(4-OH-Acrid) and acridine orange (AO), with the transition metal ions Ni(II), Pd(II) and Pt(II), are investigated. Octahedral complexes, [Ni(4-O-Acrid)2(en)] (1), and [Ni(4-O-Acrid)2(H2O)2] (2), are obtained when the 4-OH-Acrid ligand reacts with [Ni(Cl)2(en)2] and NiCl2·6H2O, respectively. Single crystal X-ray analysis of complex 1 has shown that two acridine molecules are bonded to nickel through their