A comparative theoretical study of the hydride transfer mechanisms during LiAlH4 and LiBH4 reductions

This work examined the hydride transfer processes during the reduction of formaldehyde by LiAlH4 or LiBH4, including investigations of the geometries, solvent effects and charge transfer processes along the reaction coordinate, using density functional theory (DFT). The energy and geometry results demonstrate that the transition state (TS) structure for the LiAlH4-formaldehyde complex is reactant-like, while the structure generated by LiBH4 has a product-like geometry, consistent with the Hammond postulate. From a charge density analysis, we also found that both complexes undergo the same essential hydride transfer mechanism, which consists of: (1) single electron transfer to the carbonyl carbon, (2) formation of a bridge bond (X-H-C; X=Al or B) and (3) hydrogen transfer driven by electron transfer. Subsequently, in a fourth step, a single electron flows through the X-H-C bond during transfer of the hydrogen, such that hydrogen atom or proton-coupled electron transfer occurs. In both systems, the presence of tetrahydrofuran as a solvent affects the structure and energy values during the reaction, but not the charge transfer characteristics. We propose that the rate-determining steps during hydride transfer when employing LiAlH4 and LiBH4 are one electron transfer to the carbonyl carbon and B-H bond dissociation, respectively. © 2015 Elsevier B.V.Embargo Period 24 month

新規固体核磁気共鳴シミュレーション解析法による配位空間の研究

金沢大学ナノマテリアル研究所本研究では固体重水素NMRスペクトルの測定法と解析法を発展させ,配位空間の研究に役立てることを目的としている。試料のマジック角回転(MAS)を行なって得られる重水素NMRのスピニングサイドバンドスペクトルのシミュレーションプログラムを作成し、分子運動の広いダイナミックレンジでの解析を可能にした。本研究では反磁性物質とともに常磁性物質についても解析できるようにした。重水素NMRMASスペクトルのシミュレーション解析法により,解析可能なダイナミックレンジを10^2Hz〓k〓10^8Hzに広げることができた。重水素の二次元交換NMRスペクトルは固体物質中で起こる非常に遅い分子運動(10^Hz〓k〓10^3Hz)の解析に有効であるが,これまで複数の運動が同時に起こるような複雑な運動モードの解析は困難であった。本研究ではマルチモードの分子運動を解析できる重水素二次元交換NMRスペクトルのシミュレーションプログラムを作成し,結晶中の分子ダイナミクスの解析に用いた。これらの手法を用いて,[Zn(H_2O)_6][SiF_6]結晶中の水分子の180°フリップと[Zn(H_2O)_6]^の3回軸周りの再配向運動が同時に起こる運動を解析することができた。固体NMRによる分子ダイナミクスの研究において一般に常磁性相互作用は解析を困難にするが、本研究では逆にこの常磁性相互作用を利用して、詳しい分子ダイナミクスの解析を行えるシミュレーション解析法を開発した。研究課題/領域番号:18033016, 研究期間(年度):2006 – 2007出典：「新規固体核磁気共鳴シミュレーション解析法による配位空間の研究」研究成果報告書　課題番号18033016（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-18033016/)を加工して作

Soft Crystals: Science and Photofunctions of Easy-Responsive Systems with Felxibility and Higher-Ordering

金沢大学ナノマテリアル研究所ベイポクロミズムが報告されている平面四配位白金(II)錯体 [Pt(CN)2(H2dcbpy)] (H2dcbpy = 4,4’-dicarboxy-2,2’-bipyridine)と[Pt(CN)2(H2dcphen)] (H2dcphen = 4,7-dicarboxy-1,10-phenanthroline)につい，，重水素化したエタノール，2-プロパノール，1-ブタノールをゲスト分子として導入し，固体NMRを用いて，細孔内の分子運動やホストーゲスト相互作用を解析した。ゲスト分子やホスト骨格の配位子の違いが，ホストーゲスト相互作用や分子運動にどのような影響を与えるかを考察した。2H NMRスペクトルの解析から，エタノール，2-プロパノールでは，分子内運動（メチル基の３回軸周りの回転）と分子全体の運動（等方回転運動）の情報を得ることができた。細長い形状の1-ブタノールでは，分子長軸周りの回転と分子長軸の歳差運動が観測された。2-プロパノールと1-ブタノールにおいては，細孔径が大きい[Pt(CN)2(H2dcbpy)]中でより速い運動をしていることがわかった。これに対し，エタノールにおいては[Pt(CN)2(H2dcbpy)]中で，細孔径が小さい[Pt(CN)2(H2dcphen)]中よりも等方回転運動が抑えられていることがわかった。固体高分解能13C NMRスペクトルの解析より，[Pt(CN)2(H2dcbpy)]中では，エタノールとホストのカルボキシ基に，強い相互作用が働いていることがわかった。このようなゲスト-カルボキシ基間の強い相互作用がゲスト分子の等方回転運動を抑えていることが明らかになった。また，白金(II)錯体における蒸気応答性の設計可能性を検討すべく，カリウムイオンを蒸気の配位サイトとして有する新規白金(II)錯体を合成し，性質を調べた。研究課題/領域番号:20H04666, 研究期間(年度):2020-04-01 – 2022-03-31出典：研究課題「固体NMRによる金属錯体のベイポクロミズム現象の機構解明」課題番号20H04666（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/report/KAKENHI-PUBLICLY-20H04666/20H046662021jisseki/）を加工して作

Is increased fat content of hindmilk due to the size or the number of milk fat globules?

