The interaction between Ni(II) and amino acids with an aromatic residue (such as tyrosine and tryptophan) and either 9 substituted bases or nucleosides has been studied. Ternary derivatives obtained in solid state were characterised by, among other techniques, elemental analysis, thermogravimetry, electronic and infrared spectroscopy. The following complexes have been obtained: 1: [Ni (tyr)₂(9EtAde)₂] × 4H₂O; 2: [Ni (tyr)₂(9EtGua)₂] × 5H₂O; 3: [Ni (tyr)(guo) × 5H₂O];4: [Ni (tyr)(ino) × 5H₂O];5: [Ni (trp)₂(9EtGua)(H₂O)] × 2H₂O, where tyr is tyrosinate, trp tryptophanate, ino inosinate and guo guanosinate. Thermogrammes are in agreement with the number of water molecules and nickel content (calculated as NiO), together with the ternary nature of these complexes. The binary compounds Ni(tyr)₂ × 3H₂O and Ni(trp)2 × 3.5H₂O were also obtained and the corresponding thermogrammes were registered for comparison purposes. Compounds 1, 2 and5 are water soluble; besides, 1 is fairly soluble in methanol. Compounds 3 and 4 seem to be polymeric. Infrared spectra clearly show the presence of bands either from the amino acid or the base suggesting nickel octahedral coordination through the carboxylic and amino acids groups and a nitrogen from the purine base. These compounds were obtained in water at pH close to 7.0. With other bases such as cytosine and uracil, or their corresponding nucleosides, the same synthesis failed to yield ternary compounds [1,2].