Synthesis and luminescence properties of substituted benzils

Photophysical properties of benzil (1,2-diphenylethane-1,2-dione) and its derivatives in the crystal state have recently attracted much attention. However, the study of substituted benzils has mostly been limited to para-substituted derivatives, which did not induce a significant effect on the emission wavelength compared to pristine benzil. The effects of ortho- and meta-substituents on the photophysical properties in the crystal state have not been investigated so far. Our recently developed organocatalytic pinacol coupling of substituted benzaldehydes allowed us to prepare various ortho-, meta-, and para-substituted benzil derivatives and to investigate their luminescence properties. Ortho- and meta-substituents affected the electronic states of benzils in the crystal state, resulting in differences in their luminescence properties. The luminescence wavelength and type, i.e., phosphorescence or fluorescence, were altered by these substituents. Fast self-recovering phosphorescence-to-phosphorescence mechanochromism by the para-CF3 substituent at room temperature was also discovered.

Possible Roles of Transition Metal Cations in the Formation of Interstellar Benzene via Catalytic Acetylene Cyclotrimerization

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous interstellar molecules. However, the formation mechanisms of PAHs and even the simplest cyclic aromatic hydrocarbon, benzene, are not yet fully understood. Recently, we reported the statistical and dynamical properties in the reaction mechanism of Fe+-catalyzed acetylene cyclotrimerization, whereby three acetylene molecules are directly converted to benzene. In this study, we extended our previous work and explored the possible role of the complex of other 3d transition metal cations, TM+ (TM = Sc, Ti, Mn, Co, and Ni), as a catalyst in acetylene cyclotrimerization. Potential energy profiles for bare TM+-catalyst (TM = Sc and Ti), for TM+NC--catalyst (TM = Sc, Ti, Mn, Co, and Ni), and for TM+-(H2O)8-catalyst (TM = Sc and Ti) systems were obtained using quantum chemistry calculations, including the density functional theory levels. The calculation results show that the scandium and titanium cations act as efficient catalysts in acetylene cyclotrimerization and that reactants, which contain an isolated acetylene and (C2H2)2 bound to a bare (ligated) TM cation (TM = Sc and Ti), can be converted into a benzene-metal-cation product complex without an entrance barrier. We found that the number of electrons in the 3d orbitals of the transition metal cation significantly contributes to the catalytic efficiency in the acetylene cyclotrimerization process. On-the-fly Born-Oppenheimer molecular dynamics (BOMD) simulations of the Ti+-NC- and Ti+-(H2O)8 complexes were also performed to comprehensively understand the nuclear dynamics of the reactions. The computational results suggest that interstellar benzene can be produced via acetylene cyclotrimerization reactions catalyzed by transition metal cation complexes.

Bromocyclization of Alkenoic Thioester and Access to Functionalized Sulfur-Heterocycles

Although oxygen, nitrogen, and carbon have been extensively studied as nucleophilic elements in the halocyclization of alkenes, sulfur-based nucleophiles are relatively unexplored. Herein, we investigated bromocyclization chemistry involving unsaturated thioesters, with a focus on their use as potential S-nucleophiles. We developed a bromocyclization method that uses alkenoic thioesters and N-bromoacetamide (NBA) to form cyclic bromosulfides. The resulting 5-exo products are labile and can be used in various nucleophilic substitution reactions.

(31E,32Z,71E,72Z)-4,8-Bis(3,5-di-chloro-phen-yl)-14,33,53,73-tetra-propyl-11H,32H,51H,72H-1,5(2,5),3,7(5,2)-tetra-pyrrola-2,6(2,5)-di-thiophena-cyclo-octa-phane

Purple crystals of the title compound, C50H44Cl4N4S2 were obtained from the reaction of 2,5-bis-(4-propyl-1H-pyrrol-2-yl)thio-phene and 3,5-di-chloro-benzaldehyde in the presence of tri-fluoro-acetic acid for 3 h and subsequent addition of p-chloranil. The macrocycle in the title compound can be described as a highly planar structure wthe the average deviation of the 32 macrocyclic atoms from the least-squares plane being 0.0416 Å. Its mol-ecular conformation is stabilized by two intra-molecular N-H⋯N bonds and a three-dimensional network is formed by C-H⋯π inter-actions.

