Carrier Transport Switching of Ferroelectric BTBT Derivative.

Alkylamide-substituted [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivative of BTBT-NHCOC14H29 (1), which has ferroelectric N-H···O= hydrogen-bonding network of alkylamide group and two-dimensional (2D) electric structure of BTBT π-cores, was prepared to design the external electric field-responsive organic semiconductors. The short-chain derivative of BTBT-NHCOC3H7 (1') revealed the coexistence of a 2D electronic band structure based on the herringbone BTBT arrangement and the one-dimensional (1D) hydrogen-bonding chain. 1 formed a smectic E (SmE) liquid crystal phase above 412 K and showed ferroelectric hysteresis in the electric field-polarization (P-E) curves at 403-433 K. The remanent polarization (Pr) and coercive electric field (Ec) of 1 at 408 K, 0.1 Hz were 24.0 µC cm-2 and 5.54 V µm-1, respectively. By thermal annealing of thin-film 1 at 443 K, the molecular assembly structure of 1 changed from a monolayer to a bilayer structure with high crystallinity, resulting in conducting layers of BTBT parallel to the substrate surface. The organic field-effect transistor (OFET) device with thermally annealed thin-film 1 showed p-type semiconducting behavior with the hole mobility of 1.0 × 10-3 cm2 V-1 s-1. Furthermore, device 1 showed switching behavior of semiconducting properties by electric field poling and thermal annealing cycle. The electric field response of ferroelectrics modulated the molecular orientation and conduction properties of organic semiconductors, resulting in external electric field control of carrier transport properties.

Ferroelectric Organic Semiconductor: [1]Benzothieno[3,2-b][1]benzothiophene-Bearing Hydrogen-Bonding -CONHC14H29 Chain.

An alkylamide-substituted [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivative of BTBT-CONHC14H29 (1) and C8H17-BTBT-CONHC14H29 (2) were prepared to design the multifunctional organic materials, which can show both ferroelectric and semiconducting properties. Single-crystal X-ray structural analyses of short-chain (-CONHC3H7) derivatives revealed the coexistence of two-dimensional (2D) electronic band structures brought from a herringbone arrangement of the BTBT π core and the one-dimensional (1D) hydrogen-bonding chains of -CONHC3H7 chains. The thin films of 1 and 2 fabricated on the Si/SiO2 substrate surface have monolayer and bilayer structures, respectively, resulting in conducting layers parallel to the substrate surface, which is suitable for a channel layer of organic field-effect transistors (OFETs). The thin film of 1 indicated a hole mobility µFET = 2.4 × 10-5 cm2 V-1 s-1 and threshold voltage VTh = - 29 V, whereas that of 2 showed a µFET = 2.1 × 10-2 cm2 V-1 s-1 and threshold voltage VTh = -9.7 V. Both 1 and 2 formed the smectic E (SmE) phase above 410 and 369 K, respectively, where the existence of a hole transport pathway was confirmed in the SmE phase. The ferroelectric hysteresis behavior was observed in bulk 1 and 2 in the polarization-electric field (P-E) curves at the SmE phase. 1 showed the remanent polarization Pr = 2.3 µC cm-2 and coercive electric field Ec = 5.2 V µm-1, whereas the Pr and Ec of 2 were 3.4 µC cm-2 and 7.0 V µm-1 at the conditions of 453 K and 1 Hz. Introduction of alkylamide units into the BTBT π core has the potential to develop the external stimulus-responsive organic semiconductors brought from both ferroelectricity and semiconducting properties.

Configurationally Nonselective Aquation of a Mononuclear Ru(II) Chloro Complex to Aquo Complex Isomers with Distinctive Aspects in Photoisomerization, Redox, and Catalytic Water Oxidation.

