Thermo- and Solvent-Responsive Polymer Complex Created from Supramolecular Complexation between a Helix-Forming Polysaccharide and a Cationic Polythiophene

The helical structure is one of key structural components for both biological systems and artificial chiral systems. So far, we have succeeded in fabricating “tight” insulated molecular wires consisting of a triple-stranded cohelical structure formed through supramolecular wrapping of synthetic polymers by a helix-forming polysaccharide (schizophyllan). Herein, we have designed a new modified polysaccharide (Cur-oeg) to form a “loose” macromolecular complex with a conjugated polymer (CP) that allows structural changes in response to external stimuli. Cur-oeg forms a helical complex with an achiral cationic polythiophene (PT1), and the effective conjugation length is changed by temperature, showing a large absorption peak shift from 403 to 482 nm between 85 and 5 °C. According to the change in the conjugation system, the fluorescence and the induced circular dichroism show the continuous spectral shifts under temperature control. The color changes in the absorption and the fluorescence are detectable with observation by the naked eye and are reversibly controlled under thermal cycles, indicating that this system has the function of a “molecular thermometer”. It is shown that the induced thermoresponsiveness is associated with structural rearrangement of the helical conformation of PT1 in the complex. Moreover, another unique responsiveness is discovered for the film state: that is, the film color is varied when it is exposed to the vapor of water or methanol (vaporchromism), resulting from the structural change of PT1 occurring even in the film state. These flexible molecular motions in both the solution state and the film state can be applicable to the design of CP-based smart sensors, polarized materials, switching devices, etc

Interesting Behavior of Geranic Acid during the Beer Brewing Process: Why Could Geranic Acid Remain at a Higher Level Only in the Beer Using Sorachi Ace Hops?

Hops are among the most important ingredients in beer that contribute to beer flavor. Consequently, novel types of hops have been bred and widely used worldwide. For example, the Sorachi Ace hop imparts characteristic varietal aromas, including woody, pine-like, citrus, dill-like, and lemongrass-like aromas, to the finished beer. In our previous study, the unique volatile compound geranic acid was significantly detected only in the test beer brewed with the Sorachi Ace hop; moreover, the coexistence of geranic acid and other hop-derived flavor compounds could result in the characteristic aroma of the Sorachi Ace beers. In this study, selected hop-derived flavor compounds, including geranic acid, were compared among 17 hop varieties. The geranic acid content in the Sorachi Ace hop was the highest among the studied hops. We also investigated the behavior of geranic acid and related flavor compounds throughout the fermentation process. The content of geranic acid was higher than those of the other compounds during fermentation. Next, we compared the concentrations of these compounds in kettle-, late-, and dry-hopped beers using Sorachi Ace hop. The results revealed that geranic acid remained at higher concentrations from the worts to finished beers despite the decrease in the content of other hop-derived flavor compounds as a result of evaporation and/or other factors during brewing. Further, geranic acid could remain at high levels in the test-brewed beers with Sorachi Ace hops because of its behavior as an acid throughout the brewing process, including during wort boiling and fermentation

Conformation Control of a Conjugated Polymer through Complexation with Bile Acids Generates Its Novel Spectral and Morphological Properties

Control of higher-order polymer structures attracts a great deal of interest for many researchers when they lead to the development of materials having various advanced functions. Among them, conjugated polymers that are useful as starting materials in the design of molecular wires are particularly attractive. However, an equilibrium existing between isolated chains and bundled aggregates is inevitable and has made their physical properties very complicated. As an attempt to simplify this situation, we previously reported that a polymer chain of a water-soluble polythiophene could be isolated through complexation with a helix-forming polysaccharide. More recently, a covalently self-threading polythiophene was reported, the main chain of which was physically protected from self-folding and chain–chain π-stacking. In this report, we wish to report a new strategy to isolate a water-soluble polythiophene and to control its higher-order structure by a supramolecular approach: that is, among a few bile acids, lithocholate can form stoichiometric complexes with cationic polythiophene to isolate the polymer chain, and the higher-order structure is changeable by the molar ratio. The optical and morphological studies have been thoroughly performed, and the resultant complex has been applied to the selective recognition of two AMP structural isomers

Intramolecular Noncovalent Interactions Facilitate Thermally Activated Delayed Fluorescence (TADF)

