Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll <i>a</i>

Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 131-oxo and 132-carbomethoxy substituents. Herein, a general route to stable, synthetic bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CH2Cl2, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin–carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb­(OTf)3, CH3CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrrole sites, ring A) and 132 carboalkoxy groups (R = Me or Et) were constructed in 37–61% yield from the hydrobilin analogues. The BC half and AD half are available in five and eight steps, respectively, from the corresponding pyrrole-2-carboxaldehyde and unsaturated ketone. The bacteriochlorins exhibit absorption spectra typical of bacteriopheophytins (free base bacteriochlorophylls), with a strong near-infrared absorption band (707–751 nm)

Construction of the Bacteriochlorin Macrocycle with Concomitant Nazarov Cyclization To Form the Annulated Isocyclic Ring: Analogues of Bacteriochlorophyll <i>a</i>

Bacteriochlorophylls contain a bacteriochlorin macrocycle bearing an annulated fifth ring. The fifth ring, termed the isocyclic ring or ring E, is equipped with 13¹-oxo and 13²-carbomethoxy substituents. Herein, a general route to stable, synthetic bacteriochlorophyll analogues is described. Knoevenagel condensation (∼40 mM, rt, CH₂Cl₂, piperidine/AcOH/molecular sieves) of a dihydrodipyrrin–carboxaldehyde (AD half) and a dihydrodipyrrin substituted with a β-ketoester (BC half) forms a propenone bearing the two halves (a hydrobilin analogue). Subsequent treatment (0.2 mM) with acid (Yb­(OTf)₃, CH₃CN, 80 °C) promotes a double ring-closure process: (i) condensation between the α-position of pyrrole ring A and the α-acetal unit attached to pyrroline ring B forms the bacteriochlorin macrocycle, and (ii) Nazarov cyclization of the β-(propenoyl)-substituted ring C forms the isocyclic ring (E). Five new bacteriochlorins bearing various substituents (alkyl/alkyl, aryl, and alkyl/ester) at positions 2 and 3 (β-pyrrole sites, ring A) and 13² carboalkoxy groups (R = Me or Et) were constructed in 37–61% yield from the hydrobilin analogues. The BC half and AD half are available in five and eight steps, respectively, from the corresponding pyrrole-2-carboxaldehyde and unsaturated ketone. The bacteriochlorins exhibit absorption spectra typical of bacteriopheophytins (free base bacteriochlorophylls), with a strong near-infrared absorption band (707–751 nm)

Rapid and Mild Metal-Free Reduction of Epoxides to Primary Alcohols Mediated by HFIP

The reduction of epoxides is a powerful tool to access anti-Markovnikov alcohols, but reported methods are poorly compatible with strongly electronically deactivated substrates. Here, we describe a general method for the linear-selective reduction of styryl oxides incorporating strong electron-withdrawing groups. The method remains compatible with more traditional epoxide motifs, such as aliphatic and electron-rich styrene oxides. Other (hetero)­cycles such as oxetanes, tetrahydrofurans, aziridines, and cyclopropanes can also be reductively opened. This user-friendly reaction relies on the combination of a Brønsted acid catalyst and hexafluoroisopropanol as a solvent, and thus, in contrast to existing epoxide reduction methods, it does not require anhydrous reagents or an inert atmosphere. The generated primary alcohols can be conveniently functionalized in situ by a dehydrative Friedel–Crafts arylation without preactivation

Binuclear Heteroligated Titanium Catalyst Based on Phenoxyimine Ligands: Synthesis, Characterization, and Ethylene (Co)polymerization

A binuclear heteroligated titanium­(IV) catalyst based on phenoxyimine ligands (<b>FI</b>^<b>2</b><b>-Ti</b>_<b>2</b>) with its crystal structure elucidated has been developed for the first time for olefin (co)­polymerization. In ethylene polymerization, the activity of the binuclear catalyst <b>FI</b>^<b>2</b><b>-Ti</b>_<b>2</b> can reach 3.0 × 10⁶ g mol^–1 h^–1, and the polydispersity of the resulting polymers is narrow. In copolymerization of ethylene and other olefins, similar incorporation ratios for monoenes are obtained for <b>FI</b>^<b>2</b><b>-Ti</b>_<b>2</b> and <b>FI-Ti</b>_<b>1</b>. However, the incorporation ratio of 1,5-hexadiene increases from 3.2% using <b>FI-Ti</b>_<b>1</b> to 8.8% with <b>FI</b>^<b>2</b><b>-Ti</b>_<b>2</b>. In comparison, the binuclear monophenoxyimine catalyst, [<b>FI</b>^<b>2</b><b>-Ti</b>_<b>2</b><b>(THF)</b>_<b>2</b>], exhibits higher catalytic activity and incorporates more α-olefins than its mononuclear analogue [<b>FI-Ti</b>_<b>1</b><b>(THF)</b>] in the copolymerization. These results are interpreted as consequences of two effects. First, the cooperativity between the two metal centers facilitates the coordination of olefin. Second, the substitutions near the active sites exert a steric effect by blocking and suppressing the binding of comonomers

