title: Density functional theory/time-dependent DFT studies on the structures, trend in DNA-binding affinities, and spectral properties of complexes [Ru(bpy)2(p-R-pip)]2+ (R = -OH, -CH3, -H, -NO2).
abstract: Studies on the electronic structures and trend in DNA-binding affinities of a series of Ru(II) complexes [Ru(bpy)2(p-R-pip)]2+ (bpy = 2,2-bipyridine; pip = 2-phenylimidazo[4,5-f] [1,10]-phenanthroline; R = -OH, -CH3, -H, -NO2) 1-4 have been carried out, using the density functional theory (DFT) at the B3LYP/LanL2DZ level. The electronic absorption spectra of these complexes were also investigated using time-dependent DFT (TDDFT) at the B3LYP//LanL2DZ/6-31G level. The computational results show that the substituents on the parent ligand (pip) have a significant effect on the electronic structures of the complexes, in particular, on the energies of the lowest unoccupied molecular orbital (LUMO) and near some unoccupied molecular orbitals (LUMO+x, x = 1-4). With the increase in electron-withdrawing ability of the substituent in this series, the LUMO+x (x = 0-4) energies of the complexes are substantially reduced in order, for example, epsilon(LUMO)(1) approximately epsilon(LUMO)(2) > epsilon(LUMO)(3) > epsilon(LUMO)(4), whereas the pi-component populations of the LUMO+x (x = 0-4) are not substantially different. Combining the consideration of the bigger steric hindrance of complex 2, the trend in DNA-binding affinities (K(b)) of the complexes, that is, K(b)(2) < K(b)(1) < K(b)(3) < K(b)(4) can be reasonably explained. In addition, the experimental singlet metal-to-ligand charge transfer ((1)MLCT) spectra of these complexes can be well simulated and discussed by the TDDFT calculations.
authors.affiliation: School of Chemistry and Chemical Engineering/The Key Laboratory of Gene Engineering of Ministry of Education, Sun Yat-Sen University, Guangzhou 510275, P. R. China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Lian-Cai
authors.initials: LC
authors.lastname: Xu
authors.forename: Jin-Can
authors.initials: JC
authors.lastname: Chen
authors.forename: Kang-Cheng
authors.initials: KC
authors.lastname: Zheng
authors.forename: Liang-Nian
authors.initials: LN
authors.lastname: Ji
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D001665:Binding Sites; D004247:DNA / Q000737:chemistry*; D015342:DNA Probes / Q000737:chemistry; D007364:Intercalating Agents / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship; D013997:Time Factors
chemical_list: D015342:DNA Probes; D007364:Intercalating Agents; D009942:Organometallic Compounds; D010618:Phenanthrolines; D015082:2,2'-Dipyridyl; D012428:Ruthenium; D004247:DNA