distal-[Ru(EtOtpy)(pynp)Cl]+ (d-EtO1Cl) (EtOtpy = 4'-ethoxy-2,2':6',2″-terpyridine, pynp = 2-(2-pyridyl)-1,8-naphthyridine), and distal/proximal-[Ru(EtOtpy)(pynp)OH2]2+ (d/p-EtO1H2O) complexes were newly synthesized to investigate the synergistic influence of the geometric configuration coupled with substituent introduction of an ethoxy (EtO) group on the physicochemical properties and reactions of the Ru(II) complexes. Configurationally nonselective aquation of d-EtO1Cl was uniquely observed to form d/p-EtO1H2O isomers in water, in contrast to configurationally selective aquation of distal-[Ru(tpy)(pynp)Cl]+ (d-1Cl, tpy = 2,2':6',2″-terpyridine) without the EtO group [Yamazaki, H. . J. Am. Chem. Soc. 2011, 133, 8846-8849].The kinetic profiles of the aquation reactions of d-EtO1Cl were well analyzed using a sequential reversible reaction model assuming the reversible interconversion between d/p-EtO1H2O isomers via d-EtO1Cl. The observed equilibrium constant (Kiso) of isomerization between p/d-EtO1H2O was calculated from the kinetic analysis as Kiso = 0.45, which is consistent with the final concentration ratio (1:0.43) of p/d-EtO1H2O generated in the aquation reaction of d-EtO1Cl. The irreversible photoisomerization from d-EtO1H2O to p-EtO1H2O was observed in water with an internal quantum yield (Φ) of 0.44% at 520 nm. Electrochemical measurements showed that d-EtO1H2O undergoes a 2-step oxidation reaction of 1H+-coupled 1e- processes of RuII-OH2/RuIII-OH and RuIII-OH/RuIV═O at pH 1.3-9.7, whereas p-EtO1H2O undergoes a 1-step oxidation reaction of a 2H+-coupled 2e- process of RuII-OH2/RuIV═O in the pH range of 1.8-11.5. Any redox potential of d/p-EtO1H2O isomers was decreased by the electro-donating EtO substitution, compared with distal/proximal-[Ru(tpy)(pynp)OH2]2+ (d/p-1H2O). The turnover frequency (kO2 = 1.7 × 10-2 s-1) of d-EtO1H2O for water oxidation catalysis is higher than that (3.5 × 10-4 s-1) of p-EtO1H2O by a factor of 48.6. The kO2 value (1.7 × 10-2 s-1) for d-EtO1H2O is 4.5-fold higher than those of d-1H2O (3.8 × 10-3 s-1). The higher kO2 value of d-EtO1H2O compared with d-1H2O could be explained by the fast oxidation rate from RuIV═O to RuV═O involved in the rate-determining step due to the electron-donating EtO group.

Noninvasive Three-dimensional Assessment of Single Molecular Crystals Using Multiphoton Microscopic Observation and Their Deformation-induced Emission Characteristics.

Distinguishing the luminescence contribution from the surface and bulk of a crystal is a long-standing challenge in crystal materials. Herein, three-dimensional, multiphoton, luminescence microscope imaging of the elastic molecular single crystal 1,4-bis(4-methylthien-2-yl)-2,3,5,6-tetrafluorobenzene, was conducted. Further, the luminescence contribution from the surface and bulk of the crystal was experimentally distinguished. Strong luminescence was observed only from the surface of the crystal, while the bulk did not emit strongly. Furthermore, the surface and bulk luminescence behavior responded well to the mechanical shape change of the crystal; i.e., strong luminescence was observed for the elongated side of the crystal.

Dual-radical-based molecular anisotropy and synergy effect of semi-conductivity and valence tautomerization in a photoswitchable coordination polymer.

Organic radicals are widely used as linkers or ligands to synthesize molecular magnetic materials. However, studies regarding the molecular anisotropies of radical-based magnetic materials and their multifunctionalities are rare. Herein, a photoisomerizable diarylethene ligand was used to form {[CoIII(3,5-DTSQ·-)(3,5-DTCat2-)]2(6F-DAE-py2)}·3CH3CN·H2O (o-1·3CH3CN·H2O, 6F-DAE-py2 = 1,2-bis(2-methyl-5-(4-pyridyl)-3-thienyl)perfluorocyclopentene), a valence-tautomeric (VT) coordination polymer. We directly observed dual radicals for a single crystal using high-field/-frequency (∼13.3 T and ∼360 GHz) electron paramagnetic resonance (EPR) spectroscopy along the c-axis, which was further confirmed by angle-dependent Q-band EPR spectroscopy. Moreover, a conductive anomaly close to the VT transition temperature was observed only when probes were attached at the ab plane of the single crystal, indicative of synergy between valence tautomerism and conductivity. Structural anisotropy studies and density functional theory (DFT) calculations revealed that this synergy is due to electron transfer associated with valence tautomerism. This study presents the first example of dual-radical-based molecular anisotropy and charge-transfer-induced conductive anisotropy in a photoswitchable coordination polymer.

