| | 2 | Author
| Hideta Ishihara, Keizo Horiuchi, ThorstenM. Gesing, Shi-Qi Dou, J.-Christian Buhl, Hiromitsu Terao | Requires cookie* | | | Title
| I NQR and Crystal Structure Studies of [N(CH 3 ) 4 ] 2 CdI 4  | | | | Abstract
| The temperature dependence of 127 1 NQR and DSC as well as the crystal structure at room temperature of the title compound were determined. This compound shows a first-order phase transition of an order-disorder type at 245 K. Eight 127 I(i^i: m = ±5 <-+ ±|) NQR lines of 79. corresponding eight 127 I(^ 2 : m = ±| <-» • ±|) NQR lines were observed at liquid nitrogen temperature. Three 127 I(^i) NQR lines wfth an intensity ratio of 1:1:2 in the order of decreasing frequency were observed just above the transition point and two NQR lines except for the middle-frequency line disappeared around room temperature. This temperature behavior of NQR lines is very similar to that observed in [N(CH 3)4] 2 Hgl4. Another first-order phase transition takes place at 527 K. The structure of the room-temperature phase was redetermined: orthorhombic, Pnma, Z = 4, a = 1342.8(3), b = 975.7(2), c = 1696.5(3) pm. The NQR result of three lines with an intensity ratio of 1:1:2 is in agreement with this structure. The thermal displacement parameters of atoms in both cations and anions are large. | | | |
Reference
| Z. Naturforsch. 55a, 225—229 (2000); received October 13 1999 | | | |
Published
| 2000 | | | |
Keywords
| NQR, DSC, Crystal Structure, Phase Transition | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0225.pdf | | | | Identifier
| ZNA-2000-55a-0225 | | | | Volume
| 55 | |
| 3 | Author
| Hideta Ishihara, Keizo Horiuchi, V. G. Krishnan, Ingrid Svoboda, Hartmut Fuess | Requires cookie* | | | Title
| Isolated versus Condensed Anion Structure VI: X-ray Structure Analysis and 81 Br NQR of Guanidinium Pentabromodicadmate(II), [C(NH 2 ) 3 ]Cd 2 Br 5 , fns-Hydrazinium Pentabromocadmate(II), [H 2 NNH 3 ] 3 CdBr 5 , and fo's-Hydrazinium Tetrabromocadmate(II)-Tetra Hydrate, [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0 | | | | Abstract
| The structure of the condensed bromocadmate anions in [C(NH 2) 3 ]Cd 2 Br 5 (1) and [H 2 NNH 3 ] 3 CdBr 5 (2) were studied at room temperature by X-ray diffraction. (1) crystallizes with double-chains bridged by Br atoms (orthorhombic, Pmmn, Z= 2, a = 1394.0(5), b = 394.5(1), c = 1086.9(5) pm). This chain structure was not described previously. (1) shows three 8 'Br NQR lines at temperatures between 77 and 323 K. Structural phase transitions take place at 283 K and at 535 K. (2) crystallizes with Br bridged zigzag-chains (monoclinic, P2[, Z=2,a = 943.1(1), b = 778.8(2), c = 942.0(2) pm, ß = 102.10(2)°) and shows a first-order phase transition around 304 K with a large thermal hysteresis. Below the transition point five 81 Br NQR lines are observed at temperatures between 122 and 304 K, and above the transition point four 81 Br NQR lines at tem-peratures between 288 and 353 K. Two 81 Br NQR lines are observed in [H 2 NNH 3 ] 2 CdBr 4 -4H 2 0 (3) at temperatures between 77 and around 320 K with positive temperature coefficients. | | | |
Reference
| Z. Naturforsch. 55a, 390—396 (2000); received November 19 1999 | | | |
Published
| 2000 | | | |
Keywords
| NQR, DSC, Crystal Structure, Phase Transition, Bromocadmate | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0390.pdf | | | | Identifier
| ZNA-2000-55a-0390 | | | | Volume
| 55 | |
| 4 | Author
| Hiroyuki Ishida, Setsuo Kashino, Ryuichi Ikeda | Requires cookie* | | | Title
| Crystal Structure of Trimethylammonium Tetrafluoroborate in Three Solid Phases | | | | Abstract
