Incorporation of a bromine atom into DNA-related molecules changes their electronic properties

Hirato, Misaki*; Yokoya, Akinari*; Baba, Yuji*; Mori, Seiji*; Fujii, Kentaro*; Wada, Shinichi*; Izumi, Yudai*; Haga, Yoshinori

Physical Chemistry Chemical Physics, 25(21), p.14836 - 14847, 2023/05

https://doi.org/10.1039/D3CP01597A

Kinetics of the interfacial curing reaction for an epoxy-amine mixture

Yamaguchi, Ko*; Kawaguchi, Daisuke*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Yamamoto, Satoru*; Tanaka, Keiji*

Physical Chemistry Chemical Physics, 24(36), p.21578 - 21582, 2022/09

https://doi.org/10.1039/D2CP03394A

Phase transition and chemical reactivity of 1H-tetrazole under high pressure up to 100 GPa

Gao, D.*; Tang, X.*; Wang, X.*; Yang, X.*; Zhang, P.*; Che, G.*; Han, J.*; Hattori, Takanori; Wang, Y.*; Dong, X.*; et al.

Physical Chemistry Chemical Physics, 23(35), p.19503 - 19510, 2021/09

https://doi.org/10.1039/D1CP02913D

Pressure-induced phase transition and polymerization of nitrogen-rich molecules are widely focused due to its extreme importance for the development of green high energy density materials. Here, we present a study of the phase transition and chemical reaction of 1H-tetrazole up to 100 GPa by using Raman, IR, X-ray diffraction, neutron diffraction techniques and theoretical calculation. A phase transition above 2.6 GPa was identified and the high-pressure structure was determined with one molecule in a unit cell. The 1H-tetrazole polymerizes reversibly below 100 GPa, probably through a carbon-nitrogen bonding instead of nitrogen-nitrogen bonding. Our studies updated the structure model of the high pressure phase of 1H-tetrazole, and presented the possible intermolecular bonding route for the first time, which gives new insights to understand the phase transition and chemical reaction of nitrogen-rich compounds, and benefit for designing new high energy density materials.

Radiation-induced effects on the extraction properties of hexa--octylnitrilo-triacetamide (HONTA) complexes of americium and europium

Toigawa, Tomohiro; Peterman, D. R.*; Meeker, D. S.*; Grimes, T. S.*; Zalupski, P. R.*; Mezyk, S. P.*; Cook, A. R.*; Yamashita, Shinichi*; Kumagai, Yuta; Matsumura, Tatsuro; et al.

Physical Chemistry Chemical Physics, 23(2), p.1343 - 1351, 2021/01

https://doi.org/10.1039/D0CP05720G

The candidate An(III)/Ln(III) separation ligand hexa--octylnitrilo-triacetamide (HONTA) was irradiated under envisioned SELECT (Solvent Extraction from Liquid waste using Extractants of CHON-type for Transmutation) process conditions using a solvent test loop in conjunction with cobalt-60 gamma irradiation. We demonstrate that HONTA undergoes exponential decay with increasing gamma dose to produce a range of degradation products which have been identified and quantified by HPLC-ESI-MS/MS techniques. The combination of HONTA destruction and degradation product ingrowth, particularly dioctylamine, negatively impacts the extraction and back-extraction of both americium and europium ions. The loss of HONTA was attributed to its reaction with the solvent (-dodecane) radical cation of (HONTA + R) = (7.61 0.82) 10 M s obtained by pulse radiolysis techniques. However, when this ligand is bound to either americium or europium ions, the observed -dodecane radical cation kinetics increase by over an order of magnitude. This large reactivity increase to additional reaction pathways occurring upon metal-ion binding. Lastly nanosecond time-resolved measurements showed that both direct and indirect HONTA radiolysis yielded the short-lived (100 ns) HONTA radical cation as well as a longer-lived (s) HONTA triplet excited state. These HONTA species are important precursors to the suite of HONTA degradation products observed.

Controlled deuterium labelling of imidazolium ionic liquids to probe the fine structure of the electrical double layer using neutron reflectometry

Akutsu, Kazuhiro*; Cagnes, M.*; Tamura, Kazuhisa; Kanaya, Toshiji*; Darwish, T. A.*

Physical Chemistry Chemical Physics, 21(32), p.17512 - 17516, 2019/08

https://doi.org/10.1039/C9CP02479D

We combined the deuterium labeling and neutron reflectivity techniques to determine the fine structure of the electric double layer structure in an imidazolium ionic liquid (IL). For this, a simple and large scale deuteration method for imidazolium ILs was developed, where the deuteration level can be systematically controlled.

Nuclear quantum effects in the direct ionization process of pure helium clusters; Path-integral and ring-polymer molecular dynamics simulations on the diatomics-in-molecule potential energy surfaces

Suzuki, Kento*; Miyazaki, Takaaki*; Takayanagi, Toshiyuki*; Shiga, Motoyuki

Physical Chemistry Chemical Physics, 20(41), p.26489 - 26499, 2018/11

https://doi.org/10.1039/C8CP05389H

The direct photoionization of pure helium clusters and its subsequent short-time process have been studied by path integral molecular dynamics (PIMD) and ring-polymer molecular dynamics (RPMD) simulations. The PIMD simulations reproduced the experimental ionization spectra with a broad and asymmetric nature, which can be ascribed to the inhomogeneity of the energy levels of He atoms. From the RPMD simulations, it is found that the ionized helium cluster in the highly excited state brings about fast electronic state relaxation via nonadiabatic charge transfer and subsequently slow structural relaxation.

