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Two diastereomeric crystalline steroid dimers were obtained by acid-catalyzed double acetalization of (20S)-5α-pregnan-3β,16β,20-triol 3-monoacetate with terephtalaldehyde. These compounds were characterized by NMR in solution, MS, single-crystal X-ray diffraction, and variable-temperature solid-state NMR by

In this work we report the fabrication of organic light-emitting diodes based on the carbazole derivative 1,4-bis(9H-carbazol-9-yl)phenyl)ethynyl)benzene, showing excellent CIE coordinates (0.31, 0.33). To achieve this, we developed an initial architecture where the emissive layer was sandwiched between ITO/PEDOT:PSS, that acted as anode/hole transport layer, and Ca/Ag as cathode. The electroluminescence for this initial architecture was similar to the photoluminescence of the carbazole derivative, showing blue emission with CIE coordinates (0.20, 0.22). Subsequently, when the thickness of the PEDOT:PSS layer was reduced from 60 nm to 30 nm, the electroluminescence changed from blue to greenish, with new CIE coordinates (0.26, 0.45). We attributed this effect to intermolecular interactions producing the observed emission from excitons within the emissive layer and exciplexes at the interface of the hole transport and the emissive layer. Based on these preliminary results, a second architecture using 15 nm of 4,7-diphenyl-1,10-phenanthroline as the electron transport layer (ETL) was developed. In this manner, the observed electroluminescence spectrum became wider and the devices showed white emission, with outstanding CIE coordinates (0.31, 0.33). For this architecture, new exciplexes generated at the interface between emissive and electron transport layer emitted at longer wavelengths giving the complementary emission for white light. The generation of exciplex states at the two interfaces of the emitting layer made possible the fabrication of white light organic diodes with the simplest and more commonly used OLED architecture. Interestingly, by using an ETL in the second architecture, and by changing the thickness of the hole transport layer from 60 to 30 nm, it was possible to further fine-tune the white light from cold to warm emission.

A new rotor exhibits rich solvatomorphism behavior with eight X-ray structures obtained. A heterogeneous solid obtained by mechanical stress exhibited a dominant isotropic 2H line shape at high temperatures. The motion occurs only in the amorphous component of this solid, with an Ea of 7.4 kcal mol-1 and a low pre-exponential factor A of 6.22 × 1010 s-1, which indicates that the motion requires the distortion of the molecular axis.

The aggregation behavior and its influence on the intramolecular motion of three highly conjugated solid-state molecular rotors 2–4 with alkyl groups were investigated by a combination of fluoresce...

We report for the first time the high sorption properties of a molecular rotor with no permanent voids or channels in its crystal structure. Such crystalline phase originates from THF, DCM, or the irreversible desolvation of entrapped benzene molecules. From these, the benzene in its solvate form acts as rotation stopper, as supported by dynamic characterization using solid-state 2H NMR experiments. In the solvent-free form, the diffusion of small quantities of iodine vapors caused a significant change in the intramolecular rotation, increasing the known activation energy to rotation from 8.5 to 10.6 kcal mol–1. Notably, those results paved the way for the discovery of the high CO2 uptake (201.6 cm3 g–1 at 196 K, under 1 atm) and acetone (5 wt %), a sorption property that was attributed to both, the restriction of the molecular rotation at low temperatures and the flexibility of the molecular axle made of conjugated p-(ethynylphenylene), surrounded by carbazole.

A crystalline, porous Metal–Organic Polyhedron (MOP) 4 was readily assembled starting from 9H-carbazole-3,6-dicarboxylic acid, which was synthesised in only three steps. The single crystal X-ray diffraction analysis of the resulting supramolecule evidenced voids that were occupied by coordinated as well as uncoordinated solvent molecules from the solvothermal reaction. Careful analysis of its desolvation process, activating the sample at 150 °C and 10−5 bar (followed by FTIR), evidenced that all solvents were completely removed, leaving an empty but nevertheless crystalline MOP with coordinatively-unsaturated Cu(II) sites that was studied for gas adsorption using N2 at 77 K, and CO2 at 196 K. Notably, carbon dioxide was found to be strongly adsorbed in the activated 4 (12.1 mmol g−1, 53.2 wt%) with a molar enthalpy of adsorption of ΔH = 65.12 kJ mol−1, revealing a great selectivity over nitrogen, which in turn showed negligible uptake under the same activation conditions. In situ Raman experiments demonstrated the direct interaction of CO2 molecules and coordinatively-unsaturated Cu(II) sites within 4.