Temperature-Controlled Transformation of WO3 Nanowires into Active Facets-Exposed Hexagonal Prisms toward Efficient Visible-Light-Driven Water Oxidation.

A unique transformation of WO3 nanowires (NW-WO3) into hexagonal prisms (HP-WO3) was demonstrated by tuning the temperature of the (N2H4)WO3 precursor suspension prepared from tungstic acid and hydrazine as a structure-directing agent. The precursor preparation at 20 °C followed by calcination at 550 °C produced NW-WO3 nanocrystals (ca. <100 nm width, 3-5 µm length) with anisotropic growth of monoclinic WO3 crystals to (002) and (200) planes and a polycrystalline character with randomly oriented crystallites in the lateral face of nanowires. The precursor preparation at 45 °C followed by calcination at 550 °C produced HP-WO3 nanocrystals (ca. 500-1000 nm diameter) with preferentially exposed (002) and (020) facets on the top-flat and side-rectangle surfaces, respectively, of hexagonal prismatic WO3 nanocrystals with a single-crystalline character. The HP-WO3 electrode exhibited the superior photoelectrochemical (PEC) performance for visible-light-driven water oxidation to that for the NW-WO3 electrode; the incident photon-to-current conversion efficiency (IPCE) of 47% at 420 nm and 1.23 V vs RHE for HP-WO3 was 3.1-fold higher than 15% for the NW-WO3 electrode. PEC impedance data revealed that the bulk electron transport through the NW-WO3 layer with the unidirectional nanowire structure is more efficient than that through the HP-WO3 layer with the hexagonal prismatic structure. However, the water oxidation reaction at the surface for the HP-WO3 electrode is more efficient than the NW-WO3 electrode, contributing significantly to the superior PEC water oxidation performance observed for the HP-WO3 electrode. The efficient water oxidation reaction at the surface for the HP-WO3 electrode was explained by the high surface fraction of the active (002) facet with fewer grain boundaries and defects on the surface of HP-WO3 to suppress the electron-hole recombination at the surface.

Endocytosis-Like Vesicle Fission Mediated by a Membrane-Expanding Molecular Machine Enables Virus Encapsulation for In Vivo Delivery.

Biological membranes are functionalized by membrane-associated protein machinery. Membrane-associated transport processes, such as endocytosis, represent a fundamental and universal function mediated by membrane-deforming protein machines, by which small biomolecules and even micrometer-size substances can be transported via encapsulation into membrane vesicles. Although synthetic molecules that induce dynamic membrane deformation have been reported, a molecular approach enabling membrane transport in which membrane deformation is coupled with substance binding and transport remains critically lacking. Here, we developed an amphiphilic molecular machine containing a photoresponsive diazocine core (AzoMEx) that localizes in a phospholipid membrane. Upon photoirradiation, AzoMEx expands the liposomal membrane to bias vesicles toward outside-in fission in the membrane deformation process. Cargo components, including micrometer-size M13 bacteriophages that interact with AzoMEx, are efficiently incorporated into the vesicles through the outside-in fission. Encapsulated M13 bacteriophages are transiently protected from the external environment and therefore retain biological activity during distribution throughout the body via the blood following administration. This research developed a molecular approach using synthetic molecular machinery for membrane functionalization to transport micrometer-size substances and objects via vesicle encapsulation. The molecular design demonstrated in this study to expand the membrane for deformation and binding to a cargo component can lead to the development of drug delivery materials and chemical tools for controlling cellular activities.

Structural Transformable Coulomb Lattice of n-Type Semiconductors for Guest Sorption.

