ß-keto enamide derivatives. In addition, the unique features of regio- and chemoselectivity were rationalized by the distortion and interaction analysis. Apart from fully rationalizing the experimental results, the theoretical DFT data give an important support for comprehending related types of reaction mechanisms.

DFT Quest of the Active Species of the Gallium-Mediated Coupling of Methylidenemalonates and Acetylenes.

In this study, three different Ga-containing systems based on GaCl3, Ga2Cl6, or ionic [Ga(L)3][GaCl4]3 (L = methylidenemalonate) complex were screened to elucidate the mechanism, regioselectivity, chemoselectivity, and role of Ga mediator in the reaction between two types of acetylenes (phenylacetylene and but-1-yn-1-ylbenzene) and methylidenemalonates, i.e., the 1,2-zwitterionic precursors that are similar to intermediates derived from donor-acceptor cyclopropanes (DACs). Our DFT calculation results clearly show that the ionic gallium complex [Ga(L)3][GaCl4]3 represents the key mediator in the title reaction. After the formation of such a complex, the first reaction step is the nucleophilic addition of phenylacetylene or but-1-yn-1-ylbenzene to [Ga(L)3][GaCl4]3, generating an unstable vinyl cation intermediate. In the phenylacetylene system, this vinyl cation intermediate accepts a chlorine atom from [GaCl4]- to give E-configuration intermediate. Then, the above process occurs to other two ligands of the Ga(III) complex to furnish a final product. On the other hand, in the but-1-yn-1-ylbenzene system, the vinyl cation intermediate prefers to undergo Friedel-Crafts (F-C) alkylation to generate a five-membered ring intermediate. This process is repeated on the other two methylidenemalonate ligands, giving rise to a final cyclization product. The distortion/interaction analysis shows that in the nucleophilic addition step the distortion energy of the Ga complex part is the main factor that influences the activation energy. Furthermore, the global reactivity index (GRI) analysis indicates that the Ga-complex model has the highest electrophilicity index ω, thus leading to the lowest energy barrier among three Ga-based models. In addition, DFT results reveal that the regioselectivity (E-configuration preference) and chemoselectivity (chloration or F-C alkylation) are mainly controlled by the steric effect rather than the electronic effect. The main findings of the present work provide a new way to analyze and rationalize various Ga-mediated reactions, which might also be extrapolated to organic transformations undergoing in the presence of aluminum and indium complexes.

The DFT Quest for Possible Reaction Pathways, Catalytic Species, and Regioselectivity in the InCl3-Catalyzed Cycloaddition of N-Tosyl Formaldimine with Olefins or Allenes.

The present work focuses on a theoretical investigation of the plausible mechanism, determination of catalytically active species, and understanding of the regioselectivity in the InCl3-catalyzed cycloaddition of N-tosyl formaldimine with alkenes or allenes. InCl3 and InCl2+ coordinated by dichloroethane (InCl2+-DCE) were investigated as model catalytic systems. DFT data supported that InCl2+-DCE represent the plausible in situ generated catalytic species. The catalytic cycle starts from the coordination of N-tosyl formaldimine to InCl2+-DCE, generating an In-complexed iminium intermediate. This then undergoes intermolecular reaction (aza-Prins) with alkene substrate to form a carbocation intermediate, which is chemoselectively attacked by the second N-tosyl formaldimine molecule to form a formaldiminium intermediate. In a final step, this intermediate undergoes the ring closure, leading to hexahydropyrimidine along with the regeneration of catalyst. In addition, our DFT results indicate that N-tosyl formaldimine not only acts as a reactant but also accelerates the 1,3-H-shift as a proton acceptor, giving an experimentally observed allylamide product. Also, the "iminium/alkene/imine" path was supported by calculation results for diastereoselective [2 + 2 + 2] reaction using an internal alkene. Finally, the regioselectivity of the InCl3-catalyzed cycloaddition using allenes along with N-tosyl formaldimine was also analyzed.

Risk Factor Analysis and Risk Prediction Model Construction of Pressure Injury in Critically Ill Patients with Cancer: A Retrospective Cohort Study in China.