| The crystal structure of (CH 3) 3 NHBF 4 was studied in three solid phases by X-ray diffraction techniques. The structures of the ionic plastic phase (Phase I) stable above 453 K and Phase II between 384 and 453 K are CsCl-type cubic (a = 5.772(4) Ä) and tetragonal (a = 9.815(5) and c = 6.895(5) A), respectively. The room temperature phase (Phase III) forms a monoclinic lattice (space group P2,/m, a = 5.7017(8), b = 8.5724(9), c = 7.444(1) Ä, and ß = 102.76(1)°). BF 4 ~ ions in this phase were shown to be disordered in four orientations. | | | |
Reference
| Z. Naturforsch. 55a, 765—768 (2000); received June 28 2000 | | | |
Published
| 2000 | | | |
Keywords
| Crystal Structure, X-ray Diffraction, Ionic Plastic Phase, Disorder | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0765.pdf | | | | Identifier
| ZNA-2000-55a-0765 | | | | Volume
| 55 | |
| 5 | Author
| M. Ichaela, W. Ilhelm, W. Olfgang Saak, H. Enry Strasdeit | Requires cookie* | | | Title
| Phenylmercury Chloride: Its Single-Crystal X-Ray Structure and Some Aspects of its Biological Chemistry | | | | Abstract
| A single crystal of phenylmercury chloride (PhHgCl) was obtained by serendipity from a solution of diphenylmercury (HgPh2) and dihydrolipoic acid in tetrahydrofuran / carbon tetrachloride. The crystal structure of PhHgCl is pseudotetragonal. It is best described in the orthorhombic space group Cmma with a = 6.856(1), b = 6.882(1), c = 14.309(2) A (at 193 K), and Z = 4. The Cl-Hg-C moiety of the PhHgCl moleculeois exactly linear. The bond lengths at the Hg atom are Hg-Cl 2.345(2) and Hg-C 2.044(9) Ä. In the crystal, the molecules are arranged in double layers parallel to the a,b plane. In a model medium for the gastric juice (0.1 M DC1 in D 20 / [Dg]dioxan, 37 °C), HgPh2 reacts to form PhHgCl. HgCl2, which would result from complete dearylation, cannot be isolated from the reaction mixture. However, it appears that a small equilibrium concentration of HgCl2 may be present, because on addition of 1,4,7-trithiacyclononane (ttcn) and diethyl ether, the dichloride can be trapped as solid [Hg(ttcn)2][HgCl4]. We estimate that after oral uptake of HgPh2 20 -90% are transformed into PhHgCl in the stomach after 30 min. In tro d u ctio n | | | |
Reference
| (Z. Naturforsch. 55b, 35—38 [2000]; received October 18 1999) | | | |
Published
| 2000 | | | |
Keywords
| Acidolysis, Bioinorganic Chemistry, Crystal Structure, Mercury, Organomercury Compounds | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0035.pdf | | | | Identifier
| ZNB-2000-55b-0035 | | | | Volume
| 55 | |
| 6 | Author
| K. Urt, O. Klepp | Requires cookie* | | | Title
| Preparation and Crystal Structure of Na4TiSe4. A Selenotitanate with Discrete Tetrahedral Anions | | | | Abstract
| Red crystals of Na4TiSe4 were obtained by reacting an intimate mixture of Na2Se, Ti and Se at 750°C. Na4TiSe4 is monoclinic, space group I2/a with a = 24.027(6), b = 7.346(4), c = 21.572(6) A, (3 = 104.52(2)°, Z = 16. Its crystal structure was determined from diffractometer data (AgK a-radiation) and refined to a conventional R of 0.036 for 2673 F0's and 158 variables. The crystal structure is of a new type, characterized by the presence of discrete tetrahedral complex anions, [TiSe,*]4" , which are arranged in slabs parallel to (100). The average Ti-Se bond length is 2.385(1) A. The Na+ cations are in different chalcogen environments with distorted octahedral, square pyramidal or planar configurations, respectively. | | | |
Reference
| (Z. Naturforsch. 55b, 39—44 [2000]; received September 28 1999) | | | |
Published
| 2000 | | | |
Keywords
| Crystal Structure, Chalcogenides, Titanium, Sodium, Selenium | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0039.pdf | | | | Identifier
| ZNB-2000-55b-0039 | | | | Volume
| 55 | |
| 8 | Author
| Henri Brunner, M. Arkus, N. Iem Etz, M. Anfred Zabel | Requires cookie* | | | Title
