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A crystalline hydrogen-bonded framework with permanent porosity, built by rod-like struts and engineered to bear ultra-fast molecular rotors between two triple bonds, offers the possibility of controlling the rotational rates upon CO2 adsorption. CO2 enters the pores from the gas phase and reduces the rotational rates from the extremely fast regime of 107 Hz at 216 K to 105 Hz. The CO2–rotor interaction was evident from the 2H NMR response to the dynamics of the rotors in contact with CO2 in the crystal structure. [ABSTRACT FROM AUTHOR]

Recently, applied research on stimuli-responsive materials with luminescence-switching characteristics has been conducted in various fields. A representative phenomenon of stimuli-responsive luminescent materials is mechanochromic luminescence (MCL), which exhibits luminescent color change induced by mechanical stimuli such as grinding. These materials are among the most prominent candidates for security and sensing applications. Interestingly, some mechanochromic luminescent materials have shown self-recovery character, in which their original luminescent color can be recovered by just standing under ambient conditions after grinding. Although there have been more and more reports of such materials in recent years, the fundamental principles of molecular design still remain elusive. In this concept, we summarize distinctive advances in mechanochromic luminescent materials with self-recovery according to the core structures of luminescent molecules. Controlling amorphous state by introducing substituents such as alkyl or polar groups is effective method to provide self-recovering properties., (© 2024 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

Hydrogen-bonded organic frameworks (HOFs) composed of multicomponent molecules in a non-stoichiometric composition have drawn great interest due to their tunable properties. However, the photobehavior of the single crystals of such mixed HOFs has not been explored. Here, we report on the synthesis, characterization and photobehavior of single crystalline non-stoichiometric HOFs (NS-HOFs). NS-HOFs (B T N T -1) with various composition ratios were successfully obtained as single crystals from two analogue tetratopic carboxylic acids, possessing naphthalene and benzothiadiazole cores (NTTA and BTTA, respectively). The heterogeneous distribution of the components was thoroughly confirmed by time-resolved fluorescence microscopy and local crystallographic analysis using focused synchrotron X-ray radiation. The versatile fluorescence of B T N T -1 behavior depends on the composition ratio and distribution of the component in the single crystals. We observed not only fluorescence bands with various colors such as purple, blue, green and white, depending on the composition ratios, but also different emission bands from a single crystal. We provide details on their emission lifetimes following the composition, emission color and targeted region on the crystal. This work is the first example of single crystal studies applied to organic porous co-crystals and demonstrates unique and versatile optical properties of carboxylic acid-based NS-HOFs. The results provide a concept of creating functional mixed porous materials capable of different and tunable optical properties., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Water in hydrophobic nanospaces shows specific dynamic properties different from bulk water. The investigation of these properties is important in various research fields, including materials science, chemistry, and biology. The elucidation of the correlation between properties of water and hydrophobic nanospaces requires nanospaces covered only with simple hydrophobic group (e.g., fluorine) without impurities such as metals. This work successfully fabricated all-organic diamondoid porous organic salts (d-POSs) with highly fluorinated nanospaces, wherein hydrophobic fluorine atoms are densely exposed on the void surfaces, by combining fluorine substituted triphenylmethylamine (TPMA) derivatives with tetrahedral tetrasulfonic acid. This d-POSs with a highly fluorinated nanospace significantly improved their water stability, retaining their crystal structure even when immersed in water over one week. Moreover, this highly hydrophobic and fluorinated nanospace adsorbs 160 mL(STP)/g of water vapor at P e /P 0 =0.90; this is the first hydrophobic nanospace, which water molecules can enter, in an all-organic porous material. Furthermore, this highly fluorinated nanospace exhibits very high proton conductivity (1.34×10 -2  S/cm) at 90 °C and 95 % RH. POSs with tailorable nanospaces may significantly advance the elucidation of the properties of specific "water" in pure hydrophobic environments., (© 2024 The Author(s). Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Photophysical modulation of triarylboranes (TABs) through Lewis acid-base interactions is a fundamental approach for sensing anions. Yet, design principles for anion-responsive TABs displaying significant red-shift in absorption and photoluminescence (PL) have remained elusive. Herein, a new strategy for modulating the photophysical properties of TABs in a red-shift mode has been presented, by using a nitrogen-bridged triarylborane (1,4-phenazaborine: PAzB) with a contradictory dual role as a Lewis acid and an electron donor. Following the strategy, PAzB derivatives connected with an electron-deficient azaaromatic have been developed, and these compounds display a distinct red-shift in their absorption and PL in response to an anion. Spectroscopic analyses and quantum chemical calculations have revealed the formation of a tetracoordinate borate upon the addition of fluoride, narrowing the HOMO-LUMO gap and enhancing the charge-transfer character in the excited state. This approach has also been demonstrated in modulating the photophysical properties of solid-state films., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Chiral excimers exhibit unique photophysical behaviour. However, further molecular design is required along with systematic studies on the effect of spacer groups and solvent polarity. In this study, we prepared four circularly polarised luminescence (CPL)-active molecules that exhibit intramolecular excimer emission. Bis-1,8-naphthalimide (bNI) derivatives D-LybNI, L-LybNI, D-LyMebNI, and L-LyMebNI were prepared with chiral backbones and alkyl linkages between the NI rings with chain lengths of five carbon atoms, suitable for excimer fluorescence. The fluorescence properties were investigated experimentally and theoretically using density functional theory. The molecules exhibited intramolecular excimer fluorescence in polar organic solvents. Mirror-image circular dichroism and CPL spectra were obtained for the D and L forms. D- and L-LyMebNI exhibited relatively large luminescence dissymmetry factors (| g lum |) in acetonitrile of 1.9 × 10 -3 and 1.6 × 10 -3 , respectively. Thus, this study demonstrates chiral bNI derivatives with simple synthesis procedures that emit intramolecular excimer fluorescence and have effective CPL properties. These molecules are promising for developing organic molecular systems with bright, highly polarised emission.