BACKGROUND The aim of this study was to analyze the risk factors of pressure injury (PI) in critically ill patients with cancer to build a risk prediction model for PI. MATERIAL AND METHODS Between January 2018 and December 2019, a total of 486 critically ill patients with cancer were enrolled in the study. Univariate analysis and binary logistic regression analysis were used to explore risk factors. Then, a risk prediction equation was constructed and a receiver operator characteristic (ROC) curve analysis model was used for prediction. RESULTS Of the 486 critically ill patients with cancer, 15 patients developed PI. Risk factors found to have a significant impact on PI in critically ill patients with cancer included the APACHE II score (P<0.001), semi-reclining position (P=0.006), humid environment/moist skin (P<0.001), and edema (P<0.001). These 4 independent risk factors were used in the regression equation, and the risk prediction equation was constructed as Z=0.112×APACHE II score +2.549×semi-reclining position +2.757×moist skin +1.795×edema-9.086. From the ROC curve analysis, the area under the curve (AUC) was 0.938, sensitivity was 100.00%, specificity was 83.40%, and Youden index was 0.834. CONCLUSIONS The PI risk prediction model developed in this study has a high predictive value and provides a basis for PI prevention and treatment measures for critically ill patients with cancer.

Function-Oriented: The Construction of Lanthanide MOF Luminescent Sensors Containing Dual-Function Urea Hydrogen-Bond Sites for Efficient Detection of Picric Acid.

Two novel lanthanide metal-organic framework (Ln-MOF) luminescent sensors for the detection of picric acid have been successfully assembled. Following a function-oriented strategy, urea hydrogen-bonding functional sites were introduced into two MOF frameworks. A structural analysis indicated that the two MOFs have the exact same structure, namely 2D layers with diamond-shaped holes that are accumulated into a 3D framework through the hydrogen-bonding interactions between urea and carboxylate groups. Interestingly, only half of the urea units are involved in supporting the MOF framework through N-H⋅⋅⋅O hydrogen-bonding interactions, whereas the other half are located in the pore channel and act as empty recognition sites. Abundant N-H urea bonds are present in the inner walls of three types of interpenetrating 1D channels. Luminescence studies revealed that the two Ln-MOFs exhibit high sensitivity, good selectivity, and a fast luminescence quenching response towards picric acid. In particular, the two Ln-MOFs can be simply and quickly regenerated, and exhibit excellent recyclability. In summary, we have successfully used a function-oriented strategy to achieve multiple functions in a ligand to construct lanthanide MOF luminescent sensors for the detection of picric acid, thereby providing a potential strategy for the future development of MOF luminescent sensors with a specific target.

A Multi-responsive Regenerable Europium-Organic Framework Luminescent Sensor for Fe3+ , CrVI Anions, and Picric Acid.

A novel luminescent microporous lanthanide metal-organic framework (Ln-MOF) based on a urea-containing ligand has been successfully assembled. Structural analysis revealed that the framework features two types of 1D channels, with urea N-H bonds projecting into the pores. Luminescence studies have revealed that the Ln-MOF exhibits high sensitivity, good selectivity, and a fast luminescence quenching response towards Fe3+ , CrVI anions, and picric acid. In particular, in the detection of Cr2 O72- and picric acid, the Ln-MOF can be simply and quickly regenerated, thus exhibiting excellent recyclability. To the best of our knowledge, this is the first example of a multi-responsive luminescent Ln-MOF sensor for Fe3+ , CrVI anions, and picric acid based on a urea derivative. This Ln-MOF may potentially be used as a multi-responsive regenerable luminescent sensor for the quantitative detection of toxic and harmful substances.

Pt@UiO-66 heterostructures for highly selective detection of hydrogen peroxide with an extended linear range.

In this study, a good core-shell heterostructure of Pt NPs@UiO-66 was fabricated by encapsulating presynthesized platinum nanoparticles (Pt NPs) into the host matrix of UiO-66 which possesses the slender triangular windows with a diameter of 6 Å. The transmission electron microscopy images exhibited that the number of the encapsulated Pt NPs and the crystalline morphology of as-synthesized core-shell heterostructure samples had a series of changes with increasing the volume of the injected Pt NPs precursor solution. Among these samples, the Pt NPs@UiO-66-2 sample had a good crystalline morphology with several well-dispersed Pt NPs encapsulated in UiO-66 frameworks. But there were no obvious Pt NPs observed in the Pt NPs@UiO-66-1 sample, and for the Pt NPs@UiO-66-3 sample, the number of Pt NPs encapsulated in UiO-66 matrix notably reduced and the metal organic framework (MOF) crystals became small and aggregated. The electrochemical measurements showed that the Pt NPs@UiO-66-2 sample modified glass carbon electrode (GCE) presented a remarkable electrocatalytic activity toward hydrogen peroxide (H2O2) oxidation, including an excellent anti-interference performance even if the concentration of the interference species was the same as the H2O2, an extended linear range from 5 µM to 14.75 mM, a low detection limit, as well as good stability and reproducibility. The results indicate the superiority of MOFs in H2O2 detection. And more importantly, it will provide a new opportunity to promote the anti-interference performance of the nonenzyme electrochemical sensors.

