Binding of cis-dichlorobis(1-methylimidazole-2-thiol)-palladium(II) and -platinum(II) to nucleosides: synthesis and hydrogen-1 and carbon-13 nuclear magnetic resonance studies

Abstract

The reactions of cis-[MCl₂(mit)₂](M = Pd or Pt; mit = 1-methylimidazole-2-thiol) with guanosine (guo), cytidine (cyd), and adenosine (ado) have been studied in neutral solutions. Two types of complexes have been isolated, of general formula [M(mit)₂L₂]X₂(L = guo or cyd) and [ML₄]X₂(L = cyd or ado) with X = Cl^– and [PF₆]^–. By use of i.r. spectroscopy and of the chemical shifts occurring in ¹H and ¹³C n.m.r. spectroscopy, it is possible to confirm co-ordination of Pd and Pt to N⁷ in guo and ado, and to N⁶ in cyd. The n.m.r. investigations reflect electronic modifications in the ring system of the co-ordinated nucleosides, which are discussed in terms of DNA denaturation by heavy transition-metal complexes.