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Uncovering Intramolecular π‐Type Hydrogen Bonds in Solution by NMR Spectroscopy and DFT Calculations
Prof. Dr. Piero Mastrorilli Prof. Vito Gallo Dr. Stefano Todisco Prof. Mario Latronico Dr. Giacomo Saielli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(23):7964-7969
Reaction between the phosphinito bridged diplatinum species [(PHCy2)Pt(μ‐PCy2){κ2P,O‐μ‐P(O)Cy2}Pt(PHCy2)](Pt–Pt) ( 1 ), and (trimethylsilyl)acetylene at 273 K affords the σ‐acetylide complex [(PHCy2)(η1‐Me3SiC≡C)Pt(μ‐PCy2)Pt(PHCy2){κP‐P(OH)Cy2}](Pt–Pt) ( 2 ) featuring an intramolecular π‐type hydrogen bond. Scalar and dipolar couplings involving the POH proton were detected by 2D NMR experiments. Relativistic DFT calculations of the geometry, relative energy, and NMR properties of model systems of 2 confirmed the structural assignment and allowed the energy of the π‐type hydrogen bond to be estimated (ca. 22 kJ mol?1). 相似文献
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Ji‐Ho Yoon Prof. Yun‐Je Lee Jeasung Park Dr. Taro Kawamura Dr. Yoshitaka Yamamoto Dr. Takeshi Komai Dr. Satoshi Takeya Dr. Sang Sup Han Dr. Jong‐Won Lee Prof. Yongjae Lee Prof. 《Chemphyschem》2009,10(2):352-355
Easy come, easy go: Hydroquinone forms a channel structure of cages with hydrogen‐bonded hexagons. These may provide an ideal route for the fast inclusion and facile release of hydrogen molecules (see figure), which can lead to reversible hydrogen storage under mild conditions.
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David Lachkar Debora Vilona Dr. Elise Dumont Dr. Moreno Lelli Dr. Emmanuel Lacôte 《Angewandte Chemie (International ed. in English)》2016,55(20):5961-5965
The Dawson tungstovanadate [P2W15V3O62]9? can be grafted to secondary diolamides. The electron‐withdrawing character of the polyanion increases the acidity of the amide proton, leading to an organo‐polyoxometalate, which can be used as a Brønsted organocatalyst. High‐field NMR and DFT modeling indicate that the amide proton stays on the nitrogen and that the exalted acidity derives from the interaction between the organic and inorganic parts of the organo‐polyoxometalate. The amide‐inserted vanadotungstates thus form a new family of (hybrid) heteropolyacids, offering new perspectives for the application of POM‐based catalysis in organic synthesis. 相似文献
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Hierarchical Fe3O4@poly(4‐vinylpyridine‐co‐divinylbenzene)@Au (Fe3O4@P(4‐VP–DVB)@Au) nanostructures were fabricated successfully by means of a facile two‐step synthesis process. In this study, well‐defined core–shell Fe3O4@P(4‐VP–DVB) microspheres were first prepared with a simple polymerization method, in which 4‐VP was easily polymerized on the surface of Fe3O4 nanoparticles by means of strong hydrogen‐bond interactions between ? COOH groups on poly(acrylic acid)‐modified Fe3O4 nanoparticles and a 4‐VP monomer. HAuCl4 was adsorbed on the chains of a P(4‐VP) shell and then reduced to Au nanoparticles by NaBH4, which were embedded into the P(4‐VP) shell of the composite microspheres to finally form the Fe3O4@P(4‐VP–DVB)@Au nanostructures. The obtained Fe3O4@P(4‐VP–DVB)@Au catalysts with different Au loadings were applied in the reduction of 4‐nitrophenol (4‐NP) and exhibited excellent catalytic activity (up to 3025 h?1 of turnover frequency), facile magnetic separation (up to 31.9 emu g?1 of specific saturation magnetization), and good durability (over 98 % of conversion of 4‐NP after ten runs of recyclable catalysis and almost negligible leaching of Au). 相似文献
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Intramolecular NH…O,S,N interactions in non-tautomeric systems are reviewed in a broad range of compounds covering a variety of NH donors and hydrogen bond acceptors. 1H chemical shifts of NH donors are good tools to study intramolecular hydrogen bonding. However in some cases they have to be corrected for ring current effects. Deuterium isotope effects on 13C and 15N chemical shifts and primary isotope effects are usually used to judge the strength of hydrogen bonds. Primary isotope effects are investigated in a new range of magnitudes. Isotope ratios of NH stretching frequencies, νNH/ND, are revisited. Hydrogen bond energies are reviewed and two-bond deuterium isotope effects on 13C chemical shifts are investigated as a possible means of estimating hydrogen bond energies. 相似文献
