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Electroreduction of CO2 to C2+ products provides a promising strategy for reaching the goal of carbon neutrality. However, achieving high selectivity of C2+ products at high current density remains a challenge. In this work, we designed and prepared a multi‐sites catalyst, in which Pd was atomically dispersed in Cu (Pd−Cu). It was found that the Pd−Cu catalyst had excellent performance for producing C2+ products from CO2 electroreduction. The Faradaic efficiency (FE) of C2+ products could be maintained at approximately 80.8 %, even at a high current density of 0.8 A cm−2 for at least 20 hours. In addition, the FE of C2+ products was above 70 % at 1.4 A cm−2. Experiments and density functional theory (DFT) calculations revealed that the catalyst had three distinct catalytic sites. These three active sites allowed for efficient conversion of CO2, water dissociation, and CO conversion, ultimately leading to high yields of C2+ products. [ABSTRACT FROM AUTHOR]

Planar‐chiral cyclophanes have received increasing attention for drug discovery and catalyst design. However, the catalytically asymmetric synthesis of planar‐chiral cyclophanes has been a longstanding challenge. We describe the first Pd(II)‐catalyzed enantioselective C−H olefination of prochiral cyclophanes. The low rotational barrier of less hindered benzene ring in the substrates allows the reaction to proceed through a dynamic kinetic resolution. This approach exhibits broad substrate scope, providing the planar‐chiral cyclophanes in high yields (up to 99 %) with excellent enantioselectivities (up to >99 % ee). The ansa chain length scope studies reveal that the chirality of the cyclophanes arises from the bond rotation constraint of the benzene ring around the macrocycle plane, rather than the C−N axis. The C−H activation approach is also applicable to the late‐stage modification of bioactive molecules and pharmaceuticals. [ABSTRACT FROM AUTHOR]

A porous molecular crystal (PMC) assembled by macrocyclic cyclotetrabenzoin acetate is an efficient adsorbent for CO2 separations. The 7.1×7.1 Å square pore of PMC and its ester C=O groups play important roles in improving its affinity for CO2 molecules. The benzene walls of macrocycle engage in an apparent [π⋅⋅⋅π] interaction with the molecule of CO2 at low pressure. In addition, the polar carbonyl groups pointing inward the square channels reduce the size of aperture to a 5.0×5.0 Å square, which offers kinetic selectivity for CO2 capture. The PMC features water tolerance and high structural stability under vacuum and various gas adsorption conditions, which are rare among intrinsically porous organic molecules. Most importantly, the moderate adsorbate‐adsorbent interaction allows the PMC to be readily regenerated, and therefore applied to pressure swing adsorption processes. The eluted N2 and CH4 are obtained with over 99.9 % and 99.8 % purity, respectively, and the separation performance is stable for 30 cycles. Coupled with its easy synthesis, cyclotetrabenzoin acetate is a promising adsorbent for CO2 separations from flue and natural gases. [ABSTRACT FROM AUTHOR]

The enantioselective desymmetrizing C−H activation of α‐gem‐dialkyl acyclic amides remains challenging because the availability of four chemically identical unbiased methylene C(sp3)−H bonds and increased rotational freedoms of the acyclic systems add tremendous difficulties for chemo‐ and stereocontrol. We have developed a method for the synthesis of acyclic aliphatic amides with α,β‐contiguous stereogenic centers via PdII‐catalyzed asymmetric arylation of unbiased methylene C(sp3)−H, in good yields and with high levels of enantio‐, chemo‐ and diastereoselectivity (up to >99 % ee and >20:1 d.r.). Successive application of this method enables the sequential arylation of the gem‐dialkyl groups with two different aryl iodides, giving a range of β‐Ar1‐β′‐Ar2‐aliphatic acyclic amides containing three contiguous stereogenic centers with excellent diastereoselectivity. [ABSTRACT FROM AUTHOR]

