Youzhi

Crowned: The films of large π‐extended molecular crowns and their supramolecular complexes with fullerenes, which served as the active layer, generated photocurrents under light irradiation. These molecular crowns bearing curved nanographenes as the sidewalls were synthesized in gram‐scale quantities. Their photophysical properties were investigated by steady‐state and time‐resolved fluorescence spectroscopy.

Abstract

This study presents synthesis and characterizations of two novel curved nanographenes that strongly bind with fullerene C₆₀ to form photoconductive heterojunctions. Films of the self‐assembled curved nanographene/fullerene complexes, which served as the photoconductive layer, generated a significant photocurrent under light irradiation. Gram‐scale quantities of these curved nanographenes (TCR and HCR) as the “crown” sidewalls can be incorporated into a carbon nanoring to form molecular crowns, and the molecular structure of C₆₀@TCR is determined by single‐crystal X‐ray diffraction. The UV/Vis absorption and emission spectra, and theoretical studies revealed their unique structural features and photophysical properties. Time‐resolved spectroscopic results clearly suggest fast photoinduced electron transfer process in the supramolecular heterojunctions.

Shrink to fit: A method to make rigid cylinder cycloarylenes more narrow was devised. Width‐dependent chiroptical properties were revealed. The magnetic transition dipole moment was dictated by the radius of a ring‐current‐like circle that was formed by local electric transition dipole moments on the cylinder.

Abstract

Rigid molecular cylinders with a 1 nm diameter were synthesized by assembling arylene panels with Pt‐mediated macrocylization. Chrysenylene panels that previously participated in tetrameric macrocyclization were contorted by the addition of two benzo groups on the sides to form dibenzochrysenylene, which allowed for a reduction in the numbers of participating panels to three. Consequently, narrowed cyclochrysenylene congeners were obtained. The narrowed chiral cylinders possessed width‐dependent chiroptical properties. The magnetic transition dipole moment was dictated by the radius of a ring‐current‐like circle that was formed by local electric transition dipole moments on the cylinder.

Chiral [6]helicenes serve as building blocks for the assembly of [Pd₂L₄] coordination cages and interpenetrated [Pd₄L₈] dimers. Depending on the ligand length, chiral self‐discrimination and recognition of enantiomeric guests is observed. Helical pitch modulation allows the discrimination of non‐chiral guests by a combination of CD spectroscopy and ion mobility mass spectrometry.

Abstract

Chiral nanosized confinements play a major role for enantioselective recognition and reaction control in biological systems. Supramolecular self‐assembly gives access to artificial mimics with tunable sizes and properties. Herein, a new family of [Pd₂L₄] coordination cages based on a chiral [6]helicene backbone is introduced. A racemic mixture of the bis‐monodentate pyridyl ligand L¹ selectively assembles with Pd^II cations under chiral self‐discrimination to an achiral meso cage, cis‐[Pd₂ L^1P ₂ L^1M ₂]. Enantiopure L¹ forms homochiral cages [Pd₂ L^1P/M ₄]. A longer derivative L² forms chiral cages [Pd₂ L^2P/M ₄] with larger cavities, which bind optical isomers of chiral guests with different affinities. Owing to its distinct chiroptical properties, this cage can distinguish non‐chiral guests of different lengths, as they were found to squeeze or elongate the cavity under modulation of the helical pitch of the helicenes. The CD spectroscopic results were supported by ion mobility mass spectrometry.

The endohedral fullerene CH₄@C₆₀ has been synthesized for the first time using photochemical desulfinylation of an open fullerene as the key step. Methane is a much larger molecule than has been previously encapsulated in the closed C₆₀ cage and is amongst the largest of possible guests.

Abstract

The endohedral fullerene CH₄@C₆₀, in which each C₆₀ fullerene cage encapsulates a single methane molecule, has been synthesized for the first time. Methane is the first organic molecule, as well as the largest, to have been encapsulated in C₆₀ to date. The key orifice contraction step, a photochemical desulfinylation of an open fullerene, was completed, even though it is inhibited by the endohedral molecule. The crystal structure of the nickel(II) octaethylporphyrin/ benzene solvate shows no significant distortion of the carbon cage, relative to the C₆₀ analogue, and shows the methane hydrogens as a shell of electron density around the central carbon, indicative of the quantum nature of the methane. The ¹H spin‐lattice relaxation times (T ₁) for endohedral methane are similar to those observed in the gas phase, indicating that methane is freely rotating inside the C₆₀ cage. The synthesis of CH₄@C₆₀ opens a route to endofullerenes incorporating large guest molecules and atoms.

