The stoichiometric reaction of Cu2CO3(OH)(2), ethylenediaminetetraacetic acid (H(4)EDTA=C2H4(N(CH2CO2H)(2))(2)) and adenine (AdeH) in water yields crystalline samples of adeninium aqua-(ethylenediamine-N,N,N'-triacetato-N'-acetic)copper(II) dihydrate. The compound (AdeH(2))[Cu(HEDTA)(H2O)].2H(2)O Was studied by TG analysis (with FT-IR study of the evolved gasses), IR, electronic and ESR spectra, magnetic susceptibility data, and single crystal X-ray diffraction methods (monoclinic system, space group P2(1)/c (a=7.053(1), b=42.540(5), c=7.798(1) Angstrom, beta=104.24(1)degrees, Z=4, and final R-1=0.042 for 5113 independent reflections). The asymmetric unit consists of a salt of adeninium(1+) and the aqua-copper(II) complex of HEDTA(3-) as chelating agent, and two crystallisation water molecules. The Cu(II) atom exhibits an elongated octahedral coordination (type 4+1+1). The pentadentate HEDTA(3-) ligand has a typical E,G/R configuration and a free N-carboxymethyl arm. The uncoordinated AdeH(2)(+) ion recognises the anion [Cu(HEDTA)(H2O)](-) through two rather linear N-H...O hydrogen bonds involving the protonated N1 heterocyclic atom and one H atom of the exocyclic-N6 amino group with two 0 atoms of the same HEDTA(3-) carboxylate group (173(3) or 175(3)degrees, and 2.64(1) or 2.80(1) Angstrom, respectively). This ion pair recognises itself by a pi,pi-stacking between the six-membered aromatic rings of adjacent AdeH(2)(+) ions which lay out slightly slipped (beta=gamma=10.1degrees) and anti-parallel at 3.34 Angstrom, thus forming aggregates {(AdeH(2))[Cu(HEDTA)(H2O)]}(2). The remaining O-H (carboxy or water) and N-H (heterocyclic or exocyclic) polar bonds interact with O carboxylate or water atoms or N3 and N7 adeninium atoms building the crystal in an extensive 3D-hydrogen bonded network.