摘要 :
A general scheme for reducing the center-of-mass entropy is proposed. It is based on the repetition of a cycle, composed of three concepts: velocity selection, deceleration and irreversible accumulation. Well-known laser technique...
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A general scheme for reducing the center-of-mass entropy is proposed. It is based on the repetition of a cycle, composed of three concepts: velocity selection, deceleration and irreversible accumulation. Well-known laser techniques are used to represent these concepts: Raman π-pulse for velocity selection, STIRAP for deceleration, and a single spontaneous emission for irreversible accumulation. No closed pumping cycle nor repeated spontaneous emissions are required, so the scheme is applicable to cool a molecular gas. The quantum dynamics are analytically modelled using the density matrix. It is shown that during the coherent processes the gas is translationally cooled. The internal states serve as an entropy sink, in addition to spontaneous emission. This scheme provides new possibilities to translationally laser-cool molecules for high precision molecular spectroscopy and interferometry.
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The synthesis of the new chiral ligand (3,5-di-tert-butylpyrazol-1-yl)(3',5'-dimethylpyrazol-1-yl)acetic acid (bpaH~(tBu2,Me2) (4) has been achieved.Two different synthetic routes to its precursor 3,5-di-tert-butyl-1-[(3,5-dimethy...
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The synthesis of the new chiral ligand (3,5-di-tert-butylpyrazol-1-yl)(3',5'-dimethylpyrazol-1-yl)acetic acid (bpaH~(tBu2,Me2) (4) has been achieved.Two different synthetic routes to its precursor 3,5-di-tert-butyl-1-[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-1H-pyrazole (bpm~(tBu2,Me2)(3) are repored.Deprotonation at the methylene group,followed by reaction with carbon dioxide,yielded a racemic mixture of 4.The chemical behaviour of bis(3,5-di-tert-butyl-yrazol-1-yl)acetic acid (bdtbpzaH) (2) and the new chiral N,N,O scorpionate ligand 4 involving their coordination to zinc ions was studied.[Zn(bpa~(tBu2,Me2)Cl](5) was formed from a mixture of ZnCl_2,4 and base.Reaction of bis(3,5-di-tert-butylpyrazol-1-yl)aceticacid (bdtbpzaH) (2) with Zn(CH_3)_2 or Zn(CH-2CH_3)_2 gave the alkylzinc complexes [Zn(bdtbpza)(CH_3)] (6) and [Zn(bdtbpza)(CH_2CH_3)] (7).[Zn(bpa~(tBu2,Me2)(CH_3)] (8) was obtained from a synthesis analogous to that of 6 with 4.The further reactions of 6 and 8 with acetic acid resulted in the acetto complexes [Zn(OAc)(bdtbpza)](9) and [Zn(OAc)(bpa~(tBu2,Me2)](10).The chiral methyl complex 8 may serve as a precursor for strucrual model compelxes of the active sites of zinc enzymes,such as thermolysinor carboxypeptidase A.[Zn(bpa~(tBu2,Me2) (11) was formed from a side reaction.Crystal structures of 4,5,8 and 11 were obtained;5 crystallised as the dimer [Zn(bpa~(tBu2,Me2)Cl]_2;11 presents an unusual zinc binding geometry.
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The chemical behavior of two bis(3,5-dialkylpyrazol-1-yl)-acetic acids and their coordination propertis towards ZnCl_2 and FeCl_2 was studied. Reaction of bis(3,5-Dimethylpyrazol-1-yl)acetic acid (bdmpza) (1) with ZnCl_2 and FeCl_...
