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排序方式: 共有204条查询结果,搜索用时 31 毫秒
91.
Jing Xu Xiaodong Li Jingfang Li Xiangyi Li Prof. Bao Li Yang Wang Prof. Lixin Wu Prof. Wen Li 《Angewandte Chemie (International ed. in English)》2017,56(30):8731-8735
Sessile organisms have undergone long-term evolution to develop the unique ability by positioning themselves on wet solid surface through secreting adhesive proteins. The present study reveals that natural amino acid monomers can also exhibit similar adhesion capacity. This kind of biomimetic adhesives were created by the one-step aqueous assembly of basic amino acids with assistance of anionic polyoxometalates. The polyoxometalates not only serve as multivalent scaffold to initiate the supramolecular cross-linking of amino acid molecules, but also function as a redox component, bestowing the wet adhesives with electrochromic features. 相似文献
92.
The zwitterionic 1 : 1 intermediates generated by addition of N‐heterocycles to activated acetylenes are trapped by trichloroacetonitrile to afford 1,2‐ or 1,4‐disubstituted N‐heterocycles in moderate to good yields under mild reaction conditions. 相似文献
93.
Rabindra N. Roy Lakshmi N. Roy Bennett J. Tabor Curtis A. Himes Sarah J. Richards Ashley N. Simon Andrew C. Moore Lydia A. Seing Heather D. Craig Kyle T. Robinson 《Journal of solution chemistry》2004,33(10):1199-1211
The values of the second dissociation constant, pK2, and related thermodynamic quantities of 4-(N-morpholino)butanesulfonic acid (MOBS) and N-tris(hydroxymethyl)-4-aminobutanesulfonic acid (TABS) have already been reported over the temperature range 5–55°C including 37{°}C. This paper reports the pH values of twelve equimolal buffer solutions at designated pH (s) with the following compositions: (a) mixtures of MOBS (0.05 mol-kg–1) + NaMOBS (0.05 mol-kg–1); (b) MOBS (0.08 mol-kg–1) + NaMOBS (0.08 mol-kg–1); (c) MOBS (0.08 mol-kg–1) + NaMOBS (0.08 mol-kg–1) + NaCl (0.08 mol-kg–1); (d) TABS (0.05 mol-kg–1) + NaTABS (0.05 mol-kg–1); and (e) TABS (0.08 mol-kg–1) + NaTABS (0.08 mol-kg–1); and (f) TABS (0.08 mol-kg–1) + NaTABS (0.08 mol-kg–1) + NaCl (0.08 mol-kg–1). Two buffer solutions have ionic strengths I= 0.05 mol-kg–1, another two have I=0.08 mol-kg–1, and the remaining two buffer solutions have I= 0.16 mol-kg–1, which is close to that of the clinical fluids (blood serum). These buffers have been recommended as a useful pH standard for the measurements of physiological solutions. Conventional pH values of all six buffer solutions from 5–55°C, as well as those obtained from the liquid junction potential correction at 25 and 37{°}C have been calculated. The flowing-junction calomel cell has been utilized to measure Ej, the liquid junction potential. 相似文献
94.
Three novel alkaloids, macropodumines A-C (1-3), were isolated from the stem of Daphniphyllum macropodum Miq. Interestingly, the structure of macropodumine A (1) was characterized as having a fused pentacyclic system including an unusual eleven-membered macrolactone ring, whereas macropodumine B (2) contains a rare cyclopentadienyl carbanion, which is stabilized as a zwitterion by an internal iminium cation. The structures of these new metabolites were established on the basis of their detailed spectroscopic analysis. In particular, the unique structure of zwitterion 2 was further confirmed by using single-crystal X-ray diffraction analysis. 相似文献
95.
96.
Hydroboration of Alkynes with Zwitterionic Ruthenium–Borate Complexes: Novel Vinylborane Complexes 下载免费PDF全文
R. S. Anju Bijan Mondal Koushik Saha Subir Panja Babu Varghese Prof. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11393-11400
Building upon previous studies on the synthesis of bis(sigma)borate and agostic complexes of ruthenium, the chemistry of nido‐[(Cp*Ru)2B3H9] ( 1 ) with other ligand systems was explored. In this regard, mild thermolysis of nido‐ 1 with 2‐mercaptobenzothiazole (2‐mbzt), 2‐mercaptobenzoxazole (2‐mbzo) and 2‐mercaptobenzimidazole (2‐mbzi) ligands were performed which led to the isolation of bis(sigma)borate complexes [Cp*RuBH3L] ( 2 a – c ) and β‐agostic complexes [Cp*RuBH2L2] ( 3 a – c ; 2 a , 3 a : L=C7H4NS2; 2 b , 3 b : L=C7H4NSO; 2 c , 3 c : L=C7H5N2S). Further, the chemistry of these novel complexes towards various diphosphine ligands was investigated. Room temperature treatment of 3 a with [PPh2(CH2)nPPh2] (n=1–3) yielded [Cp*Ru(PPh2(CH2)nPPh2)‐BH2(L2)] ( 4 a – c ; 4 a : n=1; 4 b : n=2; 4 c : n=3; L=C7H4NS2). Mild thermolysis of 2 a with [PPh2(CH2)nPPh2] (n=1–3) led to the isolation of [Cp*Ru(PPh2(CH2)nPPh2)(L)] (L=C7H4NS2 5 a – c ; 5 a : n=1; 5 b : n=2; 5 c : n=3). Treatment of 4 a with terminal alkynes causes a hydroboration reaction to generate vinylborane complexes [Cp*Ru(R?C?CH2)BH(L2)] ( 6 and 7 ; 6 : R=Ph; 7 : R=COOCH3; L=C7H4NS2). Complexes 6 and 7 can also be viewed as η‐alkene complexes of ruthenium that feature a dative bond to the ruthenium centre from the vinylinic double bond. In addition, DFT computations were performed to shed light on the bonding and electronic structures of the new compounds. 相似文献
97.
