991 resultados para 339.2
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"October 1971."
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"February 1971."
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In analogy to a common synthesis of 1-substituted 5-H tetrazoles (Tetrahedron Lett. 36 (1995)1759; Beloruss. Gos. Univ., Minsk, USSR. Khim. Geterotsikl. Soedin. 11 (1985) 1521; Beloruss. Gos. Univ., Minsk, USSR. Khim. Geterotsikl. Soedin. 1 (1991) 66; BGU, Belarus. Vestsi Akad. Navuk Belarusi, Ser. Khim. Navuk 1 (1992) 73), the new bidentate ligand 1,2-bis(tetrazol-1-yl)ethane [endi] was synthesized and characterized by X-ray diffraction, NMR, IR and UV–Vis spectroscopy. By using iron(II) tetrafluoroborate hexahydrate the complexation with this ligand yields a 1-dimensional linear coordination polymer similar to the recently published chain compound (Inorg. Chem. 39 (2000) 1891) exhibiting a thermally induced spin-crossover phenomenon. Similar to the 1,2-bis(tetrazol-1-yl)propane-bridged compound, our 1,2-bis(tetrazol-1-yl)ethane-bridged compound shows a gradual spin transition, but the spin-crossover temperature T1/2≈140 K is found to be 10 K above the other T1/2. The T1/2 was determined by temperature-dependent 57Fe-Mössbauer, far FT-IR and UV–Vis spectroscopy as well as by temperature-dependent magnetic susceptibility measurements. Single crystals of the complex were grown in situ from a solution of the ligand and iron(II) tetrafluoroborate. The X-ray structure determinations of both the high spin as well as the low spin state of the compound revealed a solid state structure, which is comparable to that of catena-[Fe(1,2-bis(tetrazole-1-yl)propane)3](ClO4)2 (Inorg. Chem. 39 (2000) 1891; 2nd TMR-TOSS Meeting, 4th Spin Crossover Family Meeting, Lufthansa Training Center, Seeheim/Germany, April 30–May 2, 1999). Both the 1,2-bis(tetrazol-1-yl)propane-bridged and our compound do not show a thermal hysteresis effect (J. Am. Chem. Soc. 115 (1993) 9810; Inorg. Chim. Acta 37 (1979) 169; Chem. Phys. Lett. 93 (1982) 567). The synthesis of the complex described in the experimental section yielded a fine powdered product being poorly soluble in most common solvents. The single crystal measurements were done with crystals obtained by various diffusion methods. Most of them yielded either thin needles or small hexagonal prism crystals depending on the specific conditions.
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3-Amino-1,4-benzodiazepines as well as chemically related diverse amines were prepared from oxazepam and subsequently screened on the cholecystokinin receptor in a radiolabel binding assay. Oxazepam 2 was activated via its 3-chloro-1,4-benzodiazepine intermediate 3 and was reacted with a large series of aliphatic and aromatic amines. The substituted 3-anilino-1,4-benzodiazepine structure was identified as lead structure in a diverse series of 3-amino-1,4-benzodiazepines 4-38 and the full SAR (structure-activity relationship) optimisation provided 3-anilinobenzodiazepines 16-38 with CCK 1 receptor selectivity to CCK 2. The compounds 18, 24, 28 and 33 have shown affinities at the CCK 1 receptor of 11, 10, 11 and 9 nM, respectively. These equipotent CCK 1 ligands were fully evaluated in behaviour pharmacological essays. An antidepressant effect was identified in the tail suspension- and the Porsolt swimming-test. The ED 50 values for 24 and 28 were determined in these assays as 0.46 and 0.49 mg/kg. The mixed antagonist 37 showed in addition to the antidepressant effects anxiolytic properties. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
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Although millennial-scale climate variability (<10 ka) has been well studied during the last glacial cycles, little is known about this important aspect of climate in the early Pleistocene, prior to the Middle Pleistocene Transition. Here we present an early Pleistocene climate record at centennial resolution for two representative glacials (marine isotope stages (MIS) 37-41 from approximately 1235 to 1320 ka) during the "41 ka world" at Integrated Ocean Drilling Program Site U1385 (the "Shackleton Site") on the southwest Iberian margin. Millennial-scale climate variability was suppressed during interglacial periods (MIS 37, MIS 39, and MIS 41) and activated during glacial inceptions when benthic d18O exceeded 3.2 per mil. Millennial variability during glacials MIS 38 and MIS 40 closely resembled Dansgaard-Oeschger events from the last glacial (MIS 3) in amplitude, shape, and pacing. The phasing of oxygen and carbon isotope variability is consistent with an active oceanic thermal bipolar see-saw between the Northern and Southern Hemispheres during most of the prominent stadials. Surface cooling was associated with systematic decreases in benthic carbon isotopes, indicating concomitant changes in the meridional overturning circulation. A comparison to other North Atlantic records of ice rafting during the early Pleistocene suggests that freshwater forcing, as proposed for the late Pleistocene, was involved in triggering or amplifying perturbations of the North Atlantic circulation that elicited a bipolar see-saw response. Our findings support similarities in the operation of the climate system occurring on millennial time scales before and after the Middle Pleistocene Transition despite the increases in global ice volume and duration of the glacial cycles.
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Photographs