Acylated plastoquinone is a novel neutral lipid accumulated in cyanobacteria

Although cyanobacteria do not possess bacterial triacylglycerol (TAG)-synthesizing enzymes, the accumulation of TAGs and/or lipid droplets has been repeatedly reported in a wide range of species. In most cases, the identification of TAG has been based on the detection of the spot showing the mobility similar to the TAG standard in thin-layer chromatography (TLC) of neutral lipids. In this study, we identified monoacyl plastoquinol (acyl PQH) as the predominant molecular species in the TAG-like spot from the unicellular Synechocystis sp. PCC 6803 (S.6803) as well as the filamentous Nostocales sp., Nostoc punctiforme PCC 73102, and Anabaena sp. PCC 7120. In S.6803, the accumulation level of acyl PQH but not TAG was affected by deletion or overexpression of slr2103, indicating that acyl PQH is the physiological product of Slr2103 having homology with the eukaryotic diacylglycerol acyltransferase-2 (DGAT2). Electron microscopy revealed that cyanobacterial strains used in this study do not accumulate lipid droplet structures such as those observed in oleaginous microorganisms. Instead, they accumulate polyhydroxybutyrate (PHB) granules and/or aggregates of alkane, free C16 and C18 saturated fatty acids, and low amounts of TAG in the cytoplasmic area, which can be detected by staining with a fluorescent dye specific to neutral lipids. Unlike these lipophilic materials, acyl PQH is exclusively localized in the membrane fraction. There must be DGAT2-like enzymatic activity esterifying de novo-synthesized C16 and C18 fatty acids to PQH₂ in the thylakoid membranes.

Current issues and future directions in gymnastics research: biomechanics, motor control and coaching interface

The sport of gymnastics is undergoing a global examination of its culture and the relationship between the gymnast, coach and environment is a central focus. The aim of this review is to explore biomechanics and motor control research in skill development and technique selection in artistic gymnastics with a focus on the underlying concepts and scientific principles that allow performance enhancement, skill development and injury risk reduction. The current review examines peer reviewed papers from 2000 onwards, with a focus on contemporary approaches in the field of gymnastics research, and highlights several key directions for future gymnastics research. Based on our review and the integration of the models of Newell (1986) and Irwin et al. (2005), we recommend that future gymnastics research should embrace at the very least a multidisciplinary approach and aim for an interdisciplinary paradigm.

syn and anti Metal Complexes of 24π Antiaromatic Bis(dicarbonylrhodium(I))dithiaamethyrin

From the reaction of sterically less hindered tetrapropyl[24]dithiaamethyrin(1.0.0.1.0.0) 5, with [Rh(CO)2Cl]2, a unique anti form of the bis(dicarbonylrhodium(I)) complex (6-anti), where two rhodium ions are on the opposite faces of the macrocyclic ligand, was isolated for the first time in 12% yield along with the corresponding syn isomer (6-syn, 61% yield). These structures were characterized in detail by single-crystal X-ray structure analysis. Compound 6-syn exhibited a bowl-shaped structure with the two rhodium atoms separated by a distance of ~4.5 Å. In contrast, 6-anti contained a wave-shaped macrocycle with a distance of ~5.3 Å between the two rhodium atoms. Furthermore, the 1H nuclear magnetic resonance spectra and density functional theory calculation results revealed that 6-anti had a stronger paratropic ring current and a more planar structure than 6-syn. The isolation of both 6-anti and 6-syn enabled the structure-property relationship to be discussed in detail.

Cyclometalated Platinum(II) Complexes in a Cis-N,N Configuration: Photophysical Properties and Isomerization to Trans Isomers

Synthesis, isomerization, and photophysical properties of novel cis-N,N-cyclometalated complexes [Pt(C^∧N)(l-Phe)] (C^∧N = benzoquinolinate (1), phenylpyridinate (2), 2-(p-tolyl)pyridinate (3), and 1-phenylpyrazolate (4); l-Phe^- = l-phenylalaninate) are reported herein. In solution, the cis forms of the complexes isomerize to their trans forms via an associative mechanism. This cis/trans isomerism barely influences the absorption and luminescence properties of the complexes in solution, except for a characteristic absorption at approximately 340 nm in the absorption spectra of the cis complexes that is not observed for the trans complexes. Interestingly, the cis complexes are spontaneously assembled in a crystalline phase and show bathochromic absorption and emission colors compared with those of the corresponding trans isomers, which are aggregated in an amorphous phase. cis-1 and cis-2 demonstrate hypsochromic luminescence mechanochromism. The influence of the geometrical isomerism on the photophysical properties and the isomerization mechanism are supported by density functional theory calculations.