In this study, we investigated the hydrolytic condensation of 3-aminopropyldiethoxymethylsilane over different superacid catalysts. We found that cyclic tetrasiloxanes with different stereostructures (Am-CyTS-NNf 2 and Am-CyTS-NHf 2 ) could be selectively prepared in high yields (>95%) depending on the superacid catalyst employed (bis(nonafluorobutanesulfonyl)imide or cyclohexafluoropropane-1,3-bis(sulfonyl)imide). The single-crystal X-ray structural analyses of compounds in which amino groups of Am-CyTS-NNf 2 and Am-CyTS-NHf 2 were protected by the tert -butoxycarbonyl group revealed the formation of all- cis and cis - trans - cis cyclic tetrasiloxanes, respectively.

Hydrogen-bonded organic frameworks (HOFs) are porous organic materials constructed via hydrogen bonds. HOFs have solubility in specific high-polar organic solvents. Therefore, HOFs can be returned to their components and can be reconstructed, which indicates their high recyclability. Network topologies, which are the frameworks of porous structures, control the pore sizes and shapes of HOFs. Therefore, they strongly affect the functions of porous materials. However, hydrogen bonds are usually weak interactions, and the design of the intended network topology in HOFs from their components has been challenging. Porous organic salts (POSs) are an important class of HOFs, are hierarchically constructed via strong charge-assisted hydrogen bonds between sulfonic acids and amines, and therefore are expected to have high designability of the porous structure. However, the network topology of POSs has been limited to only dia -topology. Here, we combined tetrasulfonic acid with the adamantane core (4,4',4'',4'''-(adamantane-1,3,5,7-tetrayl)tetrabenzenesulfonic acid; AdPS) and triphenylmethylamines with modified substituents in para -positions of benzene rings (TPMA-X, X = F, methyl (Me), Cl, Br, I). We changed the steric hindrance between the adamantane and substituents (X) in TPMA-X and obtained not only the common dia -topology for POSs but also rare sod -topology, and lon - and uni -topologies that are formed for the first time in HOFs. Changing template molecules under preparation helped in successfully isolating the porous structures of AdPS/TPMA-Me with dia -, lon -, and sod -topologies which exhibited different gas adsorption properties. Therefore, for the first time, we demonstrated that the steric design of HOF components facilitated the formation, diversification, and control of the network topologies and functions of HOFs., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

To develop porous organic frameworks, precise control of the stacking manner of two-dimensional porous motifs and structural characterization of the resultant framework are important. From these points of view, porous molecular crystals formed through reversible intermolecular hydrogen bonds, such as hydrogen-bonded organic frameworks (HOFs), can provide deep insight because of their high crystallinity, affording single-crystalline X-ray diffraction analysis. In this study, we demonstrate that the stacking manner of hydrogen-bonded hexagonal network (HexNet) sheets can be controlled by synchronizing a homological triangular macrocyclic tecton and a hydrogen-bonded cyclic supramolecular synthon called the phenylene triangle. A structure of the resultant HOF was crystallographically characterized and revealed to have a large channel aperture of 2.4 nm. The HOF also shows thermal stability up to 290 °C, which is higher than that of the conventional HexNet frameworks., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Co-published by University of Science and Technology of China and American Chemical Society.)

