High-resolution synchrotron data collection for charge-density work at 100 and 20 K.
For the measurement of very accurate high-resolution X-ray data for charge-density work, synchrotron beamlines provide a bright radiation source of outstanding properties. Most important are the very high primary intensity and the possibility of choosing hard radiation with lambda approximately 0.5 A or even shorter. This together with area detection and a stable low-temperature device means that accurate and large data sets can be measured in a short time. A number of data collections are reported, which were carried out at the beamlines F1 and D3 of Hasylab (DESY, Hamburg) first at 100 K and later at 15-20 K, demonstrating the quality of the measured intensities. A low temperature of around 20 K was obtained at beamline D3 with a double-stage closed-cycle helium cryostat where the standard beryllium cylinder of the vacuum chamber was replaced by a 0.1 mm Kapton film. Comparison of different data sets measured for a strychnine crystal demonstrated how I/sigma ratios favorably improve if synchrotron radiation at a low temperature of 15 K was used. Synchrotron-based studies on several biologically active compounds are briefly summarized and a synchrotron experiment of an otherwise not sufficiently diffracting crystal of a tetraphenyl barbaralane derivative is described in detail. Atomic volumes and charges of a highly substituted C(60) fullerene are reported derived from a synchrotron data set of more than 350000 reflections.
Institute for Chemistry/Crystallography, Free University Berlin, Takustrasse 6, D-14195 Berlin, Germany. luger@chemie.fu-berlin.de
Peter
P
Luger
Marc
M
Messerschmidt
Stephan
S
Scheins
Armin
A
Wagner
D000596:Amino Acids / Q000737:chemistry; D001952:Bridged-Ring Compounds / Q000737:chemistry; D003080:Cold Temperature; D003510:Cyclohexanes / Q000737:chemistry; D003521:Cyclopropanes / Q000737:chemistry; D037741:Fullerenes / Q000737:chemistry; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry; D009930:Organic Chemicals / Q000737:chemistry*; D013331:Strychnine / Q000737:chemistry; D017356:Synchrotrons / Q000295:instrumentation*
D000596:Amino Acids; D001952:Bridged-Ring Compounds; D003510:Cyclohexanes; D003521:Cyclopropanes; D037741:Fullerenes; D009842:Oligopeptides; D009930:Organic Chemicals; D013331:Strychnine; C069837:fullerene C60