Numerical Study of Triplet Dynamics in Organic Semiconductors Aimed for the Active Utilization of Triplets by TADF under Continuous-Wave Lasing

The limitation of lasing duration less than nanosecond order has been a major problem for realizing organic solid-state continues-wave (CW) lasers and organic semiconductor laser diodes. Triplets accumulation under CW excitation has been well recognized as a critical inhibiting factor. To overcome this issue, the utilization of thermally activated delayed fluorescence (TADF) emitters is a promising mechanism because of efficient reverse intersystem crossing. Herein, we model the triplet accumulation processes under lasing and propose the active utilization of TADF for lasing based on our simulation analysis. We used the rate constants experimentally determined from the optical properties of a boron difluoride curcuminoid fluorophore showing both TADF and lasing. We demonstrate that the intersystem crossing efficiency is gradually increased after the convergence of relaxation oscillation, i.e., terminating laser oscillation. In addition, we found that when the reverse intersystem crossing rate is close to the intersystem crossing rate, CW lasing becomes dominant.

o-Azophenylboronic Acid-Based Colorimetric Sensors for d-Fructose: o-Azophenylboronic Acids with Inserted Protic Solvent Are the Key Species for a Large Color Change

Many boronic acid-based chemosensors for saccharides have been developed; however, their detection mechanisms have seldom been studied. In this study, we synthesized 10 o-azophenylboronic acid derivatives (azoBs) and conducted a fundamental study on the reactivity and the sensing mechanism of azoBs, which undergoes a large color change, e.g., from red to yellow, upon a reaction with saccharides. Their pH-independent formation constants were determined by spectrophotometric titration and then converted to the conditional formation constant K' at pH 7.4. A linear free energy relationship was established between log K' and the pK_a of azoB. ¹¹B NMR measurements indicate that in aprotic solvents, azoB forms a trigonal planar structure, while in protic solvents, it forms a quasi-tetrahedral structure (azoB-ROH) with a protic solvent molecule (ROH) inserted between the boronic acid moiety and the azo group. In addition, UV-vis spectroscopic studies showed that the color change during the reaction between azoB and d-fructose in ROH was caused by the release of the ROH from azoB-ROH by d-fructose. Based on the findings in this study, we proposed a guideline for designing an azoB-based chemosensor that exhibits high reactivity toward saccharides and a sufficient color change to allow for the visual detection of saccharides.

Spin-inversion mechanisms in O2 binding to a model heme complex revisited by density function theory calculations

Spin-inversion mechanisms in O₂ binding to a model heme complex, consisting of Fe(II)-porphyrin and imidazole, were investigated using density-functional theory calculations. First, we applied the recently proposed mixed-spin Hamiltonian method to locate spin-inversion structures between different total spin multiplicities. Nine spin-inversion structures were successfully optimized for the singlet-triplet, singlet-quintet, triplet-quintet, and quintet-septet spin-inversion processes. We found that the singlet-triplet spin-inversion points are located around the potential energy surface region at short Fe-O distances, whereas the singlet-quintet and quintet-septet spin-inversion points are located at longer Fe-O distances. This suggests that both narrow and broad crossing models play roles in O₂ binding to the Fe-porphyrin complex. To further understand spin-inversion mechanisms, we performed on-the-fly Born-Oppenheimer molecular dynamics calculations. The reaction coordinates, which are correlated to the spin-inversion dynamics between different spin multiplicities, are also discussed.

Detrimental Effect of Unreacted PbI2 on the Long-Term Stability of Perovskite Solar Cells

Excess/unreacted lead iodide (PbI₂ ) has been commonly used in perovskite films for the state-of-the-art solar cell applications. However, an understanding of intrinsic degradation mechanisms of perovskite solar cells (PSCs) containing unreacted PbI₂ has been still insufficient and, therefore, needs to be clarified for better operational durability. Here, it is shown that degradation of PSCs is hastened by unreacted PbI₂ crystals under continuous light illumination. Unreacted PbI₂ undergoes photodecomposition under illumination, resulting in the formation of lead and iodine in films. Thus, this photodecomposition of PbI₂ is one of the main reasons for accelerated device degradation. Therefore, this work reveals that carefully controlling the formation of unreacted PbI₂ crystals in perovskite films is very important to improve device operational stability for diverse opto-electronic applications in the future.