Unique Temperature-Dependent Supramolecular Self-Assembly: From Hierarchical 1D Nanostructures to Super Hydrogel

Supramolecular self-assembly can not only lead to a better understanding of biological systems, but also can enable rational building of complex and functional materials. In this report, hierarchical one-dimensional (1D) architectures involving nanotubes, coiled-coil ropelike structures, nanohelices, and nanoribbons are created via lanthanum−cholate supramolecular self-assembly. These sophisticated self-assemblies are proven to be mediated by temperature. The entanglement of one-dimensional nanostructures is demonstrated to give rise to fascinating “super” hydrogel, which can realize water gelation at extremely low concentration. Unprecedented water gelation behaviors, that is, heating-enhanced stiffness and heating-promoted gelation, are found in lanthanum−cholate supramolecular hydrogel. The driving forces of self-assembled complex nanostructures and the unique role of temperature are also discussed

Janus Polyvinylidene Fluoride Membrane with Extremely Opposite Wetting Surfaces via One Single-Step Unidirectional Segregation Strategy

Janus membranes with asymmetric wettability have attracted intense attention in oil/water separation, membrane distillation, liquid/fog collection, liquid diode, etc. Facile manipulation of the paradoxical wetting/antiwetting property on opposite surfaces of a 2D membrane is challenging. Different from most postmodification methods, herein, we propose one single-step unidirectional segregation strategy to fabricate a polymeric Janus membrane with extremely opposite wetting surfaces showing almost a 150° contact angle difference for the first time. We achieved the unidirectional segregation of the hydrophilic copolymer poly­(vinylpyrrolidone-vinyltriethoxysilane) in a polyvinylidene fluoride (PVDF) membrane during phase separation. A glycerol coating on the nonwoven fabric support locally limited the phase separation on the bottom surface, blocked the segregation of hydrophilic copolymer, and promoted the segregation to the top surface. Working collaboratively with the asymmetric micro-/nanostructure on both surfaces, the resulting Janus membrane exhibited a superhydrophilic top surface and a superhydrophobic bottom surface. The Janus PVDF membrane showed switchable separation performance and high separation efficiency for both oil-in-water emulsions and water-in-oil emulsions because of its anisotropic wettability compared with solely hydrophobic or hydrophilic PVDF membranes

Controlling Electron Overflow in Phosphor-Free InGaN/GaN Nanowire White Light-Emitting Diodes

We have investigated for the first time the impact of electron overflow on the performance of nanowire light-emitting diodes (LEDs) operating in the entire visible spectral range, wherein intrinsic white light emission is achieved from self-organized InGaN quantum dots embedded in defect-free GaN nanowires on a single chip. Through detailed temperature-dependent electroluminescence and simulation studies, it is revealed that electron leakage out of the device active region is primarily responsible for efficiency degradation in such nanowire devices, which in conjunction with the presence of nonradiative surface recombination largely determines the unique emission characteristics of nanowire light-emitting diodes. We have further demonstrated that electron overflow in nanowire LEDs can be effectively prevented with the incorporation of a p-doped AlGaN electron blocking layer, leading to the achievement of phosphor-free white light-emitting diodes that can exhibit for the first time virtually zero efficiency droop for injection currents up to ∼2200 A/cm². This study also provides unambiguous evidence that Auger recombination is not the primary mechanism responsible for efficiency droop in GaN-based nanowire light-emitting diodes

Breaking the Carrier Injection Bottleneck of Phosphor-Free Nanowire White Light-Emitting Diodes

We have examined the carrier injection process of axial nanowire light-emitting diode (LED) structures and identified that poor carrier injection efficiency, due to the large surface recombination, is the primary cause for the extremely low output power of phosphor-free nanowire white LEDs. We have further developed InGaN/GaN/AlGaN dot-in-a-wire core–shell white LEDs on Si substrate, which can break the carrier injection efficiency bottleneck, leading to a massive enhancement in the output power. At room temperature, the devices can exhibit an output power of ∼1.5 mW, which is more than 2 orders of magnitude stronger than nanowire LEDs without shell coverage. Additionally, such phosphor-free nanowire white LEDs can deliver an unprecedentedly high color rendering index of ∼92–98 in both the warm and cool white regions, with the color rendering capability approaching that of an ideal light source, i.e. a blackbody

Supplementary Figure 6 from A Novel Bispecific Antibody with PD-L1–assisted OX40 Activation for Cancer Treatment

PK in mice</p

Supplementary Figure 5 from A Novel Bispecific Antibody with PD-L1–assisted OX40 Activation for Cancer Treatment

Individual tumor growth curves</p