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51.
Dr. Yifan Gu Prof. Jia-Jia Zheng Prof. Ken-ichi Otake Prof. Kunihisa Sugimoto Prof. Nobuhiko Hosono Prof. Shigeyoshi Sakaki Prof. Fengting Li Prof. Susumu Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(36):15647-15651
To achieve unique molecular-recognition patterns, a rational control of the flexibility of porous coordination polymers (PCPs) is highly sought, but it remains elusive. From a thermodynamic perspective, the competitive relationship between the structural deformation energy (Edef) of soft PCPs and the guest interaction is key for selective a guest-triggered structural-transformation behavior. Therefore, it is vital to investigate and control Edef to regulate this competition for flexibility control. Driven by these theoretical insights, we demonstrate an Edef-modulation strategy via encoding inter-framework hydrogen bonds into a soft PCP with an interpenetrated structure. As a proof of this concept, the enhanced Edef of PCP enables a selective gate-opening behavior toward CHCl3 over CH2Cl2 by changing the adsorption-energy landscape of the compounds. This study provides a new direction for the design of functional soft porous materials. 相似文献
52.
Takashi Yoshimoto Prof. Dr. Hisako Hashimoto Dr. Nozomi Takagi Prof. Dr. Shigeyoshi Sakaki Naoki Hayakawa Dr. Tsukasa Matsuo Prof. Dr. Hiromi Tobita 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3795-3798
A tungsten silylyne complex having a W≡Si triple bond reacted with two molecules of aldehydes at room temperature to give W−Si−O−C four-membered metallacycles by [2+2] cycloaddition and subsequent formyl hydrogen transfer from one aldehyde molecule to another. Upon heating to 70 °C, the four-membered metallacycles underwent metathesis-like fragmentation cleanly to afford carbyne complexes and “silanoic esters,” in a manner similar to that of metallacyclobutadiene, an intermediate of alkyne metathesis reactions, and dimerization of the latter products gave 1,3-cyclodisiloxanes. The “silanoic ester” was also trapped by pivalaldehyde to give a [2+2] cycloaddition product in high yield. 相似文献
53.
Tatsumi Ochiai Dr. Daniel Franz Dr. Elisabeth Irran Prof. Dr. Shigeyoshi Inoue 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6704-6707
The novel amino(imino)stannylene 1 was prepared by conversion of HNIPr (NIPr=bis(2,6‐diisopropylphenyl)imidazolin‐2‐imino) with one equivalent of Lappert’s tin reagent (Sn[N(SiMe3)2]2). Treatment of 1 with DMAP (4‐dimethylaminopyridine) yields its Lewis acid–base adduct 2 . The reaction of 1 with one equivalent of trimethylsilyl azide results in replacement of the amino group at the tin center by an N3 substituent with concomitant elimination of N(SiMe3)3 to afford dimeric [N3SnNIPr]2 ( 3 ). Remarkably, the reaction of 1 with B(C6F5)3 produces the novel tin(II) monocation 4 +[MeB(C6F5)3]? comprising a four‐membered stannacycle through methyl‐abstraction from the trimethylsilyl group. 相似文献
54.
55.
Comparative examination of titania nanocrystals synthesized by peroxo titanic acid approach from different precursors 总被引:1,自引:0,他引:1
Liu YJ Aizawa M Wang ZM Hatori H Uekawa N Kanoh H 《Journal of colloid and interface science》2008,322(2):497-504
Titanium dioxide nanocrystalline particles were synthesized by peroxo titanium acid (PTA) approach from titanium alkoxide and inorganic salt precursors, and their structural and surface properties, porosities, and photocatalytic activities were comparatively examined by XRD, TG/DTA, DRIFT, UV-vis, low temperature N(2) adsorption, and methyl orange (MO) degradation. It was found that nanoparticles with single anatase phase can be obtained from alkoxide precursor even near room temperature if synthesis conditions are appropriately controlled. PTA-derived anatase nanoparticles from titanium alkoxide precursor have smaller crystalline sizes and better porosities, and contain less amount of peroxo group and no organic impurities as compared to those from TiCl(4) precursor. The advantages in structural property, porosity, and surface properties (few deficiencies) lead to a much better photocatalytic activity for TiO(2) nanoparticles from titanium alkoxide precursor in comparison with those from TiCl(4) precursor. 相似文献
56.