X-ray absorption near edge structure and first-principles spectral investigations of cationic disorder in MgAlO induced by swift heavy ions

Yoshioka, Satoru*; Tsuruta, Konosuke*; Yamamoto, Tomokazu*; Yasuda, Kazuhiro*; Matsumura, Sho*; Ishikawa, Norito; Kobayashi, Eiichi*

Physical Chemistry Chemical Physics, 20(7), p.4962 - 4969, 2018/02

https://doi.org/10.1039/C7CP07591J

Cationic disorder in the MgAlO spinel induced by swift heavy ions was investigated using the X-ray absorption near edge structure. With changes in the irradiation fluences of 200 MeV Xe ions, the Mg K-edge and Al K-edge spectra were synchronously changed. The calculated spectra based on density function theory indicate that the change in the experimental spectra was due to cationic disorder between Mg in tetrahedral sites and Al in octahedral sites. These results suggest a high inversion degree to an extent that the completely random configuration is achieved in MgAlO induced by the high density electronic excitation under swift heavy ion irradiation.

The Structure of a lanthanide complex at an extractant/water interface studied using heterodyne-detected vibrational sum frequency generation

Kusaka, Ryoji; Watanabe, Masayuki

Physical Chemistry Chemical Physics, 20(4), p.2809 - 2813, 2018/01

https://doi.org/10.1039/C7CP06758E

Solvent extraction plays an integral part in the separation and purification of metals. Because extractants generally used as complexing agents for metal extractions, such as di-(2-ethylhexyl)phosphoric acid (HDEHP) for lanthanide extractions, are amphiphilic, they come to the organic/water interface, and the interface plays a crucial role as the site of the formation of metal complexes and subsequent transfer reaction to an organic phase. Despite the importance of the interface for solvent extractions, however, molecular-level structure of the interface is unclear because of experimental difficulty. Here we studied structure of a trivalent europium (Eu) complex with HDEHP formed at HDEHP monolayer/water interface by heterodyne-detected vibrational sum frequency generation (HD-VSFG) spectroscopy. The study on the HDEHP/water interface enables us to investigate the structure of the interfacial Eu complex by excluding the migration of Eu into an organic phase after the complex formation at the interface. The interface-selective vibrational Im spectra observed by HD-VSFG of HDEHP/Eu(NO) aqueous solution interface in the 2800-3500 cm region indicate that Eu at the HDEHP/water interface is bonded by HDEHP from the air side and by water molecules from the water side. To the best of our knowledge, such metal complex structures have not been identified in the organic or water solutions.

Photoexcited Ag ejection from a low-temperature He cluster; A Simulation study by nonadiabatic Ehrenfest ring-polymer molecular dynamics

Seki, Yusuke*; Takayanagi, Toshiyuki*; Shiga, Motoyuki

Physical Chemistry Chemical Physics, 19(21), p.13798 - 13806, 2017/06

https://doi.org/10.1039/C7CP00888K

Ring-polymer molecular dynamics (RPMD) simulations have been performed to understand the photoexcitation dynamics of the Ag atom embedded in a low-temperature cluster consisting of 500 helium atoms, after the electronic excitation of the Ag atom. Along the RPMD trajectory the time evolution of the electronic wavefunction within the spin-orbit P manifold is calculated, whereby the time-dependent Schrdinger equation and the RPMD equation of motion are coupled, la Ehrenfest mean field approach. It is found from the simulations that the Ag atom is mostly ejected from the helium cluster with the average time of 100 ps after photoexcitation. The average velocity of the ejected Ag atom is estimated to be 60-70 m/s. These results are qualitatively in line with previous experimental findings.

The Reaction mechanism of polyalcohol dehydration in hot pressurized water

Ruiz-Barragan, S.*; Ribas Ario, J.*; Shiga, Motoyuki

Physical Chemistry Chemical Physics, 18(47), p.32438 - 32447, 2016/12

https://doi.org/10.1039/C6CP05695D

The use of high-temperature liquid water (HTW) as a reaction medium is a very promising technology in the field of green chemistry. In order to fully exploit this technology, it is crucial to unravel the reaction mechanisms of the processes carried out in HTW. In this work, the reaction mechanism of 2,5-hexanediol dehydration in HTW has been studied by means of three different ab initio simulations: string method, metadynamics and molecular dynamics in real time. It is found that the whole reaction involving the protonation, bond exchange and the deprotonation occurs in a single step without a stable intermediate. The hydrogen bonded network of surrounding water has a vital role in assisting an efficient proton relay at the beginning and at the end of the reaction. It is confirmed that the reaction is energetically most favorable in the SN2 pathway with an estimated barrier of 36 kcal/mol, which explains the high stereo selectivity and the reaction rate observed in experiment.