A highly selective two-photon fluorescent probe for detection of cadmium(II) based on intramolecular electron transfer and its imaging in living cells.

A new quinoline-based probe was designed that shows one-photon ratiometric and two-photon off-on changes upon detecting Cd(2+) . It exhibits fluorescence emission at 407 nm originating from quinoline groups in Tris-HCl (25 mM, pH 7.40), H2 O/EtOH (8:2, v/v). Coordination with Cd(2+) causes quenching of the emission at 407 nm and simultaneously yields a remarkable redshift of the emission maximum to 500 nm with an isoemissive point at 439 nm owing to an intramolecular charge-transfer mechanism. Thus, dual-emission ratiometric measurement with a large redshift (Δλ=93 nm) and significant changes in the ratio (F500 /F439 ) of the emission intensity (R/R0 up to 27) is established. Moreover, the sensor H2 L displays excellent selectivity response, high sensitive fluorescence enhancement, and strong binding ability to Cd(2+). Coordination properties of H2 L towards Cd(2+) were fully investigated by absorption/fluorescence spectroscopy, which indicated the formation of a 2:1 H2 L/Cd(2+) complex. All complexes were characterized by X-ray crystallography, and TD-DFT calculations were performed to understand the origin of optical selectivity shown by H2 L. Two-photon fluorescence microscopy experiments have demonstrated that H2 L could be used in live cells for the detection of Cd(2+).

Rationally designed anion-responsive-organogels: sensing F⁻ via reversible color changes in gel-gel states with specific selectivity.

Through the rational introduction of the multi self-assembly driving forces and F(-) sensing sites into a gelator molecule, low-molecular-weight organogelators L1 and L2 were designed and synthesized. L1 and L2 showed excellent gelation ability in DMF and DMSO. They could form stable organogels (OGL1 and OGL2) in DMF and DMSO with very low critical gelation concentrations. OGL1 and OGL2 could act as anion-responsive organogels (AROGs). Unlike most of the reported AROGs showing gel-sol phase transition according to the anions' stimulation, OGL1 could colorimetrically sense F(-) under gel-gel states. Upon addition of F(-), OGL1 showed dramatic color changes, while the color could be recovered by adding H(+). Moreover, OGL1 showed specific selectivity for F(-), other common anions and cations could not lead to any similar response. What deserves to be mentioned is that the report on specific sensing of anions under gel-gel states is very scarce. The gel-gel state recognition can endow the organogel OGL1 with the merits of facile and efficient properties for rapid detection of F(-). Therefore, OGL1 could act as a F(-) responsive smart material.

Water-soluble colorimetric and ratiometric fluorescent probe for selective imaging of palladium species in living cells.

A novel water-soluble colorimetric and ratiometric fluorescent probe was synthesized and applied to imaging palladium species under physiological conditions in phosphate buffered saline (PBS) containing less than 1% organic cosolvent without adding any additional reagents. Based on palladium triggered terminal propargyl ethers cleavage reaction, the probe exhibited a high selectivity and sensitivity for palladium species of all the typical oxidation states (0, +2, +4), with a low detection limit (25 nM, 2.7 µg/L) and an obvious color change. Furthermore, the probe was successfully used for ratiometric fluorescence imaging of palladium in living cells.

The mechanism and regioselectivity of gold(I) or platinum(II) catalyzed intramolecular hydroarylation to pyrrolopyridinones and pyrroloazepinones.

We report here the theoretical analysis of the mechanism and regioselectivity of gold(I) or platinum(II) catalyzed intramolecular hydroarylation to pyrrolopyridinones and pyrroloazepinones. AuPH3(+) and PtCl2 have been considered to account for some experimental observations. Our calculation results indicate that in the case of cationic gold the nucleophilic attack of the pyrrole on the activated alkyne occurs in an exo-dig fashion generating a six-membered intermediate, which upon deprotonation and protodeauration forms pyrrolopyridinone. When platinum is used, an endo-dig fashion is observed generating a seven-membered intermediate. After deprotonation and protodeplatination pyrroloazepinone is formed. Whether for exo-dig (gold(I)) or endo-dig (platinum(II)) cyclization, a [1,2]-migration would not be needed.