Song YI Yang CM Kim DY Kanoh H Kaneko K 《Journal of colloid and interface science》2008,323(2):365-371
Hollow ZrO(2) microspheres with mesoporous shells have been synthesized by a novel hydrothermal reaction of zirconium oxychloride in the presence of urea, hydrochloric acid, and ethanol. The morphology and shell thickness of the hollow microspheres can be controlled by varying synthesis conditions. After calcination at high temperature, the morphologies of the hollow microspheres are essentially preserved. Pt catalyst supported on the hollow calcined ZrO(2) microspheres exhibits more excellent catalytic performance in CO oxidation than those on ZrO(2) powders derived from conventional precipitation methods. 相似文献
57.
Huihui Xu Dr. Arseni Kostenko Dr. Catherine Weetman Dr. Shiori Fujimori Prof. Shigeyoshi Inoue 《Angewandte Chemie (International ed. in English)》2023,62(11):e202216021
Facile access to dimeric heavier aluminum chalcogenides [(NHC)Al(Tipp)-μ-Ch]2 (NHC=IiPr (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, IMe4 (1,3,4,5-tetramethylimidazol-2-ylidene); Tipp=2,4,6-iPr3C6H2; Ch=Se, Te) by treatment of NHC-stabilized aluminum dihydrides with elemental Se and Te is reported. The higher affinity of IMe4 in comparison with IiPr toward the Al center in [(NHC)Al(Tipp)-μ-Ch]2 can be used for ligand exchange. Additionally, the presence of excess IMe4 allows for cleavage of the dimers to form a rare example of a neutral multiply bonded heavier aluminum chalcogenide in the form of a tetracoordinate aluminum complex, (IMe4)2(Tipp)Al=Te. This species reacts with three equivalents of CO2 across two Al−CNHC and the Al=Te bond affording a pentacoordinate aluminum complex containing a dianionic tellurocarbonate ligand [CO2Te]2−, which is the first example of tellurium analogue of a carbonate [CO3]2−. 相似文献
58.
Matano Y Miyajima T Ochi N Nakabuchi T Shiro M Nakao Y Sakaki S Imahori H 《Journal of the American Chemical Society》2008,130(3):990-1002
The syntheses, structures, and coordination chemistry of phosphole-containing hybrid calixphyrins (P,N2,X-hybrid calixphyrins) and the catalytic activities of their transition-metal complexes are reported. The 5,10-porphodimethene type 14pi-P,(NH)2,X- and 16pi-P,N2,X-hybrid calixphyrins (X = O, S, NH) are prepared via acid-promoted dehydrative condensation between a sigma4-phosphatripyrrane and the corresponding 2,5-bis[hydroxy(phenyl)methyl]heteroles followed by DDQ oxidation. Both spectroscopic and crystallographic data of the hybrid calixphyrins have revealed that the conformation and size of the macrocyclic platforms as well as the oxidation state of the -conjugated pyrrole-heterole-pyrrole (N-X-N) units vary considerably depending on the combination of heteroles. The sigma3-P,(NH)2,S- and sigma3-P,N2,S-hybrids react with Pd(OAc)2 and Pd(dba)2, respectively, to afford the same Pd(II)-P,N2,S-hybrid complex, in which the calixphyrin platform is regarded as a dianionic ligand. In the complexation with [RhCl(CO)2]2 in dichloromethane, the sigma3-P,N2,S-hybrid behaves as a neutral ligand to afford an ionic Rh(I)-P,N2,S-hybrid complex, whereas the sigma3-P,N2,NH-hybrid behaves as an anionic ligand to produce Rh(III)-P,N3-hybrid complexes. In the latter reaction, it is likely that a neutral Rh(I)-P,N3-hybrid complex, generated as a highly nucleophilic intermediate, undergoes C-Cl bond activation of the solvent. The complexation of AuCl(SMe2) with the sigma3-P,N2,X-hybrids (X = S, NH) leads to the formation of the corresponding Au(I)-monophosphine complexes. The spectral data and crystal structures of these metal complexes exhibit the hemilabile nature of the phosphole-containing hybrid calixphyrin platforms derived from the flexible phosphole unit and the redox active N-X-N units. The hybrid calixphyrin-palladium and -rhodium complexes catalyze the Heck reaction and hydrosilylations, respectively, implying that the metal center in the core is capable of activating the substrates under appropriate reaction conditions. The present results demonstrate the potential utility of the phosphole-containing hybrid calixphyrins as a new class of macrocyclic P,N2,X-mixed donor ligands for designing highly reactive transition-metal complexes. 相似文献
59.