Luminescence of mononuclear Pt(ii) complexes with glycolate: external stimuli-induced excimer emission changes to oligomer emissions

Trihydrate crystals of novel Pt^II complexes [Pt^II(bpy)(gl)] (bpy: 2,2′-bipyridine; Hgl⁻: glycolate) show excimer emission changes to two kinds of oligomer emissions depending on the type of external stimuli.

A water-soluble cyclometalated iridium(iii) complex for pH sensing based on aggregation-induced enhanced phosphorescence

The novel water-soluble monoanionic Ir(iii) complex Na[Ir(ppy)2(SB-COO)] (2; Hppy = phenylpyridine; HSB-COOH = 4-carboxylanilinesalicylaldehyde Schiff base), which was obtained by the reaction of the novel Ir(iii) complex [Ir(ppy)2(SB-COOH)] (1) with NaOEt, in its aqueous solution, showed hydrogen ion (H+)-responsive aggregation-induced enhanced phosphorescence (AIEP). Both these complexes exhibited very weak and relatively strong emissions in solution and solid states, respectively. The pH-responsiveness of 2 was evaluated from its emission spectra in aqueous solution in the pH range of 8.7-1.8. Above pH 6, 2 showed weak emission with a maximum at 508 nm. Upon decreasing the pH to 4.7, AIEP with a bathochromic shift to 618 nm was induced by the aggregation of 1, whereby the intensity at 618 nm was increased approximately by 50-fold compared to that at pH 6.0. This enhancement is due to restrictions of the geometrical changes in the six-membered chelate ring of the ancillary ligand (Ir-N-C-C-C-O-) and of the intramolecular rotations in the excited state. The enhanced luminescence originates from spin-forbidden metal-to-ligand-ligand charge transfer (3MLLCT). Below pH 2.8, the emission intensity decreased owing to the decrease in the population of the emissive complex 1 upon dissociation of the ancillary ligand from the Ir(ppy)2 unit.

The Relation of Phase-Transition Effects and Thermal Stability of Planar Perovskite Solar Cells

A power conversion efficiency of over 20% has been achieved in CH3NH3PbI3-based perovskite solar cells (PSC), however, low thermal stability associated with the presence of a phase transition between tetragonal and cubic structures near room temperature is a major issue that must be overcome for future practical applications. Here, the influence of the phase transition on the thermal stability of PSCs is investigated in detail by comparing four kinds of perovskite films with different compositions of halogen atoms and organic components. Thermally stimulated current measurements reveal that a large number of carrier traps are generated in solar cells with the perovskite CH3NH3PbI3 as a light absorber after operation at 85 °C, which is higher than the phase-transition temperature. Electrochemical impedance spectroscopy measurements further exclude effects of a possible morphology change on the formation of carrier traps. These carrier traps are detrimental to the thermal stability. The thermogravimetric analysis does not show a decomposition for any of the materials in the temperature range relevant for operation. The perovskite alloys do not have this phase transition, resulting in effectively suppressed formation of carrier traps. PSCs with improved thermal stability under the standard thermal cycling test are demonstrated.

Observation of the First Spin Crossover in an Iron(II) Complex with an S6 Coordination Environment: Tris[bis(N,N-diethylamino)carbeniumdithiocarboxylato]iron(II) Hexafluorophosphate

For the first time, the spin-crossover (SCO) phenomenon has been observed in an Fe^II -S₆ system in a tris(chelate)-type iron(II) complex with a zwitterionic sulfur donor bidentate, bis(N,N-diethylamino)carbeniumdithiocarboxylate (EtL), [Fe^II (EtL)₃ ](PF₆ )₂ (1), as synthesized by the reaction of a precursor complex [Fe^II (CH₃ CN)₆ ](PF₆ )₂ with EtL. In the solid state, the high-spin (HS) d⁶ state at ambient temperature and the low-spin (LS) d⁶ state at temperatures lower than approximately 240 K were evidenced by magnetic measurements with SQUID and Mössbauer spectra in the temperature range 4-290 K. X-ray analyses of the crystals at various temperatures disclosed that the distorted trigonal prismatic coordination environments essentially do not change; however, contraction of Fe-S distances by approximately 10 % (0.22 Å), ordering of alkyl groups in EtL and PF₆ ^- counteranions, and formation of significant intermolecular S⋅⋅⋅S interactions between adjacent molecules (average distances of 3.59 Å) take place during the transition from the HS to the LS state. A large decrease in the volume of the formula unit (78.1 ų ) might be responsible for the large activation barrier, thereby resulting in a slow phase transition upon cooling.