A colorimetric and ratiometric fluorescent probe for distinguishing cysteine from biothiols in water and living cells.

A merocyanine-based highly selective colorimetric and ratiometric fluorescent probe is described for Cys detection in water and diluted deproteinized human serum. Upon reaction with Cys in aqueous buffer solution, the probe showed a dramatic color change from faint yellow to pink and remarkable ratiometric fluorescence enhancement signals were also observed, which are ascribed to an intramolecular charge transfer (ICT) process. This strategy was based on modulating the merocyanine π-electron system by conjugation and removal of the acrylate group to release the chromophore group, resulting in a specific colorimetry and fluorescence response. The probe has low cytotoxicity and good cell permeability. It is readily employed for assessing the change of the intracellular Cys level.

Ratiometric Luminescent Thermometer Based on the Lanthanide Metal-Organic Frameworks by Thermal Curing.

The high-performance optical thermometer probes are of great significance in diverse areas; lanthanide metal-organic frameworks (Ln-MOFs) are a promising candidate for luminescence temperature sensing owing to their unique luminescence properties. However, Ln-MOFs have poor maneuverability and stability in complex environments due to the crystallization properties, which then hinder their application scope. In this work, the Tb-MOFs@TGIC composite was successfully prepared using simple covalent crosslinking through uncoordinated -NH2 or COOH on Tb-MOFs reacting with the epoxy groups on TGIC {Tb-MOFs = [Tb2(atpt)3(phen)2(H2O)]n; H2atpt = 2-aminoterephthalic acid; phen = 1,10-phenanthroline monohydrate}. After curing, the fluorescence properties, quantum yield, lifetime, and thermal stability of Tb-MOFs@TGIC were remarkably enhanced. Meanwhile, the obtained Tb-MOFs@TGIC composites exhibit excellent temperature sensing properties in the low-temperature (Sr = 6.17% K-1 at 237 K), physiological temperature (Sr = 4.86% K-1 at 323 K), or high-temperature range (Sr = 3.88% K-1 at 393 K) with high sensitivity. In the temperature sensing process, the sensing mode of single emission changed into double emission for ratiometric thermometry owing to the back energy transfer (BenT) from Tb-MOFs to TGIC linkers, and the BenT process enhanced with the increase of temperature, which further improved the accuracy and sensitivity of temperature sensing. Most notably, the temperature-sensing Tb-MOFs@TGIC can be easily coated on the surface of polyimide (PI), glass plate, silicon pellet (SI), and poly(tetrafluoroethylene) plate (PTFE) substrates by a simple spraying method, which also exhibited an excellent sensing property, making it applicable for a wider T range measurement. This is the first example of a postsynthetic Ln-MOF hybrid thermometer operative over a wide temperature range including the physiological and high temperature based on back energy transfer.

Hybrid composites of lanthanide metal-organic frameworks with epoxy silanes for highly sensitive thermometry.

Post-synthetic modification of metal-organic frameworks (MOFs) and fabrication of hybrid composites are currently hot topics in the development of new functional materials. In this study, a facile and direct approach for coupling of lanthanide MOFs with epoxy silanes was developed, providing an access to a new series of functional composites. Two types of commercially available epoxy silane, namely 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (ECTMS) and (3-glycidoxypropyl)methyl diethoxysilane (KH563), were used to modify Ln-BTB MOFs ([Ln(BTB)(H2O)]n·2n(C6H12O); Ln = Tb or Eu0.001Tb0.999; H3BTB = 1,3,5-benzenetrisbenzoic acid) via covalent grafting involving mechanical grinding, epoxide coupling and curing reactions. The fabricated composites (Tb-BTB@ECTMS, Eu0.001Tb0.999-BTB@ECTMS, Tb-BTB@KH563, Eu0.001Tb0.999-BTB@KH563) and their Ln-MOF precursors were fully characterized, including a detailed study of their stability and fluorescence properties. The obtained composites show high thermal and solution stability, under boiling water conditions and in a wide pH range of 1-12. Application of the composites as temperature sensors in the 197-297 K and 273-343 K temperature ranges was explored in detail, revealing a remarkable sensing behavior. For example, Tb-BTB@ECTMS shows a maximum relative sensitivity (Sr) of 6.85% K-1 at 343 K. Eu0.001Tb0.999-BTB@ECTMS represents a white-light emission material with the CIE coordinates (0.3194, 0.3049) that are very close to those of white light, along with good temperature sensing performance and a relative sensitivity of 4.32% K-1 at 297 K. An enhanced performance of the composites in comparison with the parent MOF materials as well as the mechanism of energy transfer were rationalized by DFT calculations. By unveiling a facile and efficient method for improving the stability of luminescent MOFs, via post-synthetic grafting with epoxy silanes, the present study will stimulate further research at the interface of materials chemistry, MOF design, photoluminescence and temperature sensing.

