Binding geometry and photophysical properties of DNA-threading binuclear ruthenium complexes.
The DNA binding conformation and the photophysical properties of the semiflexible binuclear ruthenium complex [micro-bidppz(phen)4Ru2]4+ (2) were studied with optical spectroscopy and compared to the rigid, planar homologue in syn conformation [micro-dtpf(phen)4Ru2]4+ (3) and the parent "light-switch" complex [Ru(phen)2dppz]2+ (1). Comparison of calculated and observed absorption bands of the bridging ligand, bidppz, confirm earlier suggestions that 2 is significantly nonplanar, both free in solution and when intercalated into poly(dAdT)2, but the conclusion that the intercalated conformation is an anti rotamer is not substantiated by comparison of linear and circular dichroism spectra of 2 and 3. The behavior of the emission quantum yield as a function of temperature is similar for the two binuclear complexes 2 and 3 in different protic solvents, and a quantitative analysis suggests that, in solution, the solvent is more strongly hydrogen bonded to the excited state of 2 than to 1. However, the observation that for 2 the radiative rate constant increases to a value similar to 1 upon intercalation into DNA suggests that the difference between 1 and 2 in accepting hydrogen bonds is less pronounced when intercalated.
Westerlund
Fredrik
F
Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
Eng
Mattias P
MP
Winters
Mikael U
MU
Lincoln
Per
P
D002712:Chlorides / Q000737:chemistry; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D006860:Hydrogen Bonding; D008027:Light; D008956:Models, Chemical; D015233:Models, Statistical; D008968:Molecular Conformation; D009539:Nicotinic Acids / Q000737:chemistry; D011485:Protein Binding; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods; D013997:Time Factors
D002712:Chlorides; D009539:Nicotinic Acids; D012997:Solvents; D012428:Ruthenium; D004247:DNA