In recent years, highly designable organic porous materials have attracted considerable attention in the development of new types of molecular adsorption-desorption materials. The adsorption-desorption process also changes the electronic structure via the existence of guest molecules. Therefore, it is possible to change the physical property during the guest adsorption-desorption cycle using an appropriate chemical design of the host crystal lattice. As the development of n-type organic semiconductors has been limited, we focused on designing an n-type organic semiconductor material to control the host crystal lattice, electronic dimensionality, chemical stability, and high electron mobility using an ionic naphthalenediimide (NDI) derivative. Low symmetrical dianionic bis(benzene-m-sulfonate)-naphthalenediimide (m-BSNDI2-) forms various types of single-crystal (M+)2(m-BSNDI2-)·n(guest) with a combination of M+ = Na+, K+, Rb+, and guest = H2O, CH3OH. Four crystals of (K+)2(m-BSNDI2-)·n(H2O), (K+)2(m-BSNDI2-)·n(CH3OH), α-(K+)2(m-BSNDI2-), and ß-(K+)2(m-BSNDI2-) were transformable using the guest adsorption-desorption cycle. Two kinds of single-crystal (K+)2(m-BSNDI2-)·n(CH3OH) with n = 0 and 2.0 showed a single-crystal to single-crystal (SCSC) transformation through CH3OH desorption. On the contrary, five kinds of single crystals with n = 0, 3.0, 3.3, 4.75, and 5.5 were identified in the single-crystal X-ray structural analyses of (K+)2(m-BSNDI2-)·n(H2O). Systematic change of the ionic radii in (M+)2(m-BSNDI2-) modified the crystal lattice flexibility for the guest adsorption-desorption cycles.

Proton Conduction at High Temperature in High-Symmetry Hydrogen-Bonded Molecular Crystals of RuIII Complexes with Six Imidazole-Imidazolate Ligands.

Invited for the cover of this issue is mainly the group of Makoto Tadokoro and co-workers at Tokyo University of Science. Other co-workers are Masaki Itoh, Ryota Nishimura, Kensuke Sekiguchi (TUS students), Dr. Norihisa Hoshino (Tohoku Univ.), Dr. Hajime Kamebuchi (Nihon Univ.), Dr. Jun Miyazaki (Tokyo Denki Univ.), Prof. Motohiro Mizuno (Kanazawa Univ.) and Prof. Tomoyuki Akutagawa (Tohoku Univ.). The image depicts on two mechanisms of proton transport rotations of the proton-conductive starburst molecule [RuIII (HIm)3 (Im)3 ]. Read the full text of the article at 10.1002/chem.202201397.

The strong correlations between thermal conductivities and electronic spin states in the crystals of Fe(III) spin crossover complexes.

Solids that change their thermal conductivity during a phase transition can be useful in the development of a thermal switch to allow control of heat flow and reduce energy consumption. Although a crystal of a spin crossover (SCO) complex is a representative solid with spin states correlated with heat transporting lattice vibrations, the heat transporting property of a crystal of the SCO complex during a spin state transition has not yet been reported. In this work, we report that the temperature dependence of the thermal conductivity of mononuclear Fe(III) SCO complexes is greatly affected by spin state transitions. It was found that the thermal conductivity was minimized at temperatures near the beginning edge of the spin state transitions, and the product of the velocity and the mean free path of phonons also reached a minimum close to the temperature at which the spin state transition progressed by 50%. These findings suggest that the spin state transitions accompanying the coordination bond length elongation and lowering of the vibration energy are allowed at a temperature where the mean-free path of phonons is minimized to the extent of intermolecular distances. These findings also indicate that SCO complexes reported in the literature are promising candidates for heat transportation switch materials.

Distinctive Aspects in Aquation, Proton-Coupled Redox, and Photoisomerization Reactions between Geometric Isomers of Mononuclear Ruthenium Complexes with a Large-π-Conjugated Tetradentate Ligand.