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The chemical behavior of two bis(3,5-dialkylpyrazol-1-yl)-acetic acids and their coordination propertis towards ZnCl_2 and FeCl_2 was studied. Reaction of bis(3,5-Dimethylpyrazol-1-yl)acetic acid (bdmpza) (1) with ZnCl_2 and FeCl_2 gave the 2:1 complexes [(bdmpza)_2Zn] (4) and [(bdmpza)_2Fe] (5). Crystal structures of both complexes were obtained. In contrast, the sterically more hindered ligand bis(3,5-di-tert-butylpyrazol-1-yl)acetic acid (bdtbpza) (3) coordinates only once to zinc(II) resulting in the complex [(bdtbpza)ZnCl] (6). This provides a structural model complex for the active sites of zinc enzymes such as thermolysin or carboxypeptidase. The good agreement with these active sites was demon-strated by a crystal structure of 6. To the best of our knowledge, this is the first report of zinc complexes with a monoanionic N,N,O-tridentate ligand using a carboxylate O-donor. Substitution f benzylthiolate for the chloride ligand 6 yielded [(bdtbpza)Zn(SCH_2Ph)] (8) indicating that the bulky tert-butyl groups don not prevent access to the zinc atom. Reaction of bdtbpza (3) with FeCl_2 led to [(bdtbpza)FeCl] (7), which might serve as a structural model complex for the active sites of mononuclear non-heme iron oxidases and oxygenases such as IPNS, DAOCS or CAS.
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Enediynes rac-4 were prepared in seven steps with an over-all yield of 31% starting from 4-pentyn-1-ol (5).A cobalt mediated [2+2+2]-cycloaddition of these enediynes and subsequent removal of the metal fragment afforded the decahy...
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Enediynes rac-4 were prepared in seven steps with an over-all yield of 31% starting from 4-pentyn-1-ol (5).A cobalt mediated [2+2+2]-cycloaddition of these enediynes and subsequent removal of the metal fragment afforded the decahy-drophenanthrenes rac-3/13 in 37-56% yield.
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Oximes of glucose,xylose,lactose,fructose,and mannose have been prepared.Nitrosation of the oximes of glucose,xylose,and lactose with NaNO_2/HCl afforded 2-(beta-glyco-pyranosyl)-l-hydroxydiazene-2-oxides,which were isolated as sa...
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Oximes of glucose,xylose,lactose,fructose,and mannose have been prepared.Nitrosation of the oximes of glucose,xylose,and lactose with NaNO_2/HCl afforded 2-(beta-glyco-pyranosyl)-l-hydroxydiazene-2-oxides,which were isolated as salts 13,22,and 28.Nitrosation of fructose oxime 29 furnished fructose,whereas nitrosation of mannose oxime 30 with NaNO_2/HCl afforded the l-hydroxy-2-(beta-D-manno-pyranosyl)diazene-2-oxide 32,from which the p-anisidinium salt 31 and the sodium salt 33 were prepared.However,nitrosation of 30 with isopentyl nitrite in aqueous solutions of CsOH or KOH resulted in the formation of the 2-(alpha-D-mannofuranosyl)-l-hydroxydia-zene-2-oxide salts 34 and 35,respectively.Methylation of the ammonium 2-(beta-D-glucopyranosyl)-l-hydroxydia-zene-2-oxide 13 yielded the 1-methoxy compound,which was benzoylated to afford the tetra-O-benzoate 14a,the structure of which was confirmed by X-ray diffraction analysis.From the glucose O-methyloximes 15 and 16 the N-methoxy-N-nitroso-2,3,4,6-tetra-O-ace-tyl-beta-D-glucopyranosylamine 18 was prepared.The structure of this compound was confirmed by X-ray diffraction analysis.Treatment of acetobro-moglucose with cupferron furnished the l-(2,3,4,6-tetra-O-acetyl-beta-D-gluco-pyranosyloxy)-2-phenyldiazene-2-oxide 20.
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A new enantiopure chiral tripod ligand is obtained from C_2-symmetric bis(camphorphyrazol-1-yl)methane by introducing a carboxylate group at the bridging carbon atom. A prochiral centre is formed rather than an additional stereoce...
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A new enantiopure chiral tripod ligand is obtained from C_2-symmetric bis(camphorphyrazol-1-yl)methane by introducing a carboxylate group at the bridging carbon atom. A prochiral centre is formed rather than an additional stereocentre. Therefore, a homochiral tripod ligand is achieved without separation of the stereoisomers.
