Light Emission of [10]Cyclophenacene through Energy Transfer from Neighboring Carbazolylphenyl Dendrons

A dendritic deca(carbazolylphenyl)[60]fullerene bearing a cyclic benzenoid core was synthesized. The photophysical studies indicated that intramolecular energy transfer and electron transfer took place from the linked carbazolylphenyl moieties to the core−cyclic benzenoid moiety. The fluorescence quantum yield of the deca-adduct was determined to be 0.21 in toluene. Rich photophysical functions and their dendritic structures suggest that the photoactive decaadducts will serve as luminescent scaffolds in materials application

Syntheses and Photophysical Studies of Cyclodextrin Derivatives with Two Proximate Anthracenyl Groups

A series of permethylated cyclodextrin derivatives, cyclodextrin dimers doubly bridged with two anthracene moieties (An2CD2) and singly bridged with one (AnCD2) and the monomer bearing two anthracene moieties (An2CD), were newly synthesized. For An2CD2, the two isomeric forms are also identified. All compounds are soluble in both aqueous and various organic solvents. The bisanthracene systems, An2CD2 and An2CD, show the thermal equilibrium in an aqueous solution between the intramolecularly interacting (closed) and less-interacting (open) states of the anthracene moieties, which results in the temperature-dependent absorption changes. These systems also show the characteristic excimer emission that is enhanced in water and weakened in organic solvents. The excitation spectra for the monomer and excimer fluorescence are found to be quite different from each other and similar to the absorption spectra of the open and the closed forms, respectively. The observed unique parallelism between excitation and absorption spectra for the present excimer systems indicates the dual ground state−dual excitation scheme where the excitation state formed from the closed ground state mainly gives excimer. The fluorescence lifetime analyses reveal that the rates of the conversion from the excited state of the open form to that of the closed one (6.0 × 106 s-1 for An2CD2-2) are largely retarded compared with that of the ethyleneoxy linked bisanthracene system (8.8 × 107 s-1)

A New Class of Red Fluorescent Organic Nanoparticles: Noncovalent Fabrication and Cell Imaging Applications

Cyano-substituted diarylethlene derivatives <b>R-OMe (-H, -CF</b>_<b>3</b><b>)</b> with different peripheral substituted groups were synthesized in high yield. Water-soluble red fluorescent organic nanoparticles (FONs) could be facilely prepared from them via hydrophobic interaction with polyoxyethylene–­polyoxypropylene–­polyoxyethylene triblock copolymer (Pluronic F127). The optical properties and surface morphology of the synthesized FONs were characterized, and their biocompatibilities as well as their applications in cell imaging were further investigated. We demonstrate that such red FONs exhibit antiaggregation-caused quenching properties, broad excitation wavelengths, excellent water dispersibilities, and biocompatibilities, making them promising for cell imaging

Antifreezing and Nondrying Sensors of Ionic Hydrogels with a Double-Layer Structure for Highly Sensitive Motion Monitoring

Freezing and dehydration together with interfacial failure are capable of causing the functional reduction of hydrogels for sensing applications. Herein, we develop a multifunctional bilayer that consists of a mussel-inspired adhesive layer and a functionally ionic layer that is composed of sodium p-styrene sulfonate (SSS) and an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong adhesion of the bilayer to the surface of the skin. The introduction of ionic elements of SSS-[BMIM]Cl not only provides the bilayer with sensing adaptability in a wide temperature range of −25 to 75 °C, but also endows it with elastic, stretchable, self-healing, and conductive features. These mechanical properties are utilized to assemble a wearable sensor that has unprecedented sensitivity and reusability in monitoring human motions, including stretching, pulsing, frowning, and speaking. It is thus expected that the concept in this work would provide a promising route to design soft sensing devices that can work in a wide temperature range

Antifreezing and Nondrying Sensors of Ionic Hydrogels with a Double-Layer Structure for Highly Sensitive Motion Monitoring

