Interaction of Ruthenium(II)-dipyridophenazine Complexes with CT-DNA: Effects of the Polythioether Ancillary Ligands (original) (raw)
Related papers
Journal of Molecular Structure, 2001
Nanosecond transient resonance Raman and picosecond transient absorption spectroscopic investigations of the two structurally analogous Ru-polypyridyl complexes, Ruphen 2 dppz 21 (1) and Rutap 2 dppz 21 (2), are presented (phen 1,10phenanthroline, dppz dipyrido [3,2-a:2 0 ,3 0 -c] phenazine; tap 1,4,5,8 tetraazaphenanthrene). The ®ndings offer insight into the differing nature of the lowest excited states of the two complexes, and describe the role of these states within the very distinct photophysical behaviour of each, both in relation to solvent response and their interaction with DNA (facilitated in each case through the intercalating dppz ligand). The active, solvent-sensitive, dppz-based 3 MLCT states involved in the`lightswitch' behaviour of (1) are probed, alongside evidence of a progression through a precursor transient state when the complex is in non-aqueous environment. Evidence has been provided of a photophysical pathway for (2), involving formation of a tapbased lowest 3 MLCT state. When (2) is bound to DNA through the dppz ligand, a photo-driven electron transfer process ensues between the guanine base of DNA and the lowest 3 MLCT state. q
Inorganica Chimica Acta, 2011
In our search for new DNA intercalating ligands, a novel bifunctional intercalator 11-(9-acridinyl)dipyrido[3,2-a:2 0 ,3 0 -c]phenazine, acdppz (has two potentially effective intercalators via dipyridophenazine(dppz) and acridine which are linked together via C-C bond) and its corresponding Ru(II) polypyridyl complex [Ru(phen) 2 (acdppz)] 2+ (where phen = 1,10-phenanthroline) have been synthesized and characterized. The electrochemical behaviors of the ligand and its complex have been thoroughly examined. The structure of acdppz and [Ru(phen) 2 (acdppz)] 2+ were determined by X-ray crystallography. From the crystal structure of the complex, we found that the dppz moiety is not coplanar with the acridine ring, having a dihedral angle of 64.79 in the acdppz. The selected bond lengths and angles for the crystal structure of [Ru(phen) 2 (acdppz)] 2+ were compared to the geometry-optimized molecular structure of [Ru(phen) 2 (acdppz)] 2+ derived by Gaussian. The interaction of [Ru(phen) 2 (acdppz)] 2+ with calfthymus (CT) DNA was investigated by absorption and viscometry titration, thermal denaturation studies. The above measurements indicated that the complex binds less strongly with the CT DNA due to the intercalation by the ruthenium bound acdppz with an intrinsic binding constant of 2.6 Â 10 5 M À1 . Molecular-modeling studies also support an intercalative mode of binding of the complex to the model duplex d(CGCAATTGCG) 2 possibly from the major groove with a slight preference for GC rich region. Additionally, the title complex promotes the cleavage of plasmid pBR322 DNA upon irradiation under aerobic conditions.
Inorganic Chemistry, 2011
Synthetic methods toward ruthenium(II) complexes incorporating the benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine-11,16-quinone ligand, qdppn, are reported. In several cases, it was found that complexes containing coordinated benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine, dppn, could be chemically or photochemically oxidized to their qdppn analogues. Since this method was not possible in all the cases, a new, higher yielding, convenient synthesis of qdppn was developed. The crystal structure of the complex [Ru(phen) 2 (qppn)](PF 6) 2 (phen = 1,10-phenanthroline) which was synthesized from free qdppn reveals that a combination of π−π stacking between coordinated phen and qdppn units, as well as anionligand hydrogen bonding, define large hexagonal channels which are occupied by anions and solvent molecules. Electrochemical and photophysical studies reveal that the new qdppn-based complexes are not luminescent and, in contrast to their dppn analogues, they are also poor singlet oxygen sensitizers. Time-resolved studies and density functional theory (DFT) calculations indicate that optical properties of the new complexes are due to a short-lived charge separated state involving the quinone moiety of qdppn. The DNA binding properties of the new complexes have also been investigated. It was found that they are intercalators, displaying binding affinities which are comparable to their dppn analogues.
