Purine nucleotide-copper(II) binary and ternary complexes. Synthesis, electron paramagnetic resonance and infrared investigation

Abstract

An X-band EPR and IR investigation was carried out on Cu(II) binary and ternary complexes involving ATP (adenosine 5′-triphosphate) or IMP (inosine 5′- monophosphate) and an aromatic base such as 2,2′- dipyridylamine (DPA), 2,2′-bipyridyl (BIPY) or 1,10- phenanthroline (PHEN) in the microcrystalline state or in aqueous solution. The measurements were performed at room temperature and at 100 K. A new ternary complex containing Cu(II), IMP and DPA in a 1:1:1 molar ratio was prepared and characterized. The compound crystallizes as thin green plates in the monoclinic P2 1 space group with a = 7.828(2), b = 18.552(3), c = 17.378(3) Å and β = 91.16(2)°. The Cu(II) ion interacts with phosphate oxygen atoms from IMP and with nitrogen atoms from DPA. The interpretation of out data on the basis of the coordination sphere geometries suggests that EPR is a useful tool in investigating the structure and the nature of the close-lying donors of the Cu(II) ions. The EPR and IR data show that in the ternary complexes the aromatic bases BIPY, PHEN and DPA are bound to the Cu(II) centre, probably acting as bidentate ligands both in the solid state and in aqueous solution at pH = 7.