Efficient Non‐doped Blue Fluorescent Organic Light‐Emitting Diodes Based on Anthracene–Triphenylethylene Derivatives

The development of efficient blue materials has been a continuous research topic in the field of organic light‐emitting diodes (OLEDs). In this paper, three aggregation‐induced emission enhancement active blue emitters, PIAnTPE, TPAAnTPE and CzAnTPE, are successfully synthesized by attaching a triphenylethylene unit and phenanthroimidazole/triphenylamine/carbazole moieties to the 9,10‐positions of anthracene, respectively. The three compounds exhibit good thermal stabilities, appropriate for the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels and display high photoluminescence quantum yields (PLQYs) of 65, 70 and 46 % in the solid state. Non‐doped blue devices using PIAnTPE, TPAAnTPE and CzAnTPE as the emitting layers show good electroluminescent performances, with the maximum external quantum efficiencies (EQEs) of 4.46, 4.13 and 4.04 %, respectively. More importantly, EQEs of all the three devices can be still retained when the luminescence reaches 1000 cd m^?2, exhibiting quite small efficiency roll‐offs in the non‐doped OLEDs.     

Template‐Free Synthesis of a Molecular Solomon Link by Two‐Component Self‐Assembly

A molecular Solomon link was synthesized in high yield through the template‐free, coordination‐driven self‐assembly of a carbazole‐functionalized donor and a tetracene‐based dinuclear ruthenium(II) acceptor. The doubly interlocked topology was realized by a strategically chosen ligand which was capable of participating in multiple CH ??? π and π–π interactions, as evidenced from single‐crystal X‐ray analysis and computational studies. This method is the first example of a two‐component self‐assembly of a molecular Solomon link using a directional bonding approach. The donor alone was not responsible for the construction of the Solomon link, and was confirmed by its noncatenane self‐assemblies obtained with other similar ruthenium(II) acceptors.     

Hetero Face‐to‐Face Porphyrin Array with Cooperative Effects of Coordination and Host–Guest Complexation

We successfully synthesized a hetero face‐to‐face porphyrin array composed of ZnTPP and RuTPP(DABCO)₂ (TPP: 5, 10, 15, 20‐tetraphenylporphyrin, DABCO: 1,4‐diazabi‐cyclo[2.2.2]octane) in 2:1 molar ratio. A cyclic Zn porphyrin dimer (ZnCP) was also used as the host molecule for the Ru porphyrin. In the latter, the Ru‐DABCO bonding in RuTPP(DABCO)₂ was stabilized by the host‐guest complexation. Reaction progress kinetic analysis of the ligand substitution reaction of RuTPP(DABCO)₂ and that in ZnCP revealed the stabilization mechanism of the Ru‐DABCO bonding. Photoinduced electron transfer (PET) from the Zn porphyrin to the Ru porphyrin was observed in the porphyrin array. The host‐guest stabilization of unstable complex for construction of a donor—acceptor–donor structure is expected to be a new method for an artificial photosynthesis.     

Crystal‐Structure‐Guided Design of Self‐Assembling RNA Nanotriangles

RNA nanotechnology uses RNA structural motifs to build nanosized architectures that assemble through selective base‐pair interactions. Herein, we report the crystal‐structure‐guided design of highly stable RNA nanotriangles that self‐assemble cooperatively from short oligonucleotides. The crystal structure of an 81 nucleotide nanotriangle determined at 2.6 Å resolution reveals the so‐far smallest circularly closed nanoobject made entirely of double‐stranded RNA. The assembly of the nanotriangle architecture involved RNA corner motifs that were derived from ligand‐responsive RNA switches, which offer the opportunity to control self‐assembly and dissociation.     

End‐to‐End Self‐Assembly of Semiconductor Nanorods in Water by Using an Amphiphilic Surface Design

One‐dimensional (1D) self‐assemblies of nanocrystals are of interest because of their vectorial and polymer‐like dynamic properties. Herein, we report a simple method to prepare elongated assemblies of semiconductor nanorods (NRs) through end‐to‐end self‐assembly. Short‐chained water‐soluble thiols were employed as surface ligands for CdSe NRs having a wurtzite crystal structure. The site‐specific capping of NRs with these ligands rendered the surface of the NRs amphiphilic. The amphiphilic CdSe NRs self‐assembled to form elongated wires by end‐to‐end attachment driven by the hydrophobic effect operating between uncapped NR ends. The end‐to‐end assembly technique was further applied to CdS NRs and CdSe tetrapods (TPs) with a wurtzite structure.     

