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FIZIKA A 14 (2005) 1 , 9-18
 
EPR SPECTROSCOPY OF SUPERHYPERFINE INTERACTION IN THE COPPER
PARAMAGNETIC CENTER IN THE CRYSTAL OF CYTOSINE MONOHYDRATE
DUBRAVKA KRILOVa, ANDRICA LEKIĆ b, ERIM BEŠIĆ c,
VJERAN GOMZIc
and JANKO N. HERAKc
aMedical School, University of Zagreb, Šalata 3b, 10001
Zagreb, Croatia
bMedical School, University of Rijeka, B. Branchetta 20, 51000 Rijeka, Croatia
cFaculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovačića 1,
10001 Zagreb, Croatia
Received 28 January 2005; revised manuscript received
11 April 2005
Accepted 18 April 2005 Online 21 October 2005
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.
PACS numbers: 76.30.-v
UDC 538.955
Keywords: copper complex, cytosine, EPR spectroscopy, superhyperfine interaction
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