SYNTHESIS AND CHARACTERIZATION OF A NEW DNA-BINDING BIFUNCTIONAL RUTHENIUM(II) COMPLEX

A new DNA-binding molecule, Ru(tap)2POQ2+, in which a polypyridylruthe nium(II) complex is linked to an aminochloroquinoline by a flexible ch ain, has been prepared and characterised (tap = 1,4,5,8-tetraazaphenan threne and POQ corresponds to a 1,10-phenanthroline linked to an amino chloroquinoline by an aliphatic chain). This complex is regarded as bi functional because it contains two moieties of different binding modes and photoreactivities vs. DNA. The H-1 NMR data of this compound indi cate the presence of an equilibrium between two molecular species. The spectroscopic properties of Ru(tap)2POQ2+ in absorption and luminesce nce are examined and compared with those of the corresponding rutheniu m(II) complex which does not contain the aminochloroquinoline moiety: Ru(tap)2phen2+. Luminescence relative quantum yields and lifetimes sho w that the MLCT excited-state behaviour is influenced by the presence of the linked quinoline. An intramolecular photoinduced electron trans fer in one of the two species in equilibrium, is considered to be resp onsible for a quenching of the ruthenium(II) complex luminescence. Pre liminary results on the binding characteristics of Ru(tap)2POQ2, to DN A and [poly(d[A-T])]2 from luminescence and thermal denaturation studi es are reported. The intramolecular quenching of luminescence in Ru(ta p)2POQ2+ is inhibited when it interacts with nucleic acids. Consequent ly, the resulting emission is more substantially enhanced in the prese nce of the polynucleotide relative to the luminescence increase observ ed with the reference complex, Ru(tap)2phen2+.