Porous organic salts (POSs) are organic porous materials assembled via charge-assisted hydrogen bonds between strong acids and bases such as sulfonic acids and amines. To diversify the network topology of POSs and extend its functions, this study focused on using 4,4',4'',4'''-(9,9'-spirobi[fluorene]-2,2',7,7'-tetrayl)tetrabenzenesulfonic acid (spiroBPS), which is a tetrasulfonic acid comprising a square planar skeleton. The POS consisting of spiroBPS and triphenylmethylamine (TPMA) (spiroBPS/TPMA) was constructed from the two-fold interpenetration of an orthogonal network with pts topology, which has not been reported in conventional POSs, owing to the shape of the spirobifluorene backbone. Furthermore, combining tris(4-chlorophenyl)methylamine (TPMA-Cl) and tris(4-bromophenyl)methylamine (TPMA-Br), which are bulkier than TPMA owing to the introduction of halogens at the p-position of the phenyl groups with spiroBPS allows us to construct novel POSs (spiroBPS/TPMA-Cl and spiroBPS/TPMA-Br). These POSs were constructed from a chiral helical network with pth topology, which was induced by the steric hindrance between the halogens and the curved fluorene skeleton. Moreover, spiroBPS/TPMA-Cl with pth topology exhibited circularly polarized luminescence (CPL) in the solid state, which has not been reported in hydrogen-bonded organic frameworks (HOFs)., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Bent ligands bridged by heteroatoms have drawn significant interest as supramolecular coordination architectures. Traditionally, divalent group 16 elements are preferred over trivalent group 15 elements because of the anticipated steric hindrance. In this study, we explore metal-organic frameworks (MOFs) based on dipyridinoarsoles (DPAs), 4,4'-bipyridines bridged with an arsenic atom. An MOF with methyl-substituted DPA collapsed upon solvent removal, whereas that with phenyl-substituted DPA demonstrated breathing behavior due to guest molecule adsorption/desorption. In contrast, MOFs using the phosphorus analogue dipyridinophosphole exhibit inferior adsorption and lack breathing behavior. This is the first study to investigate the interplay among substituents, bridging elements, and dynamic behavior in MOFs using bent group 15 ligands.

Charge-transfer complexes can exhibit various physical properties that depend on the relative positions of electron-donor and electron-acceptor molecules. Several studies have investigated the relationship between the relative positions of electron-donor and electron-acceptor molecules and their luminescence properties. However, elucidating the correlation between the relative positions and detailed luminescence processes without changing the molecular structures has not been explored. Herein, we report control of the relative position based on charge-assisted hydrogen bonds between sulfo and amino groups and on alkylamines' steric factors, and report concomitant modulation of the luminescent properties. Six charge-transfer complexes were prepared from anthracene-2,6-disulfonic acid and 1,2,4,5-tetracyanobenzene as electron-donor and electron-acceptor molecules, and various alkylamines. Different alkylamines' steric factors drastically and precisely changed the relative positions of the electron-donor and electron-acceptor molecules without changing their molecular structures. Consequently, the six crystals exhibited maximum emission wavelengths from 543 to 624 nm and different luminescence processes., (© 2023 Wiley-VCH GmbH.)

Understanding certain behaviors of water, e.g., its dynamics, is extremely important in various fields. Recently, using 1 H nuclear magnetic resonance spectroscopy, we have identified a metastable state of water molecules, i.e., water clusters, in hydrophobic solvents in addition to dissolved water molecules and a small bulk water domain. However, the low abundance of water clusters made observing their dynamics challenging. In this study, the dynamics of water clusters in benzene- d 6 were investigated by quasi-elastic neutron scattering measurements using the AGNES time-of-flight spectrometer of the Japan Research Reactor JRR-3. The diffusion dynamics of the hydrogen atoms were much slower than those of bulk water (with a self-diffusion coefficient of 1.15 × 10 -9 m 2 /s at 273 K) and even slower than the upper-limit dynamics at the observable scale (10 -10 m 2 /s). The dynamics of water clusters are slow, "like ice", even at 283-303 K, which is above the freezing point of water (273 K).