<p>Abstract</p> <p>Background</p> <p>It is known that the fat content of breast milk is higher in hindmilk than in foremilk. However, it has not been determined if this increased fat content results from an increase in the number of milk fat globules (MFGs), an increase in the size of MFGs, or both. This study aims to determine which factor plays the most important role.</p> <p>Methods</p> <p>Thirteen breastfeeding mothers were enrolled in the study and we obtained 52 samples from 26 breasts before (foremilk) and after (hindmilk) a breastfeeding session. The fat content was evaluated by creamatocrit (CrCt) values. MFG size was measured with the laser light scattering method. We compared CrCt values and MFG size between foremilk and hindmilk.</p> <p>Results</p> <p>Although the CrCt values were higher in the hindmilk (8.6 ± 3.6%) than in the foremilk (3.7 ± 1.7%), the MFG size did not change (4.2 ± 1.0 μm and 4.6 ± 2.1 μm, foremilk and hindmilk, respectively). There was no relationship between the changes in CrCt versus MFG size from foremilk to hindmilk.</p> <p>Conclusion</p> <p>The results indicate that the increase in fat content results mainly from the increased number of MFGs, which may be released into the milk flow as the mammary lobe becomes progressively emptied.</p

Molecular-size-distribution-dependent aggregation of humic substances by Na(I), Ag(I), Ca(II), and Eu(III)

Molecular-size-distribution (MSD)-dependent aggregation of Fluka and International Humic Substance Society humic acids (HAs) in the presence of Na(I), Ca(II), Ag(I), and Eu(III) were studied using high-performance size-exclusion chromatography. Larger molecular size fractions (>8000. Da) rich in aliphatic carbons were observed to aggregate in the presence of Na(I) and Ca(II), whereas both large and small molecular size fractions concurrently aggregated in the presence of Ag(I) and Eu(III). In view of the non-specific binding of Na(I) and Ca(II) with HAs, the electric-field screening effect is probably the main cause of HA aggregation by Na(I) and Ca(II), preserving the intrinsic hydrophobicity of the HAs. Reduced surface charges and the hydrophobic heterogeneities of different MSD fractions of HAs by direct binding of Ag(I) and Eu(III) are postulated to induce insignificant dependence of aggregation on the different MSD fractions. © 2013 Elsevier B.V

Fragment distribution of thermal decomposition for PS and PET with QMD calculations by considering the excited and charged model molecules

金沢大学理工研究域物質化学系Simulations by a quantum molecular dynamics (QMD) (MD with MO) method were demonstrated on the thermal decomposition of PS and PET polymers using the model molecules at the ground state including excited and positive charged states. For the excited and positive charged model molecules, we adopted CH3CHC6H5CH3 and CH3OCOC6H4COOCH3 of PS and PET monomers, respectively at the singlet and triplet states in single excitation, and at (+2) positive charged state by semiempirical AM1 MO method. Geometry and energy optimized results of the excited and positive charged models by MO calculations were used as the initial MD step of QMD calculations. In the QMD calculations, we controlled the total energy of the system using Nosé-Hoover thermostats in the total energy range of 0.69-0.95 eV, and the sampling position data with a time step of 0.5 fs were carried out up to 5000 steps at 60 different initial conditions. The calculated neutral, positive and negative charged fragment distributions of PS and PET models with 0.82 eV energy control were obtained as (93.5, 2.3, and 4.3%), and (87.8, 5.3, and 6.9%) to the total fragments, respectively. The ratios seem to correspond well to the values observed experimentally in SIMS. Crown Copyright © 2008

Radical polymerisation of styrene in porous coordination polymers

The first radical polymerisation of styrene in porous coordination polymers has been carried out, providing stable propagating radicals (living radicals), and a specific space effect of the host frameworks on the monomer reactivity is demonstrated. © The Royal Society of Chemistry 2005

XPS Spectral Simulation of Chitosan in Thermal Decomposition Process,

金沢大学大学院自然科学研究科物質情報解

Dynamic and static behaviors of CH4 and CO2 in small and large cavities of hydrate

We investigated the static structures and dynamic behaviors for guest molecules (CH4 and CO2) in small and large cavities which are composed of 20 and 24 water molecules, respectively, by B3LYP/6-311++G(d,p) level calculations in GAUSSIAN 09, and using quantum molecular dynamics (QMD) (NVT MD with semiempirical MO PM3 method). For the static calculations, the guest CO2 and CH4 molecules are around at the center of small and large cavities with weak H-bond formations of HOH⋯O 2C and H2O⋯H4C van der Waals interaction systems. Calculated carbon NMR chemical shifts of the CH4 in the gas-state and in the small and large cavities reflected the C-13 experimental tendency, while the calculated carbon NMR chemical shifts of the CO2 in the three states almost correspond to the experimental value in the gas-state. For QMD calculations, we used a cluster model containing 73 water molecules, and examined dynamic behavior of guest molecules in the shell cluster model of 39 water molecules which own small and large cavities. The dynamic behavior of guest molecules are simulated from the trajectory distribution of molecular center of the mass due to the translational motion, and also analyzed using librational motions of guest molecules in the cavities. © 2012 Elsevier B.V. All rights reserved