Diffusion Enhancement in Highly Excited MAPbI3 Perovskite Layers with Additives

Carrier mobility is one of the crucial parameters determining the electronic device performance. We apply the light-induced transient grating technique to measure independently the carrier diffusion coefficient and lifetime, and to reveal the impact of additives on carrier transport properties in wet-cast CH₃NH₃PbI₃ (MAPbI₃) perovskite films. We use the high excitation regime, where diffusion length of carriers is controlled purely by carrier diffusion and not by the lifetime. We demonstrate a four-fold increase in diffusion coefficient due to the reduction of localization center density by additives; however, the density dependence analysis shows the dominance of localization-limited diffusion regime. The presented approach allows us to estimate the limits of technological improvement-carrier diffusion coefficient in wet-cast layers can be expected to be enhanced by up to one order of magnitude.

Syn and anti conformers of di-ammonium aqua-bis(malonato)oxidovanadate(IV) in an anhydrate crystal

The asymmetric unit of the title anhydrate compound, (NH4)2[VO(C3H2O4)2(H2O)], consists of two independent complex anions and four ammonium cations. In the complex anions, the VIV atoms are each coordinated by two malonate ligands, one water mol-ecule and one oxide O atom in a distorted octa-hedral geometry. The equatorial plane is formed by the malonate O atoms, while the axial positions are occupied by water and oxide O atoms. The difference between the two independent complexes is the relative conformation of the malonate ligands. The two ligands in one complex anion are in a syn conformation, while in the other they adopt an anti conformation. In the crystal, the complex anions inter-act with the counter-cations and adjacent anions through O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds. Stacks of alternating layers consisting of either anti or syn isomers, formed with the aid of the hydrogen bonding, are observed. DFT calculations for the anti and syn isomers show a similar thermodynamic stability to each other. The crystal used for this analysis was an inversion twin with the ratio of the twin components being 0.270 (13):0.730 (13).

Characteristic Aromas of Quercus crispula (Japanese Oak)

Nature is important in Japanese culture. Many tree species produce diverse fragrances, making Japan's forests a botanical treasure. However, there have been no detailed investigations of the aroma characteristics of trees, a vital factor in forest bathing. Previously, we applied our analytical method to three tree species found mainly in Japan: Chamaecyparis pisifera, Lindera praecox, and Lindera obtusiloba Blume. In this paper, we report investigations of the aroma of Quercus crispula Blume (Japanese oak) using this analysis method. Japanese oak grows mainly in Japan. The odor compounds of Japanese oak were obtained by hexane extraction and monolithic material sorptive extraction and each extracted compound was identified by gas chromatography olfactometry and gas chromatography-mass spectrometry. Comparison of the aromas and compounds in the extracts resulted in the identification of important aroma compounds in Japanese oak: 10 (including eugenol) in the leaves and 15 (including 3-methyl-4-octanolide) in the wood.

A red fluorophore comprising a borinate-containing xanthene analogue as a polyol sensor

A xanthene derivative containing a borinate moiety emitted red fluorescence with a high quantum yield. The interaction between the borinate and a sugar molecule induced a fluorescence change based on the change in the HOMO-LUMO gap. The response was pH-resistant in a wide range. In addition, catechol quenched through photoinduced electron transfer. The red fluorescence and polyol binding ability of dyes will pave the way for new biological applications of chemical sensors.

The Aroma Profiles of Thai Green Teas Derived from Two Varieties, Chinese and Assam

Camellia sinensis cultivated for tea has two varieties: Camellia sinensis var. sinensis (Chinese variety) and Camellia sinensis var. assamica (Assam variety). Japanese green teas are mainly produced from the Chinese variety, whereas Thai green teas are made from both varieties. The odors of Thai green teas made from each variety differ from each other and are also distinct from that of Japanese green tea. Here, we investigated the characteristics of the aroma of Thai green teas (Chinese and Assam varieties) and Japanese green tea (Chinese variety) following fractional distillation of their hexane extracts. Each fraction was analyzed by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). We found that the rich aroma characteristics of Thai green tea depend on whether the Chinese or the Assam variety is used.