Tertiary Amines Differentiated from Primary and Secondary Amines by Active Ester‐Functionalized Hexabenzoperylene in Field Effect Transistors

Herein, we report two novel derivatives of hexabenzoperylene (HBP) that are functionalized with ester groups. Methyl acetate functionalized HBP ( 1 ) in single crystals self‐assembles into a supramolecular nanosheet, which has a two‐dimensional π‐stack of HBP sandwiched between two layers of ester groups. With the same self‐assembly motif, active ester‐functionalized HBP ( 2 ) in field effect transistors has enabled differentiation of tertiary amines from primary and secondary amines, in agreement with the fact that active ester reacts with primary and secondary amines but not with tertiary amines to form amides.     

Synthesis of Poly(benzothiadiazole‐co‐dithienobenzodithiophenes) and Effect of Thiophene Insertion for High‐Performance Polymer Solar Cells

We describe herein the synthesis of novel donor–acceptor conjugated polymers with dithienobenzodithiophenes (DTBDT) as the electron donor and 2,1,3‐benzothiadiazole as the electron acceptor for high‐performance organic photovoltaics (OPVs). We studied the effects of strategically inserting thiophene into the DTBDT as a substituent on the skeletal structure on the opto‐electronic performances of fabricated devices. From UV/Vis absorption, electrochemical, and field‐effect transistor analyses, we found that the thiophene‐containing DTBDT derivative can substantially increase the orbital overlap area between adjacent conjugated chains and thus dramatically enhance charge‐carrier mobility up to 0.55 cm² V^?1 s^?1. The outstanding charge‐transport characteristics of this polymer allowed the realization of high‐performance organic solar cells with a power conversion efficiency (PCE) of 5.1 %. Detailed studies on the morphological factors that enable the maximum PCE of the polymer solar cells are discussed along with a hole/electron mobility analysis based on the space‐charge‐limited current model.     

Smart Organic Two‐Dimensional Materials Based on a Rational Combination of Non‐covalent Interactions

Rational design of organic 2D (O2D) materials has made some progress, but it is still in its infancy. A class of self‐assembling small molecules is presented that form nano/microscale supramolecular 2D materials in aqueous media. A judicial combination of four different intermolecular interactions forms the basis for the robust formation of these ultrathin assemblies. These assemblies can be programmed to disassemble in response to a specific protein and release its non‐covalently bound guest molecules.     

Porous,Conductive Metal‐Triazolates and Their Structural Elucidation by the Charge‐Flipping Method

A new family of porous crystals was prepared by combining 1H‐1,2,3‐triazole and divalent metal ions (Mg, Mn, Fe, Co, Cu, and Zn) to give six isostructural metal‐triazolates (termed MET‐1 to 6). These materials are prepared as microcrystalline powders, which give intense X‐ray diffraction lines. Without previous knowledge of the expected structure, it was possible to apply the newly developed charge‐flipping method to solve the complex crystal structure of METs: all the metal ions are octahedrally coordinated to the nitrogen atoms of triazolate such that five metal centers are joined through bridging triazolate ions to form super‐tetrahedral units that lie at the vertexes of a diamond‐type structure. The variation in the size of metal ions across the series provides for precise control of pore apertures to a fraction of an Angstrom in the range 4.5 to 6.1 Å. MET frameworks have permanent porosity and display surface areas as high as some of the most porous zeolites, with one member of this family, MET‐3, exhibiting significant electrical conductivity.     

Tyrosine‐Based Ionic Liquid Crystals: Switching from a Smectic A to a Columnar Mesophase by Exchange of the Spherical Counterion

Synthetic strategies were developed to prepare l ‐tyrosine‐based ionic liquid crystals with structural variations at the carboxylic and phenolic OH groups as well as the amino functionality. Salt metathesis additionally led to counterion variation. The liquid‐crystalline properties were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X‐ray diffraction (WAXS, SAXS). The symmetrical ILC chlorides bearing the same alkyl chain at both the ester and ether but either an acyclic or cyclic guanidinium group displayed enantiotropic SmA₂ mesophases with phase widths of 31–88 K irrespective of the head group. It was particularly the replacement of chloride in the acyclic guanidinium ILC by hexafluorophosphate that induced a phase change from SmA₂ to Col_r. This phase change was attributed to a higher curvature of the interface due to the larger anion, which increased the effective head group cross‐sectional area of the amphiphilic ILC. The unsymmetrical acyclic guanidinium chlorides, bearing a constant C₁₄ ester and variable alkyl chains on the phenolic position, formed enantiotropic SmA₂ phases. The derivative with the largest difference in chain lengths, however, displayed a Col_r phase, resulting from discoid aggregates of the cone‐shaped guanidinium chloride. The results are discussed in terms of the packing parameters, which indicate that the phase behaviour of the thermotropic tyrosine‐based ILCs shows analogies to those of lyotropic liquid crystals.     