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Release of the Water Molecule Encapsulated Inside an Open‐Cage Fullerene through Hydrogen Bonding Mediated by Hydrogen Fluoride 下载免费PDF全文
Liang Xu Hongjiang Ren Sisi Liang Jiahao Sun Prof. Dr. Yajun Liu Prof. Dr. Liangbing Gan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13539-13543
A reversible wetting/dewetting procedure is reported for an open‐cage fullerene with an 18‐membered orifice. In a homogeneous mixture of H2O/EtOH/CHCl3, water was encapsulated into the cavity of the open‐cage compound quantitatively at 80 °C. Addition of aqueous hydrogen fluoride into the water‐encapsulated complex removed the encapsulated water completely at room temperature. H‐bonding between the trapped water and fluoride is shown to play a key role for the water release process. 相似文献
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α‐Fluoro‐o‐cresols: The Key Role of Intramolecular Hydrogen Bonding in Conformational Preference and Hydrogen‐Bond Acidity 下载免费PDF全文
Dr. Elena Bogdan Alexis Quarré de Verneuil François Besseau Dr. Guillaume Compain Prof. Dr. Bruno Linclau Prof. Dr. Jean‐Yves Le Questel Dr. Jérôme Graton 《Chemphyschem》2016,17(17):2702-2709
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[{Ni4(OH)3AsO4}4(B‐α‐PW9O34)4]28−: A New Polyoxometalate Structural Family with Catalytic Hydrogen Evolution Activity 下载免费PDF全文
Hongjin Lv Dr. Yingnan Chi Jan van Leusen Prof. Paul Kögerler Dr. Zheyuan Chen Dr. John Bacsa Dr. Yurii V. Geletii Weiwei Guo Prof. Tianquan Lian Prof. Craig L. Hill 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17363-17370
A new structural polyoxometalate motif, [{Ni4(OH)3AsO4}4(B‐α‐PW9O34)4]28?, which contains the highest nuclearity structurally characterized multi‐nickel‐containing polyanion to date, has been synthesized and characterized by single‐crystal X‐ray diffraction, temperature‐dependent magnetism and several other techniques. The unique central {Ni16(OH)12O4(AsO4)4} core shows dominant ferromagnetic exchange interactions, with maximum χmT of 69.21 cm3 K mol?1 at 3.4 K. Significantly, this structurally unprecedented complex is an efficient, water‐compatible, noble‐metal‐free catalyst for H2 production upon visible light irradiation (photosensitizer=[Ir(ppy)2(dtbbpy)][PF6]; sacrificial electron donor=triethylamine or triethanolamine). The highest turnover number of approximately 580, corresponding to a best quantum yield of approximately 4.07 %, is achieved when using triethylamine as electron donor in the presence of water. The mechanism of this photodriven process has been probed by time‐solved luminescence and by static emission quenching. 相似文献
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Yi‐An Chen Fan‐Yi Meng Yen‐Hao Hsu Cheng‐Hsien Hung Chi‐Lin Chen Kun‐You Chung Wei‐Feng Tang Prof. Dr. Wen‐Yi Hung Prof. Dr. Pi‐Tai Chou 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14688-14695
A series of compounds containing 5‐(2‐aminobenzylidene)‐2,3‐dimethyl‐3,5‐dihydro‐4H‐imidazol‐4‐one ( o ‐ABDI ) as the core chromophore with a seven‐membered‐ring N?H‐type intramolecular hydrogen bond have been synthesized and characterized. The acidity of the N?H proton and thus the hydrogen‐bond strength can be fine‐tuned by replacing one of the amino hydrogen atoms by a substituent R, the acidity increasing with increasing electron‐withdrawing strength of R, that is, in the order H<COCH3<COPh<Tosyl<COCF3. The tosyl and trifluoroacetyl derivatives undergo ultrafast, irreversible excited‐state intramolecular proton transfer (ESIPT) that results in proton‐transfer emission solely in the red region. Reversible ESIPT, and hence dual emission, involving the normal and proton‐transfer tautomers was resolved for the acetyl‐ and benzyl‐substituted counterparts. For o ‐ABDI , which has the weakest acidity, ESIPT is prohibited due to its highly endergonic reaction. The results clearly demonstrate the harnessing of ESIPT by modifying the proton acidity and hydrogen‐bonding strength in a seven‐membered‐ring intramolecular hydrogen‐bonding system. For all the compounds studied, the emission quantum yields are weak (ca. 10?3) in dichloromethane, but strong in the solid form, ranging from 3.2 to 47.4 %. 相似文献
