[n]Cyclo‐3,6‐phenanthrenylenes: Synthesis,Structure, and Fluorescence

Five congeners of [n ]cyclo‐3,6‐phenanthrenylene with 3, 4, 5, 7, and 8 panels were obtained from one‐pot macrocyclization of dibromophenanthrene, and their crystal structures with diverse molecular shapes were revealed by X‐ray crystallography. The compounds, except the four‐panel congener, were highly fluorescent in solution, with quantum yields up to 85 %. The least fluorescent four‐panel congener showed the smallest change in its absorption spectrum from that of monomeric phenanthrene, which provided an interesting structure–activity relationship for fluorescent macrocycles to guide future studies.     

Orthogonal Surface Tags for Whole‐Cell Biocatalysis

We herein describe the engineering of E. coli strains that display orthogonal tags for immobilization on their surface and overexpress a functional heterologous “protein content” in their cytosol at the same time. Using the outer membrane protein Lpp‐ompA, cell‐surface display of the streptavidin‐binding peptide, the SpyTag/SpyCatcher system, or a HaloTag variant allowed us to generate bacterial strains that can selectively bind to solid substrates, as demonstrated with magnetic microbeads. The simultaneous cytosolic expression of functional content was demonstrated for fluorescent proteins or stereoselective ketoreductase enzymes. The latter strains gave high selectivities for specific immobilization onto complementary surfaces and also in the whole‐cell stereospecific transformation of a prochiral C_S‐symmetric nitrodiketone.     

Heterogeneous Fenton-like reactions with a novel hybrid Cu–Mn–O catalyst for the degradation of benzophenone-3 in aqueous media

This study focuses on the heterogeneous Fenton-like reaction performed over a novel hybrid Cu–Mn–O catalyst for the degradation of a model compound benzophenone-3 (BP-3) in aqueous media. The hybrid Cu–Mn–O catalysts with different Cu/Mn molar ratios were synthesized using co-precipitation and hydrothermal methods, and their composition and morphology were characterized using XRD and SEM analyses. Key parameters including the Cu/Mn ratio in the synthesis, pH and titration of H₂O₂ were shown to significantly influence the degradation of BP-3. A hybrid catalyst with a chemical composition of Cu_1.4Mn_1.6O₄, Mn₃O₄, and Mn₂O₃ exhibiting a morphology of nanofibers and nanoparticles demonstrated the highest catalytic activity in the degradation of BP-3. After 240 min of degradation, 81.5% of BP-3 was removed, which could be mostly related to the presence of hydroxyl radicals (˙OH). Unlike the conventional Fenton reaction that performs well under highly acidic conditions, BP-3 can be degraded in a wider pH range (2.6–7.1) in the Fenton-like reaction presented herein. Considering the mild conditions used for this Fenton-like system, this novel hybrid catalyst remains promising for wastewater treatment.     

Bending,Curling, Rolling,and Salient Behavior of Molecular Crystals Driven by [2+2] Cycloaddition of a Styrylbenzoxazole Derivative

We report interesting photomechanical behaviors of the dynamic molecular crystals of (E )‐2‐(2,4‐dichlorostyryl)benzo[d]oxazole ( BOACl24 ). The photosalient effect of the rod‐like crystal based on a metal‐free olefin driven by photodimerization is observed. Moreover, the needle‐like crystals of BOACl24 exhibit a reversible bending away from a UV light source. The nanofibers curl easily under UV irradiation in an organogel, in which the photo‐induced rolling of a small slice occurs. This suggests that the rapid release of the accumulated strain during photodimerization may lead to a photosalient effect, and the bending or curling happens when the strain is released slowly. Notably, [2+2] cycloaddition takes place between two different conformational isomers of BOACl24 on account of the rotation of the benzoxazole ring around the C−C bond in an excited state before photodimerization. Such topo‐photochemical reaction has not been reported elsewhere.     