Geometric isomers of mononuclear ruthenium(II) complexes, distal-/proximal-[Ru(tpy)(dpda)Cl]+ (d-/p-RuCl, tpy = 2,2':6',2″-terpyridine, dpda = 2,7-bis(2-pyridyl)-1,8-diazaanthracene), were newly synthesized to comprehensively investigate the geometric and electronic structures and distinctive aspects in various reactions between isomers. The ultraviolet (UV)-visible absorption spectra of d-/p-RuCl isomers show intense bands for metal-to-ligand charge transfer (MLCT) at close wavelengths of 576 and 573 nm, respectively. However, time-dependent density functional theory (TD-DFT) calculations suggest that the MLCT transition of d-RuCl involves mainly single transitions to the π* orbital of the dpda ligand in contrast to mixing of the π* orbitals of the dpda and tpy ligands for p-RuCl. The aquation reaction (1.5 × 10-3 s-1) of p-RuCl to yield proximal-[Ru(tpy)(dpda)(OH2)]2+ (p-RuH2O) is faster than that (5.3 × 10-6 s-1) of d-RuCl in D2O/CD3OD (4:1 v/v) by three orders of magnitude, which resulted from the longer Ru-Cl bond by 0.017 Å and the distorted angle (100.2(3)°) of Cl-Ru-N (a nitrogen of dpda, being on a tpy plane) due to the steric repulsion between Cl and dpda for p-RuCl. Electrochemical measurements showed that d-RuH2O undergoes a 2-step oxidation reaction of 1H+-coupled 1e- processes of RuII-OH2/RuIII-OH and RuIII-OH/RuIV═O at pH 1-9, whereas p-RuH2O undergoes a 1-step oxidation reaction of a 2H+-coupled 2e- process of RuII-OH2/RuIV═O in the pH range of pH 1-10. The irreversible photoisomerization from d-RuH2O to p-RuH2O was observed in aqueous solution with an internal quantum yield (Φ) of 5.4 × 10-3% at 520 nm, which is lower compared with Φ = 1.1-2.1% of mononuclear Ru(II) aquo complexes with similar bidentate ligands instead of dpda by three orders of magnitude. This is possibly ascribed to the faster nonradiative decay rate from the excited 3MLCT state to the ground state for d-RuH2O due to the lower π* level of dpda ligands according to the energy-gap law: the rate decreases exponentially with the increasing energy gap.

Proton Conduction at High Temperature in High-Symmetry Hydrogen-Bonded Molecular Crystals of RuIII Complexes with Six Imidazole-Imidazolate Ligands.

A new H-bonded crystal [RuIII (Him)3 (Im)3 ] with three imidazole (Him) and three imidazolate (Im- ) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N-H⋅⋅⋅N H-bonds between the RuIII complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10-5  S cm-1 at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [RuIII (Him)3 (Im)3 ] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state 2 H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered.

Benzenetriimide-Based Molecular Conductor with Antiferro- to Ferromagnetic Switching Induced by Structural Change of π-stacked Array.

Benzenetriimide (BTI) is a promising building block for materials chemistry due to its characteristic 3-fold symmetry and redox properties, whereas little is known about its conductive and magnetic properties. In this study, we synthesized three charge-transfer complexes based on N,N',N''-trimethylbenzenetriimide (BTI-Me). One of the complexes contains isolated dimers of BTI-Me radical anion (BTI-Me⋅- ), while the other two have the infinite π-stacked array of BTI-Me with the formal charge of -0.5. The latter two complexes did not show metallic behavior but showed semiconducting behavior probably due to the characteristic insulation in one-dimensional electron system, so-called charge ordering and dimer-Mott insulation. The magnetic susceptibility of the complex in dimer-Mott state exhibits an unusual transition from antiferromagnetic to ferromagnetic spin states with the hysteresis loop of 15 K derived from the structural phase transition around 130 K. These properties were also supported by DFT calculations.

Heterospin frustration in a metal-fullerene-bonded semiconductive antiferromagnet.

Lithium-ion-encapsulated fullerenes (Li+@C60) are 3D superatoms with rich oxidative states. Here we show a conductive and magnetically frustrated metal-fullerene-bonded framework {[Cu4(Li@C60)(L)(py)4](NTf2)(hexane)}n (1) (L = 1,2,4,5-tetrakis(methanesulfonamido)benzene, py = pyridine, NTf2- = bis(trifluoromethane)sulfonamide anion) prepared from redox-active dinuclear metal complex Cu2(L)(py)4 and lithium-ion-encapsulated fullerene salt (Li+@C60)(NTf2-). Electron donor Cu2(L)(py)2 bonds to acceptor Li+@C60 via eight Cu‒C bonds. Cu-C bond formation stems from spontaneous charge transfer (CT) between Cu2(L)(py)4 and (Li+@C60)(NTf2-) by removing the two-terminal py molecules, yielding triplet ground state [Cu2(L)(py)2]+(Li+@C60•-), evidenced by absorption and electron paramagnetic resonance (EPR) spectra, magnetic properties and quantum chemical calculations. Moreover, Li+@C60•- radicals (S = ½) and Cu2+ ions (S = ½) interact antiferromagnetically in triangular spin lattices in the absence of long-range magnetic ordering to 1.8 K. The low-temperature heat capacity indicated that compound 1 is a potential candidate for an S = ½ quantum spin liquid (QSL).

