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961.
Wilfredo Hernndez Evgenia Spodine Rainer Richter Karl‐Heinz Hallmeier Uwe Schrder Lothar Beyer 《无机化学与普通化学杂志》2003,629(14):2559-2565
The platinum(II) mixed ligand complexes [PtCl(L1‐6)(dmso)] with six differently substituted thiourea derivatives HL, R2NC(S)NHC(O)R′ (R = Et, R′ = p‐O2N‐Ph: HL1; R = Ph, R′ = p‐O2N‐Ph: HL2; R = R′ = Ph: HL3; R = Et, R′ = o‐Cl‐Ph: HL4; R2N = EtOC(O)N(CH2CH2)2N, R′ = Ph: HL5) and Et2NC(S)N=CNH‐1‐Naph (HL6), as well as the bis(benzoylthioureato‐κO, κS)‐platinum(II) complexes [Pt(L1, 2)2] have been synthesized and characterized by elemental analysis, IR, FAB(+)‐MS, 1H‐NMR, 13C‐NMR, as well as X‐ray structure analysis ([PtCl(L1)(dmso)] and [PtCl(L3, 4)(dmso)]) and ESCA ([PtCl(L1, 2)(dmso)] and [Pt(L1, 2)2]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square‐planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the PtII atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt—S‐bonds to the DMSO are significant shorter than those to the thiocarbonyl‐S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p‐NO2, o‐Cl) cause a significant elongation of the Pt—S(dmso)‐bond trans arranged to the benzoyl‐O—Pt‐bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f7/2 electron binding energies of the complexes [PtCl(L1, 2)(dmso)] are higher than those of the bis(benzoylthioureato)‐complexes [Pt(L1, 2)2]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands. 相似文献
962.
The heterospirocyclic N-methyl-N-phenyl-2H-azirin-3-amines (3-(N-methyl-N-phenylamino)-2H-azirines) 1a - d with a tetrahydro-2H-thiopyran, tetrahydro-2H-thiopyran, and a N-protected piperidine ring, respectively, were synthesized from the corresponding heterocyclic 4-carboxamides 2 by consecutive treatment with lithium diisopropylamide (LDA), diphenyl phosphorochloridate (DPPCI), and sodium azide (Scheme 4). The reaction of these aminoazirines with thiobenzoic acid in CH2Cl2 at room temperature gave the thiocarbamoyl-substituted benzamides 13a - d in high yield. The azirines 1a-d were used as synthons for heterocyclic α-amino acids in the preparation of tripeptides of the type Z-Aib-Xaa-Aib-N(Ph)Me ( 18 ) by following the protocol of the ‘azirine/oxazolone method’: treatment of Z-Aib with 1 to give the dipeptide amide 15 , followed by selective hydrolysis to the corresponding acid 16 and coupling with the 2,2-dimethyl-2H-azirin-3-amine 17 gave 18 , again in high yield (Scheme 5). With some selected examples of 18 , the selective deprotection of the amino and the carboxy group, respectively, was demonstrated (Scheme 6). The solid-state conformations of the protected tripeptides 18a - d , as well as that of the corresponding carbocyclic analogue 18e , were determined by X-ray crystallography (Figs. 1-3 and Tables 1-3). All five tripeptides adopt a β-turn conformation of type III or III′. The solvent dependence of the chemical shifts of the NH resonances (Fig. 6) suggests that there is an intramolecular H-bond between H-N(4) and O(11) in all cases, which is an indication that a relatively rigid β-turn structure also persists in solution. Surprisingly, the tripeptide acid 20a shows no intramolecular H-bond in the crystalline state (Fig. 7); O(11) is involved in an intermolecular H-bond with the OH group of the carboxy function. 相似文献
963.
Although crystalline 6-deoxy-L -idose ( 2 ) and crystalline 6-deoxy-L -sorbose ( 3 ) have similar melting points and specific rotations, they can be conclusively differentiated from one another through paper chromatography and paper electrophoresis. 6-Deoxy-L -idose cannot be converted into 6-deoxy-L -sorbose on short heating in very dilute aequeous mineral acids. The synthesis of amorphous 6-deoxy-L -psicose ( 17 ), through oxidative fermentation of 6-deoxy-L -allitol with Acetobacter suboxydans, has been described. 相似文献
964.