Stimulus-responsive organic materials with luminescence switching properties have attracted considerable attention for their practical applications in sensing, security, and display devices. In this paper, bent-type bisbenzofuropyrazine derivatives, Bent-H and Bent-sBu, with good solubilities were synthesized, and their physical and optical properties were investigated in detail. Bent-H gave three crystalline polymorphs, and they showed different luminescence properties depending on their crystal packing structures. In addition, Bent-H exhibited mechanochromic luminescence in spite of its rigid skeleton. Bent-sBu exhibited unique concentration-dependent vapochromic luminescence. Ground Bent-sBu was converted to blue-emissive, green-emissive, and green-emissive high-viscosity solution states at low, moderate, and high concentrations of CHCl 3 vapor, respectively. This finding represents a concentration-dependent multi-phase transition with an organic solvent, which is of potent interest for application in sensing systems., (© 2023 Wiley-VCH GmbH.)

Anion binding and ion pairing of dipyrrolyldiketone Pt II complexes as anion-responsive π-electronic molecules resulted in photophysical modulations, as observed in solid-state phosphorescence properties. Modifications to arylpyridine ligands in the Pt II complexes significantly impacted the assembling behaviour and photophysical properties of anion-free and anion-binding (ion-pairing) forms. The Pt II complexes, in the presence of guest anions and their countercations, formed various anion-binding modes and ion-pairing assembled structures depending on constituents and forms (solutions and crystals). The Pt II complexes emitted strong phosphorescence in deoxygenated solutions but showed extremely weak phosphorescence in the solid state owing to self-association. In contrast, the solid-state ion-pairing assemblies with tetraalkylammonium cations exhibited enhanced phosphorescence owing to the formation of hydrogen-bonding 1D-chain Pt II complexes dispersed by stacking with aliphatic cations. Theoretical studies revealed that the enhanced phosphorescence in the solid-state ion-pairing assembly was attributed to preventing the delocalisation of the electron wavefunction over Pt II complexes., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

We propose a mechanism for substituent-responsive reactivities of p-quinodimethane derivatives with four ester groups through their hierarchical and asymmetric assembly modes. Four asymmetric 7,8,8-tris(methoxycarbonyl)-p-quinodimethanes with a 7-positioned ethoxycarbonyl (2 a(H)), 2'-fluoroethoxycarbonyl (2 b(F)), 2'-chloroethoxycarbonyl (2 c(Cl)), or 2'-bromoethoxycarbonyl (2 d(Br)) were synthesized and crystallized. 2 a(H), 2 b(F) and 2 d(Br) afforded only one shape crystal, while 2 c(Cl) did two polymorphic 2 c(Cl)-α and 2 c(Cl)-β. UV-irradiation induced topochemical polymerization for 2 a(H), no reactions for 2 b(F) and 2 c(Cl)-α, and [6+6] photocycloaddition dimerization for 2 c(Cl)-β and 2 d(Br). Such substituent-responsive reactivities and crystal structures were compared with those of the known symmetric 7,7,8,8-tetrakis(alkoxycarbonyl)-p-quinodimethanes such as 7,7,8,8-tetrakis(methoxycarbonyl)- (1 a(Me)-α and 1 a(Me)-β), 7,7,8,8-tetrakis(ethoxycarbonyl)- (1 b(Et)), and 7,7,8,8-tetrakis(bromoethoxycarbonyl)- (1 c(BrEt)). The comparative study clarified that the reactivities and crystal structures are classified into four types that link to each other. This linkage is understandable when we analyze the crystal structures through the following hierarchical and asymmetric assemblies; conformers, dimers, one dimensional (1D)-columns, two dimensional (2D)-sheets, and three dimensional (3D)-stacked sheets (3D-crystals). This supramolecular viewpoint is supported by intermolecular interaction energies among neighbored molecules with the density functional theory (DFT) calculation. Such research enables us to elucidate the substituent-responsive reactivities of the crystals, and reminds us of the selection of the right path in a so-called "maze game"., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Expression of room-temperature phosphorescence (RTP) in organic materials requires complicated molecular design and specific intermolecular interactions, and therefore types of RTP materials are restricted. This work presents cage-like sodalite-type porous organic salts (s-POSs) as host materials for luminescent molecules to induce RTP, using tetrasulfonic acid with an adamantane core and triphenylmethylamines that are modified with substituents in the para-positions of benzene rings (TPMA-X). By adding a representative luminescent molecule (pyrene) to a reaction solution during construction of s-POSs, the molecule is incorporated in a facile manner. s-POSs with a heavy halogen atom (X: Iodine) on the pore surface give heavy atom effects, suppression of thermal vibration, and protection from oxygen, for the incorporated molecule, which induce its RTP even in air. This strategy can be applied to various luminescent molecules, which may lead to the achievement of RTP of various colors., (© 2023 Wiley-VCH GmbH.)