The Electronic State of Hydrogen in the α Phase of the Hydrogen‐Storage Material PdH(D)x: Does a Chemical Bond Between Palladium and Hydrogen Exist?

The palladium–hydrogen system is one of the most famous hydrogen‐storage systems. Although there has been much research on β‐phase PdH(D)_x, we comprehensively investigated the nature of the interaction between Pd and H(D) in α‐phase PdH(D)_x (x<0.03 at 303 K), and revealed the existence of Pd?H(D) chemical bond for the first time, by various in situ experimental techniques and first‐principles theoretical calculations. The lattice expansion, magnetic susceptibility, and electrical resistivity all provide evidence. In situ solid‐state ¹H and ²H NMR spectroscopy and first‐principles theoretical calculations revealed that a Pd?H(D) chemical bond exists in the α phase, but the bonding character of the Pd?H(D) bond in the α phase is quite different from that in the β phase; the nature of the Pd?H(D) bond in the α phase is a localized covalent bond whereas that in the β phase is a metallic bond.     

Phloroglucinol derivatives and a chromone glucoside from the leaves of Myrtus communis

Seven new phloroglucinol derivatives, myrtucommunins A–D (1–4), 6-methylisomyrtucommulone B (5), 4-methylmyrtucommulone B (6), and 2-isobutyryl-4-methylphloroglucinol 1-O-β-d-glucopyranoside (7), and one new chromone derivative, undulatoside A 6′-O-gallate (8), were isolated from the leaves of Myrtus communis (Myrtaceae). Myrtucommunins A–D (1–4) were conjugates of polymethylated acylphloroglucinol and flavonol rhamnoside. The absolute configurations of the rhamnosyl moieties for 1–4 were confirmed to be l in each case by HPLC analyses, while those of the aglycones were assigned by comparisons of the experimental and TDDFT calculated ECD spectra. 6-Methylisomyrtucommulone B (5) and 4-methylmyrtucommulone B (6) were assigned as 6/6/6 tricyclic acylphloroglucinol derivatives with a racemic nature. Antimicrobial activities of 1–8 and related known compounds were evaluated.     

Stereospecific construction of a trans-1,4-diphosphacyclohexane skeleton

trans-1,4-Diphosphacyclohexanes were successfully synthesized by the stereospecific intramolecular coupling reaction of the optically active bisphosphine. This is a new route for the construction of the trans-1,4-diphosphacyclohexane skeleton. A cis isomer was also prepared along with the trans isomer from a mixture of rac- and meso-bisphosphines. The coordinated boranes were easily removed to afford the corresponding 1,4-diphosphacyclohexanes.     

Letter: correlation between phosphorylation ratios by matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis and enzyme kinetics

To identify the correlation between the phosphorylation ratios by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-ToF MS) analysis and enzyme kinetics (K(m), V(max), and V(max)/K(m)) is important to understand whether MALDI-TOF MS can be applied for monitoring the properties of peptides that are substrates of protein kinases. The correlation between phosphorylation ratios and enzyme kinetics was examined using peptides for protein kinase C (PKC) and for 60 kDa phosphoprotein, encoded by the cellular sarcoma gene (c-Src). Phosphorylation ratios, analyzed by MALDI-ToF MS, showed higher correlation coefficient (r = > +0.7) for V(max)/K(m) compared with that (r = < -/+0.6) for K(m) or V(max). For ion modes, a higher correlation coefficient between phosphorylation ratios and V(max)/K(m) was identified in the positive mode (r = > +0.7) compared to that in the negative mode (r = < +0.5). These results suggest that MALDI-ToF MS is a useful tool to evaluate V(max)/K(m) of peptides for protein kinases.     

Structure determination and magnetic studies of triazole chelated Co(II) coordination polymers

Two cobalt(II) halide complexes with 1,2,4-triazole as a ligand were synthesized. Their structures were determined by extended x-ray absorption fine structure (EXAFS) and powder x-ray diffraction (XRD). Both complexes [Co(Htrz)Cl₂]_n ( 1 ) and {[Co(Htrz)₂(trz)]BF₄}_n ( 2 ) form one-dimensional polymeric chain and the distances of Co⋯Co are 3.3521(2) Å and 3.8629(2) Å, respectively. The Htrz and Cl⁻ are bridging ligands to connect two Co(II) ions in 1 , and the local environment of Co site is in a distorted octahedron with {CoN₂Cl₄} core. In complex 2 , two Htrz and one trz are bridging ligands to connect two Co(II) ions, and the local geometry of Co is in a pseudo octahedron with {CoN₆} core. The analysis of Co L_II,III-edge XAS indicates that the Co(II) of both complexes are at high spin state with t_2g⁵e_g² configuration and the crystal field strength (10Dq) is about 1.2 eV. The broken-symmetry DFT calculations indicate that antiferromagnetic coupling state of Co⋯Co is the most stable state in both complexes; and the coupling constants of 1 and 2 are −0.32 cm⁻¹ and −3.70 cm⁻¹, respectively. Based on the distances of Co⋯Co and coupling constants, such antiferromagnetic interaction is achieved through triazole ligands.     

Fine Pore-Structure Engineering by Ligand Conformational Control of Naphthalene Diimide-Based Semiconducting Porous Coordination Polymers for Efficient Chemiresistive Gas Sensing

Exploring new porous coordination polymers (PCPs) that have tunable structure and conductivity is attractive but remains challenging. Herein, fine pore structure engineering by ligand conformation control of naphthalene diimide (NDI)-based semiconducting PCPs with π stacking-dependent conductivity tunability is achieved. The π stacking distances and ligand conformation in these isoreticular PCPs were modulated by employing metal centers with different coordination geometries. As a result, three conjugated PCPs (Co−pyNDI, Ni−pyNDI, and Zn−pyNDI) with varying pore structure and conductivity were obtained. Their crystal structures were determined by three-dimensional electron diffraction. The through-space charge transfer and tunable pore structure in these PCPs result in modulated selectivity and sensitivity in gas sensing. Zn−pyNDI can serve as a room-temperature operable chemiresistive sensor selective to acetone.     

Accessibility and size of <Emphasis Type="Italic">Valonia</Emphasis> cellulose microfibril studied by combined deuteration/rehydrogenation and FTIR technique

We report an FTIR method to measure the accessibility and the size of cellulose microfibrils from the cell wall of Valonia ventricosa. This method is similar to the conventional deuteration technique for measuring the accessibility of cellulosic materials; however, the difference in our method is that the hydroxyl groups O2H, O3H, and O6H in the crystalline region were initially completely deuterated. The sample was then rehydrogenated by soaking in water at 25 °C, so that the OD groups on the surface were rehydrogenated. The ratio of OH to OD absorbance was used to calculate the number of surface vs. core cellulose chains in a microfibril. The obtained experimental ratio of 0.934 was consistent with the value calculated for a previously published 33 × 38 chain Valonia model (Sugiyama et al. 1984). The rehydrogenation process was further investigated by immersing the sample in water at elevated temperatures. At temperatures above 120 °C, rehydrogenation was more efficient, and the efficiency plots vs. rehydrogenation temperature showed two inflection. These points may correspond to the temperature where the cleavage of inter-chain hydrogen bonds and/or crystalline-phase transition would have been occurred.     

Design of polymeric carriers for cancer-specific gene targeting: utilization of abnormal protein kinase Calpha activation in cancer cells

We succeeded in cancer cell specific gene expression by using a polyplex responsive to protein kinase Calpha, which is activated in various types of cancer cells.