Exchange of Coordinated Solvent During Crystallization of a Metal–Organic Framework Observed by In Situ High‐Energy X‐ray Diffraction

Using time‐resolved monochromatic high energy X‐ray diffraction, we present an in situ study of the solvothermal crystallisation of a new MOF [Yb₂(BDC)₃(DMF)₂]?H₂O (BDC=benzene‐1,4‐dicarboxylate and DMF=N,N‐dimethylformamide) under solvothermal conditions, from mixed water/DMF solvent. Analysis of high resolution powder patterns obtained reveals an evolution of lattice parameters and electron density during the crystallisation process and Rietveld analysis shows that this is due to a gradual topochemical replacement of coordinated solvent molecules. The water initially coordinated to Yb³⁺ is replaced by DMF as the reaction progresses.     

Self‐Directed Orientation of Molecular Columns Based on n‐Type Hexaazatrinaphthylenes (HATNAs) for Electron Transport

Self‐organizing n‐type hexaazatrinaphthylenes (HATNAs) with various bay‐located side chains have been synthesized. The HATNA derivatives are able to form long‐range molecular columns with self‐directed growth directions. In particular, alkyl‐substituted HATNAs showed in‐plane molecular columns with axes parallel to substrates, whereas the columnar orientation of the HATNAs with alkylethynyl or alkylthio groups strongly depended on the length of the introduced side chains. Interestingly, the derivative with octylthio chains exhibited out‐of‐plane molecular columns, in which electron mobility of up to 10^?3 cm² V^?1 s^?1 was determined through the time‐of‐flight technique, highlighting the fact that such molecular columns based on bay‐substituted HATNAs are promising n‐type semiconductors for device applications.     

Synthesis of l‐ and d‐Ubiquitin by One‐Pot Ligation and Metal‐Free Desulfurization

Native chemical ligation combined with desulfurization has become a powerful strategy for the chemical synthesis of proteins. Here we describe the use of a new thiol additive, methyl thioglycolate, to accomplish one‐pot native chemical ligation and metal‐free desulfurization for chemical protein synthesis. This one‐pot strategy was used to prepare ubiquitin from two or three peptide segments. Circular dichroism spectroscopy and racemic protein X‐ray crystallography confirmed the correct folding of ubiquitin. Our results demonstrate that proteins synthesized chemically by streamlined 9‐fluorenylmethoxycarbonyl (Fmoc) solid‐phase peptide synthesis coupled with a one‐pot ligation–desulfurization strategy can supply useful molecules with sufficient purity for crystallographic studies.     

Benign‐by‐Design Solventless Mechanochemical Synthesis of Three‐, Two‐, and One‐Dimensional Hybrid Perovskites

Organic–inorganic hybrid perovskites have attracted significant attention owing to their extraordinary optoelectronic properties with applications in the fields of solar energy, lighting, photodetectors, and lasers. The rational design of these hybrid materials is a key factor in the optimization of their performance in perovskite‐based devices. Herein, a mechanochemical approach is proposed as a highly efficient, simple, and reproducible method for the preparation of four types of hybrid perovskites, which were obtained in large amounts as polycrystalline powders with high purity and excellent optoelectronics properties. Two archetypal three‐dimensional (3D) perovskites (MAPbI₃ and FAPbI₃) were synthesized, together with a bidimensional (2D) perovskite (Gua₂PbI₄) and a “double‐chain” one‐dimensional (1D) perovskite (GuaPbI₃), whose structure was elucidated by X‐ray diffraction.     

A Study of the Interaction Between Cucurbit[8]uril and Alkyl‐Substituted 4‐Pyrrolidinopyridinium Salts

The interaction between cucuribit[8]uril (Q[8]) and a series of 4‐pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4‐(C₄H₈N)C₅H₅NRBr, where R=Et (g1), n‐butyl (g2), n‐pentyl (g3), n‐hexyl (g4), n‐octyl (g5), n‐dodecyl (g6), has been studied in aqueous solution by ¹H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. Single crystal X‐ray diffraction revealed the structure of the host–guest complexes for g1, g2, g3, and g5. In each case, the Q[8] contains two guest molecules in a centrosymmetric dimer. The orientation of the guest molecule changes as the alkyl chain increases in length. Interestingly, in the solid state, the inclusion complexes identified are different from those observed in solution, and furthermore, in the case of g3, Q[8] exhibits two different interactions with the guest. In solution, the length of the alkyl chain plays a significant role in determining the type of host–guest interaction present.     

