Design of a solid inclusion compound with optimal properties as a linear dichroic filter for X-ray polarization analysis

Angewandte Chemie - International Edition

Volumn 42, Issue 26, 2003, Pages 2982-2985

  Chao, Mao Hsun ^a   Kariuki, Benson M ^a   Harris, Kenneth D M ^a   Collins, Steven P ^b   Laundy, David ^b  

^a UNIVERSITY OF BIRMINGHAM   (United Kingdom)

^b DARESBURY LABORATORY   (United Kingdom)

Author keywords

Host guest systems; Inclusion compounds; X ray diffraction; X ray polarization analysis

Indexed keywords

INCLUSIONS; OPTICAL FILTERS; POLARIZATION; X RAY ANALYSIS;

DICHROIC FILTERS;

BROMINE COMPOUNDS;

1 BROMOADAMANTANE; 1,10 DIBROMODECANE; AMANTADINE; DECANE; THIOUREA DERIVATIVE; UNCLASSIFIED DRUG; UREA DERIVATIVE;

ARTICLE; FILTER; LINEAR DICHROIC FILTER; POLARIZATION; RADIATION ATTENUATION; X RAY; X RAY ANALYSIS; X RAY DIFFRACTION; X RAY POLARIZATION ANALYSIS;

EID: 0041305984     PISSN: 14337851     EISSN: None     Source Type: Journal    
DOI: 10.1002/anie.200350891     Document Type: Article

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18. The thiourea/guest molar ratio of 4:1 was confirmed from the results of elemental analysis. This stoichiometry of 1-bromoadamantane/thiourea differs from that of conventional thiourea-inclusion compounds, for which there are typically two guest molecules per 12 Å along the tunnel and the thiourea/guest molar ratio is 3:1.
19. Analysis of the single-crystal diffraction data cannot distinguish whether this disorder represents (1) disorder in the orientations of individual molecules within a given tunnel, or (2) an ordered arrangement of the C-Br bond vectors within each tunnel, with the disorder in the average crystal structure arising from different tunnels having different orientations of the (ordered) C-Br bond directions. Interpretation of our disorder model in terms of situation (1) would correspond to unfavourable local interactions between Br atoms (Br⋯Br separations as short as 2.14-2.75 Å), and therefore we believe that situation (2) is more plausible. For comparison, the Br⋯Br separation for two Br atoms in van der Waals contact is ≈3.7 Å. Bromine K-edge EXAFS spectroscopy would be informative for directly determining the Br⋯Br separations between neighbouring guest molecules in this structure.
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22. Linear polarization of incident X-ray beam ≈95%.
23. From the investigations that we have carried out so far, the 1-bromoadamantane/thiourea inclusion compound does not undergo any thermal decomposition (e.g. by loss of the guest component) at ambient temperature, and no beam damage was observed during the X-ray studies described in this paper. The 1,10-dibromodecane/urea inclusion compound studied previously also exhibited suitable characteristics with regard to stability for applications in X-ray polarization analysis.