Structure of Free Radical in γ-Irradiated 21-Hydroxyprogesterone (Deoxycorticosterone) Single Crystals. ESR/ENDOR and DFT Studies

A. Szyczewskia, J. Pietrzaka and K. Möbiusb aInstitute of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland bInstitute of Molecular Physics, Free University of Berlin, Arnimallee 14, 14195 Berlin, Germany

Full Text PDF

Received: 24 04 2005;

Single crystals of 21-hydroxyprogesterone have been γ-irradiated at 295 K and studied using X-band ESR and ENDOR. The structure of the one type radical has been determined on the basis of an analysis of the angular variation of the spectra. This radical is formed by abstraction of the hydrogen atom from the C(6) carbon, while the unpaired electron is delocalised onto the system O(3), C(3), C(4), C(5), C(6). Hyperfine splitting constants and unpaired electron density distribution have been calculated for the proposed radical structure by using the Gaussian98 set of programs. The results are in very good agreement with the experimental data. The effect of the hydrogen bond and biological activity on the anisotropy of α-hyperfine splitting tensor have also been discussed.

DOI: 10.12693/APhysPolA.108.119 PACS numbers: 76.30.-v, 76.70.-r, 78.70.-g, 31.15.Ew