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61.
L. P. Szabó D. Kalló L. Szotyory H. Major K. Bélafi-Bakó P. Hadik Cs. Sisak 《Chromatographia》1997,45(1):378-382
Summary A lipophilic buffered aqueous mobile phase, without organic modifier, was used for the high performance liquid chromatographic
enantioseparation of D,L-lactic acid on a Merck ChiraSpher (250 mm×4 mm i.d.) column in which the chiral selector is poly(N-acryloyl-S-phenylalanine ethyl ester) bonded to a spherical silica particle. The lipophilicity of the buffer was achieved by addition
of triethylammonium phosphate, the ‘ethyl’ apolar chains of which dynamically modified the ChiraSpher stationary phase and
increased its hydrophobic character. The ion-paired (cethyltrimethylammonium bromide) analyte enantioseparation was realized
by hydrogen-bonding and dipole-dipole complexation on the ChiraSpher stationary phase, superimposed on simultaneous reversed-phase
partitioning.
Presented at the 21st ISC held in Stuttgart, Germany, 15th–20th September, 1996 相似文献
62.
A. Sisak C. Sisak F. Ungváry G. Pályi L. Markó 《Journal of organometallic chemistry》1975,90(1):77-83
In reactions of Co4(CO)9(arene) with carbon monoxide, phosphines and acetylenes, displacement of the arene takes place and known derivatives of Co4(CO)12 and Co2(CO)8 are formed. With phosphites, however, displacement of one carbon monoxide can be achieved, to give Co4(CO)8(arene)P(OR)3. The same type of complexes can also be prepared by treatment of Co4(CO)11P(OR)3 with arenes. 相似文献
63.
Zora Popović Željka Soldin Gordana Pavlović Dubravka Matković-Čalogović Draginja Mrvoš-Sermek Maša Rajić 《Structural chemistry》2002,13(5-6):425-436
Mercury(II) halides, HgX2 (X = Cl–, Br–, I–) react with 1,3-benzothiazole-2-thione (btztH) in methanol solutions giving the HgX2(btztH) and HgX2(btztH)2 types of compounds. Mercury(II) acetate gives the thiolato compound Hg(btzt)2 because of the deprotonation of btztH. Hg(btzt)2 reacts with 2,2-bipyridine (bipy) giving a 1:1 complex. IR, 1H, and 13C NMR spectral studies indicate that btztH acts as a monodenatate ligand through the S thione donor atom in all complexes. The X-ray crystal structure determinations of [HgI2(btztH)]2, HgBr2(btztH)2, Hg(btzt)2, and Hg(btzt)2(bipy) have been carried out revealing tetrahedrally coordinated mercury atom in [HgI2(btztH)]2 and HgBr2(btztH)2, while in Hg(btzt)2(bipy) 2 + 2 coordination is achieved through strong Hg (N(bipy) contacts. A linear coordination in Hg(btzt)2 is not affected by the Hg N contacts, which are longer than in Hg(btzt)2(bipy), but still shorter than the van der Waals sum of mercury and nitrogen covalent radii. [HgI2(btztH)]2 exists as centrosymmetrical dimer with a Hg2I2 bridging core. The dimeric molecules are linked by the intermolecular hydrogen bonds between the terminal iodine atom and the NH group [3.63(1) Å] into infinite chains along the z-axis. There are N–H Br(bridging) intermolecular hydrogen bonds in HgBr2(btztH)2 joining molecules into endless chains along the x-axis. The Br(bridging) atom acts as double proton acceptor and two NH groups as proton donors [NH Br(bridging) 3.278(9) and 3.338(7) Å]. The mercury to sulfur and mercury to halogen bond distances in [HgI2(btztH)]2 and HgBr2(btztH)2 are discussed in relation to the analogous compounds, revealing strong influence of hydrogen bonds on their relative strengths as well as crystal packing requirements of the ligand. The sulfur and halogen atoms are more tightly bound to mercury implicating severe distortion of the coordination polyhedron in the structures in which they do not take part in hydrogen bonds formation. The influence of steric requirements of the ligands in Hg(btzt)2 and Hg(btzt)2(bipy) on the distortion of the mercury coordination polyhedra accompanied with the relative strength of Hg N contacts is considered. 相似文献
64.
ESI‐MS studies of the non‐covalent interactions between biologically important metal ions and N‐sulfonylcytosine derivatives
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Valentina Ključarić Renata Kobetić Jasmina Rinkovec Snježana Kazazić Dubravka Gembarovski Dijana Saftić Josipa Matić Željka Ban Biserka Žinić 《Journal of mass spectrometry : JMS》2016,51(11):998-1005
The aim of this report is to present the electrospray ionization mass spectrometry results of the non‐covalent interaction of two biologically active ligands, N‐1 ‐ (p‐toluenesulfonyl)cytosine, 1‐TsC, 1 and N‐1 ‐ methanesulfonylcytosine, 1‐MsC, 2 and their Cu(II) complexes Cu(1‐TsC‐N3)2Cl2, 3 and Cu(1‐MsC‐N3)2Cl2 and 4 with biologically important cations: Na+, K+, Ca2+, Mg2+ and Zn2+. The formation of various complex metal ions was observed. The alkali metals Na+ and K+ formed clusters because of electrostatic interactions. Ca2+ and Mg2+ salts produced the tris ligand and mixed ligand complexes. The interaction of Zn2+ with 1–4 produced monometal and dimetal Zn2+ complexes as a result of the affinity of Zn2+ ions toward both O and N atoms. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
65.
