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21.
The crystal and molecular structure ofH
4a
,H
9a
-cis-H
9,H
9a
-trans-2-methyl-9-phenyl-2, 3,4,4
a
,9,9
a
-hexahydro-1H-indeno[2,1-c]pyridine hydrochloride was determined. The compound crystallizes in the orthorhombic space groupPbca, with eight molecules in the unit cell of dimensionsa = 10.461(2),b = 20.141(10), andc = 15.469(3) Å. Intensity data were measured using Mo radiation and a – scan method. The structure was solved by direct methods and refined by least-squares techniques to a finalR of 4.6%. Thecis-trans isomer has higher antihistamine activity compared to thecis-cis isomer but is less active than phenindamine, the 2,3,4,9-tetrahydro derivative. The bond distances in thecis-trans andcis-cis derivatives are identical so that the differences in activity must be related to differences in conformation. The difference in the conformation is discussed from a receptor-site view of the two molecules. 相似文献
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A simple method for calculating the oxidation state of Cr in complexes containing only Cr-O bonds is presented. A total of 242 CrOn fragments with n = 3-6 were retrieved from the Cambridge Structural Database (CSD) and, together with the data for K3CrO8, were analyzed using the bond valence sum method. New R0 values for Cr(II) of 1.739(21) A, Cr(III) of 1.708(7) A, Cr(V) of 1.762(14) A, and Cr(VI) of 1.793(7) A were derived. An average R0 value of 1.724 A for Cr-O reproduces the oxidation state of 96 of the 110 Cr(II), Cr(III), and Cr(IV) CrOn complexes (n = 3-6) and that of K3CrO8 within 0.30 valence units. The crystal structure of K3CrO8 was redetermined at 173 K to provide accurate data for a Cr complex with both high oxidation state and coordination number. Potassium tetraperoxochromate(V), K3CrO8, is tetragonal, Space group I42m, a = b = 6.6940(3) A, c = 7.7536(5) A, Z = 2. The difficulties with fitting the observed valence for Cr(V) and Cr(VI) complexes with coordination numbers 4 and 5 are discussed. The use of bond valence sums in gaining chemical insight into Cr complexes with noninnocent ligands and in establishing oxidation states in Cr clusters is presented. An analysis of the Cr-O bond distances used in the calculations shows a large range of values that can be understood in terms of the bond valence sum calculation. 相似文献
24.
A. E. Kozioł J. Davis R. C. Palenik G. J. Palenik 《Journal of chemical crystallography》1992,22(4):493-501
The crystal structures of two tetracycline derivatives, 4-dedimethylaminotetracycline hydrate and 6-methylene-5-oxytetracycline hydrochloride (methacycline·HCl), were determined using X-ray intensity data measured on a diffractometer. The first compound crystallizes with two chemical formula and one water molecule per asymmetric unit. The monoclinic crystal [a=7.174(5),b=12.029(9),c=21.117(15) Å,=93.16(6)°] shows the space groupP21. Crystals of methacycline hydrochloride are orthorhombic, space groupP212121,a=9.472(1),b=11.921(3),c=18.945(4)Å, with one molecule in the asymmetric unit. 相似文献
25.
Gordon G. Cash John F. Helling M. Mathew Gus J. Palenik 《Journal of organometallic chemistry》1973,50(1):277-285
The reaction of π-cyclopentadienyl-π-1,5-cyclooctadienerhodium(I) and diphenylacetylene gives hexaphenylbenzene as the principal product with a low yield of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I). The crystal structure of π-cyclopentadienyl-π-tetraphenylcyclobutadienerhodium(I) was determined by X-ray diffraction techniques using diffractometer data. The crystals are monoclinic with unit cell dimensions of a=13.416(3), b=19.534(6), c=13.411(2) Å and β=135.01 (1)°. The space group is P21/c and, with four molecules per unit cell, no molecular symmetry is required (Dm=1.40 g/cm3 and Dc=1.411 g/cm3). The structure was solved by the heavy atom method and refined by least-squares methods to a final R of 0.043 for the 3675 observed reflections used in the analysis. The rhodium atom is coordinated to both the cyclopentadienyl group (Rh-ring distance is 1.868 Å) and the tetraphenylcyclobutadiene group (Rh-ring distance is 1.828 Å). The phenyl groups are twisted relative to the C4 ring and bent away from the rhodium atom. 相似文献
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Palenik GJ 《Inorganic chemistry》2003,42(8):2725-2728
A simple method is presented for calculating the oxidation state of Sm in complexes where Sm is bonded only to O ligands. A total of 88 SmO(n)() fragments with n = 4-12 were retrieved from the Cambridge Structural Database and were analyzed using the bond valence sum (BVS) method. New R(0) values for Sm(II)-O of 2.116(21) A and for Sm(III)-O of 2.055(13) A were derived. The average R(0) value of 2.086 A gives a good approximation of the oxidation state of the Sm ion, either +2 or +3, from the observed distances without any assumptions. The Sm-O distances for +2 and +3 complexes with coordination numbers of 4-11 are tabulated and reflect the requirement that the BVS must equal the oxidation state. The distances for CN = 12 were not included because of problems with the reported crystal structures. Several X-ray structure determinations where the BVS and the oxidation state did not agree are discussed. 相似文献
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Mora JF Van Berkel GJ Enke CG Cole RB Martinez-Sanchez M Fenn JB 《Journal of mass spectrometry : JMS》2000,35(8):939-952
Editorial Comment Last month we presented, as a Special Feature, a set of five articles that constituted a Commentary on the fundamentals and mechanism of electrospray ionization (ESI). These articles produced some lively discussion among the authors on the role of electrochemistry in ESI. Six authors participated in a detailed exchange of views on this topic, the final results of which constitute this month's Special Feature. We particularly hope that younger scientists will find value in this month's Special Feature, not only for the science that it teaches but also what it reveals about the processes by which scientific conclusions are drawn. To a degree, the contributions part the curtains on these processes and show science in action. We sincerely thank the contributors to this discussion. The give and take of intellectual debate is not always easy, and to a remarkable extent this set of authors has maintained good humor and friendships, even when disagreeing strongly on substance. Graham Cooks and Richard Caprioli Copyright 2000 John Wiley & Sons, Ltd. 相似文献