EPR investigations of Cu(II) complexes with 5 '-CMP and 5 '-GMP

Electron paramagnetic resonance investigation of the Cu(II) complexes with guanosine-5'-monophosphate (5'-GMP) and cytidine-5'-monophosphate (5'-CMP) shows the affinity of the Cu(II) ion to interact with the base and the phos phate group. The different modes of the coordination of the metal ion at th e nucleotide and the water molecules lead to octahedral species, distorted by dynamical Jahn-Teller effect (g(0) = 2.106) for the Cu(II)-5'-CMP comple x and rhombically distorted (g(1) = 2.358, g(2) = 2.126, g(3) = 2.068) or t etragonally distorted (g(parallel to)' = 2.299, g(perpendicular to)' = 2.12 6) for the Cu(II)5'-GMP complex. The compound with 5'-CMP presents also a m ore stable in time square-planar species (g(parallel to) = 2.265, A(paralle l to) = 162 G, g(perpendicular to) = 2.076). The local symmetry changes in aqueous solution by coordination of water molecules.