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1.
Proton Order–Disorder Phenomena in a Hydrogen‐Bonded Rhodium–η5‐Semiquinone Complex: A Possible Dielectric Response Mechanism 下载免费PDF全文
Dr. Minoru Mitsumi Kazunari Ezaki Yuuki Komatsu Prof. Dr. Koshiro Toriumi Dr. Tatsuya Miyatou Prof. Dr. Motohiro Mizuno Nobuaki Azuma Prof. Dr. Yuji Miyazaki Prof. Dr. Motohiro Nakano Prof. Dr. Yasutaka Kitagawa Dr. Takayasu Hanashima Dr. Ryoji Kiyanagi Dr. Takashi Ohhara Prof. Dr. Kazuhiro Nakasuji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9682-9696
A newly synthesized one‐dimensional (1D) hydrogen‐bonded (H‐bonded) rhodium(II)–η5‐semiquinone complex, [Cp*Rh(η5‐p‐HSQ‐Me4)]PF6 ([ 1 ]PF6; Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl; HSQ=semiquinone) exhibits a paraelectric–antiferroelectric second‐order phase transition at 237.1 K. Neutron and X‐ray crystal structure analyses reveal that the H‐bonded proton is disordered over two sites in the room‐temperature (RT) phase. The phase transition would arise from this proton disorder together with rotation or libration of the Cp* ring and PF6? ion. The relative permittivity εb′ along the H‐bonded chains reaches relatively high values (ca., 130) in the RT phase. The temperature dependence of 13C CP/MAS NMR spectra demonstrates that the proton is dynamically disordered in the RT phase and that the proton exchange has already occurred in the low‐temperature (LT) phase. Rate constants for the proton exchange are estimated to be 10?4–10?6 s in the temperature range of 240–270 K. DFT calculations predict that the protonation/deprotonation of [ 1 ]+ leads to interesting hapticity changes of the semiquinone ligand accompanied by reduction/oxidation by the π‐bonded rhodium fragment, producing the stable η6‐hydroquinone complex, [Cp*Rh3+(η6‐p‐H2Q‐Me4)]2+ ([ 2 ]2+), and η4‐benzoquinone complex, [Cp*Rh+(η4‐p‐BQ‐Me4)] ([ 3 ]), respectively. Possible mechanisms leading to the dielectric response are discussed on the basis of the migration of the protonic solitons comprising of [ 2 ]2+ and [ 3 ], which would be generated in the H‐bonded chain. 相似文献
2.
Dr. Yoji Horii Prof. Dr. Keiichi Katoh Prof. Dr. Yuji Miyazaki Dr. Marko Damjanović Tetsu Sato Prof. Dr. Liviu Ungur Prof. Dr. Liviu F. Chibotaru Prof. Dr. Brian K. Breedlove Prof. Dr. Motohiro Nakano Prof. Dr. Wolfgang Wernsdorfer Prof. Dr. Masahiro Yamashita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8076-8082
Gd3+ complexes have been shown to undergo unusual slow magnetic relaxation processes similar to those of single-molecule magnets (SMMs), even though Gd3+ does not exhibit strong magnetic anisotropy. To reveal the origin of the slow magnetic relaxation of Gd3+ complexes, we have investigated the magnetic properties and heat capacities of two Gd3+-phthalocyaninato triple-decker complexes, one of which has intramolecular Gd3+–Gd3+ interactions and the other does not. It was found that the Gd3+–Gd3+ interactions accelerate the magnetic relaxation processes. In addition, magnetically diluted samples, prepared by doping a small amount of the Gd3+ complexes into a large amount of diamagnetic Y3+ complexes, underwent dual magnetic relaxation processes. A detailed dynamic magnetic analysis revealed that the coexistence of spin–lattice relaxation and phonon-bottleneck processes is the origin of the dual magnetic relaxation processes. 相似文献
3.
Prof. Ki-Young Lee Prof. Mitsuhiko Ikura Dr. Christopher B. Marshall 《Angewandte Chemie (International ed. in English)》2023,62(18):e202218698
KRAS is a peripheral membrane protein that regulates multiple signaling pathways, and is mutated in ≈30 % of cancers. Transient self-association of KRAS is essential for activation of the downstream effector RAF and oncogenicity. The presence of anionic phosphatidylserine (PS) lipids in the membrane was shown to promote KRAS self-assembly, however, the structural mechanisms remain elusive. Here, we employed nanodisc bilayers of defined lipid compositions, and probed the impact of PS concentration on KRAS self-association. Paramagnetic NMR experiments demonstrated the existence of two transient dimer conformations involving alternate electrostatic contacts between R135 and either D153 or E168 on the “α4/5-α4/5” interface, and revealed that lipid composition and salt modulate their dynamic equilibrium. These dimer interfaces were validated by charge-reversal mutants. This plasticity demonstrates how the dynamic KRAS dimerization interface responds to the environment, and likely extends to the assembly of other signaling complexes on the membrane. 相似文献
4.