Inorganica Chimica Acta, 2006
A series of mixed ligand Ru(II) complexes of 5,6-dimethyl-1,10-phenanthroline (5,6-dmp) as primary ligand and 1,10-phenanthroline (phen), 2,2 0-bipyridine (bpy), pyridine (py) and NH 3 as co-ligands have been prepared and characterized by X-ray crystallography, elemental analysis and 1 H NMR and electronic absorption spectroscopy. The X-ray crystal structure of the complex [Ru(phen) 2 (bpy)]Cl 2 reveals a distorted octahedral coordination geometry for the RuN 6 coordination sphere. The DNA binding constants obtained from the absorption spectral titrations decrease in the order, tris(5,6-dmp)Ru(II) > bis(5,6-dmp)Ru(II) > mono(5,6-dmp)Ru(II), which is consistent with the trend in apparent emission enhancement of the complexes on binding to DNA. These observations reveal that the DNA binding affinity of the complexes depend upon the number of 5,6-dmp ligands and hence the hydrophobic interaction of 5,6-dimethyl groups on the DNA surface, which is critical in determining the DNA binding affinity and the solvent accessibility of the exciplex. Among the bis(5,6-dmp)Ru(II) complexes, those with monodentate py (4) or NH 3 (5) co-ligands show DNA binding affinities slightly higher than the bpy and phen analogues. This reveals that they interact with DNA through the co-ligands while both the 5,6-dmp ligands interact with the exterior of the DNA surface. All these observations are supported by thermal denaturation and viscosity measurements. Two DNA binding modes-surface/electrostatic and strong hydrophobic/partial intercalative DNA interaction-are suggested for the mixed ligand complexes on the basis of time-resolved emission measurements. Interestingly, the 5,6-dmp ligands promote aggregation of the complexes on the DNA helix as a helical nanotemplate, as evidenced by induced CD signals in the UV region. The ionic strength variation experiments and competitive DNA binding studies on bis(5,6-dmp)Ru(II) complexes reveal that EthBr and the partially intercalated and kinetically inert [Ru(phen) 2 (dppz)] 2+ (dppz = dipyrido[3,2-a:2 0 ,3 0-c]phenazine) complexes revert the CD signals induced by exciton coupling of the DNA-bound complexes with the free complexes in solution.
Chemical Communications, 1996
Resonance Raman (RR) spectroscopy has been used to probe the interaction between dipyridophenazine (dppz) complexes of ruthenium(II), [Ru(L) 2 (dppz)] 2+ (L) 1,10-phenanthroline (1) and 2,2-bipyridyl (2)), and calfthymus DNA. Ground electronic state RR spectra at selected probe wavelengths reveal enhancement patterns which reflect perturbation of the dppz-centered electronic transitions in the UV-vis spectra in the presence of DNA. Comparison of the RR spectra recorded of the short-lived MLCT excited states of both complexes in aqueous solution with those of the longer-lived states of the complexes in the DNA environment reveals changes to excited state modes, suggesting perturbation of electronic transitions of the dppz ligand in the excited state as a result of intercalation. The most prominent feature, at 1526 cm-1 , appears in the spectra of both 1 and 2 and is a convenient marker band for intercalation. For 1, the excited state studies have been extended to the ∆ and Λ enantiomers. The marker band appears at the same frequency for both but with different relative intensities. This is interpreted as reflecting the distinctive response of the enantiomers to the chiral environment of the DNA binding sites. The results, together with some analogous data for other potentially intercalating complexes, are considered in relation to the more general application of time-resolved RR spectroscopy for investigation of intercalative interactions of photoexcited metal complexes with DNA.