Herein we report the synthesis of the highly stable crystalline carbazole-based rotor 3 with simultaneous rapid solid state internal rotation and good fluorescence emission. Single crystal and powder X-ray diffraction studies along with microscopy revealed a phase transition from a labile benzene solvate (phase I) to highly stable crystals (phase II) that feature fast intramolecular rotation in the megahertz regime at room temperature, according to variable temperature 2H solid state NMR experiments using isotopically enriched analogues. In addition to the megahertz rotation within its crystals, this crystal phase II displays enhanced solid state fluorescence with a higher quantum yield of ϕ = 0.28, relative to the emission of this compound in THF solution (ϕ = 0.06). These two solid state properties are significantly different from shorter compounds 1 and 2 (static and nonemissive) included here for comparison purposes.

Materials Acceleration Platforms are an emerging paradigm to accelerate materials discovery as an effort to develop technology solutions that can help address or mitigate climate change concerns. These platforms combine artificial intelligence, robotic systems, and high-performance computing to achieve autonomous experimentation. Nevertheless, their development faces challenges to achieve full autonomy. In this work, we present state-of-the-art robotic platforms and machine learning approaches for autonomous experimentation, their integration, and applications, particularly in the field of materials for clean energy technologies. Later, we discuss the challenges and suggest improvements to be considered in the endeavor to accomplish autonomous experimentation.

The use of the multicomponent Ugi reaction to rapidly prepare a library of dumbbell-like molecular rotors is highlighted here. The synthetic strategy consisted of the atom-economic access to 15 bulky and structurally diverse iodinated stators, which were cross-coupled to the 1,4-diethynylphenylene rotator. From those experiments, up to six rotors 1a–c and 1l–n were obtained, with yields ranging from 35 to 69% per coupled C–C bond. In addition to the framework diversity, five of these compounds showed aggregate-enhanced emission properties thanks to their conjugated 1,4-bis(phenylethynyl)benzene cores, a property that rises by increasing the water fraction (fw) in their THF solutions. The results highlight the significance of the diversity-oriented synthesis of rapid access to new molecular fluorescent rotors.

We describe the synthesis and crystallization of two macrocyclic steroidal compounds labeled (Z)-1F2 and (E)-1F2, envisioned to work as molecular rotors with 1,4-diethynyl-2,3-difluorophenylene rotators. The introduction of the fluorine atoms rendered different crystal arrays that were fully characterized by X-ray diffraction, solid state 13C NMR, and calorimetric experiments. In both isomers, the central molecular fragments point the o-fluorine atoms toward their cavity, highlighting the preferred orientation in the solid state. By analyzing the crystal array, it can be seen that while the fluorinated Z isomer is isomorphic to its non-fluorinated analogue, the E isomer shows significant structural variations in an unanticipated crystal array with two molecules per asymmetric unit (Z′ = 2).

Thirteen steroidal derivatives were synthesized through a Sonogashira cross-coupling reaction which has been found to be an excellent synthetic strategy to introduce halo-aromatic groups into C-17-ethynyl substituted steroidal frameworks. The structural modification was performed on ethynylestradiol, mestranol, norethisterone, ethisterone and 3-ethynyl-3-epi-sarsasapogenin. The solid state study by X-ray diffraction showed that most of them belong to the orthorhombic P212121 space group and the whole family has an “L” conformation, regardless of the nature of the steroid A-ring (3-hydroxy-aromatic or 3-oxo). Due to the presence of several moieties which are susceptible to forming secondary interactions, the crystalline packing is governed by O–H⋯O, C–H⋯O, and C–H⋯π interactions, and only 17α-(4′-iodophenylethynyl)-3-methoxy-estra-1,3,5(10)-trien-17-β-ol (mestranol derivative 3) showed an iodine–iodine interaction (dI⋯I = 4.116 A). The crystalline packing for ethynylestradiol derivatives 1, 2 and 4 showed the formation of holes with diameters greater than 5.2 A suggesting their potential application in host guest chemistry or as porous materials.