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  • Chemistry  (3)
  • PACS. 33.15.Vb Correlation times in molecular dynamics - 33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics) - 33.25.+k Nuclear resonance and relaxation  (1)
  • 1
    ISSN: 1434-6079
    Keywords: PACS. 33.15.Vb Correlation times in molecular dynamics - 33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics) - 33.25.+k Nuclear resonance and relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: 19 F and 11 B spin-lattice relaxation times were measured in [ Zn ( ptz ) 6 ] ( BF 4 ) 2 and in the spin-crossover compound [ Fe ( ptz ) 6 ] ( BF 4 ) 2 . For both compounds BF 4 - anion reorientation is active above 50 K. For [ Zn ( ptz ) 6 ] ( BF 4 ) 2 , the anion-reorientation dynamics is different in the temperature regions of 50-90 K, 90-120 K, and above 150 K; between 120 and 150 K it changes rapidly reflecting a structural change. In [ Fe ( ptz ) 6 ] ( BF 4 ) 2 the mechanism for the paramagnetic relaxation involving the 19 F nuclei is found to be of the diffusion-limited type according to the theory of Lowe and Tse. The present results prove that the spin-crossover takes place in a dynamic surrounding and not in a static crystal lattice.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 1026-1030 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry is demonstrated as a means for rapidly differentiating bacteria based upon their water-soluble-protein profiles. The procedure involves release of cell contents by breaking cell membranes using a sonication method, and is performed with minimal sample preparation. Minimal purification of cell contents is required for the procedure. Protein profile signals obtained are found to be enhanced greatly by the use of a Nafion substrate.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 486 (1982), S. 153-164 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Infrared-spectroscopic Characterization of Iron(II) Complexes with a Triplet Ground StateThe infrared spectra of [Fephen2(NCS)2] · 2 H2O and of some similar iron(II) complexes with a well defined triplet ground state have been studied between 4000 and 180 cm-1. In comparison to the i.r. spectra of [Fephen2(NCS)2] and related compounds with quintet and singlet ground states (corresponding to S = 2 and S = 0) it has been found that the bands typically for the 1.10-phenanthroline ligand are similar for S = 0 and S = 1, whereas the CN stretching vibrations of the thiocyanate and the metal-nitrogen stretching vibrations in the three ground states are different (ν1(SCN) for S = 1 2 056 cm-1, for S = 2 2 075 and 2 063 cm-1, for S = 0 2 116 and 2 108 cm-1; ν(Fe—N)(NCS) für S = 1 307 cm-1, for S = 2 252 cm-1, S = 0 533 and 529 cm-1; ν(Fe—N)(phen) for S = 1 374 and 360 cm-1, for S = 2 220 cm-1, for S = 0 379 and 371 cm-1). The differences in the infrared spectra are sufficient for the identification of the three ground states also in mixed spin iron(II) compounds.
    Notes: Die IR-Spektren des [Fephen2(NCS)2] · 2 H2O und einiger analoger Eisen(II)-Komplexe mit einem eindeutig definierten Triplett-Grundzustand wurden im Bereich von 4 000 bis 180 cm-1 ausführlich untersucht. Der Vergleich mit den IR-Spektren des [Fephen2(NCS)2] und ähnlicher Verbindungen mit einem Quintett- (S = 2) bzw. Singulett-Grundzustand (S = 0) zeigt, daß die für den 1.10-Phenanthrolin-Liganden typischen Banden sich für S = 0 und S = 1 wenig unterscheiden, während die CN-Valenzschwingung des Thiocyanatoliganden und ebenso die Metall-Stickstoff-Valenzschwingungen in den drei Grundzuständen deutlich voneinander verschieden sind (ν1(SCN) für S = 1 2 056 cm-1; für S = 2 2 075 und 2 063 cm-1; für S = 0 2 116 und 2 108 cm-1; ν(Fe—N)(NCS) für S = 1 307 cm-1, für S = 2 252 cm-1, für S = 0 533 und 529 cm-1; ν(Fe—N)(phen) für S = 1 374 und 360 cm-1, für S = 2 220 cm-1, für S = 0 379 und 371 cm-1). Die auftretenden Unterschiede reichen aus, um die drei Grundzustände anhand der IR-Spektren auch nebeneinander identifizieren zu können.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Influence of Ligands on the Magnetic Ground State and the 1A1—5T2 Transition in Some Dithiocyanato-bis-diimine Iron(II) ComplexesA new series of pseudooctahedral complexes of the type [Fe(diimine)2(NCS)2] with the diimine ligands 1,10-phenanthrolin-4-n-butylester (I), 1,10-phenanthroline-4,7-di-n-butylester (II), 4,7-diphenyl-1,10-phenanthroline (III), 2,2′-dipyridyl-4,4′-di-n-butylester (IV), 2-pyridinealdehyd-N-isopropylimine (V) and 2-pyridinealdehyd-N-methylimine has been prepared. Magnetic susceptibility, Mössbauer parameters and IR spectra demonstrate the following types of physical behaviour in the solid state: gradual 1A1—5T2 transition with temperature, which goes to completion in (V), but which is interrupted untimely in (I) and (II). The compound (II) also contains an obviously constant part of molecules with S = 1. In (III), (IV), and (VI), on the other hand, there exists a constant and temperature independent ratio of molecules with S = 1 and S = 2 (“mixed spin solids”).
    Notes: Eine neue Reihe pseudooktaedrischer Komplexe des Typs [Fe(diimin)2 (NCS)2] mit den Diiminliganden 1,10-Phenanthrolin-4-n-butylester (I), 1,10-Phenanthrolin-4,7-di-n-butylester (II), 4,7-Diphenyl-1,10-phenanthrolin (III), 2,2′-Dipyridyl-4,4-di-n-butylester (IV), 2-Pyridinaldehyd-N-isopropylimin (V) und 2-Pyridinaldehyd-N-methylimin (VI) wurde dargestellt. Die magnetischen Suszeptibilitäten, die Mößbauer-Parameter und die IR-Spektren dieser Verbindungen zeigen, daß im Festzustand folgende Typen physikalischen Verhaltens vorliegen: Ein allmählicher, mit Änderung der Temperatur einsetzender 1A1—5T2-Übergang, der bei (V) vollständig verläuft, bei (I) und (II) jedoch vorzeitig abgebrochen wird. (II) enthält außerdem einen offenbar konstanten Anteil von Molekeln mit S = 1. Bei (III), (IV) liegt dagegen ein konstantes, temperaturunabhängiges Mischungsverhältnis von Molekeln mit S = 1 und S = 2 vor.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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