| Optisch aktive Ubergangsmetall-Komplexe, 122 [1]. Synthese von Palladium(II)-Schiff-Base-Komplexen -intramolekulare Wechselwirkungen O ptically Active Transition M etal C om plexes, 122 [1], Synthesis of Palladium (II) Com plexes w ith Schiff B ase Ligands -Intram olecular Interactions | | | | Abstract
| Imines of salicylaldehyde and 2,6-diformyl-p-cresol have been used as ligands in palla d iu m ^) complexes. Enantiomerically pure ligands give enantiomerically pure complexes, racemic ligands give racemates and meso-forms. Differences between the respective isomers of the ligands within the complexes and between the diastereomers of the complexes were investigated. Crystal structure analyses established the trans configuration at the metal center. | | | |
Reference
| Z. Naturforsch. 55b, 145—154 (2000); eingegangen am 25. Oktober 1999 | | | |
Published
| 2000 | | | |
Keywords
| Schiff Bases, Palladium(II) Complexes, Diastereomers, Crystal Structure | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0145.pdf | | | | Identifier
| ZNB-2000-55b-0145 | | | | Volume
| 55 | |
| 9 | Author
| C. Bender, D. W. Ulff-M, H. Older, F. Vogt, M. M. Ritschl, Eisel | Requires cookie* | | | Title
| Synthese und Kristallstruktur des Bromdifluormethyl-triphenyl- phosphoniumbromids, [(C6H5)3 PCF2Br]+ Br" Synthesis and Crystal Structure o f B rom odifluorom ethyl-triphenylphosphonium Brom ide, [(C6H5)3PC F2Br]+ Br~ | | | | Abstract
| Difluorobromomethyl-triphenylphosphonium bromide [(C6H5)3PCF2Br]+ Br-(1) has been prepared by the reaction of triphenylphosphine with dibromodifluoro-methane in acetonitrile or methylene chloride. The colorless crystals are monoclinic, space group P 2,/n, Z=4, a = 1067.1(2), b = 1488,5(2), c = 1178,2(2) pm, ß = 95,67(3)°. The lattice contains Br~ anions and [(C6H5)3PCF2Br]+ cations with a Br-Br distance of 322,33(11) pm.. For the title compound the results of AM 1, PM 3 ,and MNDO calculations are in good agreement with corresponding values determined by the X-ray analysis only in the case of PM 3. The yellow-red [(C6H5)3PCF2Br]+ Br3~ (2) has been obtained by treating 1 with equimolar quantities of elemental bromine in methylene chloride solution. E inleitung | | | |
Reference
| Z. Naturforsch. 55b, 167—170 (2000); eingegangen am 28. Oktober 1999 | | | |
Published
| 2000 | | | |
Keywords
| Bromodifluoromethyl-triphenylphosphonium Bromide, Synthesis, Crystal Structure | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0167.pdf | | | | Identifier
| ZNB-2000-55b-0167 | | | | Volume
| 55 | |
| 10 | Author
| AlfonsoC. Astiñeiras-C, Am, IgnacioS. De L, Cueva -Torregrosab, JosefaM. G Onzález-Pérezb, A. Urora, G. Sicilia-Z, ElenaB. Afrab, A. Ugella-, JuanN. Ltam Iranob, S-G Icló, Utiérrezb | Requires cookie* | | | Title
| Synthesis, Structure and Properties of / > o/j-[(Ar-(2-Hydroxyethyl)- Af'-carboxymethyl-l,2-ethyIenediamine-AyV'-Diacetato)copper(II) Hydrate], {[Cu(Hhedta)] * H20 } n | | | | Abstract
| The stoichiometric reaction of /V-(2-hydroxyethyl)-1,2-ethylenediamine-/V,/V,7V'-triacetic acid [hbhedta = (H0CH2CH2)(H02CCH2)NC2H4N(CH2C02H)2)] and copper(II) hydroxy-carbo-nate in water yields crystalline samples of /?0/v-{(/V-(2-hydroxyethyl)-/V'-carboxymethyl-l,2-ethylenediamine-./V,./V'-diacetato)copper(II) hydrate}, {[Cu(Hhedta)] TTOjn (I)-The com pound was studied by TG analysis (with FT-IR study of the evolved gases), IR, electronic and ESR spectra, magnetic susceptibility data and single crystal X-ray diffraction methods. It crystallises in the orthorhombic system, space group Fdd2 (a = 21.906(2), b = 36.602(4), c = 6.928(1) A, Z = 16, and final R\ = 0.029 for 1554 independent reflections). The Cu(II) atom exhibits a very distorted octahedral coordination (type 4+1 + 1). The Hhedta ligand plays a yV,yV',0,C>',(9"-pentadentate chelating role as well as a O,0'-carboxylate bridging one and has a free /V-carboxymethyl arm. The bridging carboxylate group of the Hhedta ligand leads to polymeric chains {[Cu(Hhedta)] H20}n parallel the c axis. A hydrogen bonding network involves all O-H polar bonds (non-ionised carboxylic and alcoholic hydroxyl groups and water molecules). The structure reveals the preferred formation of a copper(II)-(/V-2-hydroxyethyl-amino) or copper(II)-(ethanolamino) versus a copper(II)-(/V-carboxymethylamino) chelate ring. In tro d u c tio n | | | |