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Intramolecular Hydrogen Bond Reverting the Solvent Effect on Phosphorus Hyperfine Coupling Constants of β‐Phosphorylated Nitroxides 下载免费PDF全文
Prof. Gérard Audran Dr. Lionel Bosco Dr. Paul Brémond Teddy Butscher Prof. Sylvain R. A. Marque Prof. Stéphane Viel 《Chemphyschem》2016,17(23):3954-3963
Recently, we reported a dramatic solvent effect on the phosphorus hyperfine coupling constant aP of β‐phosphorylated six‐membered ring nitroxides, that is, approximately 25 G of difference in aP from n‐hexane to water (Org. Biomol. Chem. 2016 , 14, —1228‐1292). In this article, we report on the effect of intramolecular hydrogen bonding (IHB) in three nitroxides exhibiting IHB between the hydroxyl and diethylphosphoryl groups and one exhibiting IHB between the hydroxyl group and the nitroxyl moiety. It is observed that for the first three nitroxides, aP increases with increasing polarity/polarizability and hydrogen bond donor (HBD) properties of the solvent (π* and α, respectively)—in sharp contrast to the data reported in the literature—and for the last nitroxide, aP decreases with π* and α. In fact, the occurrence of IHB induces a large strain, its suppression by hydrogen bond acceptor (HBA) solvents affords an increase in aP. 相似文献
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Rui Fu Soon Mog So Alan J. Lough Jik Chin 《Angewandte Chemie (International ed. in English)》2020,59(11):4335-4339
l to d conversion of unactivated α‐amino acids was achieved by solubility‐induced diastereomer transformation (SIDT). Ternary complexes of an α‐amino acid with 3,5‐dichlorosalicylaldehyde and a chiral guanidine (derived from corresponding chiral vicinal diamine) were obtained in good yield as diastereomerically pure imino acid salt complexes and were hydrolysed to obtain enantiopure α‐amino acids. A combination of DFT computation, NMR spectroscopy, and crystal structure provide detailed insight into how two types of strong hydrogen bonds assist in rapid epimerization of the complexes that is essential for SIDT. 相似文献
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Claire Besson Djamaladdin G. Musaev Vanina Lahootun Rui Cao Lise‐Marie Chamoreau Richard Villanneau Françoise Villain René Thouvenot Yurii V. Geletii Craig L. Hill Anna Proust 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10233-10243
Reaction of the divacant polyoxometalate K8[γ‐XW10O36] (X=Si, Ge) with two equivalents of the metal‐nitrido precursor Cs2[RuVINCl5], at room temperature in water, produces K2(Me2NH2)2H2[γ‐XW10O38{RuN}2], X=Si ( DMA ‐ 1 a ) or Ge ( DMA ‐ 1 b ). The X‐ray crystal structures of both complexes show monomeric complexes with highly unusual vicinal terminal metal‐nitrido units. The Ru?N bond lengths are 1.594(10) and 1.612(11) Å in 1 a and 1 b , respectively. EXAFS studies confirmed the key structural assignments from X‐ray crystallography. The XANES spectrum of DMA‐1 a , diamagnetism, NMR (29Si and 183W) chemical shifts, voltammetric behavior, reductive titrations with [PW12O40]4?, and computational data are all consistent with d2 RuVI centers in these complexes. The FT‐IR and Raman spectra show the expected vibrational modes of the {γ‐XW10} unit and the Ru?N stretch at 1080 cm?1, respectively. Interestingly, reduction of DMA‐1 a by 4 equivalents of [PW12O40]4? produces NH3 in nearly quantitative yield. Cyclic voltammetry versus pH and calculations provide the energetics for the possible two‐electron reduction and two‐proton addition processes in this reaction. 相似文献