G. Wojcik1, J. Holband1, P. Kafarski2
1Institute of Physical and
Theoretical Chemistry
2Institute of Organic
Chemistry, Biochemistry and Biotechnology Wroclaw University of
Techology, Wyb. Wyspiankiego 27 27, 50-370 Wroclaw, Poland
In course of the synthesis of some phosphonic analogues of aminoacids having potential biological activity we obtained intermediates which had to be identified by X-ray structure analysis. One of them occured in two polymorphic forms (IA and IB) depending on the reaction conditions. Their crystal structure parameters are as follows.
IA: C24H21N209P, P21/n, a=8.023 A, b=12.092 A, c=24.103 A, b=92.39°, Z=4, Dx =1.457 Mg/m3, m=0.176 mm-1, R1=0.07 (for I)4s);
IB: C24.H21N2O9P, P21/c, a=8.298 A, b=16.287 A, c=18.365 A, b=101.1°, Z=4, Dx=1.397 Mg/m3, m=0.169 mm-1, R1=0.09 (I)4s).
The molecules in the IA and IB crystals differ by their conformation: the mutual orientations of two phtalyl rings in a molecule are different. The IB polymorph seems to be less stable than the IA one because its density is smaller. its melting point lies at lower temperature and its atomic thermal vibration amplitudes are larger comparing with IA.
Another compound (labeled II) was obtained as a phosphopeptide analogue of herbicides. Its crystal structure is: II: C26H31N2O8P, P212121, a=9.570 A, b=14.320 A, c=20.370 A, Z=4, Dx=1.262 Mg/m3, m=0.147, R1=0.056 (I)4s).
The three crystal structures have many similar features. The conformation and packing of sterically overcrowded and conformationally flexible molecules seem to be stabilized by very weak intermolecular C-H...O= hydrogen bondings. The extremely large thermal vibration amplitudes of the phosphonic group atoms suggest the occurrence of their disorder. This disorder has probably a dynamical character because it becomes frozen below room temperature. The differential scanning calorimetry (DSC) measurements revealed the occurrence of glassy phase transitions in the crystals under consideration.