Graphene news, publications and commentary from the two-dimensional community.

In fatty acid photodecarboxylase (FAP), light-induced formation of the primary radical product RCOO● from fatty acid RCOO– occurs in 300 ps, upon which CO2 is released quasi-immediately. Based on the hypothesis that aliphatic RCOO● (spectroscopically uncharacterized because unstable) absorbs in the red similarly to aromatic carbonyloxy radicals such as 2,6‑dichlorobenzoyloxy radical (DCB●), much longer-lived linear RCOO● has been suggested recently. We performed quantum chemical reaction pathway and spectral calculations. These calculations are in line with the experimental DCB● decarboxylation dynamics and spectral properties and show that in contrast to DCB●, aliphatic RCOO● radicals a) decarboxylate with a very low energetic barrier and on the timescale of a few ps and b) exhibit little red absorption. A time-resolved infrared spectroscopy experiment confirms very rapid,

Published in: "Angewandte Chemie International Edition".

Metal–organic cages (MOCs), which are formed via coordination-driven assembly, are being extensively developed for various applications owing to the utility of their accessible molecular-sized cavity. While MOC structures are uniquely and precisely predetermined by the metal coordination number and ligand configuration, tailoring MOCs to further modulate the size, shape, and chemical environment of the cavities has become intensively studied for a more efficient and adaptive molecular binding. Herein, we report self-expanding MOCs that exhibit remarkable structural variations in cage size and flexibility while maintaining their topology. A cyclic ligand with an oligomeric chain tethering the two benzene rings of stilbene was designed and mixed with RhII ions to obtain the parent MOCs. These MOCs were successfully transformed into expanded MOCs via the selective cleavage of the double bond in stilbene. The expanded MOCs could effectively trap multidentate N-donor molecules in their enlarged cavity, in contrast to the original MOCs with a narrow cavity. As the direct synthesis of expanded MOCs is impractical because of the entropically disfavored structures, self-expansion using ring-openable ligands is a promising approach that allows precision engineering and the production of functional MOCs that would otherwise be inaccessible.

Published in: "Angewandte Chemie International Edition".

Conjugated polymers (CPs) with low molecular packing order are promising candidates for application in organic thermoelectrics (OTEs), particularly in flexible devices, because the disordered structures can effectively accommodate dopants and ensure robust resistance to bending. On the other hand, n-doped CPs usually exhibit inferior thermoelectric performance, restricting the development of high-performance thermoelectric generators. Herein, we report an n-type CP (ThDPP-CNBTz) by alternating two acceptor units of thiophene-flanked diketopyrrolopyrrole and cyano-functionalized benzothiadiazole. ThDPP-CNBTz shows a low-lying LUMO level below -4.20 eV and features low crystallinity, enabling the attainment of high doping efficiency. Moreover, the dual-acceptor molecular design enhances polaron delocalization, thereby improving the thermoelectric performance of the polymer. After n-doping, ThDPP-CNBTz exhibits an electrical conductivity (s) of 50.6 S cm-1 and a power factor (PF) of 126.8 μW m-1 K-2, which ranks among the highest reported for solution-processed n-type CPs to date. Additionally, solution-processed flexible OTE device employing doped ThDPP-CNBTz achieves a PF of 70 μW m-1 K-2. Meanwhile, the flexible OTE devices present remarkable resistance to bending strain, with marginal change in σ after 600 bending cycles. The findings presented in this work will advance the development of n-type CPs for OTE devices, with a particular focus on flexible properties.

Published in: "Angewandte Chemie International Edition".

The first systematic exploration of the synthesis and reactivity of naphthoquinonynes is described. Routes to two regiosomeric Kobayashi-type naphthoquinonyne precursors have been developed, and the reactivity of the ensuing 6,7- and 5,6-aryne intermediates has been investigated. Remarkably, these studies have revealed that a broad range of cycloadditions, nucleophile additions and difunctionalizations can be achieved while maintaining the integrity of the highly sensitive quinone unit. The methodologies offer a powerful diversity oriented approach to C6 and C7 functionalized naphthoquinones, which are typically challenging to access. From a reactivity viewpoint, the study is significant because it demonstrates that aryne-based functionalizations can be utilized strategically in the presence of highly reactive and directly competing functionality.

Published in: "Angewandte Chemie International Edition".

Realizing protein analysis in organelles of living cells is of great significance for developing diagnostic and therapeutic methods of diseases. Fluorescent-labeled antibodies with well imaging performance and high affinity are classical biochemical tools for protein analysis, while due to the inability to effectively enter into cells, not to mention organelles and the uncontrollable reaction sites that might cause antibodies inactivation when chemically modification, they are hard to apply to living cells. Inspired by the structure of fluorescent-labeled antibodies, we designed as a universal detection platform that was based on the peptide-conjugated probes (PCPs) and consisted of three parts: a) a rotor type fluorescent molecular scaffold for conjugation and signal output; b) the cell penetration protein recognition unit; c) the subcellular organelle targeting unit. In living cells, PCPs could firstly localize at organelles and then proceed protein specific recognition, thus jointly leading to the restriction of twisted intramolecular charge transfer and activation of fluorescence signal. As a proof-of-concept, six different proteins in three typical intracellular organelles could be detected by our platform through simply replacing the recognition sequence of proteins and matching organelle targeting units. The position and intensity of fluorescence signals demonstrated specificity of PCPs and universality of the platform.