Toward continuous-wave operation of organic semiconductor lasers

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture.

Luminescence of tartrate bridged dinuclear 2,2′-bipyridine platinum(ii) complexes: emission color controlled by intra- and inter-molecular interactions in the solid state

Mono- and dinuclear Pt^II complexes with tartrate (tartH₂²⁻) [Pt(bpy)(tartH₂)] and [{Pt(bpy)}₂(μ-tart)], respectively, in crystals exhibited an emission color controlled by intra- and inter-molecular Pt–Pt and/or π–π interactions.

Multifunctional Benzoquinone Additive for Efficient and Stable Planar Perovskite Solar Cells

Device stability of planar perovskite solar cells is improved by virtue of multifunctional BQ additive. The morphology and crystal quality of the perovskite films are improved because BQ slows the rate of perovskite crystal formation. Electron transfer from perovskite to BQ reduces charge-recombination losses, and the oxidizing ability of BQ effectively suppresses the formation of metallic lead and improves device lifetime.

Solution-Processed Organic-Inorganic Perovskite Field-Effect Transistors with High Hole Mobilities

A very high hole mobility of 15 cm² V^-1 s^-1 along with negligible hysteresis are demonstrated in transistors with an organic-inorganic perovskite semiconductor. This high mobility results from the well-developed perovskite crystallites, improved conversion to perovskite, reduced hole trap density, and improved hole injection by employing a top-contact/top-gate structure with surface treatment and MoO_x hole-injection layers.

Aroma Profile of Galangal Composed of Cinnamic Acid Derivatives and Their Structure-Odor Relationships

Cinnamic acid derivatives are important odorants due to their characteristic scent. Some fragrance materials, such as cinnamon bark, matsutake mushrooms, and Kaempferia galanga L. rhizome (galangal), contain several cinnamic acid derivatives as important odor constituents. The main odor constituent of glangal is (E)-ethyl 4-methoxycinnamate, but the odor of this compound is different from that of galangal. We investigated the aroma profile of galangal using our previously described method that considers the intermolecular interactions of the odorant compounds with their receptors. Odorant compounds in galangal were extracted by hexane extraction, steam distillation, and headspace sampling. The odor of the hexane extract was different from that of the steam - distillate and similar to that of galangal; therefore, we searched for the key compounds contributing to the aroma profile of galangal by separating the constituents of the hexane extract. A fraction with a galangal-like odor was obtained by bulb-to-bulb distillation of the hexane extract. The main component of this fraction was not (E)-ethyl 4-methoxycinnamate, but rather ethyl cinnamate. These results indicate that ethyl cinnamate is more important in the aroma profile of galangal than (E)-ethyl 4-methoxycinnamate. GC-MS analysis revealed that this fraction contained aromatic compounds, cyclic terpenes, and linear chain compounds in addition to ethyl cinnamate. We synthesized cinnamic acid derivatives and examined the importance of the odor expression of these cinnamic acid derivatives. Cinnamic acid derivatives lacking a p-methoxy group had a strong fruity odor. Replacement of the hydrogen atom at the para position with a methoxy group altered and weakened the odor. We found that a p-methoxy group in cinnamic acid derivatives plays an important role in the aroma profile of galangal.

Aroma Profile of Galangal Composed of Cinnamic Acid Derivatives and Their Structure-Odor Relationships