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The syntheses of ruthenium(II) acetato and benzoato complexes [Ru(bdmpza)(O_2CCH_3)(PPh_3)] (6) and [Ru(bdmpza)(O_2CPh)(PPh_3)] (7) [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] are reported. The complexes 6 and 7 are synthesize...
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The syntheses of ruthenium(II) acetato and benzoato complexes [Ru(bdmpza)(O_2CCH_3)(PPh_3)] (6) and [Ru(bdmpza)(O_2CPh)(PPh_3)] (7) [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] are reported. The complexes 6 and 7 are synthesized in high yield from [Ru(bdmpza)Cl(PPh_3)_2] (1) and thallium acetate (2) or thallium benzoate (3). In a similar substitution reaction a benzoylformate complex [Ru(bdmpza){O_2CC(O)Ph}(PPh_3)] (8) is obtained from 1 and thallium benzoylformate (4). Reaction of 6 or 7 with benzoylformic acid also yields 8. In analogous reactions several 2-oxocarboxylato ruthenium(II) complexes [Ru(bdmpza){O_2CC(O)R}(PPh_3)] (9: R = CH_2CH_2CO_2H, 10: R = Me, 11: R = Et) can be obtained. The low-spin ruthenium(II) complexes 8 to 11 exhibit a purple or brownish-red colour caused by MLCT transitions and thus a HOMO-LUMO gap which is almost identical to that of high-spin 2-oxoglutarate dependent iron oxygenases. 6 crystallises as a water adduct, 6·H_2O and 8 forms an acetonitrile adduct 12. Crystal structures of the water adduct 6·H2O and 8 were obtained.
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(s)-(-)-Acromelobic acid (1)was synthesized in nine steps in enantiomerically pure form form citrazinic acid (4)in an overall yield of 21%.The key steps of this synthesis are the introductin of the amino function by the bis(lactim...
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(s)-(-)-Acromelobic acid (1)was synthesized in nine steps in enantiomerically pure form form citrazinic acid (4)in an overall yield of 21%.The key steps of this synthesis are the introductin of the amino function by the bis(lactim)ether method and the introductin of the acid function by stille coupling.
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New ruthenium(II) and ruthenium(III) complexes with the ligands bis(pyrazol-1-yl)acetate (bpza) and bis(3,5-dimethyl-pyrazol-1-yl)acetate (bdmpza) are reported. The reaction of ruthenium trichloride hydrate, H[bpza], and excess PP...
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New ruthenium(II) and ruthenium(III) complexes with the ligands bis(pyrazol-1-yl)acetate (bpza) and bis(3,5-dimethyl-pyrazol-1-yl)acetate (bdmpza) are reported. The reaction of ruthenium trichloride hydrate, H[bpza], and excess PPh_3 yielded [Ru(bpza)Cl(PPh_3)_2] as a racemic mixture of an unsymmetrical isomer with traces of a symmetrical isomer. Similar reaction conditions using the more bulky H[bdmpza) yielbed [Ru(bdmpza)Cl_2(PPh_3)]. Reaction of K[bpza] with [RuCl_2(PPh_3)_3] offered a second route to [Ru(bpza)Cl(PPh_3)_2]. Also, [Ru(bdmpza)Cl(PPh_3)_2] was accessed by this synthetic approach. All three new complexes were characterized by X-ray structure determination.
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We give a critical analysis of projective relativity theory. Examining Kaluza's own intention and the following development by Klein, Jordan, Pauli, Thiry, Ludwig and others, we conclude that projective relativity was abused in it...
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We give a critical analysis of projective relativity theory. Examining Kaluza's own intention and the following development by Klein, Jordan, Pauli, Thiry, Ludwig and others, we conclude that projective relativity was abused in its own terms and much more in the case of newer higher dimensional Kaluza-Klein theories with non-Abelian gauge groups. Reviewing the projective formulation of the Jordan isomorphy theorem yields some hints how one can proceed in a different direction. We can interpret the condition R_(μν)~5 = 0 not as a field equation in a 5-dimensional Riemannian space, e.g. as vacuum Einstein-Hilbert equation, but can (or should) interpret it as a geometrical object, a null-quadric. Projective aspects of quantum (field) theory are discussed under this viewpoint.
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