title: EPR study of a copper impurity center in a single crystal of 2-thiothymine.
abstract: EPR spectroscopy was used to study the complex formed in crystals of 5-methyl-2-thiouracil (2-thiothymine) containing traces of copper. The copper impurities, originally present as Cu(I)-complex of 2-thiothymine in the lattice of 2-thiothymine, are transformed into paramagnetic Cu(II)-complex by ionizing radiation. It was found that the complex is planar, the plane being defined by two pairs of S and N atoms, from two adjacent 2-thiothymine molecules. The structure of the complex suggests that a pair of hydrogen bonds between two neighboring molecules is replaced by a stronger Cu-coordination bonding, with two sulfur and two nitrogen atoms as ligands. The spectroscopic parameters (g-tensor, A(63Cu) and A(14N) tensors) are essentially similar to those earlier observed for copper planar centers in other systems.
authors.affiliation: Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovacića 1, 10002 Zagreb, Croatia.
authors.forename: Erim
authors.initials: E
authors.lastname: Besić
authors.forename: Vjeran
authors.initials: V
authors.lastname: Gomzi
authors.forename: Kresimir
authors.initials: K
authors.lastname: Sanković
authors.forename: Janko N
authors.initials: JN
authors.lastname: Herak
authors.forename: Dubravka
authors.initials: D
authors.lastname: Krilov
mesh_terms: D003300:Copper / Q000032:analysis* / Q000737:chemistry; D003460:Crystallization; D004578:Electron Spin Resonance Spectroscopy; D008968:Molecular Conformation; D013941:Thymine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C101233:2-thiothymine; D003300:Copper; D013941:Thymine