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Novel thermally-activated delayed fluorescence (TADF) materials 2Cz2SB and 2Mi2SB, possessing N-heterocycle and arylsulfonyl groups, were synthesized and their photophysical properties in solution and the solid state were characterized. 2Cz2SB and 2Mi2SB exhibit typical TADF characteristics and aggregation-induced emission or crystallization-induced emission behaviour. Specifically, they display a blueshift of photoluminescence wavelength and an increase in photoluminescence quantum yield (ΦPL) in the aggregate and solid states, owing to suppression of thermal deactivation. The results of time-resolved IR analysis suggest that aggregate and solid state promoted suppression of geometrical changes in the excited state causes the observed increases in ΦPL. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (GCN) has garnered broad research interest due to its unique catalytic properties. However, GCN, prepared by general methods, possesses myriad structural defects and it has been difficult to elucidate their intrinsic physical properties. We report the development of azacalix[3]triazines (AC3Ts), a substructure of triazine‐based GCN (Tz‐GCN). Despite the electron‐deficient natures of triazine, AC3Ts capture protons as organic superbases. We reveal the unique anion‐π interactions of AC3Ts that alters the ionization potentials of AC3Ts. To the best of our knowledge, these features have not yet been recognized for Tz‐GCN. These unveiled features of AC3Ts are expected to expand the usage scope and possibilities for GCNs. [ABSTRACT FROM AUTHOR]

Polar materials attract wide research interest due to their unique properties, such as ferroelectricity and the bulk photovoltaic effect (BPVE), which are not accessible with nonpolar materials. However, in general, rationally designing polar materials is difficult because nonpolar materials are more favorable in terms of dipole‐dipole interactions. Here, we report a rational strategy to form polar assemblies with bowl‐shaped π‐conjugated molecules and a molecular design principle for this strategy. We synthesized and thoroughly characterized 12 single crystals with the help of various theoretical calculations. Furthermore, we demonstrated that it can be possible to predict whether polar assemblies become more favorable or not by estimating their lattice energies. We believe that this study contributes to the development of organic polar materials and their related studies. [ABSTRACT FROM AUTHOR]

In this study, we observed that methylenecyclopropane 1 c, possessing geminal phenyl and 1‐naphthyl groups at C‐2 of the three membered ring, emits green thermoluminescence (TL) in a low temperature matrix, associated with two sets of bands in the 480–600 and 600–700 nm regions. The bands are assigned to phosphorescence from 31 c* and triplet‐triplet (T−T) fluorescence (FL) from the corresponding trimethylenemethane biradical 32 c..*, respectively. In contrast, as previously reported, the analogous 2‐naphthyl derivative 1 b emits red TL associated with two bands in the 350–450 and 600–700 nm regions, which are assigned to FL from 11 b* and T−T FL from 32 b..*. The results of spectroscopic studies and density functional theory calculations show that the observed dissimilarity in the TL properties of 1 b and 1 c is a consequence of differences in the rate of methylenecyclopropane ring opening of 1 b.+ and 1 c.+ associated with stereoelectronic effects of the naphthyl groups. [ABSTRACT FROM AUTHOR]

2‐(3,6‐Bis(4‐methoxyphenyl)‐2,2,5,5‐tetramethyl‐4‐oxo‐4,5‐dihydropentalen‐1(2H)‐ylidene)malononitrile (DPM‐An) and 2,2′‐(3,6‐bis(4‐methoxyphenyl)‐2,2,5,5‐tetramethyl‐2,5‐dihydropentalene‐1,4‐diylidene)dimalononitrile (DPD‐An), both bearing the 2,5‐dihydropentalene core and intramolecular electron donor–acceptor moieties, were prepared and subjected to photophysical studies. The absorption spectra of DPM‐An and DPD‐An in CH2Cl2 at room temperature contain maxima at similar wavelengths of 406 and 409 nm, respectively. These substances do not luminesce in CH2Cl2 solution at room temperature, but they do emit light when present in poly(methyl methacrylate) films. Interestingly, DPM‐An and DPD‐An in the film forms display nearly identical emission (EM) spectra with respective maxima at 592 and 594 nm. In contrast, DPD‐An has a longer EM lifetime than does DPM‐An. Therefore, the dihydropentalene derivatives, exemplified by DPM‐An and DPD‐An, may be a family of substances in which excited state decay rate can be varied without changing EM wavelengths. [ABSTRACT FROM AUTHOR]