Ion polarisation-assisted hydrogen-bonded ferroelectrics in liquid crystalline domains.

An alkylamide-substituted (-NHCOC10H21) hydrogen-bonded dibenzo[18]crown-6 derivative (1) was prepared to stabilise the ionic channel structure in a discotic hexagonal columnar (Colh) liquid crystal. The introduction of simple M+X- salts such as Na+PF6 - and K+I- into the ionic channel of 1 enhanced the ionic conductivity of the Colh phase of the M+·(1)·X- salts, with the highest ionic conductivity reaching ∼10-6 S cm-1 for K+·(1)·I- and Na+·(1)·PF6 - at 460 K, which was approximately 5 orders of magnitude higher than that of 1. The introduction of non-ferroelectric 1 into the ferroelectric N,N',N''-tri(tetradecyl)-1,3,5-benzenetricarboxamide (3BC) elicited a ferroelectric response from the mixed Colh phase of (3BC) x (1)1-x with x = 0.9 and 0.8. The further doping of M+X- into the ferroelectric Colh phase of (3BC)0.9(1)0.1 enhanced the ferroelectric polarisation assisted by ion displacement in the half-filled ionic channel for the vacant dibenzo[18]crown-6 of (3BC)0.9[(M+)0.5·(1)·(X-)0.5]0.1.

Dynamics of proton, ion, molecule, and crystal lattice in functional molecular assemblies.

Dynamic molecular processes, such as short- or long-range proton (H+) and ion (M+) motions, and molecular rotations in electrical conducting and magnetic molecular assemblies enable the fabrication of electron-H+ (or M+) coupling systems, while crystal lattice dynamics and molecular conformation changes in hydrogen-bonded molecular crystals have been utilised in external stimuli responsive reversible gas-induced gate opening and molecular adsorption/desorption behavior. These dynamics of the polar structural units are responsible for the dielectric measurements. The H+ dynamics are formed from ferroelectrics and H+ conductors, while the dynamic M+ motions of Li+ and Na+ involve ionic conductors and coupling to the conduction electrons. In n-type organic semiconductors, the crystal lattices are modulated by replacing M+ cations, with cations such as Li+, Na+, K+, Rb+, and Cs+. The use of polar rotator or inversion structures such as alkyl amides, m-fluoroanilinium cations, and bowl-shaped trithiasumanene π-cores enables the formation of ferroelectric molecular assemblies. The host-guest molecular systems of ESIPT fluorescent chromic molecules showed interesting molecular sensing properties using various bases, where the dynamic transformation of the crystal lattice and the molecular conformational change were coupled to each other.

Effective Na+-Binding Ability and Molecular Assembly of an Alkylamide-Substituted Penta(ethylene)glycol Derivative.

A new amphiphilic penta(ethylene glycol) derivative (1) bearing two hydrogen-bonding -CONHC14H29 chains was prepared. Compound 1 exhibited ion-recognition abilities for Na+ and K+, and its properties were compared with those of the macrocyclic [18]crown-6. Although both compound 1 and [18]crown-6 have six ether oxygen atoms (-OC2H2-), the Na+-binding ability of the former was much higher than that of the latter. K+-binding ability of cyclic [18]crown-6 was much higher than its Na+-binding ability, while the reverse was true for acyclic compound 1. Single-crystal X-ray structural analysis of Na+·1·B(Ph)4-·(hexane)2 at 100 K revealed the existence of a wrapped Na+-coordination by six ether and one carbonyl oxygen atoms of 1, which was further stabilized by intramolecular N-H···O═ hydrogen-bonding interactions. The complex phase transition during glass (G) formation and recrystallization was confirmed in the thermal cycle of Na+·1·B(Ph)4-, whose molten state showed two kinds of liquid phases, Na+-complexed (Na+·1) + B(Ph)4- and completely dissociated Na+ + 1 + B(Ph)4-. The Na+ conductivity of the molten state was 2 orders of magnitude higher than that of the G phase.