Indeno[1,2‐b]fluorene‐based [2,2]cyclophanes with 4n/4n and 4n/[4n+2] π‐electron systems were prepared, and their structures were identified by X‐ray crystallography. With short π–π distances around 3.0 Å, [2.2](5,11)indeno[1,2‐b]fluorenophane and its precursor [2.2](5,11)indeno[1,2‐b]fluorene‐6,12‐dionophane exhibit remarkable transannular interactions, leading to their unusual electrochemical and photophysical properties. With the aid of femtosecond transient absorption spectroscopy, the transition from the monomeric excited state to the redshifted H‐type dimeric state was first observed, correlating to the calculated excitonic energy splitting and the steady‐state absorption spectra induced by charge‐transfer‐mediated superexchange interaction. [ABSTRACT FROM AUTHOR]

This investigation demonstrates that a series of biphenylenes can be easily prepared from their corresponding halobiphenyls by the cyclization of in situ generated 2′,3′-didehydro-2-lithiobiphenyls at low temperature. Two remarkable advantages of this synthetic method include 1) the lack of any need for transition-metal catalysts or reagents in the cyclization, and 2) the ability to obtain C1-functionalized products by treating the reaction intermediate 1-lithiobiphenylene with an electrophilic reagent. π-Extended derivatives, such as benzobiphenylenes, dibenzobiphenylene, linear/angular [3]phenylenes, and biphenyleno[2,3- b]biphenylenes, were synthesized similarly using suitable biaryls or teraryls. [ABSTRACT FROM AUTHOR]

A crystalline coordination polymer (CP) photocatalyst (Cu-RSH) which combines redox-active copper centers with photoactive rhodamine-derived ligands remains stable in acid and basic solutions from pH 2 to 14, and efficiently catalyzes dihydrogen evolution at a maximum rate of 7.88 mmol g−1 h−1 in the absence of a mediator and a co-catalyst. Cyclic voltammetry, control experiments, and DFT calculations established that copper nodes with open coordination sites and favorable redox potentials, aided by spatially ordered stacking of rhodamine-based linkers, account for the high catalytic performance of Cu-RSH. Emission quenching, time-resolved fluorescence decay, and transient photocurrent experiments disclosed the charge separation and transfer process in the catalytic system. The present study demonstrates the potential of crystalline copper CPs for the practical utilization of light. [ABSTRACT FROM AUTHOR]

The syntheses, structures, and physical properties of dibenzozethrenes were explored. The results thus obtained were compared with those for zethrenes. Dibenzozethrenes were synthesized by the nickel-catalyzed cyclodimerization of 9-ethynyl-1-iodoanthracenes. The substituents in zethrene and dibenzozethrene twisted their backbones, and remarkably influenced their properties. Unlike closed-shell disubstituted derivatives, the parent zethrene and dibenzozethrene are singlet open-shell biradicals, which were studied by variable-temperature 1H NMR, ESR, SQUID and computational methods. Since substituents were observed to affect significantly the biradical properties, the relevant mechanisms were analyzed. The nonlinear optical performance of each of these compounds depends on its π-conjugation and biradical properties. Dibenzozethrenes have larger two-photon absorption cross-sections than zethrenes, as most strongly evidenced by the parent dibenzothrene [ σmax=4323 GM at 530 nm]. [ABSTRACT FROM AUTHOR]

Polygons: [8]Circulenes were easily prepared by Pd‐catalyzed annulations of tetraiodotetraphenylenes with alkynes. Their saddle‐shaped structure with an [8]radialene character was identified by X‐ray crystallography. Similar to 1,3,5,7‐cyclooctatetraene, they have a tub‐shaped eight‐membered ring, but all of the bond lengths and bond angles are almost equal. Variable‐temperature NMR investigations showed interesting dynamic behavior. [ABSTRACT FROM AUTHOR]

Super bowl: Fragments of C70 or higher fullerenes were easily prepared from 1,8‐bis(arylethynyl)naphthalenes. The curved structures were identified by X‐ray crystallography. These rigid bowl‐shaped molecules have a deep bowl depth (approximately 2.30 Å) and their bowl inversions proceed via an S‐shaped transition structure with a very high inversion barrier (approximately 80 kcal mol−1). [ABSTRACT FROM AUTHOR]

Throwing a curve: The first example of a through‐bond stereoelectronic effect for curved aromatic compounds is described for buckybowls, that is, benzylic‐substituted sumanenes. Methyl‐ and hydroxysumanene favor the endo‐R conformer because of a difference in the strength, between the conformers, of the hyperconjugation of the benzylic CH bond with the bowl. [ABSTRACT FROM AUTHOR]