Photoinduced electron transfer (PET) followed by back electron transfer (BET) reactions of 1,2-bis(α-styryl)benzenes 1, generates o-quinodimethane derivative 2 via the corresponding radical cation 2⋅+. This process serves as a facile method to form o-quinodimethane intermediates. The intermediacy of 2⋅+ and 2 were confirmed by using various spectroscopic methods and trapping reactions with 3O2 and dienophiles. Kinetic analysis using nanosecond time-resolved absorption showed that 2⋅+ was transformed to 2 via a BET process, in which the decay of 2⋅+ and rise of 2 have almost the same rate constants of kDECAY=5.6×105 s−1 and kRISE=5.9×105 s−1, respectively. The net BET rate constant evaluated by using Marcus theory is much faster than these experimental values, owing to the reduction based on diffusion. [ABSTRACT FROM AUTHOR]

Trisilatruxene and trioxatruxene were synthesized by intramolecular triple cyclization of triphenylbenzene derivatives. The results of photophysical studies with these substances show that absorption, fluorescence, and phosphorescence of trisilatruxene appear at longer wavelengths compared to those of hexamethyltruxene. The results of DFT calculations suggest that these effects are a consequence of a decrease in the energy of the LUMO caused by σ*-π* orbital interactions in the silole rings. In contrast, trioxatruxene absorbs and emits light at shorter wavelengths than those of hexamethyltruxene as a result of aromatic stabilization of the furan rings. Moreover, all of the truxenes display long-lived phosphorescence with lifetimes in the range of 4.4-16.4 s, attributable to the symmetry-forbidden nature of T1→S0 transitions essentially linked with the C3-symmetric structures. [ABSTRACT FROM AUTHOR]

Ninja power: The picture represENts C3 ‐ symmetric structures of truxENe and its sila ‐ and oxa ‐ analogues as “ShurikEN”, which is a traditional star ‐ shaped throwing weapon used by a “Ninja”, a covert agENt in feudal Japan. The “ShurikEN” pierces C, Si, and O elemENts in the periodic table on the board. All of the synthesized truxENes display long ‐ lived phosphorescENce with lifetimes in the range of 4.4–16.4   s. More information can be found in the Full Paper by Hiroshi Ikeda and co ‐ workers on page   290 in Issue 3, 2017 (DOI: 10.1002/ajoc.201600560). [ABSTRACT FROM AUTHOR]

Photochemical reactions of 2,5-bis[2,2-di(thien-2-yl)ethenyl]thiophene ( 1a ) and its tetramethyl derivative 1b , under direct photoexcitation, and photoinduced electron-transfer conditions, were studied. Our initial prediction was that 1b would undergo a photoreaction as part of a reversible photochromic system, while a reaction of its non-methyl substituted analog 1a would undergo a typical double sequence of 6π-electrocyclization (6π-EC)/aromatization (AR) (double dehydrogenation, 2H) to give 7,11-di(thien-2-yl)trithia[5]helicene ( 2a ). In fact, we observed that photoirradiation of 1b leads to formation of the 7,11-bis(3-methylthien-2-yl)trithia[5]helicene ( 2b ). In this process, 2b is formed via a double sequence of 6π-EC/AR (dehydrogenation/demethylation, H/ Me). Moreover, the yield of formation of 2b is much higher than that of 2a , which reacts through a double sequence of 6π-EC/AR ( 2H). Thus, this photochemically-induced paradoxical cascade reaction based on the newly uncovered reactivity serves as an efficient method to construct the trithia[5]helicene framework. [ABSTRACT FROM AUTHOR]

Inspired by the previous machine-learning study that the number of hydrogen-bonding acceptor (NHBA) is important index for the hole mobility of organic semiconductors, seven dithienobenzothiazole (DBT) derivatives 1a-g (NHBA = 5) were designed and synthesized by one-step functionalization from a common precursor. X-ray single-crystal structural analyses confirmed that the molecular arrangements of 1b (the diethyl and ethylthienyl derivative) and 1c (the di(n-propyl) and n-propylthienyl derivative) in the crystal are classified into brickwork structures with multidirectional intermolecular charge-transfer integrals, as a result of incorporation of multiple hydrogen-bond acceptors. The solution-processed top-gate bottom-contact devices of 1b and 1c had hole mobilities of 0.16 and 0.029 cm2 V-1s-1, respectively., (© 2024 Wiley‐VCH GmbH.)