Stabilization of High Oxidation State Upconversion Nanoparticles by N‐Heterocyclic Carbenes

The stabilization of high oxidation state nanoparticles by N‐heterocyclic carbenes is reported. Such nanoparticles represent an important subset in the field of nanoparticles, with different and more challenging requirements for suitable ligands compared to elemental metal nanoparticles. N‐Heterocyclic carbene coated NaYF₄:Yb,Tm upconversion nanoparticles were synthesized by a ligand‐exchange reaction from a well‐defined precursor. This new photoactive material was characterized in detail and employed in the activation of photoresponsive molecules by low‐intensity near‐infrared light (λ =980 nm).     

Protein‐Templated Formation of an Inhibitor of the Blood Coagulation Factor Xa through a Background‐Free Amidation Reaction

Protein‐templated reactions enable the target‐guided formation of protein ligands from reactive fragments, ideally with no background reaction. Herein, we investigate the templated formation of amides. A nucleophilic fragment that binds to the coagulation factor Xa was incubated with the protein and thirteen differentially activated dipeptides. The protein induced a non‐catalytic templated reaction for the phenyl and trifluoroethyl esters; the latter was shown to be a completely background‐free reaction. Starting from two fragments with millimolar affinity, a 29 nm superadditive inhibitor of factor Xa was obtained. The fragment ligation reaction was detected with high sensitivity by an enzyme activity assay and by mass spectrometry. The reaction progress and autoinhibition of the templated reaction by the formed ligation product were determined, and the structure of the protein–inhibitor complex was elucidated.     

Metal‐Free,Room‐Temperature Oxygen‐Atom Transfer in the N2O/CO Redox Couple as Catalyzed by [Si2Ox].+ (x=2–5)

The thermal reduction of N₂O by CO mediated by the metal‐free cluster cations [Si₂O_x]^.+ (x =2–5) has been examined in the gas phase using Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry in conjunction with quantum chemical calculations. Three successive oxidation/reduction steps occur starting from [Si₂O₂]^.+ and N₂O to form eventually [Si₂O₅]^.+; the latter as well as the intermediate oxide cluster ions react sequentially with CO molecules to regenerate [Si₂O₂]^.+. Thus, full catalytic cycles occur at ambient conditions in the gas phase. Mechanistic aspects of these sequential redox processes have been addressed to reveal the electronic origins of these unparalleled reactions.     

Metal‐Free Nitrile Diboration through Activation by an Electron‐Rich Diborane

Diboration of unsaturated organic compounds is an extremely useful reaction in synthetic chemistry. Herein, we report the first diboration of a nitrile by an electron‐rich diborane, mediated by an electrophilic borane. The reaction is metal‐free, and all of the reagents are readily available.     

Visible-Light-Mediated [4+2] Cycloaddition of Styrenes: Synthesis of Tetralin Derivatives

We report a formal [4+2] cycloaddition reaction of styrenes under visible-light catalysis. Two styrene molecules with different electronic or steric properties were found to react with each other in good yield and excellent chemo- and regioselectivity. This reaction provides direct access to polysubstituted tetralin scaffolds from readily available styrenes. Sophisticated tricyclic and tetracyclic tetralin analogues were prepared in high yield and up to 20/1 diasteroselectivity from cyclic substrates.     

Corona[5]arenes Accessed by a Macrocycle-to-Macrocycle Transformation Route and a One-Pot Three-Component Reaction

Corona[5]arenes, a novel type of macrocyclic compound that is composed of alternating heteroatoms and para-arylenes, were synthesized efficiently by two distinct methods. In a macrocycle-to-macrocycle transformation approach, S₆-corona[3]arene[3]tetrazine underwent sequential S_NAr reactions with HS-C₆H₄-X-C₆H₄-SH (X=S, CH₂, CMe₂, SO₂, and O) to produce the corresponding corona[3]arene[2]tetrazines. Different corona[3]arene[2]tetrazine compounds were also constructed in a straightforward manner by a one-pot three-component reaction of HS-C₆H₄-X-C₆H₄-SH (X=S, CH₂, CMe₂, SO₂, and O) with diethyl 2,5-dimercaptoterephthalate and 2 equiv of 3,6-dichlorotetrazine under very mild conditions. All corona[5]arenes adopted 1,2,4-alternate conformational structures in the crystalline state yielding similar nearly regular pentagonal cavities. Both the cavity size and the electronic property of the acquired macrocycles were fine-tuned by the nature of the bridging element X.