| | 1 | Author
| Andreas Nägele3, Cynthia Dayb, Abdessadek Lachgarb, H.-Jürgen Meyer3, Sonderdruckanforderungen An, ProfH. Dr, -J Meyer | Requires cookie* | | | Title
| Interpenetrierende Clusterstränge in der Kristallstruktur von Ko,77Nb6Cl15 Interpenetrating Cluster Chains in the Structure of Ko.77Nb6Cl15  | | | | Abstract
| The solid state reaction of KCl, NbCl5 and Nb powder at 760 °C yielded black crystals of KNb6Cl15. The structure of the compound has been determ ined using single-crystal X-ray m e thods. KNb6Cli5 crystallizes in the orthorhombic space group Pmma (no. 51) with lattice constants a = 1780.1(2), b = 1341.4(1), and c = 925.5(1) pm, Z = 4, and R1 = 0.039 for all 2727 observed reflec tions. [ (N ^ C l ^ C l ^ 3'3]-anions in the structure are linked via two Cla a bridges to form one set of li near and one set of kinked chains along the cry stallographic c and a directions. Four remaining Cla a bridges interconnect both sets of chains to a three-dim ensional network. The potassium occu pancy on a 4k site was refined to a value of 0.384(3) consistent with the formula K0 77Nb6C li5. Ternäre Niobchloride des Formeltyps A Nb6Cl15 wurden bereits verschiedentlich beschrieben. Ver bindungen mit A = Li [1] und Na [2] kristallisieren kubisch (Ia3d) mit identischen Schweratomstruk-turen. Die Alkalim etall-Ionen Li (KZ = 4) und Na (KZ = 6) besetzen in den Strukturen A N b6Cl15 aber unterschiedliche Splitlagen und sind dyna misch fehlgeordnet. Die V ertreter mit A = In und TI [3] kristallisieren orthorhombisch (Pmma). Ihre Kationen befinden sich in zweifach überdachten, würfelförmigen Cl-Umgebungen (KZ = 10). Die Kenntnis des Formeltyps A N b6Cl15 mit schweren Alkalim etallen ist noch unvollständig. Einkristall | | | |
Reference
| Z. Naturforsch. 56b, 1238—1240 (2001); eingegangen am 26. Juli 2001 | | | |
Published
| 2001 | | | |
Keywords
| Niobium, Chloride, Cluster | | | |
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| default:Reihe_B/56/ZNB-2001-56b-1238_n.pdf | | | | Identifier
| ZNB-2001-56b-1238_n | | | | Volume
| 56 | |
| 2 | Author
| Isabel Díaza, Vicente Fernández3, VitalyK. Belskyb, Jose Luis, M. Artínez0 | Requires cookie* | | | Title
| Synthesis and Structural Study of the Thermochromic Compounds Bis(2-amino-4-oxo-6-methylpyrimidinium) Tetrachlorocuprate(II) and Bis(2-amino-4-chloro-6-methylpyrimidinium) Hexachlorodicuprate(II) | | | | Abstract
| The compound bis(2-am ino-4-oxo-6-methylpyrimidinium) tetrachlorocuprate(II) 1 contains CuCU2-square-planar anions, and bis(2-am ino-4-chloro-6-m ethylpyrim idinium) hexachlorod-icuprate(II) 2 quasi-planar CU2CI62-anions. Both compounds show thermochromic behaviour. This phenomenon has been studied by X-ray crystallography at variable temperature, with the result that no major change is observed in the geometry o f the copper atom. Thus it is possible to assume som e influence o f the hydrogen bonds and o f the different geometries o f interme diate states on the color o f the compounds due to the modifications provoked in the L —>M charge transfer and in the energy o f the metal d-d transitions. Magnetic measurements o f the compounds give information on magneto-structural correlations. Compound 1 is ferromagnetic (Tc = 20 K) due to the perpendicular arrangement o f the square anions that allows exchange pathways only via Cu-Cl -Cu , H-bonding or cationic n electron interactions. Compound 2 shows a very complicated behavior at low temperature with local antiferromagnetic fluctua tions. Crystal data: 1 CioHioNftC^CUCu, triclinic, P i; 393(2) K: a = 11.053(2), b = 11.334(2), c = 14.038(3) (Ä), a = 95.76(3), ß = 101.35(3), 7 = 9 0 .1 5 (3) 0 ; 293(2) K: a = 11.022(2), b = 11.289(2), c = 14.001(3) (A), a = 95.86(2), ß = 101.34(2), 7 = 9 0 .0 9 (3) 0 ; 155(2) K: a = 11.008(2), b = 11.231 (2), c = 13.967(3) (A), a = 95.86(2), ß = 101.37(2), 7 = 8 9 .9 9 (2) 0 ; Z = 4. 2 (C5H7N 3C l3Cu)2, monoclinic, P 2,/c; 293(2) K: a = 5.998(1), b =18.669(4), c = 9.466(2) (A), ß = 1 0 0 .9 3 (3)0 ; 150(2) K: a = 5.971(1), b = 18.655(4), c = 9.3 8 3 (2) (Ä), ß = 1 0 1 .6 4 (1) 0 ; Z = 4. | | | |
Reference
| Z. Naturforsch. 54b, 718 (1999); received March 1 1999 | | | |
Published
| 1999 | | | |
Keywords
| Thermochromic Compounds, Copper, Chloride | | | |
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| default:Reihe_B/54/ZNB-1999-54b-0718.pdf | | | | Identifier
| ZNB-1999-54b-0718 | | | | Volume
| 54 | |
