Development of an iron(II) complex exhibiting thermal- and photoinduced double proton-transfer-coupled spin transition in a short hydrogen bond

Nakanishi, Takumi*; Hori, Yuta*; Shigeta, Yasuteru*; Sato, Hiroyasu*; Kiyanagi, Ryoji; Munakata, Koji*; Ohara, Takashi; Okazawa, Atsushi*; Shimada, Rintaro*; Sakamoto, Akira*; et al.

Journal of the American Chemical Society, 145(35), p.19177 - 19181, 2023/08

https://doi.org/10.1021/jacs.3c06323

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

https://doi.org/10.1021/jacs.8b09068

The first ionization potential (IP) yields information on valence electronic structure of an atom. IP values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

Melting of Pb charge glass and simultaneous Pb-Cr charge transfer in PbCrO as the origin of volume collapse

Yu, R.*; Hojo, Hajime*; Watanuki, Tetsu; Mizumaki, Masaichiro*; Mizokawa, Takashi*; Oka, Kengo*; Kim, H.*; Machida, Akihiko; Sakaki, Koji*; Nakamura, Yumiko*; et al.

Journal of the American Chemical Society, 137(39), p.12719 - 12728, 2015/10

https://doi.org/10.1021/jacs.5b08216

no abstracts in English

Active sites and mechanisms for oxygen reduction reaction on nitrogen-doped carbon alloy catalysts; Stone-Wales defect and curvature effect

Chai, G.-L.*; Hou, Z.*; Shu, D.-J.*; Ikeda, Takashi; Terakura, Kiyoyuki*

Journal of the American Chemical Society, 136(39), p.13629 - 13640, 2014/10

https://doi.org/10.1021/ja502646c

Carbon alloy catalysts (CACs) are promising catalysts for oxygen reduction reaction (ORR) to substitute Pt. However, despite extensive studies on CACs the reaction sites and mechanisms for ORR are still in controversy. Herein, we present rather general consideration on possible ORR mechanisms for various structures in nitrogen doped CACs based on the first principles calculations. Our study indicates that only a particular structure of a nitrogen pair doped Stone-Wales defect provides a good active site. The ORR activity of this structure can be tuned by the curvature around the active site, which makes its limiting potential approaching the maximum limiting potential (0.80 V) in the volcano plot for the ORR activity of CACs. The calculated results can be compared with the recent experimental ones of the half wave potential for CAC systems that range from 0.60 V to 0.80 V in the reversible-hydrogen-electrode scale.

Dynamic structural changes at LiMn2O/electrolyte interface during lithium battery reaction

Hirayama, Masaaki*; Ido, Hidekazu*; Kim, K.-S.*; Cho, W.*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Journal of the American Chemical Society, 132(43), p.15268 - 15276, 2010/11

https://doi.org/10.1021/ja105389t

Epitaxial LiMnO thin films with restricted lattice planes (111) and (110) are grown on SrTiO substrates by pulsed laser deposition. In situ SXRD studies have revealed dynamic structural changes that reduce the atomic symmetry at the electrode surface during the initial electrochemical reaction. The surface structural changes commence with the formation of an electric double layer, which is followed by surface reconstruction when a voltage is applied in the first charge process. Transmission electron microscopy images after 10 cycles confirm the formation of a solid electrolyte interface (SEI) layer on both the (111) and (110) surfaces and Mn dissolution from the (110) surface. The (111) surface is more stable than the (110) surface. The electrode stability of LiMnO depends on the reaction rate of SEI formation and the stability of the reconstructed surface structure.

Anisotropic and inhomogeneous magnetic interactions observed in all-organic nitroxide radical liquid crystals

Uchida, Yoshiaki*; Suzuki, Katsuaki*; Tamura, Rui*; Ikuma, Naohiko*; Shimono, Satoshi*; Noda, Yohei; Yamauchi, Jun*

Journal of the American Chemical Society, 132(28), p.9746 - 9752, 2010/06

https://doi.org/10.1021/ja101930d

An anisotropic and inhomogeneous magnetic interaction (the average spin-spin interaction constant, 0) was observed in the various liquid crystalline (LC) phases of racemic and nonracemic all-organic radical LC compounds. We discussed how the LC superstructures induced the magnetic interaction to operate in the LC phases in terms of spin-spin dipole and exchange interactions by means of VT-EPR spectroscopy. The magnitude of the magnetic interaction depended on the type of LC phase, or the superstructure. Furthermore, these radical LC droplets floating on water were commonly attracted to a permanent magnet and moved freely under the influence of this magnet, whereas the crystallized particles of the same compounds never responded to the magnet. The response of the LC droplets to the magnet also varied depending on the type of LC phase, that is, the extent of the magnetic interaction.