Triplet-triplet annihilation (TTA)-assisted photon upconversion (TTA-UC) in three dyads (DPA-Cn-DPA), comprised of two diphenylanthracene (DPA) moieties connected by nonconjugated C1, C2, and C3 linkages (Cn), has been investigated. The performance of these dyads as energy acceptors in the presence of the energy donor platinum octaethylporphyrin are characterized by longer triplet lifetimes (τ T ) and different TTA rate constants than those of the parent DPA. The larger τ T of the linked systems, caused by "intramolecular energy hopping" in the triplet dyad 3 DPA*-Cn-DPA, results in a low threshold intensity, a key characteristic of efficient TTA-UC.

We report terahertz electromagnetic wave emission by optical rectification from hydrogen-bonded single molecular crystal 4-nitro-2,5-bis(phenylethynyl)aniline designed to be polar via the hydrogen bonding between nitroaniline cores. The terahertz emission efficiency is comparable to the representative inorganic terahertz emitter ZnTe. We show terahertz emission characteristics, optical spectrum, and theoretical molecular orbital calculations. Another three kinds of nitroaniline-based organic molecules are revealed to form polar crystal structure, and they have large hyperpolarizabilities and have potential for terahertz photonics.

Polar materials attract wide research interest due to their unique properties, such as ferroelectricity and the bulk photovoltaic effect (BPVE), which are not accessible with nonpolar materials. However, in general, rationally designing polar materials is difficult because nonpolar materials are more favorable in terms of dipole-dipole interactions. Here, we report a rational strategy to form polar assemblies with bowl-shaped π-conjugated molecules and a molecular design principle for this strategy. We synthesized and thoroughly characterized 12 single crystals with the help of various theoretical calculations. Furthermore, we demonstrated that it can be possible to predict whether polar assemblies become more favorable or not by estimating their lattice energies. We believe that this study contributes to the development of organic polar materials and their related studies., (© 2020 Wiley-VCH GmbH.)

We carried out a systematic investigation of packing structures of a series of dimethoxyanthracenes, i. e., 1,4- (1), 1,8- (2), 1,5- (3), 2,6- (4), and 2,7-derivatives (5). The packing structures of the dimethoxyanthracenes are classified into two types, a rubrene-like pitched π-stack (1-3) and a typical herringbone packing (4 and 5), which evidently show that the position of methoxy groups is crucial to determine the packing structure of dimethoxyanthracenes. Effects of the substitution position on intermolecular interactions are analyzed by the noncovalent intermolecular interaction (NCI) method, Hirshfeld surface analysis, and symmetry-adapted perturbation theory (SAPT) method, thus clarifying active roles of the methoxy groups in the formation of rubrene-like pitched π-stack. The present results shed light on a molecular design strategy to realize the rubrene-like pitched π-stack in the solid state, which had been regarded as a packing structure limited for rubrene and its closely related derivatives., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Novel boron-containing drugs have recently been suggested as a new class of pharmaceuticals. However, the majority of current boron-detection techniques require expensive facilities and/or tedious pretreatment methods. Thus, to develop a novel and convenient detection method for boron-based pharmaceuticals, imine-type boron-chelating-ligands were previously synthesized for use in a fluorescent sensor for boronic acid containing compounds. However, the fluorescence quantum yield of the imine-type sensor was particularly low, and the sensor was easily decomposed in aqueous media. Thus, in this paper, we report the development of a novel, convenient, and stable fluorescent boron-sensor based on O - and N -chelation (i.e., 2-(pyridine-2yl)phenol), and a corresponding method for the quantitative and qualitative detection of boronic acid-containing compounds using this commercially available sensor is presented., Competing Interests: The authors declare no conflict of interest.