Original scientific paper
EPR spectroscopy of superhyperfine interaction in the copper paramagnetic center in the crystal of cytosine monohydrate
Dubravka Krilov
; Medical School, University of Zagreb, Šalata 3b, 10001 Zagreb, Croatia
Andrica Lekić
; Medical School, University of Rijeka, B. Branchetta 20, 51000 Rijeka, Croatia
Erim Bešić
; Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10001 Zagreb, Croatia
Vjeran Gomzi
; Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10001 Zagreb, Croatia
Janko N. Herak
; Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1, 10001 Zagreb, Croatia
Abstract
The planar complex of Cu(II) with two cytosine bases was formed by gamma irradiation of the cytosine monohydrate crystal, containing copper impurities. The paramagnetic complex was probably formed by trapping the radiation-induced migrating holes by Cu(I), that is originally present in the crystal lattice. The structure of the complex was analyzed from the superhyperfine pattern of its EPR spectra. The experimentally evaluated tensor elements of the three 14N couplings and the observation of an additional proton coupling unequivocally confirm the structure. The ab initio B3LYP density functional method calculations are in good agreement with the experiments. Both experiments and the calculations demonstrate large spin delocalization in the cytosine ring plane.
Keywords
copper complex; cytosine; EPR spectroscopy; superhyperfine interaction
Hrčak ID:
301812
URI
Publication date:
1.3.2005.
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