BowtieArene: A Dual Macrocycle Exhibiting Stimuli-Responsive Fluorescence

Although highly useful in supramolecular chemistry, pillararenes lack a fluorophore in their skeleton. Here we present BowtieArene, a novel fluorescent dual macrocycle, featuring a central tetraphenylethylene-derived fluorophore and two pillar-like, pentagon-shaped cavities which are comparable to pillar[5]arene. This concisely prepared, figure-of-eight molecule exhibits vapor absorption and host–guest capabilities, as well as intriguing switchable fluorescence. The fluorochromism of BowtieArene can be triggered by multiple external stimuli including solvent, vapor, and mechanical force, with excellent reversibility and stability. Experimental and theoretical evidence indicate that the fluorochromism should be closely related to molecular packing.     

Construction of Cyclobutanes by Multicomponent Cascade Reactions in Homogeneous Solution through Visible-Light Catalysis

[2+2] Photocycloaddition of two olefins is a general method to assemble the core scaffold, cyclobutane, found in numerous bioactive molecules. A new approach to synthesize cyclobutanes through multicomponent cascade reactions by merging aldol reaction and Witting reaction with visible-light-induced [2+2] cycloaddition is reported. An array of cyclobutanes with high selectivity has been achieved from commercially available aldehydes, ketones (or phosphorus ylide), and olefins with visible-light irradiation of a catalytic amount of (fac-tris(2-phenylpyridinato-C₂,N)iridium) ([Ir(ppy)₃]) at room temperature. Control experiments and spectroscopic studies revealed that the triplet–triplet energy transfer from the excited [Ir(ppy)₃]* to enones, generated in situ from aldehyde and ketone or aldehyde and phosphorus ylide, is responsible for these simple and efficient muticomponent transformations.     

C–HPt(II) interaction-controlled self-assembly and photophysics of chiral bis(pyrrol-2-ylmethyleneamino)cyclohexane platinum(II) complexes

Reaction of (R,R)-(−)- and (S,S)-(+)-1,2-bis(pyrrol-2-ylmethyleneamino)cyclohexane with K₂PtCl₄ afforded chiral, neutral platinum(II) Schiff base complexes of (R,R)-PtL and (S,S)-PtL with high yields. The rare C–HPt(II) intermolecular interaction was found to show considerable strength and directionality for controlling M and P helical supramolecular architectures of (R,R)-PtL and (S,S)-PtL, respectively, in crystal lattices. More importantly, the open square-planar geometry of platinum(II) complexes allows axial C–HPt(II) interaction, resulting in the ³(ππ^*) excited state with some mixing of the Pt(II) metal character observed both in concentrated solutions and in the solid state at room temperature.     

Formation of cubane-like photodimers from 2-naphthalenecarbonitrile

Irradiation of 2-naphthalenecarbonitrile (2-NpCN) in solution with a light lambda > 280 nm results in the formation of three rigid cubane-like photodimers, anti-head-to-head 1, anti-head-to-tail 2, and syn-head-to-tail 3, which are not in line with the previously recognized regioselectivity. These cubane-like photodimers have been well characterized by spectroscopic investigation and/or X-ray crystal structural analysis in this work. Moreover, the separation of the optically pure enantiomers of 1, 2, and 3 has been achieved by HPLC resolution.     

Tracking an FeV(O) Intermediate for Water Oxidation in Water

High-valent iron-oxo species are appealing for conducting O−O bond formation for water oxidation reactions. However, their high reactivity poses a great challenge to the dissection of their chemical transformations. Herein, we introduce an electron-rich and oxidation-resistant ligand, 2-[(2,2′-bipyridin)-6-yl]propan-2-ol to stabilize such fleeting intermediates. Advanced spectroscopies and electrochemical studies demonstrate a high-valent Fe^V(O) species formation in water. Combining kinetic and oxygen isotope labelling experiments and organic reactions indicates that the Fe^V(O) species is responsible for O−O bond formation via water nucleophilic attack under the real catalytic water oxidation conditions.     

