annual report annual report annual report annual report 2005

RADIOCHEMISTRY, STABLE ISOTOPES,
NUCLEAR ANALYTICAL METHODS, GENERAL CHEMISTRY
91
termediate concentration is gradual and there, especially
for 0.5%, a mix of both types is detected.
The results suggest the appearance of structural
Fig.2. Model aggregate for (a) 0.1% gel and (b) 3% gel.
Fig.1. Fractal analysis, log-log curves with fitted straight-line
segments.
transformation caused by the change of gelator
concentration. The transition acts gradually with
concentration change. The process of glucofuranose-based
gels formation occurred not caused by
the same kind of self-assembly of aggregates but
its course is dependent on the concentration of the
gelator molecules in solvent.
This work was supported by the Polish Ministry
of Scientific Research and Information Technology
under contract No. 3 IO9A 136 27 and by the
European Community – Research Infrastructure
Action under the FP6 “Structuring of the European
Research Area” Programme (through the Integrated
Infrastructure Initiative “Integating Activity on
Synchrotron and Free Electron Laser Science”).
References
[1]. Luboradzki R., Pakulski Z.: Tetrahedron, 60, 4613-4616
(2004).
[2]. Koch M.H.J.: OTOKO – program package, release
01.90 EMBL-DESY.
[3]. Svergun D.I.: J. Appl. Crystallogr., 25, 495 (1992).
[4]. Svergun D.I.: Biophys. J., 76, 2875 (1999).
[5]. Svergun D.I.: J. Appl. Crystallogr., 33, 530 (2000).
CRYSTAL CHEMISTRY OF COORDINATION COMPOUNDS
WITH HETEROCYCLIC CARBOXYLATE LIGANDS.
PART LIV. THE CRYSTAL AND MOLECULAR STRUCTURE
OF BIS[HEXAQUAMAGNESIUM(II)]
PYRAZINE-2,3,5,6-TETRACARBOXYLATE TETRAHYDRATE
Michał Gryz 1/ , Wojciech Starosta, Janusz Leciejewicz
1/
Office for Registration of Medicinal Products, Medical Devices and Biocides, Warszawa, Poland
Triclinic unit cell [space group P1(bar)] of the title
compound contains two hexaquamagnesium(II)
cations, one fully deprotonated pyrazine-2,3,5,6-tetracarboxylate
(2,3,5,6-PZTC) anion with its geometrical
centre situated at the inversion centre and
four solvation water molecules. Figure 1 shows the
relevant ions with atom numbering scheme, Fig.2
– the content of the unit cell. The magnesium(II)
ion is sorrounded by six water molecules with their
oxygen atoms located at the apices of a fairly regular
octahedron. Mg-O bond distances range from
2.036(1) to 2.115(1) Å (mean 2.065 Å). The pyrazine
ring of the anion is planar (rms 0.0001 Å), the carboxylate
groups are inclined to the pyrazine ring
by 22.8 and 99.1 o . A three-dimensional network of
hydrogen bonds with d(O-H...O)>2.70 Å is oper-