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.