Dual-Emissive Tris-Heteroleptic Ruthenium Complexes: Tuning the DNA-Triggered Ratiometric Emission Response by Ancillary Ligands

Abstract

Three tris-heteroleptic mononuclear Ru­(II) complexes with dual fluorescence and phosphorescence[Ru­(dpma)­(bpy)­(phen)]2+ (1 2+), [Ru­(dpma)­(bpy)­(dppz)]2+ (2 2+), and [Ru­(dpma)­(phen)­(dppz)]2+ (3 2+)have been designed and used as ratiometric light-response probes for DNA, where dpma is di­(pyrid-2-yl)­(methyl)-amine, bpy is 2,2′-bipyridine, phen is 1,10-phenanthroline, and dppz is dipyridophenazine, respectively. Single crystals of complex 2(PF6)2 have been obtained and studied by X-ray analysis. The interactions of these complexes with different DNAs are investigated by means of spectroscopic methods, viscosity measurements, and molecular modeling. In the presence of calf thymus DNA, complexes 2(PF6)2 and 3(PF6)2 show the emergence of a new lower-energy phosphorescence emission band; meanwhile, the higher-energy fluorescence emission band is essentially unchanged, functioning as an intrinsic internal reference. These two complexes exhibit stronger preference for calf thymus DNA over single-strand DNA (d­(A)16 and d­(C)16). In contrast, no binding interaction between 1(PF6)2 and calf thymus DNA is observed. The intrinsic binding constants (K b) of 2(PF6)2 and 3(PF6)2 with calf thymus DNA are determined to be (1.4 ± 0.4) × 105 and (9.5 ± 0.15) × 104 M–1, respectively. In addition, these spectroscopic results are compared with those of the prototype complex [Ru­(bpy)2(dppz)]2+ (4 2+), and density functional theory and time-dependent density functional theory calculations are employed to elucidate these experimental findings.

Increasing the cytotoxicity of Ru(ii) polypyridyl complexes by tuning the electron-donating ability of 1,10-phenanthroline ligands

“…Moreover, the labile Cl 4h. [62][63][64] This phenomenon also was corroborated by the fact that the novel fluorescence emission signal displayed bathochromic shifts from complex 1 to 4 with emission peaks at 709, 723, 724, and 744 nm, respectively, in agreement with the electron-donating abilities as the discussion above for the DFT calculations part. Additionally, there was a saturation effect for the Ru(II)-DNA complexes because the decreasing intensities of the emission peaks were not in a linear relationship with the increase in concentrations of Ru(II) complexes.…”

Dual-Emissive Monoruthenium Complexes of N(CH3)-Bridged Ligand: Synthesis, Characterization, and Substituent Effect

“…Based on these experimental observations, the higher-and the lower-energy emission bands are ascribed to the admixtures of the singlet (N(CH 3 )-bridged ligand to bpy 1 LLCT and N(CH 3 )-bridged ligand 1 ICT charge transfer) and the triplet 3 MLCT (ruthenium component to bpy charge transfer) character, respectively. A number of studies suggest that the dual fluorescence/phosphorescence character of a single complex was found in different luminescent TMCs such as platinum [18][19][20]27,29], osmium [21], copper [22], and iridium [24,30], as well as ruthenium complexes [28,32,34]. Kasha's rule states that only the lowest energy excited state of a given spin multiplicity is emissive.…”

“…cent TMCs such as platinum [18][19][20]27,29], osmium [21], copper [22], and iridium [24,30], as well as ruthenium complexes [28,32,34]. Kasha's rule states that only the lowest energy excited state of a given spin multiplicity is emissive.…”

“…Related phenomenon can be divided into three categories including dual fluorescence [3][4][5][6][7][8][9][10], dual phosphorescence [11][12][13][14][15][16][17], and dual fluorescence/phosphorescence [18][19][20][21][22][23][24][25]. Compared with luminescent materials with a single emission band, dual-emissive materials have been used in ratiometric sensing (metal ion [26], molecular oxygen [27][28][29][30], protein [31,32], DNA [33,34], and other species [35,36]), white-emitting generation [37][38][39], near-infrared circularly polarized luminescence [40], and multicolor bioimaging [41,42].…”

Substituent and redox effects on the second-order NLO response of Ru(ii) complexes with polypyridine ligands: a theoretical study

“…Recently, Wu and co-workers synthesized three tris-heteroleptic mononuclear Ru(II) complexes, [Ru(dppz)(dpma)(bpy)] 2+ , [Ru(phen) (dpma)(bpy)] 2+ , and [Ru(dppz)(dpma)(phen)] 2+ , and reported the comparison with the complex [Ru(dppz)(bpy) 2 ] 2+ on the photophysics and electrochemical properties, where phen is 1,10-phenanthroline, dpma is di(pyrid-2-yl)(methyl)-amine, bpy is 2,2 0 -bipyridine, and dppz is dipyridophenazine. 44 The DNA-triggered radiometric light responses of these complexes were tuned by the different ancillary ligands. As we know, the ligands of polypyridine, bipyridine and phenanthroline have s electron-donating and p electron-withdrawing capacities, so they are not only an excellent chromogenic group, but also a good intramolecular charge transfer unit.…”