Yongjuan Du Edda Rädlein Günther Heinz Frischat 《Journal of Sol-Gel Science and Technology》1998,13(1-3):763-767
Atomic force microscopy (AFM) was used to study the performance of 80 nm thick Al2O3-TiO2-SiO2 sol-gel coatings on glass substrates following corrosion in 1 M NaOH solutions at 60°C. The as-prepared coatings were homogeneous on a nanoscale and displayed the glass pattern before corrosion. Layers with different compositions behaved differently during the corrosion process. Thus, TiO2 or TiO2-dominated layers had tetragonal-like crystals on their surfaces after corrosion, possibly of anatase composition. On the other hand, layers with a molar ratio Al2O3 : SiO2 near 1 : 2 displayed a pseudo-hexagonal morphology, possibly with a nepheline (Na2O · Al2O3 · 2SiO2) composition. Layers of 5Al2O3-40TiO2-55SiO 2 were corroded is a stepwise fashion and had no special surface morphology. 相似文献
965.
The molecular structure of S-methyl thioacetate, CH3C(O)SCH3, was determined by gas electron diffraction (GED) with the assistance of quantum chemical calculations (B3LYP/6-31G and MP2/6-31G). Experimental and theoretical methods result in a structure with syn conformation (C=O double bond syn with respect to the S-C(H3) single bond). The following skeletal geometric parameters were derived from the GED analysis (ra values with 3sigma uncertainties): C=O = 1.214(3), C-C = 1.499(5), S-C(sp2) = 1.781(6), S-C(sp3) = 1.805(6) angstroms, O=C-C = 123.4(8) degrees, O=C-S = 122.8(5) degrees and C-S-C = 99.2(9) degrees. 相似文献
966.
Karl Heinz Koch 《Fresenius' Journal of Analytical Chemistry》1992,343(11):821-822
Conclusion Analytical Chemistry is the application of principles of analytical measurement to generate information about chemical systems or to solve chemical problems as well. That means that Analytical Chemistry, as defined above as a multidiscipline, is from a philosophical point of view an information science, and from an applied pragmatic point of view a problem solving science [8].It must be stated that there is a steady increase of the importance of analytics, and that Analytical Chemistry is never finalized regarding e.g. problems on earth such as the nutrition problem, the exploration of new sources of energy and raw materials, the support of the introduction of new technologies and the development of medical care and, last but not least, the dispassionate control of the environment.When speaking about hi-fi and high-tech as expressions of the highest level of technological development, the term high-QA for high-quality analytics or Analytical Chemistry can be used when characterizing the state-of-the-art and future developments in Analytical Chemistry [9].These facts give the Analytical Chemist identity and demonstrate that he is not only a (poor) information gatherer but possesses, as the controlling conscience, a high responsibility to the general public because his results serve their direct interests. 相似文献
967.
968.
Heinz Krüger 《Theoretical chemistry accounts》1979,51(4):311-322
Franck-Condon matrix elements are calculated approximately for vibrational transitions of a diatomic molecule from a bound electronic potential curve to a purely repulsive curve. The bound states are approached by exactly normalized Miller-Good wavefunctions uniform in both turning points. For the continuum wavefunction a single turning point uniform Airy approximation is taken. The resulting Franck-Condon matrix element is approximately done in closed form with the help of a new canonical integral for a product of harmonic oscillator wavefunctions and Airy functions. The degree of agreement with a closed form exact result is qualitatively discussed for transitions from the ground state of a Morse curve to the continuum of a particular repulse exponential curve.Dedicated to Professor Hermann Hartmann on the occasion of his 65th birthday. 相似文献
969.
Heinz Falk Günther Höllbacher Otmar Hofer 《Monatshefte für Chemie / Chemical Monthly》1979,110(4):1025-1027
A force field constructed for bile pigments and parametrized on partial structures of bile pigments was used to calculate the minimum energy geometries of diastereomeric bilatrienes-abc. In addition the relative energies of these isomers were deduced and the energies of interconversion between the mirror images of the more or less helical (Z,Z,Z)-syn, syn, syn-form were calculated for various paths. 相似文献
970.
Synthesis of 3-Dimethylamino-3a,4,5, 7a-tetrahydro-1H-isoindol-1-ones by Intramolecular Diels-Alder Reaction Thermolysis of N2-acylamidines, the acyl group of which derives from an α,β,γ,δ-unsaturated carboxylic acid ( 2, 5 – 7 ), yields 3-dimethylamino-3a,4,5,7a-tetrahydro-1H-isoindol-1-ones ( 3,8 – 10 , Schemes 1 and 3) in 63–78%. Only the thermodynamically controlled cis-fused ring system is formed. The starting materials are readily available by the reaction of 3-dimethylamino2H-azirines ( 1 and 4 ) and carboxylic acid chlorides. 相似文献