A Donor‐Stabilized Zwitterionic “Half‐Parent” Phosphasilene and Its Unusual Reactivity towards Small Molecules 下载免费PDF全文
Kerstin Hansen Tibor Szilvási Dr. Burgert Blom Dr. Elisabeth Irran Prof. Dr. Matthias Driess 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):1947-1956
The stabilization of the labile, zwitterionic “half‐parent” phosphasilene 4 L′Si?PH (L′=CH[(C?CH2)CMe(NAr)2]; Ar=2,6‐iPr2C6H3) could now be accomplished by coordination with two different donor ligands (4‐dimethylaminopyridine (DMAP) and 1,3,4,5‐tetramethylimidazol‐2‐ylidene), affording the adducts 8 and 9 , respectively. The DMAP‐stabilized zwitterionic “half‐parent” phosphasilene 8 is capable of transferring the elusive parent phosphinidene moiety (:PH) to an unsaturated organic substrate, in analogy to the “free” phosphasilene 4 . Furthermore, compounds 4 and 8 show an unusual reactivity of the Si?P moiety towards small molecules. They are capable of adding dimethylzinc and of activating the S?H bonds in H2S and the N?H bonds in ammonia and several organoamines. Interestingly, the DMAP donor ligand of 8 has the propensity to act as a leaving group at the phosphasilene during the reaction. Accordingly, treatment of 8 with H2S affords, under liberation of DMAP, the unprecedented thiosilanoic phosphane LSi?S(PH2) 16 (L=HC(CMe[2,6‐iPr2C6H3N])2). Compounds 4 and 8 react with ammonia both affording L′Si(NH2)PH2 17 , respectively. In addition, the reaction of 8 with isoproylamine, p‐toluidine, and pentafluorophenylhydrazine lead to the corresponding phosphanylsilanes L′Si(PH2)NHR (R=iPr 18 a ; R=C6H5?CH3 18 b , R=NH(C6F5) 18 c ), respectively. 相似文献
98.
99.
Lakshmi N. Roy Rabindra N. Roy Cole E. Denton Sean R. LeNoue Curtis A. Himes Sarah J. Richards Ashley N. Simon Chandra N. Roy Vikram S. Somal 《Journal of solution chemistry》2006,35(4):551-566
The values of the second dissociation constant, pK
2, and related thermodynamic quantities of N-[tris(hydroxymethyl)methyl-3-amino]propanesulfonic acid (TAPS) have already been reported at 12 temperatures over the temperature range 5–55 ∘C, including 37 ∘C. This paper reports the results for the pH of five equimolal buffer solutions with compositions: (a) TAPS (0.03 mol⋅kg−1) + NaTAPS (0.03 mol⋅kg−1); (b) TAPS (0.04 mol⋅ kg−1) + NaTAPS (0.04 mol⋅kg−1); (c) TAPS (0.05 mol⋅kg−1) + NaTAPS (0.05 mol⋅kg−1); (d) TAPS (0.06 mol⋅kg−1) + NaTAPS (0.06 mol⋅kg−1); and (d) TAPS (0.08 mol⋅kg−1) + NaTAPS (0.08 mol⋅kg−1). The remaining eight buffer solutions consist of saline media of the ionic strength I = 0.16 mol⋅kg−1, matching closely to that of the physiological sample. The compositions are: (f) TAPS (0.04 mol-kg−1) + NaTAPS (0.02 mol-kg−1) + NaCl (0.14 mol⋅kg−1); (g) TAPS (0.05 mol⋅kg−1) + NaTAPS (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (h) TAPS (0.6 mol⋅kg−1) + NaTAPS (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (i) TAPS (0.08 mol⋅kg−1) + NaTAPS (0.06 mol⋅kg−1) + NaCl (0.10 mol⋅kg−1); (j) TAPS (0.04 mol⋅ kg−1) + NaTAPS (0.04 mol⋅kg−1) + NaCl (0.12 mol⋅kg−1); (k) TAPS (0.05 mol⋅kg−1) + NaTAPS (0.05 mol⋅kg−1) + NaCl (0.11 mol⋅kg−1); (l) TAPS (0.06 mol⋅kg−1) + NaTAPS (0.06 mol⋅kg−1) + NaCl (0.10 mol⋅kg−1); and (m) TAPS (0.08 mol⋅kg−1) + NaTAPS (0.08 mol⋅kg−1) + NaCl (0.08 mol⋅kg−1). These buffers are recommended as a pH standard for clinical measurements in the range of physiological application. Conventional pH values, designated as pH(s), for all 13 buffer solutions from 5 to 55 ∘C have been calculated. The operational pH values with liquid junction corrections, at 25 and 37 ∘C for buffer solutions, designated above as (b), (c), (d), (e), (j), (l), and (m); have been determined based on the difference in the values of the liquid junction potentials between the accepted phosphate standard and the buffer solutions under investigation. 相似文献
100.