Published in: "Angewandte Chemie International Edition".

In the sunlight (oil phase), the Morning Stars (the Ag29 nanoclusters) shine brightly, but when night falls (aqueous phase transfer), the stars may lose their luster (photoluminescence quenching). Yet, there are always some special stars. When they come together (supramolecular recoupling), they become the shining Big Dipper (emission recovery) for guiding the direction (downstream hydrophilic applications). Details of the research are reported by Xi Kang, Wenxiong Shi, Manzhou Zhu et al. (e202317995).

Published in: "Angewandte Chemie International Edition".

Synthesis of bicyclic scaffolds has emerged as an important research topic in modern drug development because they can serve as saturated bioisosters to enhance the physicochemical properties and metabolic profiles of drug candidates. Here we report a remarkably simple silver-enabled strategy to access polysubstituted 3-azabicyclo[3.1.1]heptanes in a single operation from readily accessible bicyclo[1.1.0]butanes (BCBs) and isocyanides. The process is proposed to involve a formal [3+3]/[3+2]/retro-[3+2] cycloaddition sequence. This novel protocol allows for rapid generation of molecular complexity from simple starting materials, and the products can be easily derivatized, further enriching the BCB cycloaddition chemistry and the growing set of valuable sp3-rich bicyclic building blocks.

Published in: "Angewandte Chemie International Edition".

A recently introduced saddle-shaped supramolecular unit “carpyridine”, which strongly relies on aromatic curvature to self-assemble, was engineered to form 1D supramolecular polymers. This modified mode of assembly allowed us to gain a deeper understanding of the process, including enthalpy values comparable to those of hydrogen-bonded systems. The minimalism of the molecular design showcases the versatility of curvature in molecular design. Abstract The extent of the influence that molecular curvature plays on the self-assembly of supramolecular polymers remains an open question in the field. We began addressing this fundamental question with the introduction of “carpyridines”, which are saddle-shaped monomers that can associate with one another through π–π interactions and in which the rotational and translational movements are restricted. The topography displayed by the monomers led, previously, to the assembly of highly ordered 2D materials even in the absence of strong directional interactions such as hydrogen bonding. Here, we introduce a simple strategy to gain control over the dimensionality of the formed structures yielding classical unidimensional polymers. These have been characterized using well-established protocols allowing us to determine and confirm the self-assembly mechanism of both fibers and sheets. The calculated interaction energies are significantly higher than expected for flexible self-assembling units lacking classical “strong” non-covalent interactions. The versatility of this supramolecular unit to assemble into either supramolecular fibers or 2D sheets with strong association energies highlights remarkably well the potential and importance of molecular shape for the design of supramolecular materials and the applications thereof.

Published in: "Angewandte Chemie International Edition".

Distinctive π-extended diaza[7]helicenes with fused negative curvature and helicity have been facilely synthesized by twofold heptagonal cyclization. In addition to intriguing features arising from the dynamic chiral skeleton, the molecular packing of these curved helicenes can be modulated by the periphery groups and the extension of the skeleton. This leads to the formation of crystals with 31 helices and also homochiral nanosheets upon exfoliation. Abstract We report a unique category of π-extended diaza[7]helicenes with double negative curvatures. This is achieved by two-fold regioselective heptagonal cyclization of the oligoarylene-carbazole precursors through either intramolecular C−H arylation or Scholl reaction. The fusion of two heptagonal rings in the helical skeleton dramatically increases the intramolecular strain and forces the two terminal carbazole moieties to stack in a compressed fashion. The presence of the deformable negatively curved heptagonal rings endows the resulting diaza[7]helicenes with dynamic chiral skeletons, aggregation-induced emission feature and relatively low racemization barrier of ca. 25.6 kcal mol−1. Further π-extension on the carbazole moieties subsequently leads to a more sophisticated C 2-symmetric homochiral triple helicene. Notably, these π-extended diaza[7]helicenes show structure-dependent stacking upon crystallization, switching from heterochiral packing to intra-layer homochiral stacking. Interestingly, the C 2-symmetric triple helicene molecules spontaneously resolve into a homochiral lamellar structure with 31 helix symmetry. Upon ultrasonication in a nonsolvent, the crystals can be readily exfoliated into large-area ultrathin nanosheets with height of ca. 4.4 nm corresponding to two layers of stacked triple helicene molecules and relatively thicker nanosheets constituted by even-numbered molecular lamellae. Moreover, regular hexagonal thin platelets with

Published in: "Angewandte Chemie International Edition".