| 3 | Author
| A. N. Ägele3, E. A. Nokhinab, J. Sitarb, H.-JM. Eyer3, A. Lachgarb | Requires cookie* | | | Title
| Synthesis and Crystal Structures of ATi[Nb6Cli8] Compounds (A = K, Rb, Cs, In, Tl) | | | | Abstract
| New quaternary niobium cluster chlorides corresponding to the general formula ATi[Nb6Clis] (A = K, Rb, Cs, In, Tl) have been synthesized in sealed quartz tubes at 720 °C, starting from stoichiometric amounts of NbCls, niobium metal, TiCb, and AC1 (A = K, Rb, Cs), or In or Tl metals. The structures of RbTi[Nb6Clis] and CsTifNböClis] were determined using single crystal X-ray diffraction. RbTifNböClis] crystallizes in the rhombohedral crystal system, space group R3 (no. 148), Z = 3, with lattice parameters: a = 9.163(4), c = 25.014(14) A (hexagonal setting). The structure refinement converged to R] = 0.044 and wRi = 0.058 for all data. In this structure, discrete [NböClig]4-cluster units are linked by Rb+ and Ti3+ cations, located in a 12-coordinated anticubeoctahedral and octahedral chloride coordination environment, respectively. In contrast, CsTifNböClis] crystallizes in the trigonal crystal system, space group P31c (no. 163), Z = 2. The lattice parameters were determined to be a -9.1075(6), c = 17.0017(8) A. The structure refinement gives the reliability factors Ri = 0.029 and wRa = 0.063 for all data. The structure is built up of discrete octahedral [N bödis]4-cluster units, linked by Cs+ and Ti3+ cations which are located in a distorted hexagonal antiprismatic and octahedral chloride coordination environment, respectively. The structures of the compounds ATifNböClis] (A = K, In, Tl) were found to be isotypic with RbTi[NböCli8], and their unit cell parameters were refined using X-ray powder diffraction analysis. In tro d u ctio n | | | |
Reference
| Z. Naturforsch. 55b, 139—144 (2000); received September 13 1999 | | | |
Published
| 2000 | | | |
Keywords
| Niobium, Titanium, Cluster, Chlorides, Synthesis | | | |
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| default:Reihe_B/55/ZNB-2000-55b-0139.pdf | | | | Identifier
| ZNB-2000-55b-0139 | | | | Volume
| 55 | |
| 4 | Author
| Markus Ströbele, H.-Jtirgen Meyer | Requires cookie* | | | Title
| Synthesen | | | | Abstract
| , Kristallstrukturen und magnetische Eigenschaften von [Li(12-Krone-4)2][Li(12-Krone-4)(OH2)]2[Nb6Cl18], [Li(15-Krone-5)2(OH2)]3[Nb6Cl18] und [(18-Krone-6)2(0 2H5)]3[Nb6Cl18] Syntheses, Crystal Structures and Magnetic Behaviour of [Li(12-crown-4)2 ] [Li(12-crown-4)OH2 ]2 [Nb6Cl x8], [Li(15-crown-5)2(OH2)]3[Nb6C l18], and [(18-crown-6)2(0 2H5)]3[Nb6C l18] The title compounds were prepared through reactions of Li2Nb6Cl16 with the corresponding crown ethers in acetone. All three compounds were obtained as dark brown crystals. Their structures were solved with the means of single-crystal X-ray diffraction. [Li(12-crown-4),][Li(12-crown-4)(OHi)]2 [Nb6Cl 18]: space group P 2 ,In, Z =2, a = 1320.4(1), b = 1879.1(1), c = 1321.7(1) pm, ß = 92.515(6)°, P, = 0.0297 (I>2a(I)). The crystal structure contains Li+ sandwiched by two 12-crown-4-ethers plus Li+ coordinated by one 12-crown-4-ether and one water molecule. [Li(15-crown-5)2(OH2)]3[Nb6C l|8]: space group R3, Z = 3, a = b = 2081.7(1), c = 1991.7(1) pm, R\ = 0.0395 (/ > 2<r(/)). In the crystal structure Li+ and one water molecule are sandwiched by two 15-crown-5-ethers. [(18-crown-6)2(0 2H5)]3[Nb6Cl18]: space group P i, Z = 1 ,a = 1405.1(1),/?= 1461.1(2), c = 1492.2(2) pm; a = 98.80(1)°, ß = 98.15(1)°, 7 = 97.41(1)°, P, = 0.0538 (/ > 2a(I)). H5 0 2+ was found in the structure refinement sandwiched between two 18-crown-6-ethers. All compounds reported contain [Nb6Cl18] clusters with Nb-Nb distances between 299 and 301 pm. The paramagnetic behaviour expected for [Nb6C l|8]3~ in all three compounds was confirmed by magnetic measurements. | | | |
Reference
| Z. Naturforsch. 56b, 1025—1034 (2001); eingegangen am 5. Juli 2001 | | | |
Published
| 2001 | | | |
Keywords
| Niobium Cluster, Chloride, Crown Ether | | | |
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| default:Reihe_B/56/ZNB-2001-56b-1025.pdf | | | | Identifier
| ZNB-2001-56b-1025 | | | | Volume
| 56 | |
| 6 | Author
| Wilhelm Hasselbach, Andrea Migala | Requires cookie* | | | Title
| Modulation by Monovalent Anions of Calcium and Caffeine Induced Calcium Release from Heavy Sarcoplasmic Reticulum Vesicles | | | | Abstract