Engineering Graphdiyne for Solar Photocatalysis

Graphdiyne (GDY) with a direct band gap, excellent carrier mobility and uniform pores, is regarded as a promising photocatalytic material for solar energy conversion, while the research on GDY in photocatalysis is a less developed field. Herein, the distinctive structure, adjustable band gap, and electronic properties of GDY for photocatalysis is firstly summarized. The construction and progress of GDY-based photocatalysts for solar energy conversion, including H₂ evolution reaction (HER), CO₂ reduction reaction (CO₂RR) and N₂ reduction reaction (NRR) are then elaborated. At last, the challenges and perspectives in developing GDY-based photocatalysts for solar fuel production are discussed. It is anticipated that a timely Minireview will be helpful for rapid progress of GDY in solar energy conversion.     

Synthesis and photophysical studies of calix[4]arene-based binuclear platinum(II) complexes: probing metal-metal and ligand-ligand interactions

A series of calix[4]arene-based binuclear platinum(II) complexes, Pt2LCl2 (1, L = 5,11,17,23-tetra- tert-butyl-25,27-di[methoxy(4-phenyl)-(C;N;N)]-26,28-dihydroxycalix[4]arene, HC;N;N = 6-phenyl-2,2'-bipyridine), [Pt2L(mu-dppCn)](ClO4)2 (dppCn = bis(diphenylphosphino)-methane (2, n = 1), -ethane (3, n = 2), -propane (4, n = 3), and [Pt2L(PPh3)2](ClO4)2 (5), have been designed and synthesized in this work. Spectroscopic investigation demonstrates that p- tert-calix[4]arene is capable of assembling the two square-planar [(C;N;N)Pt(II)] units in a face-to-face manner, simultaneously suppressing intermolecular aggregation and increasing the solubility of the studied complexes. Facile replacement of the chloride ligand in 1 by the strongly sigma-donating ancillary phosphine ligands affords binuclear platinum(II) complexes with improved photophysical properties. All of the complexes are emissive both in the fluid/glassy solution and in the solid state, except for 1 in the solid state at room temperature. Moreover, the absorption and emission energies of the complexes are sensitive to the ancillary ligands. Varying the tethered phosphine auxiliaries from dppm (2) and dppe (3) to dppp (4) and PPh3 (5) modulates the intramolecular metal-metal (Pt...Pt) and ligand-ligand (pi-pi) distances, thereby leading to a switch of 3MMLCT and excimeric 3(pipi*) excited states to a common 3MLCT excited state.     

Adsorptive separation of cyclohexanol and cyclohexanone by nonporous adaptive crystals of RhombicArene

As feedstock chemicals with similar boiling points, cyclohexanol (CHOL) and cyclohexanone (CHON) are often obtained as mixtures during production processes. Separation of mixed CHOL and CHON is important but energy-consuming by distillation. Here we report the development of a new macrocycle RhombicArene, which forms a host–guest complex with CHON through C–H⋯π interactions and hydrogen bonds. The nonporous adaptive crystals of RhombicArene exhibit excellent capability for rapid (30 minutes), exclusive (>99.9%), and recyclable vapor adsorption of CHON in the presence of CHOL under mild and user-friendly conditions.

The novel macrocycle RhombicArene features excellent capability for rapid, exclusive, and recyclable vapor adsorption of cyclohexanone in the presence of cyclohexanol, showing potential for energy-saving separation of these feedstock chemicals.     

High cumulants of conserved charges and their statistical uncertainties

We study the influence of measured high cumulants of conserved charges on their associated statistical uncertainties in relativistic heavy-ion collisions. With a given number of events, the measured cumulants randomly fluctuate with an approximately normal distribution, while the estimated statistical uncertainties are found to be correlated with corresponding values of the obtained cumulants. Generally, with a given number of events, the larger the cumulants we measure, the larger the statistical uncertainties that are estimated. The error-weighted averaged cumulants are dependent on statistics. Despite this effect, however, it is found that the three sigma rule of thumb is still applicable when the statistics are above one million.