The (arylazo-6-aminouracil)nickel(II) derivatives [Ni II (DMA 3 U) 2 ] [HDMA 3 U = 1,3-dimethyl-5-(arylazo)-6-aminouracil; arylazo = phenylazo (1), p-Me-phenylazo (2), p-Cl-phenylazo (3)] have been synthesized and isolated in crystalline form. Single-crystal X-ray diffraction study of [Ni(1) 2 ] reveals that, in the complex, the metal center has a square-planar environment. The intramolecular N-H/π and C-H/π interactions hold in the solid state as well as in poor hydrogen-bond acceptor (HBA) solvents, but are disrupted in good HBA solvents.Crystal-structure analysis further shows that the NH groups of [a]