Reference
| Z. Naturforsch. 55b, 171—177 (2000); received October 10 1999 | | | |
Published
| 2000 | | | |
Keywords
| Copper(II) Chelate, Crystal Structure, Amino-polycarboxylates, Ethanolamine | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0171.pdf | | | | Identifier
| ZNB-2000-55b-0171 | | | | Volume
| 55 | |
| 11 | Author
| Masao Hashimoto, Shinichi Hashimoto, Hiromitsu Terao, Masayuki Kuma, Haruo Niki, Hiroyuki Ino | Requires cookie* | | | Title
| Crystal Structure and Phase Transition of 4-Aminopyridinium Tetrabromoantimonate(III) as Studied by Bromine and Antimony NQR, Proton NMR, and Single Crystal X-Ray Diffraction | | | | Abstract
| The crystal structure of the room temperature phase (RTP) of the title compound was determined at 297 K (monoclinic, space group C2/c, a = 1384.2(2), b = 1377.8(3), c = 755.5(2) pm, ß = 121.58(1)°). A complicated disorder was found for the cation. A phase transition from the low-temperature phase (LTP) to the RTP was found at (224 ±1) K (T c). The 'H NMR spectra showed a sharp motional narrowing at ca. T=T C , indicating the occurrence of a reorientational motion of the cation in the RTP in accord with the disorder. It was found that another reorientational motion is excited in the LTP. Four 81 Br NQR lines (132.71, 115.38, 61.54 and 59.31 MHz at 77 K) and two Sb NQR lines (53.78 and 33.76 MHz at 77 K) were found in the LTP, while a single 81 Br NQR line was observed at T> 276 K (ca. 121.80 MHz at 300 K). Crystal dynamics are discussed on the basis of the temperature dependence of the NQR, *H NMR line width, and 'H NMR Tj. | | | |
Reference
| Z. Naturforsch. 55a, 167—172 (2000); received August 24 1999 | | | |
Published
| 2000 | | | |
Keywords
| 4-NH 2 PyHSbBr 4, Crystal Structure, Phase Transition, NQR, 'H NMR | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0167.pdf | | | | Identifier
| ZNA-2000-55a-0167 | | | | Volume
| 55 | |
| 13 | Author
| Gerhard Bringmanna, Doris Feineis3, Ralph Brückner, Eva-Maria Petersb, Karl Petersb | Requires cookie* | | | Title
| 2-Hexanoyl-l-tribromomethyl-l,2,3,4-tetrahydro-/?-carboline: Crystal Structure Analysis of a Potent Inhibitor of Complex I of Mitochondrial Respiration | | | | Abstract
| The molecular structure of the title com pound 2-hexanoyl-l-tribromomethyl-l,2,3,4-tetra-hydro-/3-carboline (3), a potent inhibitor of complex I of the mammalian mitochondrial respi ratory chain, has been studied by single-crystal X-ray diffraction analysis. In the crystal, two heterochiral molecules of 3 (i.e., one R-and one S-configured molecule each) were found to be connected with one other in pairs via two intermolecular hydrogen bonds [0(215) • • • H(212)' and 0(215)' • • • H(212)] to form an overall achiral 'dimeric' subunit. | | | |
Reference
| (Z. Naturforsch. 55b, 94—99 [2000]; received O ctober 21 1999) | | | |
Published
| 2000 | | | |
Keywords
| Crystal Structure, Bromal-Derived Tetrahydro-ß-carbolines Mitochondrial Respiration, Parkinson's Disease, Neurotoxicity | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0094.pdf | | | | Identifier
| ZNB-2000-55b-0094 | | | | Volume
| 55 | |
| 14 | Author
| Hiromitsu Terao, Masao Hashimoto, Shinichi Hashimoto, Yoshihiro Furukawa | Requires cookie* | | | Title