| Both calcium and caffeine induced calcium release from actively loaded heavy sarcoplasmic reticulum vesicles were studied to analyze the dependence o f both activities on the com position o f the release medium with respect to monovalent anions. Calcium is unable to induce net cal cium release while caffeine remains effective as releasing agent when the experimental media contain neither chloride nor nitrate ions. Caffeine induced calcium release is not suppressed by chelating residual medium calcium (approximately 0 .5 -1 (j m) with 2 m M EGTA added 15 s prior to 10 m M caffeine. Calcium release from vesicles loaded in media containing 0.2 m glu conate as monovalent anion is induced when the medium is supplemented with chloride or nitrate. The release amplitude increases linearly when K-gluconate is replaced by KC1. At con stant ionic strength the release amplitude becomes maximal at a chloride concentration o f 0.2 m . The chloride effect com pletely disappears when 2 m M EGTA are added simultaneously. When chloride is replaced by nitrate, as releasing agent, maximal release is achieved already by addition o f 0.1 m K-nitrate. The releasing effect o f nitrate can only partially be suppressed by EGTA. The different effectiveness o f gluconate, chloride and nitrate as calcium release sup porting ions corresponds to their activating effect on the binding o f ryanodine to the calcium release channel in the vesicular membranes. | | | |
Reference
| Z. Naturforsch. 47c, 440 (1992); received December 4 1991/March 16 1992 | | | |
Published
| 1992 | | | |
Keywords
| Sarcoplasmic Reticulum, Calcium Release, Chloride, Nitrate, Ryanodine | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0440.pdf | | | | Identifier
| ZNC-1992-47c-0440 | | | | Volume
| 47 | |
| 7 | Author
| ElfriedeK. Pistorius | Requires cookie* | | | Title
| Further Evidence for a Functional Relationship between L-Amino Acid Oxidase Activity and Photosynthetic Oxygen Evolution in Anacystis nidulans. Effect of Chloride on the Two Reactions | | | | Abstract
| The L-amino acid oxidase from Anacystis nidulans is inhibited by cations as well as anions. The inhibition by cations has been previously described (E. K. Pistorius, Eur. J. Biochem. 135, 217—222 [1983]). We have shown that the order of effectiveness was > M2+ > M +, when e.g. La3+, Ca2+ and K+ were compared. However, in the concentration range where the monovalent cations inhibited, the inhibition was not entirely due to the cation, but an influence of the anion could also be observed. When monovalent anions were compared as the corresponding sodium salts, the order of effectiveness was SCN~ > N 0 3_ > CL, Br > I~ > F ' > H CO O " > CH,COO . The inhibition of the L-amino acid oxidase activity by the various salts was strongly influenced by the pH of the reaction mixture. It could be shown that the inhibition by cations increased in the alkaline pH region, while the inhibition by anions increased in the acidic pH region. Our previous results have also shown that a functional relationship might exist between L-amino acid oxidase activity and photosynthetic 0 2 evolution (E. K. Pistorius and H. Voss, Eur. J. Biochem. 126, 203—209 [1982]). Since the water-splitting complex of photosystem II is affected by a number of anions, although only Cl-and Br" lead to activation of 0 2 evolution, we investigated whether a correlation could be obtained between the anion effect on the L-amino acid oxidase and on photosynthetic 0 2 evolution. The results show that those anions which have a higher affinity for the enzyme than CL or Br", are especially effective in causing inactivation of the 0 2 evolu tion. Moreover, we show that L-arginine which is a substrate of the L-amino acid oxidase, and Cl-have antagonistic effects on the L-amino acid oxidase reaction and on photosynthetic 0 2 evolu tion. We suggest that this flavoprotein with L-amino acid oxidase activity is modified by Ca:+ and CL in such a way that it can now interact with Mn2* and catalyze the water-splitting reaction of photosystem II. | | | |
Reference
| Z. Naturforsch. 40c, 806—813 (1985); received June 7 1985 | | | |
Published
| 1985 | | | |
Keywords
| Anacystis nidulans, 0 2 Evolution, L-Amino Acid Oxidase, Chloride | | | |
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| default:Reihe_C/40/ZNC-1985-40c-0806.pdf | | | | Identifier
| ZNC-1985-40c-0806 | | | | Volume
| 40 | |
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