A sticky situation: An unprecedented pure, dynamic, crystalline framework held together with weak “sticky fingers” van der Waals interactions has been developed. The fullerene‐based material exhibits a remarkable single‐crystal‐to‐single‐crystal hydrogenation reaction accompanied by a color change in the visible range.

Abstract

Engineering high‐recognition host–guest materials is a burgeoning area in basic and applied research. The challenge of exploring novel porous materials with advanced functionalities prompted us to develop dynamic crystalline structures promoted by soft interactions. The first example of a pure molecular dynamic crystalline framework is demonstrated, which is held together by means of weak “sticky fingers” van der Waals interactions. The presented organic‐fullerene‐based material exhibits a non‐porous dynamic crystalline structure capable of undergoing single‐crystal‐to‐single‐crystal reactions. Exposure to hydrazine vapors induces structural and chemical changes that manifest as toposelective hydrogenation of alternating rings on the surface of the [60]fullerene. Control experiments confirm that the same reaction does not occur when performed in solution. Easy‐to‐detect changes in the macroscopic properties of the sample suggest utility as molecular sensors or energy‐storage materials.

New twist: The first hexapole [9]helicene with an extremely twisted structure has been synthesized and characterized. Formation of each embedded [9]helicene (see scheme, cyan) involves forging of a new C−C bond (purple) to stitch together two [4]helicene subunits, reminiscent of the initial approach Martin developed in the 1960s to make the pristine [9]helicene.

Abstract

Herein we present the first hexapole [9]helicene (H9H). Co‐catalyzed [2+2+2] cyclotrimerization of a dinaphthopyrene (DNP) functionalized alkyne provides the hexaaryl benzene precursor 2, which is transformed into H9H via a dehydrocyclization reaction. Formation of each embedded [9]helicene involves forging of a new C−C bond, which stitches together two [4]helicene subunits of the neighboring DNP blades, reminiscent of the initial method Martin developed for the preparation of [9]helicene in the 1960s. Single‐crystal X‐ray analysis of both 2 and H9H discloses their extremely distorted and crowded structural features. Chiral resolution, optical and electronic properties of H9H are also presented.

Just add salt! Water with added NaCl was a very effective reaction medium for performing direct and fast (within 20 s) Pd‐catalysed cross‐coupling reactions between organolithiums and a variety of (hetero)aryl halides at room temperature and under air. Catalyst and water recyclability and reusability were added advantages of the proposed protocol.

Abstract

Direct palladium‐catalysed cross‐couplings between organolithium reagents and (hetero)aryl halides (Br, Cl) proceed fast, cleanly and selectively at room temperature in air, with water as the only reaction medium and in the presence of NaCl as a cheap additive. Under optimised reaction conditions, a water‐accelerated catalysis is responsible for furnishing C(sp³)–C(sp²), C(sp²)–C(sp²), and C(sp)–C(sp²) cross‐coupled products, in competition with protonolysis, within a reaction time of 20 s, in yields of up to 99 %, and in the absence of undesired dehalogenated/homocoupling side products even when challenging secondary organolithiums serve as the starting material. It is worth noting that the proposed protocol is scalable and the catalyst and water can easily and successfully be recycled up to 10 times, with an E‐factor as low as 7.35.

Dehydrative π-extension to nanographenes with zig-zag edges

Dehydrative π-extension to nanographenes with zig-zag edges, Published online: 12 November 2018; doi:10.1038/s41467-018-07095-z

Nanographenes with zig-zag peripheries are expected to have unique electronic properties, but their application in organic electronics has been curbed by their difficult synthesis. Here, the authors develop a facile route to zig-zag nanographenes based on a key dehydrative π-extension reaction.

A kind of large nanographene imide featuring dual‐core arrangement of [5]helicenes and imide groups has a D ₂‐symmetric “four‐bladed propeller” conformation which could not convert into other conformations even at 200 °C. The single chiral nanographene imide also exhibits excellent resistance to thermally induced racemization.

Abstract

A novel kind of nanographene imide, namely pentaperylene decaimides (PPD) featuring dual‐core sixfold [5]helicenes and ten imide groups, was efficiently obtained. Among the possible 28 stereoisomers, which include 14 pairs of enantiomers, only one pair of enantiomers was obtained selectively which could be separated by chiral HPLC. Single‐crystal X‐ray diffraction analyses revealed that it exhibits a D ₂‐symmetric “four‐bladed propeller” conformation composed of conjoined double “three‐bladed propeller”, which is very stable and could not convert into other conformations even when heated up to 200 °C. Meanwhile, enantiomerically pure PPD also exhibits an excellent resistance to thermally induced racemization, which makes it a promising candidate for various applications in chiral material science.