Freezing and dehydration together with interfacial failure are capable of causing the functional reduction of hydrogels for sensing applications. Herein, we develop a multifunctional bilayer that consists of a mussel-inspired adhesive layer and a functionally ionic layer that is composed of sodium p-styrene sulfonate (SSS) and an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong adhesion of the bilayer to the surface of the skin. The introduction of ionic elements of SSS-[BMIM]Cl not only provides the bilayer with sensing adaptability in a wide temperature range of −25 to 75 °C, but also endows it with elastic, stretchable, self-healing, and conductive features. These mechanical properties are utilized to assemble a wearable sensor that has unprecedented sensitivity and reusability in monitoring human motions, including stretching, pulsing, frowning, and speaking. It is thus expected that the concept in this work would provide a promising route to design soft sensing devices that can work in a wide temperature range

Antifreezing and Nondrying Sensors of Ionic Hydrogels with a Double-Layer Structure for Highly Sensitive Motion Monitoring

Freezing and dehydration together with interfacial failure are capable of causing the functional reduction of hydrogels for sensing applications. Herein, we develop a multifunctional bilayer that consists of a mussel-inspired adhesive layer and a functionally ionic layer that is composed of sodium p-styrene sulfonate (SSS) and an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong adhesion of the bilayer to the surface of the skin. The introduction of ionic elements of SSS-[BMIM]Cl not only provides the bilayer with sensing adaptability in a wide temperature range of −25 to 75 °C, but also endows it with elastic, stretchable, self-healing, and conductive features. These mechanical properties are utilized to assemble a wearable sensor that has unprecedented sensitivity and reusability in monitoring human motions, including stretching, pulsing, frowning, and speaking. It is thus expected that the concept in this work would provide a promising route to design soft sensing devices that can work in a wide temperature range

Antifreezing and Nondrying Sensors of Ionic Hydrogels with a Double-Layer Structure for Highly Sensitive Motion Monitoring

Freezing and dehydration together with interfacial failure are capable of causing the functional reduction of hydrogels for sensing applications. Herein, we develop a multifunctional bilayer that consists of a mussel-inspired adhesive layer and a functionally ionic layer that is composed of sodium p-styrene sulfonate (SSS) and an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong adhesion of the bilayer to the surface of the skin. The introduction of ionic elements of SSS-[BMIM]Cl not only provides the bilayer with sensing adaptability in a wide temperature range of −25 to 75 °C, but also endows it with elastic, stretchable, self-healing, and conductive features. These mechanical properties are utilized to assemble a wearable sensor that has unprecedented sensitivity and reusability in monitoring human motions, including stretching, pulsing, frowning, and speaking. It is thus expected that the concept in this work would provide a promising route to design soft sensing devices that can work in a wide temperature range

Mechanistic Insight into Lewis Acid-Catalyzed Cycloaddition of Bicyclo[1.1.0]butanes with Ketene: Bicyclo[1.1.0]butanes Serving as an Electrophile

Lewis acid-catalyzed cycloaddition between bicyclo[1.1.0]butanes (BCBs) and unsaturated substrates has recently been demonstrated to be a powerful strategy for synthesizing bicyclo[2.1.1]hexanes. However, their reaction mechanisms remain elusive. This computational work explored the recently developed TMSOTf-catalyzed cycloaddition of BCB ketone to ketene and determined the rate-determining step as the activation of BCB ketone. Contrary to the previous proposal of BCB enolate as the active species, this work instead identified the catalytically active species to be a partially Lewis acid-activated BCB cation, which shows a greater electrophilicity and larger orbital interactions with ketene compared to those of the pristine BCB. The most favorable reaction pathway uniquely utilizes this activated BCB species as an electrophile to react with ketene as a nucleophile, while the previously proposed enolate is relatively inactive. Moreover, the in situ-generated TfO anion is revealed to be non-innocent, and its coordination mode and orientation could affect the reaction kinetics

New Insights and Predictions into Complex Homogeneous Reactions Enabled by Computational Chemistry in Synergy with Experiments: Isotopes and Mechanisms