A DFT study on the mechanism of gold(III)-catalyzed synthesis of highly substituted furans via [3, 3]-sigmatropic rearrangements and/or [1, 2]-acyloxy migration based on propargyl ketones.

The mechanisms of gold(III)-catalyzed synthesis of highly substituted furans via [3,3]-sigmatropic rearrangements and/or [1,2]-acyloxy migration based on propargyl ketones have been investigated using density functional theory calculations at BHandHLYP/6-31G(d,p) (SDD for Au) level of theory. Solvent effects on these reactions were explored using calculations that included a polarizable continuum model (PCM) for the solvent (toluene). Two plausible pathways that lead to the formation of Au(III) vinyl carbenoid and an allenyl structure through [3,3]-sigmatropic rearrangements, [1,2]-acyloxy migration via oxirenium and dioxolenylium were performed. Our calculated results suggested: (1) the major pathway of the cycle causes an initial Rautenstrauch-type [1,2]-migration via oxirenium to form an Au(III) vinyl carbenoid. Subsequent cycloisomerization of this intermediate then provides the corresponding furan whether for the methyl-substituted propargylic acetates or the phenyl-substituted propargylic acetates; (2) for the methyl-substituted propargylic acetates, the formation of Au(III) vinyl carbenoid structures was the rate-determining step. However, intramolecular nucleophilic attack and subsequent cycloisomerization to give the final product was rate-determining for the phenyl-substituted propargylic acetates. The computational results are consistent with the experimental observations of Gevorgyan, et al. for gold(III)-catalyzed synthesis of highly substituted furans based on propargyl ketones.

DFT Study on Zr-Catalyzed Alkene Hydroaminoalkylation: Origin of Regioselectivity, Diastereoselectivity, and Influence of Substrate.

A DFT study was carried out to investigate a zirconium-catalyzed hydroaminoalkylation of alkenes with N-silylated benzylamine. A global reactivity index (GRI) analysis showed that that substrates act as electrophiles while the active zirconaaziridine behaves as a nucleophile. Furthermore, the distortion/interaction analysis unveiled the role of the distortion and interaction energies in controlling the regioselectivity and diastereoselectivity when different alkene substrates are used. These results provide an in-depth analysis on how the substrate type influences the product selectivity.

Epoxy Functional Composites Based on Lanthanide Metal-Organic Frameworks for Luminescent Polymer Materials.

The integration of metal-organic frameworks (MOF) into organic polymers represents a direct and effective strategy for developing innovative composite materials that combine the exceptional properties of MOFs with the robustness of organic polymers. However, the preparation of MOF@polymer hybrid composites requires an efficient dispersion and interaction of MOF particles with polymer matrices, which remains a significant challenge. In this work, a new simple and direct approach was applied for the development of Ln-MOF@polymer materials. A series of Ln-MOF@TGIC composites {Ln-MOF = [Ln(µ3-BTC)(H2O)6]n (Ln-BTC), where Ln = Eu, Tb, Eu0.05Tb0.95; H3BTC = 1,3,5-benzenetricarboxylic acid; TGIC = triglycidyl isocyanurate} were successfully obtained by applying a grinding method via the chemical bonding between uncoordinated carboxylate groups in Ln-BTC and epoxy groups in TGIC. The Ln-BTC@TGIC materials possess significant fluorescence characteristics with superior emission lifetimes and quantum yields if compared to parent Ln-MOFs. Interestingly, under the UV irradiation, a considerable color change from yellow in Eu0.05Tb0.95-BTC to red in Eu0.05Tb0.95-BTC@TGIC was observed. The energy-transfer mechanism was also rationalized by the density functional theory (DFT) calculations. The developed Ln-BTC@TGIC composites were further applied as functional fluorescent coatings for the fabrication, via a simple spraying method, of the flexible polyimide (PI) films, Ln-BTC@TGIC@PI. Thus, the present work unveils a new methodology and expands its applicability for the design and assembly of stable, multicomponent, and soft polymer materials with remarkable fluorescence properties.