Cinnamic acid derivatives are important odorants due to their characteristic scent. Some fragrance materials, such as cinnamon bark, matsutake mushrooms, and Kaempferia galanga L. rhizome (galangal), contain several cinnamic acid derivatives as important odor constituents. The main odor constituent of galangal is ( E)-ethyl 4-methoxycinnamate, but the odor of this compound is different from that of galangal. We investigated the aroma profile of galangal using our previously described method that considers the intermolecular interactions of the odorant compounds with their receptors. Odorant compounds in galangal were extracted by hexane extraction, steam distillation, and headspace sampling. The odor of the hexane extract was different from that of the steam distillate and similar to that of galangal; therefore, we searched for the key compounds contributing to the aroma profile of galangal by separating the constituents of the hexane extract. A fraction with a galangal-like odor was obtained by bulb-to-bulb distillation of the hexane extract. The main component of this fraction was not ( E)-ethyl 4-methoxycinnamate, but rather ethyl cinnamate. These results indicate that ethyl cinnamate is more important in the aroma profile of galangal than ( E)-ethyl 4-methoxycinnamate. GC-MS analysis revealed that this fraction contained aromatic compounds, cyclic terpenes, and linear chain compounds in addition to ethyl cinnamate. We synthesized cinnamic acid derivatives and examined the importance of the odor expression of these cinnamic acid derivatives. Cinnamic acid derivatives lacking a p-methoxy group had a strong fruity odor. Replacement of the hydrogen atom at the para position with a methoxy group altered and weakened the odor. We found that a p-methoxy group in cinnamic acid derivatives plays an important role in the aroma profile of galangal.

Characteristic Aroma Features of Tencha and Sencha Green Tea Leaves Manufactured by Different Processes

There are many varieties of tea ( Camellia sinensis) obtained by different processing methods. In Japan, sencha tea has been used to brew beverages for centuries, and tencha leaves are used to make powdered green tea, matcha, which is used as an important food additive to impart the odor of green tea. We investigated the differences between the odors of sencha and tencha and their aroma profiles. We used our new technique to evaluate the odor of green tea, based on the theory that the aroma characteristics of materials arise from the interactions of groups of compounds with similar structures. Hexane extracts from sencha and tencha leaves were analyzed by gas chromatography-olfactometry. We detected several important compounds for tencha. The hexane extracts were separated by distillation, and groups of compounds with different boiling points were obtained. We investigated the group of high-boiling point constituents, which had a matcha-like odor and consisted of a group of odor constituents common to sencha and tencha. Tencha had a characteristic seaweed-like odor, and the low-boiling point constituents caused the differences in the tencha and sencha odors.

Characteristic Aroma Features of Tencha and Sencha Green Tea Leaves Manufactured by Different Processes

There are many varieties of tea (Camellia sinensis) obtained by different processing methods. In Japan, sencha tea has been used to brew beverages f6r centuries, and tencha leaves are used to make powdered green tea, matcha, which is used as an important food additive to impart the odor of green tea. We investigated the differences between the odors of sencha and tencha and their aroma profiles. We used our new technique to evaluate the odor of green tea, based on the theory that the aroma characteristics of materials arise from the interactions of groups of compounds with similar structures. Hexane extracts from sencha and tencha leaves were analyzed by gas chromatography-olfactometry. We detected several important compounds for tencha. The hexane extracts were separated by distillation, and groups of compounds with different boiling points were obtained. We investigated the group of high-boiling point constituents, which had a matcha-like odor and consisted of a group of odor constituents common to sencha and tencha. Tencha had a characteristic seaweed-like odor, and the low-boiling point constituents caused the differences in the tencha and sencha odors.

Degradation Mechanisms of Solution-Processed Planar Perovskite Solar Cells: Thermally Stimulated Current Measurement for Analysis of Carrier Traps

Degradation mechanisms of CH3 NH3 PbI3 -based planar perovskite solar cells (PSCs) are investigated using a thermally stimulated current technique. Hole traps lying above the valence-band edge of the CH3 NH3 PbI3 are detected in PSCs degraded by continuous simulated solar illumination. One source of the hole traps is the photodegradation of CH3 NH3 PbI3 in the presence of water.

Mechanochromism in the luminescence of novel cyclometalated platinum(ii) complexes with α-aminocarboxylates

Cyclometalated platinum(ii) complexes with α-aminocarboxylato ligands [Pt^II(ppy)L] (ppy = 2-phenylpyridinato, L⁻ = Gly, Ala, Leu, Ile, Phe, Sar) in the solid state exhibited reversible luminescent mechanochromism.

Crystal structure of 4,4′-dimethoxy-2,2′-bipyridine

In the title compound, C12H12N2O2, the dihedral angle between the planes of the two pyridine rings is 5.8 (1)°. Neighbouring molecules are linkedviaC(Me)—H...N interactions, generating a two-dimensional sheet structure; C—H...π interactions further link the molecules into a three-dimensional network. An overlapped arrangement of parallel pyridine rings in neighbouring molecules [centroid-to-centroid distance = 3.6655 (15) Å] is observed in the crystal structure.