Ferroelectric columnar assemblies from the bowl-to-bowl inversion of aromatic cores.

Organic ferroelectrics, in which the constituent molecules retain remanent polarization, represent an important topic in condensed-matter science, and their attractive properties, which include lightness, flexibility, and non-toxicity, are of potential use in state-of-the-art ferroelectric devices. However, the mechanisms for the generation of ferroelectricity in such organic compounds remain limited to a few representative concepts, which has hitherto severely hampered progress in this area. Here, we demonstrate that a bowl-to-bowl inversion of a relatively small organic molecule with a bowl-shaped π-aromatic core generates ferroelectric dipole relaxation. The present results thus reveal an unprecedented concept to produce ferroelectricity in small organic molecules, which can be expected to strongly impact materials science.

Crystal Lattice Design of H2O-Tolerant n-Type Semiconducting Dianionic Naphthalenediimide Derivatives.

Dianionic bis(propionate)-naphthalenediimide (PCNDI2-) formed simple 2:1 cation-anion salts of (M+)2(PCNDI2-)·(H2O)n (M+ = Li+, Na+, K+, Rb+, and Cs+), which exhibited reversible H2O adsorption-desorption behavior because of the presence of their electrostatically binding crystal lattices. The maximum H2O adsorption amounts (n) for M+ = Li+, Na+, K+, Rb+, and Cs+ were 0.25, 6.0, 4.0, 6.0, and 2.0, respectively, whereas the reversible gate-opening (gate-closing) H2O adsorption-desorption isotherms were observed at 273 and 298 K, except for M+ = Li+. High ionic conductivities of around 10-4-10-5 S cm-1 were observed in M+ = Na+ and K+ salts, whereas short-range thermal fluctuations occurred in large cations of M+ = Rb+ and Cs+. The change in the electrostatic lattice energy for M+ = Na+ and K+ salts during the H2O adsorption-desorption cycles was significantly larger than those for M+ = Rb+ and Cs+. Therefore, the Na+ and K+ salts had a considerably flexible electrostatic crystal lattice with a large amplitude of lattice modulation during the H2O sorption cycle. In contrast, the lattice modulation for M+ = Rb+ and Cs+ salts involved a low magnitude of ion displacements, forming a relatively rigid cation-anion electrostatic crystal lattice. The flash-photolysis time-resolved microwave conductivity and transition absorption spectroscopy results revealed the high electron mobility of H2O-adsorbed thin films, wherein the crystallized H2O molecules did not act as electron-trapping sites. The values of electron mobility increased in the order of Cs+ ≈ Rb+ > K+ > Na+ > Li+.

Inversion Symmetry Breaking in Order-Disorder Transitions of Globular Ligands Coordinating to Cobalt(II) and Nickel(II) Bisacetylacetonato Complexes During Heating.

Unexpected inversion-symmetry breaking was observed in the order-disorder phase transitions of [M(acac)2 (abco)2 ] (1; M=Co2+ , 2; Ni2+ , acac- =2,4-pentanedionato, abco=1-azabicyclo-[2.2.2]-octane=quinuclidine) during heating. The isostructural, transition-free complexes [M(acac)2 (cabco)2 ] (3; M=Co2+ , 4; Ni2+ , cabco=3-chloro-1-azabicyclo-[2.2.2]-octane=3-chloroquinuclidine) were also studied for comparison. Complexes 1 and 2 crystallized in ordered phases in the centrosymmetric I2/m space group at 100 K, whereas they crystallized in disordered phases in the non-symmetric I2 space group at 300 K. The 60° step rotation disordering of the abco ligands was observed in the electron density maps of 1 and 2, which was consistent with the transition enthalpies estimated by differential scanning calorimetry (DSC). Gradual phase transitions were observed for 1 and 2 by DSC and powder X-ray diffraction (PXRD) at approximately 225 K. The inversion-symmetry disordering was likely induced by the local pseudo-symmetry of the abco ligands, increasing from trigonal to hexagonal and the increased steric repulsion pathways among them.