Genta Kawaguchi Prof. Dr. Mitsuhiko Maesato Dr. Tokutaro Komatsu Prof. Dr. Hiroshi Kitagawa Prof. Dr. Tatsuro Imakubo Dr. Andhika Kiswandhi Dr. David Graf Prof. Dr. James S. Brooks 《Angewandte Chemie (International ed. in English)》2015,54(35):10169-10172
Simultaneous manipulation of both spin and charge is a crucial issue in magnetic conductors. We report on a strong correlation between magnetism and conductivity in the iodine‐bonded molecular conductor (DIETSe)2FeBr2Cl2 [DIETSe=diiodo(ethylenedithio)tetraselenafulvalene], which is the first molecular conductor showing a large hysteresis in both magnetic moment and magnetoresistance associated with a spin‐flop transition. Utilizing a mixed‐anion approach and iodine bonding interactions, we tailored a molecular conductor with random exchange interactions exhibiting unforeseen physical properties. 相似文献
5.
Cover Picture: Electron–Proton Decoupling in Excited‐State Hydrogen Atom Transfer in the Gas Phase (Angew. Chem. Int. Ed. 50/2015) 下载免费PDF全文
6.
Lee V. Ya. Miyazaki S. Gapurenko O. A. Minyaev R. M. Minkin V. I. Sekiguchi A. 《Russian Chemical Bulletin》2021,70(11):2233-2235
(Thiatrisila)bicyclo[1.1.0]butane 1 quantitatively transformed under either photochemical or thermal conditions into the isomeric (thiatrisila)cyclobutene 2, which was isolated and fully characterized.
相似文献7.
Keigo Kobayashi Prof. Hirokazu Kobayashi Prof. Mitsuhiko Maesato Dr. Mikihiro Hayashi Tomokazu Yamamoto Dr. Satoru Yoshioka Prof. Syo Matsumura Prof. Takeharu Sugiyama Dr. Shogo Kawaguchi Prof. Yoshiki Kubota Prof. Hiroshi Nakanishi Prof. Hiroshi Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6678-6682
We report on hexagonal close-packed (hcp) palladium (Pd)–boron (B) nanocrystals (NCs) by heavy B doping into face-centered cubic (fcc) Pd NCs. Scanning transmission electron microscopy–electron energy loss spectroscopy and synchrotron powder X-ray diffraction measurements demonstrated that the B atoms are homogeneously distributed inside the hcp Pd lattice. The large paramagnetic susceptibility of Pd is significantly suppressed in Pd–B NCs in good agreement with the reduction of density of states at Fermi energy suggested by X-ray absorption near-edge structure and theoretical calculations. 相似文献
8.
Miyazaki Reona Sakaguchi Isao Hihara Takehiko 《Journal of Solid State Electrochemistry》2021,25(6):1927-1936
Journal of Solid State Electrochemistry - In the present work, the conduction ions in 15NaI∙LiBH4 are investigated by secondary ion mass spectroscopy (SIMS) and galvanostatic measurements. An... 相似文献
9.
Prof. Makoto Tadokoro Masaki Itoh Ryota Nishimura Kensuke Sekiguchi Dr. Norihisa Hoshino Dr. Hajime Kamebuchi Prof. Jun Miyazaki Dr. Fumiya Kobayashi Prof. Motohiro Mizuno Prof. Tomoyuki Akutagawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(47):e202201397
A new H-bonded crystal [RuIII(Him)3(Im)3] with three imidazole (Him) and three imidazolate (Im−) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the RuIII complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10−5 S cm−1 at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [RuIII(Him)3(Im)3] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state 2H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered. 相似文献
10.
Dr. Santiago Alonso-Gil Dr. Kamil Parkan Dr. Jakub Kaminský Dr. Radek Pohl Dr. Takatsugu Miyazaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(14):e202200148
The conformational changes in a sugar moiety along the hydrolytic pathway are key to understand the mechanism of glycoside hydrolases (GHs) and to design new inhibitors. The two predominant itineraries for mannosidases go via OS2→B2,5→1S5 and 3S1→3H4→1C4. For the CAZy family 92, the conformational itinerary was unknown. Published complexes of Bacteroides thetaiotaomicron GH92 catalyst with a S-glycoside and mannoimidazole indicate a 4C1→4H5/1S5→1S5 mechanism. However, as observed with the GH125 family, S-glycosides may not act always as good mimics of GH's natural substrate. Here we present a cooperative study between computations and experiments where our results predict the E5→B2,5/1S5→1S5 pathway for GH92 enzymes. Furthermore, we demonstrate the Michaelis complex mimicry of a new kind of C-disaccharides, whose biochemical applicability was still a chimera. 相似文献