Influence of Backbone Chlorination on the Electronic Properties of Diketopyrrolopyrrole (DPP)‐Based Dimers

Chlorination of π‐conjugated backbones is garnering great interest because of fine‐tuning electronic properties of conjugated materials for organic devices. Herein we report a synthesis of thiophene‐based diketopyrrolopyrrole (DPP) dimers and their chlorinated counterparts by introducing a chlorine atom in the outer thiophene ring to investigate the influence of the chlorination on charge transport. The backbone chlorination lowers both the HOMO and the LUMO of the dimers and leads to a blue‐shift of maximum absorption in compared to unsubstituted counterparts. X‐ray analysis reveals that the chlorine atom prompts the outer thiophene ring out of the planarity of the backbone with a relatively large torsional angle. The chlorinated dimers exhibit slipped one‐dimensional packing decorated with multiple intermolecular interactions, because of a combination of a negative inductive effect and a positive mesomeric effect of the halogen atom, which might facilitate charge transport within the oligomeric backbones. The mobility in the single‐crystal OFET devices of the chlorinated dimers is up to 1.5 cm² V^?1 s^?1, which is two times higher than that of the non‐chlorinated DPP dimers. Our results indicate that the chlorine atom plays a key role in directing non‐covalent interactions to lock the slipped stacks, enabling electronic coupling between adjacent molecules for efficient charge transport. In addition, our results also demonstrate that these DPP dimers with straight n‐octyl chains exhibit higher mobilities than the dimers with branched 2‐ethylhexyl chains.     

Effect of the Molecular Weight of AB Diblock Copolymers on the Lamellar Orientation in Thin Films: Theory and Experiment

We propose a theoretical explanation of the parallel and perpendicular lamellar orientations in free surface films of symmetric polystyrene‐block‐polybutadiene diblock copolymers on silicon substrates (with a native SiO_x layer). Two approaches are developed: A correction to the strong segregation theory and a qualitative analysis of the intermediate segregation regime. We show that the perpendicular orientation of the lamellae formed by the molecules of high molecular weight is stabilized by A–B interfacial interactions. They are weaker in the case of the perpendicular orientation of the lamellae, whereas the surface tension coefficient of the A–B interface decreases with the increase of the molecular weight.

     

Differential Adsorption of l‐ and d‐Lysine on Achiral MFI Zeolites as Determined by Synchrotron X‐Ray Powder Diffraction and Thermogravimetric Analysis

Reported here is the first crystallographic observation of stereospecific bindings of l ‐ and d ‐lysine (Lys) in achiral MFI zeolites. The MFI structure offers inherent geometric and internal confinement effects for the enantiomeric difference in l ‐ and d ‐Lys adsorption. Notable differences have been observed by circular dichroism (CD) spectroscopy and thermogravimetric analysis (TGA). Distinct l ‐ and d ‐Lys adsorption behaviours on the H‐ZSM‐5 framework have been revealed by the Rietveld refinement of high‐resolution synchrotron X‐ray powder diffraction (SXRD) data and the density‐functional theory (DFT) calculations. Despite demonstrating the approach for l ‐ and d ‐Lys over MFI zeolites at an atomistic resolution, the differential adsorption study sheds light on the rational engineering of molecular interaction(s) with achiral microporous materials for chiral separation purposes.     

Morphology of Imidazolium‐Based Ionic Liquids as Deposited by Vapor Deposition: Micro‐/Nanodroplets and Thin Films

The morphology of micro‐ and nanodroplets and thin films of ionic liquids (ILs) prepared through physical vapor deposition is presented. The morphology of droplets deposited on indium‐tin‐oxide‐coated glass is presented for the extended 1‐alkyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([C_nC₁im][Ntf₂]; n=1–8) series, and the results show the nanostructuration of ILs. The use of in‐vacuum energetic particles enhances/increases the nanodroplets mobility/coalescence mechanisms and can be a pathway to the fabrication of thin IL films.     

Molecular Design,Circularly Polarized Luminescence,and Helical Self‐Assembly of Chiral Aggregation‐Induced Emission Molecules

Aggregation‐induced emission luminogens (AIEgens) are a new class of luminophors, which are non‐emissive in solution, but emit intensively upon aggregation. By properly designing the chemical structures of the AIEgens, their aggregation process can be tuned towards a desired direction to give diverse novel luminescent architectures of micelles, rods, and helical fibers. AIEgens represent a kind of promising building block for the fabrication of luminescent micro/nanostructures with controllable morphologies. In this review, we describe our recent work in this research area, focusing on the molecular design, circularly polarized luminescence properties, and helical self‐assembly behavior of AIEgens.