Panče Naumov

Organic single-crystal heterostructures (OSCHs) constitute a promising platform for advanced flexible optoelectronics, yet imparting mechanical flexibility to these multiblock systems, especially given the susceptibility to failure at the interfaces between individual crystal segments, remains challenging. This obstacle is particularly aggravated at cryogenic temperatures, where the freezing of vibrational motion may cause brittleness and lead to mechanical failure. Herein, we describe an epitaxial growth strategy using molecular alloys for the fabrication of crystals of cryogenically flexible two-color (blue–cyan–blue) triblock heterostructures, prepared by growing triphenylene (TP) segments onto perylene (PER)-doped alloy seed crystals via crystallization under controlled cooling. The compatibility between the host and guest molecules provides interfaces with low defect densities. Analysis of the crystal structure reveals an abundance of weak intermolecular interactions that are thought to enable the reversible elastic deformation observed at both 298 and 77 K, thereby preventing cracking. Simultaneously, efficient Förster resonance energy transfer (FRET) between TP and PER enables continuous emission tuning and doping-ratio-controlled programmability of the optoelectronic properties. The resulting heterostructures not only support low-loss active optical waveguiding and programmable multichannel optical logic and information encoding but also remain fully operational for optical transduction during bending under cryogenic conditions. This work establishes a general molecular alloying approach to structures that integrate low-temperature mechanical compliance with sophisticated photonic functionalities, providing a pathway to deformable, multiemissive optoelectronics elements that remain operational in extreme environments.

While fivefold point symmetry is common in nature, fivefold spatial symmetry is seldom observed. Regular pentagons cannot tile a plane without leaving voids, and even the densest “ice-ray” packing is exceptionally rare. Fivefold helices are equally elusive. We report a small molecule that self-assembles into hydrogen-bonded pseudo-fivefold helices and adopts an ice-ray pentagonal packing motif over crystallographic length scales using peripheral disorder that partially occupies regions that would otherwise be void in an ideal pentagonal tessellation. The resulting structure exhibits weak and nondirectional interhelical interactions within the ( bc ) plane and comparatively strong and directional intrahelical hydrogen bonding along the a axis. This structural anisotropy gives rise to single crystals with large aspect ratios and distinct mechanical behavior. This realization of two rare structural motifs within a single crystal shows the capability of simple organic molecules to form complex structures and highlights an untapped potential for symmetry engineering in molecular solids through the interplay of intermolecular interactions with pronounced differences in strength and directionality.

The ability of polymer and metallic materials to deform without breaking is one of their most useful properties, however, this behavior was only recently discovered in crystalline molecular materials. Attempts to categorize molecular crystals as either mechanically plastic or elastic have relied on basic qualitative observations. In this study, we employ X‐ray quantum crystallography (QCr) to distinguish these distinct mechanical behaviors through a comparative quantitative analysis of three pairs of isostructural organic crystals that demonstrate both plastic and elastic bending. QCr analysis identified subtle yet consistent differences in lattice cohesive energies (LCE) of 1–4 kJ mol ^{− 1} , with higher dispersion energy components and potential energy densities at the bond critical points of intermolecular interactions in elastic relative to plastic crystals. While the intermolecular force constants ( k ) of elastic crystals are systematically higher, k _elastic > k _plastic , the trend in the corresponding pairwise compressibilities (), _elastic > _plastic , is counterintuitive. Contrary to some intuitive considerations, our analysis of slip planes and rugosity does not effectively differentiate between elasticity and plasticity; instead, the QCr‐derived atomic displacement parameters implicate more pronounced lattice vibrations and higher entropy and thus, shallower intermolecular potential wells, in plastically bending crystals.

The explicit confirmation of the identity of desired or side products of a chemical reaction often requires lengthy or iterative purification protocols, combined with multiple analytical procedures that could be restricted by the available sample quantity and purity, or might provide only qualitative information on the chemical composition. Product mixtures with overlapping spectroscopic signals, low solubility, reactivity in solution, poor crystallinity, and multiple sample preparation steps could pose further challenges and currently stand in the way of full automation of product characterization. Being capable of rapidly providing structural details down to atomic scale resolution from nanosized crystalline samples, three-dimensional electron diffraction (3D ED) (microcrystal electron diffraction) effectively overcomes several of these obstacles. Here, we demonstrate the potential for the application of 3D ED in the efficient and rapid characterization of reaction products that are difficult to characterize. Furthermore, the technology utilized in this paper comes with the benefits of reducing the carbon footprint of a synthesis procedure, eliminating redundant steps needed for common characterization methods, and providing a shortcut for characterization without increased costs. We suggest that, based on the speed and minimal sample requirements demonstrated here, coupling 3D ED/MicroED with automated synthetic workflows could help accelerate future drug discovery efforts.

Complex biological visual systems capable of processing light stimuli by variety of synaptic responses to channelize information to brain have been modelled using organic molecular materials which display tunable neuromorphic response.

