Preferred orientation in an angled intercalation site of a chloro-substituted Ë-[Ru(TAP)2(dppz)]2+ complex bound to d(TCGGCGCCGA)2
The crystal structure of the ruthenium DNA 'light-switch' complex Λ-[Ru(TAP)2(11-Cl-dppz)](2+) (TAP=tetraazaphenanthrene, dppz=dipyrido[3,2-a':2',3'-c]phenazine) bound to the oligonucleotide duplex d(TCGGCGCCGA)2 is reported. The synthesis of the racemic ruthenium complex is described for the first time, and the racemate was used in this study. The crystal structure, at atomic resolution (1.0 Å), shows one ligand as a wedge in the minor groove, resulting in the 51(°) kinking of the double helix, as with the parent Λ-[Ru(TAP)2(dppz)](2+). Each complex binds to one duplex by intercalation of the dppz ligand and also by semi-intercalation of one of the orthogonal TAP ligands into a second symmetrically equivalent duplex. The 11-chloro substituent binds with the major component (66%) oriented with the 11-chloro substituent on the purine side of the terminal step of the duplex.
- [Show abstract] [Hide abstract] ABSTRACT: Polypyridyl ruthenium complexes have been intensively studied and possess photophysical properties that are both interesting and useful. They can act as probes for DNA, with a substantial enhancement in emission when bound, and can induce DNA damage upon photoirradiation. Therefore, the synthesis and characterization of DNA binding of new complexes is an area of intense research activity. While knowledge of how the binding of derivatives compares to that of the parent compound is highly desirable, this information can be difficult to obtain. Here we report the synthesis of three new methylated complexes, [Ru(TAP)2(dppz-10-Me)]Cl2, [Ru(TAP)2(dppz-10,12-Me2)]Cl2, and [Ru(TAP)2(dppz-11-Me)]Cl2 (TAP = 1,4,5,8-tetraazaphenanthrene; dppz = dipyrido[3,2-a:2′,3′-c]phenazine), and examine the consequences for DNA binding through the use of atomic-resolution X-ray crystallography. We find that the methyl groups are located in discrete positions with a complete directional preference. This may help to explain the quenching behavior found in solution for analogous [Ru(phen)2(dppz)]2+ derivatives.0Comments 2Citations