Four kinds of 3,5-dialkylpyrazolate(R2pz)-bridged dinuclear platinum(II) complexes [Pt2(mu-R2pz)2(dfppy)2] (dfppy=2-(2,4-difluorophenyl)pyridine; R2pz=pyrazolate in 1, 3,5-dimethylpyrazolate in 2, 3-methyl-5- tert-butylpyrazolate in 3, and 3,5-bis(tert-butyl)pyrazolate in 4) were theoretically investigated by the DFT(B3PW91) method. The Stokes shift of their phosphorescence spectra was discussed on the basis of the potential energy curve (PEC) of the lowest energy triplet excited state (T1). This PEC significantly depends on the bulkiness of substituents on pz. In 1 and 2, bearing small substituents on pz, one local minimum is present in the T1 state besides a global minimum. The local minimum geometry is similar to the S0-equilibrium one. The T1 state at this local minimum is characterized as the pi-pi* excited state in dfppy, where the dpi orbital of Pt participates in this excited state through an antibonding interaction with the pi orbital of dfppy; in other words, this triplet excited state is assigned as the mixture of the ligand-centered pi-pi* excited and metal-to-ligand charge transfer excited state ((3)LC/MLCT). The geometry of the T1-global minimum is considerably different from the S0-equilibrium one. The T1 state at the global minimum is characterized as the triplet metal-metal-to-ligand charge transfer ((3)MMLCT) excited state, which is formed by the one-electron excitation from the dsigma-dsigma antibonding orbital to the pi* orbital of dfppy. Because of the presence of the local minimum, the geometry change in the T1 state is suppressed in polystyrene at room temperature (RT) and frozen 2-methyltetrahydrofuran (2-MeTHF) at 77 K. As a result, the energy of phosphorescence is almost the same in these solvents. In fluid 2-MeTHF at RT, on the other hand, the geometry of the T1 state easily reaches the T1-global minimum. Because the T1-global minimum geometry is considerably different from the S0-equilibrium one, the phosphorescence occurs at considerably low energy. These are the reasons why the Stokes shift is very large in fluid 2-MeTHF but small in polystyrene and frozen 2-MeTHF. In 3 and 4, bearing bulky tert-butyl substituents on pz, only the T1-global minimum is present but the local minimum is not. The electronic structure of this T1-global minimum is assigned as the (3)MMLCT excited state like 1 and 2. Though frozen 2-MeTHF suppresses the geometry change of 3 and 4 in the T1 state, their geometries moderately change in polystyrene because of the absence of the T1-local minimum. As a result, the energy of phosphorescence is moderately lower in polystyrene than in frozen 2-MeTHF. The T1-global minimum geometry is much different from the S0-equilibrium one in 3 but moderately different in 4, which is interpreted in terms of the symmetries of these complexes and the steric repulsion between the tert-butyl group on pz and dfppy. Thus, the energy of phosphorescence of 3 is much lower in fluid 2-MeTHF than in frozen 2-MeTHF like 1 and 2 but that of 4 is moderately lower; in other words, the Stokes shift in fluid 2-MeTHF is small only in 4. 相似文献
60.
Umakoshi K Kojima T Saito K Akatsu S Onishi M Ishizaka S Kitamura N Nakao Y Sakaki S Ozawa Y 《Inorganic chemistry》2008,47(12):5033-5035
The platinum dimer and heteropolynuclear platinum complexes of 3,5-dimethylpyrazolate, [Pt2M4(mu-Me2pz)8] [M = H (1), Ag (2), Cu (3)], were synthesized and structurally characterized. They exhibit yellow, sky-blue, and orange luminescence, respectively, in the solid state. The absorption bands of 2 and 3 are mainly assigned to the combination of the metal-metal-to-ligand charge-transfer and [Pt2 --> Pt2M4] transitions by the time-dependent density functional theory (DFT) method. DFT calculations also indicate that the emissive states of 2 and 3 are 3[Pt2 --> Pt2Ag4] and 3[Cu(d) --> Pt2Cu4], respectively. 相似文献