| Studies of Structure and Phase Transition in [C(NH 2 ) 3 ]HgBr 3 and [C(NH 2 ) 3 ]HgI 3 by Means of Halogen NQR, NMR, and Single Crystal X-Ray Diffraction | | | | Abstract
| The crystal structure of [C(NH 2) 3 ]HgBr 3 was determined at room temperature: monoclinic, space group C2/c, Z = 4, a = 775.0(2), b = 1564.6(2), c = 772.7(2) pm, ß = 109.12(2)°. In the crystal, almost planar HgBr 3 ~ ions are connected via Hg -Br bonds, resulting in single chains of trigonal bipyramidal HgBr 5 units which run along the c direction. [C(NH 2) 3 ]HgI 3 was found to be isomorphous with the bromide at room temperature. The temperature dependence of the halogen NQR frequencies (77 < 77K < ca. 380) and the DTA measurements evidenced no phase transition for the bromide, but a second-order phase transition at (251 ± 1) K (7 tl) and a first-order one at (210 ± 1) K (T C2) for the iodide. The transitions at T C2 are accompanied with strong supercooling and significant superheating. The room temperature phase (RTP) and the intermediate temperature phase (ITP) of the iodide are characterized by two I(m =i/2~3/2) NQR lines which are assigned to the terminal and the bridging I atoms, respectively. There exist three lines in the lowest temperature phase (LTP), indicating that the resonance line of the bridging atom splits into two. The signal intensities of the 127 I (m =i/2—3/2) NQR lines in the LTP decrease with decreasing temperature resulting in no detection below ca. 100 K. The 127 I(m =i/ 2 ~3/2) NQR frequency vs. temperature curves are continuous at T CL , but they are unusual in the LTP. The T X vs. Tcurves of 'H NMR for the bromide and iodide are explainable by the reorientational motions of the cations about their pseudo three-fold axes. The estimated activation energies of the motions are 35.0 kJ/mol for the bromide, and 24.1, 30.1, and 23.0 kJ/mol for the RTP, FTP, and LTP of the iodide, respectively. | | | |
Reference
| Z. Naturforsch. 55a, 230—236 (2000); received August 23 1999 | | | |
Published
| 2000 | | | |
Keywords
| [C(NH 2 ) 3 ]HgX 3, Crystal Structure, Phase Transition, NQR, 'H NMR | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0230.pdf | | | | Identifier
| ZNA-2000-55a-0230 | | | | Volume
| 55 | |
| 15 | Author
| W. Preetz | Requires cookie* | | | Title
| Kristallstrukturen | | | | Abstract
| , Schwingungsspektren und Normalkoordinatenanalyse von (Ph3PNPPh3)[O sF5C l] CH2Cl2 und cis-(Ph3PNPPh3)[OsF4C\2]C H 2Ch Crystal Structures, Vibrational Spectra and N orm al C oordinate A nalysis o f (Ph3P N PP h3) [O sF5Cl] C H 2C12 and ris-(P h 3PN PPh3)[O sF4C l2]-CH2C l2 B. L orenzen By careful oxidation of the pure fluorochloroosmates(IV) with BrF3 in dichloromethane the mixed pentavalent complex anions [OsF5C1]_ and m -[O sF 4Cl2] _ are formed. X-ray structure determinations on single crystals have been performed of (Ph3PNPPh3)[OsF5C l]C H 2Cl2 (1) (triclinic, space group P i, a = 12.153(5), b = 12.387(5), c = 14.229(5) A , a = 70.07(1), ß = 65.46(1), 7 = 72.87(1)°, Z = 2) and ds-(P h 3PNPPh3)[OsF4Cl2] C H 2Cl2 (2) (triclinic, space group P i, a = 11.987(2) b = 13.083(2), c = 14.456(2) A , a = 66.30(1), ß = 65.47(1), 7 = 71.22(1)°, Z = 2). Based on the molecular parameters of the X-ray determinations the IR and Raman spectra for the anions of 1 and 2 have been assigned by normal coordinate analysis. Due to the mutual trans influences the valence force constants of asymmetrically coordinated octahedral axes F*-Os-Cl' differ from those of the symmetric F-Os-F axes. The data are for 1: fd(OsF*) = 3.95, fd(OsF) = 4.07, fd(OsCl') = 2.51 and for 2: fd(OsF*) = 3.45, fd(OsF) = 3.97, fd(OsCl') = 2.42 mdyn/A. | | | |
Reference
| (Z. Naturforsch. 55b, 45—50 [2000]; eingegangen am 9. November 1999) | | | |
Published
| 2000 | | | |
Keywords