Various valence states of square-coordinated Mn in A-site-ordered perovskites

Long, Y.*; Saito, Takashi*; Mizumaki, Masaichiro*; Agui, Akane; Shimakawa, Yuichi*

Journal of the American Chemical Society, 131(44), p.16244 - 16247, 2009/10

https://doi.org/10.1021/ja906668c

A-site-ordered perovskites LaMnCrO and LaMnTiO were synthesized under high-pressure and high-temperature conditions. The charge formula of LaMnCrO was found to be LaMnCrO with Mn at the square-coordinated A site. The valence of the A-site Mn ions in LaMnTiO appeared to be less than +2, and the charge combination in this compound seemed to be LaMnTiO. Although the square-coordinated A site in A-site-ordered perovskites has been widely known to be occupied by Jahn-Teller active Mn, the present results show that the valence of Mn at the A site can vary from +3 to possible +1.67.

Combined high-resolution neutron and X-ray analysis of inhibited elastase confirms the active-site oxyanion hole but rules against a low-barrier hydrogen bond

Tamada, Taro; Kinoshita, Takayoshi*; Kurihara, Kazuo; Adachi, Motoyasu; Ohara, Takashi; Imai, Keisuke*; Kuroki, Ryota; Tada, Toshiji*

Journal of the American Chemical Society, 131(31), p.11033 - 11040, 2009/07

https://doi.org/10.1021/ja9028846

To help resolve long-standing questions regarding the catalytic activity of the serine proteases the structure of porcine pancreatic elastase has been analyzed by high-resolution neutron and X-ray crystallography. In order to mimic the tetrahedral transition intermediate a peptidic inhibitor was used. A single large crystal was used to collect room-temperature neutron data to 1.65 resolution and X-ray data to 1.20 resolution. Another crystal provided a low-temperature X-ray data set to 0.94 resolution. The neutron data are to higher resolution than previously reported for a serine protease and the X-ray data are comparable with other studies. The neutron and X-ray data show that the hydrogen bond between His57 and Asp102 (chymotrypsin numbering) is 2.60 in length and that the hydrogen-bonding hydrogen is 0.80-0.96 from the histidine nitrogen. This is not consistent with a low-barrier hydrogen which is predicted to have the hydrogen midway between the donor and acceptor atom. The observed interaction between His57 and Asp102 is essentially a short but conventional hydrogen bond, sometimes described as a short ionic hydrogen bond. The neutron analysis also shows that the oxygen of the oxopropyl group of the inhibitor is present as an oxygen anion rather than a hydroxyl group, supporting the role of the "oxyanion hole" in stabilizing the tetrahedral intermediate in catalysis.

Does Gd@C have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct

Akasaka, Takeshi*; Kono, Takayoshi*; Takematsu, Yuji*; Nikawa, Hidefumi*; Nakahodo, Tsukasa*; Wakahara, Takatsugu*; Ishitsuka, Midori*; Tsuchiya, Takahiro*; Maeda, Yutaka*; Liu, M. T. H.*; et al.

Journal of the American Chemical Society, 130(39), p.12840 - 12841, 2008/10

https://doi.org/10.1021/ja802156n

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C carbene adduct (Gd@C(ad), Ad=adamantylidene). The Gd atom in Gd@C(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C cage, as found for M@C (M = Sc and La) and La@C(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.

study of ultrafast photochemical reaction dynamics of phenol blue

Kobayashi, Takao*; Shiga, Motoyuki; Murakami, Akinori*; Nakamura, Shinichiro*

Journal of the American Chemical Society, 129(20), p.6405 - 6424, 2007/05

https://doi.org/10.1021/ja066994w

Phenol Blue (PB) is a primary skeletal structure part of indoaniline dyes. It has been recently observed by pump-probe transient absorption measurements that PB show ultrafast ground state recovery within a few hundred femtoseconds after photoexcitation. In this work, the ultrafast photochemical reaction mechanism of PB has been investigated using direct non-adiabatic molecular dynamics with the trajectory surface hopping method.