In the conventional molecular design of thermally activated delayed fluorescence (TADF) organic emitters, simultaneously achieving a fast rate of reverse intersystem crossing (RISC) from the triplet to the singlet manifold and a fast rate of radiative decay is a challenging task. A number of recent experimental data, however, point to TADF emitters with intramolecular π–π interactions as a potential pathway to overcome the issue. Here, we report a comprehensive investigation of TADF emitters with intramolecular π···π or lone-pair···π noncovalent interactions. We uncover the impact of those intramolecular noncovalent interactions on the TADF properties. In particular, we find that folded geometries in TADF molecules can trigger lone-pair···π interactions, introduce a n → π* character of the relevant transitions, enhance the singlet–triplet spin–orbit coupling, and ultimately greatly facilitate the RISC process. This work provides a robust foundation for the molecular design of a novel class of highly efficient TADF emitters in which intramolecular noncovalent interactions play a critical function

Utilization of Multi-Heterodonors in Thermally Activated Delayed Fluorescence Molecules and Their High Performance Bluish-Green Organic Light-Emitting Diodes

We report a series of pentacarbazolyl-benzonitrile derivatives such as 2,4,6-tri­(9H-carbazol-9-yl)-3,5-bis­(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)­benzonitrile (mPyBN), 3,5-bis­(3,6-bis­(4-(trifluoromethyl)­phenyl)-9H-carbazol-9-yl)-2,4,6-tri­(9H-carbazol-9-yl)­benzonitrile (pCF3BN), 2,4,6-tri­(9H-carbazol-9-yl)-3-(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)-5-(3,6-diphenyl-9H-carbazol-9-yl)­benzonitrile (PyPhBN), 3-(3,6-bis­(4-(trifluoromethyl)­phenyl)-9H-carbazol-9-yl)-2,4,6-tri­(9H-carbazol-9-yl)-5-(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)­benzonitrile (PyCF3BN), and 3-(3,6-bis­(4-(trifluoromethyl)­phenyl)-9H-carbazol-9-yl)-2,6-di­(9H-carbazol-9-yl)-5-(3,6-di­(pyridin-3-yl)-9H-carbazol-9-yl)-4-(9H-pyrido­[3,4-b]­indol-9-yl)­benzonitrile (CbPyCF3BN) in which some of the carbazoles are substituted with modified 3,5-diphenyl carbazoles, exhibiting thermally activated delayed fluorescence (TADF) properties. These emitters comprised two, three, and four different types of donors, capable of bluish-green emission of around 480 nm with relatively high photoluminescence quantum yields over 90% in solution. Emitters, namely, PyPhBN, PyCF3BN, and CbPyCF3BN, composed of three and four different types of donors endowed a rather short delayed lifetime (τd) of 4.25, 5.01, and 3.65 μs in their film state, respectively. Bluish-green organic light-emitting diodes based on PyPhBN, PyCF3BN, and CbPyCF3BN exhibit a high external quantum efficiency of 20.6, 19.5, and 19.6%, respectively, with unsurpassed efficiency roll-off behavior. These results indicate that the TADF properties of multidonor type molecules can be manipulated by controlling the types and number of electron donor units

Stereochemistry-Dependent, Mechanoresponsive Supramolecular Host Assemblies for Fullerenes: A Guest-Induced Enhancement of Thixotropy

Self-assembly behaviors of a series of systems (G1, G2, and G3) possessing same organic building blocks based on a substituted anthracene have been investigated in decalin. G2 and G3 are dominated by head-to-tail (ht) and head-to-head (hh) type dimers of G1, respectively. G1 gives a thermoresponsive gel that behaves ideally, showing frequency-independent elastic and viscous moduli. Interestingly, G2 produces a thixotropic gel that shows the signature of structural relaxation, signifying the dynamic nature of the system. In contrast, G3 remains fluidlike. As investigated by scanning electron microscopy (SEM), in the assembly process of G2, first disklike nanoaggregates are formed, and in the second step these aggregates interact to construct the densely packed secondary assembly. A transition from secondary assembly to primary assembly under shear initiates the mechanoresponsive destruction of the gel. In the self-assembly process, G1 propagates in a one-dimensional fashion, whereas G2 and G3 can propagate in a two-dimensionional fashion. The same side orientation of the substituents in G3 facilitates the formation of a compact closed-shell-type structure, which results in the generation of isolated nanocrystals. The long-range weak interaction together with the capability of propagating in two dimensions is found to be essential for the construction of such a mechanoresponsive assembly. C60 and C70 could be incorporated successfully in G2 assembly to develop mechanoresponsive fullerene assemblies. The presence of fullerenes not only enhances the elastic properties of G2 but also intensifies the thixotropy. C70 appears to be a superior guest in terms of property enhancement due to its better size fitting with the concave-shaped host