| Pentachlorofluoroosmate(V), ds-Tetrachlorodifluoroosmate(V), Crystal Structure, Vibrational Spectra, Normal Coordinate Analyses | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0045.pdf | | | | Identifier
| ZNB-2000-55b-0045 | | | | Volume
| 55 | |
| 16 | Author
| Jürgen Schatz3, Frank Schildbacha, AxelL. | Requires cookie* | | | Title
| The Inclusion of Carbon Disulfide in /?-rerf-Butylcalix[4]-and [6 ]arene - A Combined Crystallographic and Vibrational Spectroscopic Study | | | | Abstract
| en tzb, Sylvia R a stä tte rb, Joachim Schilling5, Jö rg D o rm an n c, A n d reas R uoffc, and Tony D eb ae rd em ae k erd The inclusion complexes formed from carbon disulfide and /?-r£7-r-butylcalix[4]arene (1 C S 2) or /?-rm-butylcalix[6]arene (2-C S2) were investigated by X-ray crystal structure analysis, infrared (IR) and Raman spectroscopy. The complex 1 C S 2 crystallises in the space group P4/n, 2 C S 2 in the space group P2xln. In case of /?-rm-butylcalix[4]arene as host the carbon disulfide molecule is included in the cavity. In the crystal structure of p-rm -butylcali-x[6]arene clathrate, self-com plexation o f one rm-butyl group in the cavity o f another ca-lix[6]arene can be observed. Due to inclusion, the symmetry of CS2 is lowered both in the p-rm -butylcalix[4]arene and p-rm-butylcalix[6]arene case causing significant shifts in the fully assigned infrared and Raman spectra. | | | |
Reference
| Z. Naturforsch. 55b, 213—221 (2000); received N ovem ber 16. 1999 | | | |
Published
| 2000 | | | |
Keywords
| p-rerz-Butylcalixarenes, Inclusion Complexes, Crystal Structure, IR Data, Raman Data | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0213.pdf | | | | Identifier
| ZNB-2000-55b-0213 | | | | Volume
| 55 | |
| 17 | Author
| M. Ath, O. S. Enge | Requires cookie* | | | Title
| A Conformational Study of 5,10,15,20-Tetraalkyl-22//+,24//+-porphyrindiium Salts (Dication Salts) | | | | Abstract
| N-protonation of 5,10,15,20-tetraalkylporphyrins with n-butyl, isobutyl, isopropyl, 1-ethyl-propyl or ferf-butyl substituents yields the respective 22,24-dihydroporphyrins (22//+,24//+-porphyrindiium salts) that exhibit highly nonplanar conformations. Depending on the steric demand of the meso substituents, the free base porphyrins have planar to moderately ruffled macrocycles (primary or secondary alkyl residues) or are severely ruffled (tertiary alkyl resi dues). X-ray crystallographic studies show that protonation of porphyrins with «-Bu (2), i-Pr (3) or EtPr (4) substituents leads to steric congestion of the core resulting in symmetric, saddle distorted macrocycles as evidenced by average displacements of the Cb positions from the mean plane ranging from 0.79 to 1.01 A. The structures observed for these porphyrin diacids are very similar in distortion mode and degree of nonplanarity to 5,10,15,20-tetraaryl-22f/+,24//+-porphyrindiium salts and to 2,3,7,8,12,13,17,18-octaalkyl-5,10,15,20-tetraaryl-porphyrins. In contrast, protonation of the highly ruffled 5,10,15,20-tetrakis(teA-r-butyl)porph-yrin results in a switch of the conformational distortion mode. The dication 6 shows both saddle distortion (Cb displacements -1.3 A) and ruffling of the macrocycle (Cm displacements of approx. 0.48 A). Thus, the need to accomodate four N-H units in the porphyrin core with its associated out-of-plane tilting of the pyrrole rings and the steric strain induced at the meso carbon atoms results in a highly nonplanar porphyrin with mixed distortion modes. | | | |
Reference
| Z. Naturforsch. 55b, 336—344 (2000); received January 20 2000 | | | |
Published
| 2000 | | | |
Keywords
| Porphyrins, Steric Strain, Porphyrin Dications, Crystal Structure, Conformational Analysis, 22, 24-Dihydroporphyrins | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0336.pdf | | | | Identifier
| ZNB-2000-55b-0336 | | | | Volume
| 55 | |
|
