MODE OF COORDINATION AND STABILITY OF CU(II) AND ZN(II) COMPLEXES WITH ADENOSINE, DEOXYADENOSINE, CYTIDINE AND DEOXYCYTIDINE

Stability constants of Cu(II) and Zn(II) complexes with nucleosides ha ve been determined from a computer analysis of potentiometric titratio n results. Spectral investigations prove that in acidic solution adeno sine coordinates to Cu(II) via its N1 or N7 atoms, while at pH > 7 onl y N7 is involved. Similar interactions are observed for dAdo complexes . Spectral and potentiometric studies suggest that Zn does not form st able complexes with dAdo. In the case of cytidine and deoxycytidine, t he preferred site of coordination is the N3 atom of the nucleoside. Ox ygen atoms from the carbonyl groups are not involved in Cu(II) or Zn(I I) coordination. The results of the spectral investigation have exclud ed the ribose and deoxyribose moieties of all studied ligands from par ticipation in the interactions. In general, the mode of coordination o f nucleosides and deoxynucleosides with Cu(II) and Zn(II) has been fou nd analogous.