Exact Solution of Kinetic Analysis for Thermally Activated Delayed Fluorescence Materials

The photophysical analysis of thermally activated delayed fluorescence (TADF) materials has become instrumental for providing insights into their stability and performance, which is not only relevant for organic light-emitting diodes but also for other applications such as sensing, imaging, and photocatalysis. Thus, a deeper understanding of the photophysics underpinning the TADF mechanism is required to push materials design further. Previously reported analyses in the literature of the kinetics of the various processes occurring in a TADF material rely on several a priori assumptions to estimate the rate constants for forward and reverse intersystem crossing. In this report, we demonstrate a method to determine these rate constants using a three-state model together with a steady-state approximation and, importantly, no additional assumptions. Further, we derive the exact rate equations, greatly facilitating a comparison of the TADF properties of structurally diverse emitters and providing a comprehensive understanding of the photophysics of these systems

Sequential Multiple Borylation Toward an Ultrapure Green Thermally Activated Delayed Fluorescence Material

Multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters have emerged as an important component of organic light-emitting diodes (OLEDs) because of their narrowband emission and high exciton utilization efficiency. However, the chemical space of MR-TADF emitters remains mostly unexplored because of the lack of suitable synthetic protocols. Herein, we demonstrate a sequential multiple borylation reaction that provides new synthetically accessible chemical space. ω-DABNA, the proof-of-concept material, exhibited narrowband green TADF with a full width at half-maximum of 22 nm and a small singlet–triplet energy gap of 13 meV. The OLED employing it as an emitter exhibited electroluminescence at 512 nm, with Commission International de l’Éclairage coordinates of (0.13, 0.73) and a high external quantum efficiency (EQE) of 31.1%. Moreover, the device showed minimum efficiency roll-off, with an EQE of 29.4% at 1000 cd m–2

DataSheet1_Multiple resonance type thermally activated delayed fluorescence by dibenzo [1,4] azaborine derivatives.docx

We studied the photophysical and electroluminescent (EL) characteristics of a series of azaborine derivatives having a pair of boron and nitrogen aimed at the multi-resonance (MR) effect. The computational study with the STEOM-DLPNO-CCSD method clarified that the combination of a BN ring-fusion and a terminal carbazole enhanced the MR effect and spin-orbit coupling matrix element (SOCME), simultaneously. Also, we clarified that the second triplet excited state (T2) plays an important role in efficient MR-based thermally activated delayed fluorescence (TADF). Furthermore, we obtained a blue–violet OLED with an external EL quantum efficiency (EQE) of 9.1%, implying the presence of a pronounced nonradiative decay path from the lowest triplet excited state (T1).</p

Investigation of Charge Transport Properties in a 2D Dion–Jacobson Halide Perovskite Based on Terphenyl Dications

Type II heterostructures formed by organic semiconducting ligands and inorganic layers in two-dimensional (2D) hybrid perovskites can offer separated charge transport channels for holes and electrons. In this work, we studied a new lead-based 2D Dion–Jacobson perovskite structure incorporating simple terphenyl diammonium salts as organic spacers. The investigations of the electronic and photophysical properties, combined with theoretical calculations, indicate that this 2D perovskite structure forms a type II heterostructure producing intercalated separate pathways for electrons and holes that can migrate within the inorganic and organic sublayers, respectively. The charge transport properties of this unusual type II 2D perovskite heterostructure have also been successfully investigated for the first time by the space charge limited current (SCLC) method, and maximum electron and hole mobilities based on single-crystal devices were evaluated to be 0.3 cm2 V–1 s–1 and 7.0 × 10–4 cm2 V–1 s–1, respectively. This work gives valuable insights into the charge transport mechanisms of type II heterostructures and paves the way toward optoelectronic device applications for such Dion–Jacobson-type 2D perovskites