Synthesis And DNA Binding Studies Of New Polypyridyl Dinuclear Ruthenium And Copper Complexes

Polypyridyl ruthenium and copper complexes play an important role in the research fields such as photophysics, electrochemistry and molecular assembling. Recently, much attention has been paid in their potentials for DNA structure recognition, spectroscopic probes, hydrolytic reagents and anticancer drugs. Most of these applications demand the existence of ligands capable of intercalating DNA base pairs.This thesis presented the synthesis of a novel polypyridyl ligand, 2,9-bis(2-imidazol[4,5-f][l,10]phenanthroline)-l,10-phenanthroline (abbreviated as BIPP), starting from 1,10-phenanthroline throughl,10-phenanthroline-5,6-dione and l,10-phenanthroline-2,9-dialdehyleintermediates. Using this ligand as bridging block, two new dinuclear complexes [(bpy)2Ru(u-BIPP)Ru(bpy)2]4+ and [(phen)Cu(|i-BIPP)Cu(phen)]4+, where bpy and phen denote 2,2'-bipyridine and 1,10-phenanthroline respectively, have also been synthesized. Means of elemental analysis, MS, HPLC, thermal analysis, IR, electrochemistry, ID and 2D proton NMR, electronic absorption and emission spectra have been utilized for characterizing and property studies of these compounds.Photophysical methods involving electronic absorption, emission and emission quenching, and viscosity measurement have been used to study the interaction of the dinuclear complexes with calf thymus DNA. The results and conclusion are as follows:[(bpy)2Ru(|i-BIPP)Ru(bpy)2]4+ binds significantly with DNA, as shown by the significant effect of DNA on the photophysical properties. The ultraviolet and visible absorption bands decreased in intensity and the band around 370 nm, which is attributable to BIPP decreased much more than the MLCT bandsaround 445 nm, reaching ca 50% at saturation and the band shifted red 8 nm. The emission band around 601 nm increased remarkably by 1.4 fold, and shifted red 14 nm when DNA was added to saturation. The emission quenching of this complex by K|[Fe(CN)<] was decreased greatly when DNA was present. The relative viscosity of DNA was raised ca 40% after adding this complex to saturation. Since the small planarity of bpy makes bpy a poor moiety for intercalating DNA, the above facts imply that [(bpy)2Ru(u-BIPP)Ru(bpy)2]4+ binds to DNA by intercalation of BIPP into the DNA base pairs.In the absence of DNA [(bpy)2Ru(|i-BIPP)Ru(bpy)2]4+ could form 1:1 complex with Cu2*, as told by the electronic absorption and emission spectra. The binding sites should be the chelating positioned N atoms located in the phenanthroline moiety in the middle part of BIPP. But for DNA bound [(bpy)2Rir(u.-BIPP)Ru(bpy)2]4+, its photophysical behavior could not be affected by adding Cu2*, indicating no coordination could occur in such case. This also strongly 'supported the speculation that BIPP, especially its middle phenananthroline moiety is responsible for insertion to DNA.As for [(phen)Cu(fi-BIPP)Cu(phen)]4+, its absorption band around 270 nm also decreased notably (maximum ca 18%), but the bands between 320 to 400 nm almost remained unchanged while interacting with DNA. Since the band between 320 to 400 nm was mainly determined by BIPP, it could be deduced that [(phen)Cu(n-BIPP)Cu(phen)]4+ binds to DNA by intercalating the two terminal planar (phen)Cu2+ moieties, but not the BIPP moiety into the DNA base pairs. The emission band around 366 nm decreased markedly (maximum 85%) in the presence of DNA, indicating DNA could contact tightly with [(phen)Cu(u,-BIPP)Cu(phen)]4+ so non-emission energy transfer could occur. The relative viscosity increasing of DNA induced by [(phen)Cu(u.-BIPP)Cu(phen)]4+ was much more obvious than that by [(bpy)2Ru(u.-BIPP)Ru(bpy)2]4*, which could well explained by the difference in the intercalating moieties between the two complexes: two terminal (phen)Cu2* in the former and only one phenanthroline part of BIPP in the latter.