CO2‐Induced Spin‐State Switching at Room Temperature in a Monomeric Cobalt(II) Complex with the Porous Nature

CO₂‐responsive spin‐state conversion between high‐spin (HS) and low‐spin (LS) states at room temperature was achieved in a monomeric cobalt(II) complex. A neutral cobalt(II) complex, [Co^II(COO‐terpy)₂]?4 H₂O ( 1?4 H₂O ), stably formed cavities generated via π–π stacking motifs and hydrogen bond networks, resulting in the accommodation of four water molecules. Crystalline 1?4 H₂O transformed to solvent‐free 1 without loss of porosity by heating to 420 K. Compound 1 exhibited a selective CO₂ adsorption via a gate‐open type of the structural modification. Furthermore, the HS/LS transition temperature (T_1/2) was able to be tuned by the CO₂ pressure over a wide temperature range. Unlike 1 exhibits the HS state at 290 K, the CO₂‐accomodated form 1?CO₂ (P =110 kPa) was stabilized in the LS state at 290 K, probably caused by a chemical pressure effect by CO₂ accommodation, which provides reversible spin‐state conversion by introducing/evacuating CO₂ gas into/from 1 .     

Studies on the constituents of Syringa species. X. Five new iridoid glycosides from the leaves of Syringa reticulata (Blume) Hara

Five new iridoid glycosides, (8Z)-ligstroside (1), (8Z)-nüzhenide (3), 6'-O-alpha-D-glucopyranosylsyringopicroside (4), 3'-O-beta-D-glucopyranosylsyringopicroside (5) and 4'-O-beta-D-glucopyranosylsyringopicroside (6) were isolated, together with a known one, (8E)-nüzhenide (2), from the leaves of Syringa reticulata. Their structures were established on the basis of chemical and spectral data. Compounds 1 and 3 are the first findings of a (8Z)-oleoside-type secoiridoid. Compound 4 is the first naturally occurring iridoid di-glycoside having an isomaltose.     

Two triterpenoid saponins from Neonauclea sessilifolia

From the dried roots of Neonauclea sessilifolia (Rubiaceae), two new triterpenoid saponins, 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-quinovopyranosyl quinovic acid (1) and 3-O-alpha-L-rhamnopyranosyl-(1-->4)-beta-D-quinovopyranosyl pyrocincholic acid 28-O-beta-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl ester (2), were isolated, together with five known saponins. The structures of the new saponins were determined by spectroscopic and chemical means.     

7-endo selective aryl radical cyclization onto enamides leading to 3-benzazepines: concise construction of a cephalotaxine skeleton

Bu3SnH-mediated radical cyclizations of 2-(2-bromophenyl)-N-ethenylacetamide gave 6-exo cyclization product 15 as the major product, whereas N-[2-(2-bromophenyl)ethyl]-N-ethenylamides gave almost exclusively 7-endo cyclization products. These results indicated that the position of the carbonyl group on enamide played an important role in deciding the course of the cyclization. The 7-endo selective cyclization was applied to concise construction of a cephalotaxine skeleton.     

Alkali effects on the electronic states of K3C60 and Rb3C60

The electronic states in metallic alkali fullerides K₃C₆₀ and Rb₃C₆₀, are studied in detail by cw- and pulsed-ESR. The ESR linewidth associated with conduction electrons varies substantially, depending sensitively on the alkali metals used. It is clearly revealed that the linewidth is homogeneous and is strongly controlled by the spin-lattice relaxation times (T₁) determined via the spin-orbit interactions of the small fraction of s electrons remaining on the alkali atoms. The results indicate that the electron transfer from the alkali atoms to C₆₀ is not perfectly complete, with the remaining fraction being much greater in the tetrahedral sites than in the octahedral sites of the face-centered cubic lattice.     

New and efficient dehalogenative coupling and reduction of α-haloketones with active nickel complex. Facile syntheses of 1,4-diketones and bicyclo[4.2.O]oct-3-ene-2,5-diones

The active nickel complex generated in situ by reduction of NiBr₂(PPh₃)₂ with zinc in the presence of Et₄NI is a useful reagent for the dehalogenative coupling of phenacyl halides to 1,4-diaryl-1,4-diketones and for the dechlorination of 3,4-dichlorobicyclo[4.2.0]-octane-2,5-diones to bicyclo[4.2.0]oct-3-ene-2,5-diones.     

Formation mechanism and luminescence appearance of Mn-doped zinc silicate particles synthesized in supercritical water

Luminescence appearance of Mn-doped zinc silicate (Zn₂SiO₄:Mn²⁺, ZSM) formed in supercritical water at 400 °C and 29 MPa at reaction times from 1 to 4320 min was studied in the relation to its phase formation mechanism. Appearance of luminescent ZSM from green emission by α-ZSM and yellow emission by β-ZSM occurred over the same time period during the onset of phase formation at a reaction time of 2 min. Luminescence appeared at a much lower temperature and at shorter reaction times than the conventional solid-state reaction. Needle-like-shaped α-ZSM was the most stable particle shape and phase in the supercritical water reaction environment and particles formed via two routes: a homogenous nucleation route and a heterogenous route that involves solid-state diffusion and recrystallization.     

Evaluation of bitterness suppression of macrolide dry syrups by jellies

The purpose of this study was to evaluate the bitterness-suppressing effect of three jellies, all commercially available on the Japanese market as swallowing aids, on two dry syrups containing the macrolides clarithromycin (CAM) or azithromycin (AZM). The bitterness intensities of mixtures of the dry syrups and acidic jellies were significantly greater than those of water suspensions of the dry syrups in human gustatory sensation tests. On the other hand, the mixture with a chocolate jelly, which has a neutral pH, was less bitter than water suspensions of the dry syrups. The bitterness intensities predicted by the taste sensor output values correlated well with the observed bitterness intensities in human gustatory sensation tests. When the concentrations of CAM and AZM in solutions extracted from physical mixtures of dry syrup and jelly were determined by HPLC, concentrations in the solutions extracted from mixtures with acidic jellies were higher than those from mixtures with a neutral jelly (almost 90 times higher for CAM, and almost 7-10 times higher for AZM). Thus, bitterness suppression is correlated with the pH of the jelly. Finally, a drug dissolution test for dry syrup with and without jelly was performed using the paddle method. There was no significance difference in dissolution profile. It was concluded the appropriate choice of jelly with the right pH is essential for taste masking. Suitable jellies might be used to improve patient compliance, especially in children. The taste sensor may be used to predict the bitterness-suppressing effect of the jelly.