ConspectusHomogeneous catalysis and biocatalysis have been widely applied in synthetic, medicinal, and energy chemistry as well as synthetic biology. Driven by developments of new computational chemistry methods and better computer hardware, computational chemistry has become an essentially indispensable mechanistic “instrument” to help understand structures and decipher reaction mechanisms in catalysis. In addition, synergy between computational and experimental chemistry deepens our mechanistic understanding, which further promotes the rational design of new catalysts. In this Account, we summarize new or deeper mechanistic insights (including isotope, dispersion, and dynamical effects) into several complex homogeneous reactions from our systematic computational studies along with subsequent experimental studies by different groups. Apart from uncovering new mechanisms in some reactions, a few computational predictions (such as excited-state heavy-atom tunneling, steric-controlled enantioswitching, and a new geminal addition mechanism) based on our mechanistic insights were further verified by ensuing experiments.The Zimmerman group developed a photoinduced triplet di-π-methane rearrangement to form cyclopropane derivatives. Recently, our computational study predicted the first excited-state heavy-atom (carbon) quantum tunneling in one triplet di-π-methane rearrangement, in which the reaction rates and 12C/13C kinetic isotope effects (KIEs) can be enhanced by quantum tunneling at low temperatures. This unprecedented excited-state heavy-atom tunneling in a photoinduced reaction has recently been verified by an experimental 12C/13C KIE study by the Singleton group. Such combined computational and experimental studies should open up opportunities to discover more rare excited-state heavy-atom tunneling in other photoinduced reactions. In addition, we found unexpectedly large secondary KIE values in the five-coordinate Fe­(III)-catalyzed hetero-Diels–Alder pathway, even with substantial C–C bond formation, due to the non-negligible equilibrium isotope effect (EIE) derived from altered metal coordination. Therefore, these KIE values cannot reliably reflect transition-state structures for the five-coordinate metal pathway. Furthermore, our density functional theory (DFT) quasi-classical molecular dynamics (MD) simulations demonstrated that the coordination mode and/or spin state of the iron metal as well as an electric field can affect the dynamics of this reaction (e.g., the dynamically stepwise process, the entrance/exit reaction channels).Moreover, we unveiled a new reaction mechanism to account for the uncommon Ru­(II)-catalyzed geminal-addition semihydrogenation and hydroboration of silyl alkynes. Our proposed key gem-Ru­(II)–carbene intermediates derived from double migrations on the same alkyne carbon were verified by crossover experiments. Additionally, our DFT MD simulations suggested that the first hydrogen migration transition-state structures may directly and quickly form the key gem-Ru–carbene structures, thereby “bypassing” the second migration step. Furthermore, our extensive study revealed the origin of the enantioselectivity of the Cu­(I)-catalyzed 1,3-dipolar cycloaddition of azomethine ylides with β-substituted alkenyl bicyclic heteroarenes enabled by dual coordination of both substrates. Such mechanistic insights promoted our computational predictions of the enantioselectivity reversal for the corresponding monocyclic heteroarene substrates and the regiospecific addition to the less reactive internal CC bond of one diene substrate. These predictions were proven by our experimental collaborators. Finally, our mechanistic insights into a few other reactions are also presented. Overall, we hope that these interactive computational and experimental studies enrich our mechanistic understanding and aid in reaction development

Antifreezing and Nondrying Sensors of Ionic Hydrogels with a Double-Layer Structure for Highly Sensitive Motion Monitoring

Freezing and dehydration together with interfacial failure are capable of causing the functional reduction of hydrogels for sensing applications. Herein, we develop a multifunctional bilayer that consists of a mussel-inspired adhesive layer and a functionally ionic layer that is composed of sodium p-styrene sulfonate (SSS) and an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong adhesion of the bilayer to the surface of the skin. The introduction of ionic elements of SSS-[BMIM]Cl not only provides the bilayer with sensing adaptability in a wide temperature range of −25 to 75 °C, but also endows it with elastic, stretchable, self-healing, and conductive features. These mechanical properties are utilized to assemble a wearable sensor that has unprecedented sensitivity and reusability in monitoring human motions, including stretching, pulsing, frowning, and speaking. It is thus expected that the concept in this work would provide a promising route to design soft sensing devices that can work in a wide temperature range