Krilov D Gomzi V Herak JN 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):1238-1242
Two different copper complexes with cytosine molecules are formed in the process of crystal growth from the aqueous solution with traces of copper. One of them is diamagnetic, turning into paramagnetic upon ionizing irradiation (complex I). The other, the subject of the present study, is paramagnetic (complex II) as prepared. For complex II, EPR spectra demonstrate that the copper ion is coordinated with one nitrogen atom and three oxygen atoms. On the basis of the detailed EPR spectroscopic analysis and quantum-chemical calculations (in the DFT approach) the model of the complex has been proposed. Both experimental data and the theoretical results support the model with the copper atom, located between the two cytosine ribbons, ligated to a nitrogen and an oxygen atom from two opposing cytosine molecules and two oxygen atoms from water molecules. For complex II the Raman spectra demonstrated concerted restructuring of the hydrogen bonding in the cytosine crystal matrix upon insertion of copper ions. 相似文献
66.
We give the Langlands classification for a non-connected reductive quasisplitp-adic groupG, under the assumption thatG/G
0 is abelian (here,G
0 denotes the connected component of the identity ofG). The Langlands classification for non-connected groups is an extension of the Langlands classification from the connected
case. 相似文献
67.
Gordana Pavlovi Zora Popovi
eljka Soldin Dubravka Matkovi‐alogovi 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(1):61-63
The Hg atom in the title monomeric complex, dichlorobis(3‐imidazolium‐2‐thiolato‐S)mercury(II), [HgCl2(C3H4N2S)2], is four‐coordinate having an irregular tetrahedral geometry composed of two Cl atoms [Hg—Cl 2.622 (2) and 2.663 (2) Å] and two thione S atoms [Hg—S 2.445 (2) and 2.462 (2) Å]. The monodentate thione ligand adopts a zwitterionic form and exists as the 3‐imidazolium‐2‐thiolate ion. The bond angle S1—Hg—S2 of 130.87 (8)° has the greatest deviation from ideal tetrahedral geometry. Intermolecular hydrogen bonds between two of the four N—H groups and one of the Cl atoms [3.232 (8) and 3.238 (7) Å] stabilize the crystal structure, while the other two N—H groups contribute through the formation of N—H?Cl intramolecular hydrogen bonds with the other Cl atom [3.121 (7) and 3.188 (7) Å]. 相似文献
68.
Dubravka Šišak Lynne B. McCusker Dr. Andreas Buckl Georg Wuitschik Dr. Yi‐Lin Wu W. Bernd Schweizer Dr. Jack D. Dunitz Prof. em. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(24):7224-7230
Although listed in organic chemistry textbooks as one of the strongest carbon acids, and in spite of more than a hundred years of attempts to prepare the compound, tricyanomethane (cyanoform) has resisted isolation and characterization, either as the carbon‐acid 1 or as the dicyanoketenimine tautomer 2 . Only in the vapor phase at very low pressure has the compound been identified from its microwave spectrum. Here we review and partially repeat the preparative work. With the aid of spectroscopic and diffraction methods (including powder diffraction) we have identified some of the products obtained as: hydronium tricyanomethanide ( 3 ), (Z)‐3‐amino‐2‐cyano‐3‐iminoacrylimide ( 4 ), a co‐crystal of 4 with sulfuric acid (or corresponding iminium salt), and an addition product of 2 with hydrochloric acid ( 5 / 6 ). Quantum‐mechanical calculations at the MP2/6‐311++g(2d,2p) level have been made to assess the relative energies of some of the molecules involved. 相似文献
69.
Dubravka Pokrajac Lorna Jane Campbell Vladimir Nikora Costantino Manes Ian McEwan 《Experiments in fluids》2007,42(3):413-423
We explore a new application of the quadrant method in the context of the double-averaged Navier–Stokes equations for studying
open channel flow near rough beds. Quadrant analysis is applied to spatial disturbances of time-averaged velocity components,
using the experimental data from flow over two-dimensional regular transverse square-bar roughness. The spatial velocity disturbances
change periodically performing a full cycle over a single roughness element, so that the quadrant diagrams are regular closed
orbits. A colour code is used to produce a quadrant map of the flow cross-section, which reveals contributions from each quadrant
to the time-averaged momentum transfer. 相似文献