Solid-state photoreactions are unmatched by their liquid or gaseous counterparts for being spatially and temporally controllable and selective; however, these assets usually come with compromised yields―localized surface reactions are favored that generate a passivating layer of photoproducts and shield the crystal interior from reacting. Here, we demonstrate that this inherent limitation could be circumvented by capitalizing on the disintegrative effects of photodynamic crystals, such as cracking and fracturing, which can expose freshly cleaved surfaces and effectively increase the overall conversion. Upon irradiation with natural or artificial visible light, crystals of two 2-azido-5-phenyl-2,4-dienoate derivatives (1a and 1b) are converted into the corresponding 5-phenyl-1H-pyrrole-2-carboxylate derivatives (2a and 2b). Crystals were observed to crack and fracture throughout the reaction due to the release of dinitrogen, and the cracking occurs preferentially along planes defined by the weakest intermolecular interactions. Laser-flash photolysis in conjunction with density functional theory calculations confirmed that in both solution and in the solid, the triplet excited states of 1a and 1b rearrange to biradicals ³Br1a and ³Br1b, which then release dinitrogen to afford biradicals ³Br2a and ³Br2b; however, in the solid state, the crystal lattice rigidity extends the triplet lifetimes of both 1 and ³Br1. This work highlights the benefits of the “photofracking” that stands for photoinduced crystal disintegration, as a convenient strategy that naturally increases the efficiency of the solid-state reactions without external intervention.

Flexible photothermal materials made of particulate carbon, metal, polymer, or semiconductors often suffer from interfacial incompatibility, leading to cracking and delamination over prolonged use. These limitations make it difficult for flexible composite materials to simultaneously meet the requirements of long‐term interfacial stability and high photothermal performance. Here we circumvented these persistent challenges by using flexible organic crystals, where the absorber is a structurally homogeneous radical cocrystal and strong light absorption is accomplished by charge transfer (CT) between two molecular components. We cocrystallized electron donor perylene (PE) and acceptor naphthalene diimide (NDI) to prepare mechanically flexible, centimeter‐size cocrystals (PE‐NDI), which demonstrate persistent radical characteristics with a spin coherence time of 2.1 µs. Prominent donor–acceptor interaction (−87.7 kJ mol ⁻¹ ) facilitates strong light absorption from 200 to 780 nm, while hydrogen bonds are thought to account for the reversible elastic bending. Excitation at 685 nm yields an extraordinarily high photothermal conversion efficiency of 94%. Integration of PE‐NDI in a thermoelectric generator enabled direct solar energy harvesting via a photo‐thermo‐electric conversion sequence, demonstrating the potential of flexible cocrystals for renewable energy harvesting. This work highlights the untapped potential of mechanically compliant organic crystals as flexible, single‐component, lightweight photothermal materials.

Flexible photothermal materials made of particulate carbon, metal, polymer, or semiconductors often suffer from interfacial incompatibility, leading to cracking and delamination over prolonged use. These limitations make it difficult for flexible composite materials to simultaneously meet the requirements of long‐term interfacial stability and high photothermal performance. Here we circumvented these persistent challenges by using flexible organic crystals, where the absorber is a structurally homogeneous radical cocrystal and strong light absorption is accomplished by charge transfer (CT) between two molecular components. We cocrystallized electron donor perylene (PE) and acceptor naphthalene diimide (NDI) to prepare mechanically flexible, centimeter‐size cocrystals (PE‐NDI), which demonstrate persistent radical characteristics with a spin coherence time of 2.1 µs. Prominent donor–acceptor interaction (−87.7 kJ mol ⁻¹ ) facilitates strong light absorption from 200 to 780 nm, while hydrogen bonds are thought to account for the reversible elastic bending. Excitation at 685 nm yields an extraordinarily high photothermal conversion efficiency of 94%. Integration of PE‐NDI in a thermoelectric generator enabled direct solar energy harvesting via a photo‐thermo‐electric conversion sequence, demonstrating the potential of flexible cocrystals for renewable energy harvesting. This work highlights the untapped potential of mechanically compliant organic crystals as flexible, single‐component, lightweight photothermal materials.

Flexible organic crystals offer significant opportunities for organic electronics; however, their potential applications in fields like flexible sensors are at present limited by poor charge transport that result in failure under reversible conditions. In this report, we propose a universal interfacing design strategy for the fabrication of versatile conductive MXene coatings on the surface of flexible organic crystals that preserve the electric conductivity of the MXenes while they also remain mechanically flexible and robust across a wide temperature range of nearly 300°C both above and below ambient temperature. This new sub‐class of hybrid materials based on adaptive organic crystals undergoes reversible changes in the crystal structure upon deformation, while they also engender stable electrical conductivity and retain deformation sensitivity from about −196°C to 100°C. A wireless sensing system based on these materials was constructed to monitor bionic finger movements that demonstrate the potential for human‐machine interfacing and medical monitoring applications. The structural stability of this and similar devices that utilize crystal‐MXene hybrid materials under non‐ambient temperatures provide an innovative solution to the current challenges with occasional failure of low‐temperature mechanical sensing systems in extreme environments, and specifically such that are used in lunar and deep‐space explorations.

Fruits and nuts develop resilient outer shells to safeguard their embryos against environmental hazards and predators. The nuts of the marri tree ( Corymbia calophylla ) possess unusual strength and toughness. In contrast to other tough nuts, seasoned parrots avoid cracking them and instead resort to drawn‐out attempts to snatch their seeds from a dispersal opening at their base. Here, we reveal the subtle strengthening mechanisms of the marri nut and compare its mechanical response and properties to those of other nuts and commercial materials. The analysis involves an extensive examination of the various material phases of the nutshell, the chemical composition of its fibers, and an analysis of its microscopic and macroscopic mechanical properties. The study reveals that, akin to self‐standing structures, the interplay of the densely packed fibers of the shell held together by a highly ductile soft matrix, while arranged in a spherical configuration, gives the nut its notable toughness, ductility, strength, and remarkable fracture resistance. Additionally, we design and test the mechanical behavior of a bioinspired interpenetrating phase composite material mimicking the nut's microstructure, demonstrating comparable deformability and toughness. These findings lay a new foundation for designing highly efficient bioinspired structures for energy absorption, protection, and armor.