DNA-Binding Studies of Mixed-Ligand (Ethylenediamine)ruthenium(II) Complexes
Chemistry & Biodiversity, 2006
A series of mixed-ligand ruthenium(II) complexes of the type [Ru(en) 2 bpy] 2 þ (bpy ¼ 2,2-bipyridine; 1), [Ru(en) 2 phen] 2 þ (phen ¼ 1,10-phenantroline; 2), [Ru(en) 2 IP] 2 þ (IP ¼ imidazo[4,5-f][1,10]phenanthroline; 3), and [Ru(en) 2 PIP] 2 þ (PIP ¼ 2-phenylimidazo[4,5-f][1,10]phenanthroline; 4) have been isolated and characterized by UV/VIS, IR, and 1 H-NMR spectral methods. The binding of the complexes with calf thymus DNA has been investigated by absorption, emission spectroscopy, viscosity measurements, DNA melting, and DNA photo-cleavage. The spectroscopic studies together with viscosity measurements and DNA melting studies support that complexes 1 and 2 bind to CT DNA (¼ calf thymus DNA) by groove mode. Complex 2 binds more avidly to CT DNA than complex 1, complexes 3 and 4 bind to CT DNA by intercalation mode, 4 binds more avidly to CT DNA than 3. Noticeably, the four complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA.
Dalton Transactions, 2010
Cr(phen) 2 (X 2 dppz)] 3+ {X = H, Me, or F} have been synthesised, characterised, and chromatographically resolved into their constituent D and K enantiomers. The DNA-binding interactions of each of the racemic complexes were investigated, with the results of linear dichroism, thermal denaturation, and emission quenching studies indicative of intercalative binding to CT-DNA with a significant electrostatic contribution. UV/Vis absorption titrations suggest strong DNA binding by each of the racemic complexes, with the methylated analogue [Cr(phen) 2 (Me 2 dppz)] 3+ exhibiting the largest equilibrium binding constant. Emission quenching and UV-Vis titrations of the enantiomers of [Cr(phen) 2 (dppz)] 3+ imply similar binding affinities for the D and K isomers, although significant differences between the circular dichroism spectra of the enantiomers in the presence of DNA connote differences in binding orientation and/or conformation between the two. † Electronic supplementary information (ESI) available: UV/vis absorption titrations, steady state emissions, and CD titrations of complexes with CT-DNA; selected bond lengths and bond angles of crystals of 1 and 3; packing diagrams of crystals 1 and 3. CCDC reference numbers 761094 and 68103. For ESI and crystallographic data in CIF or other electronic format see their ruthenium(II) analogues. They are also expected to be better photoxidising agents and indeed Kane-Maguire and co-workers have previously shown that when [Cr(phen) 2 (dppz)] 3+ binds to DNA the 2 E emission is quenched, presumably a consequence of photo-induced electron transfer. 10
Dalton Transactions, 2008
A series of mixed ligand ruthenium(II) complexes [Ru(pdto)(diimine)](ClO4)2/(PF6)2 1-3 and [Ru(bbdo)(diimine)](ClO4), 4-6, where pdto is 1,8-bis(pyrid-2-yl)-3,6-dithiooctane, bbdo is 1,8-bis(benzimidazol-2-yl)-3,6-dithiooctane and diimine is 1,10-phenanthroline (phen), dipyrido-[3,2-d:2',3'-f]-quinoxaline (dpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz), have been isolated and characterised by analytical and spectral methods. The complexes [Ru(pdto)(phen)](PF6)2 la, [Ru(pdto)(dpq)(Cl](PF6) 2a, [Ru(bbdo)(phen)](PF6)2 4a and [Ru(bbdo)(dpq)](ClO4)2 5 have been structurally characterized and their coordination geometries around ruthenium(II) are described as distorted octahedral. In la, 4a and 5 the two thioether sulfur and two py/bzim nitrogen atoms of the tetradentate pdto/bbdo ligand are folded around Ru(II) to give predominantly a "cis-alpha" configuration. (I)H NMR spectral data of the complexes support this configuration in solution. In [Ru(pdto)(dpq)Cl](PF6) 2a with a distorted octahedral coordination geometry, one of the two py nitrogens of pdto is not coordinated. The DNA binding constants (Kb: 2, 2.00 +/- 0.02 x 10(4) M(-1), s = 1.0; 3, 3.00 +/- 0.01 x 10(6) M(-1), s = 1.3) determined by absorption spectral titrations of the complexes with CT DNA reveal that 3 interacts with DNA more tightly than 2 through partial intercalation of the extended planar ring of coordinated dppz with the DNA base stack. The DNA binding affinities of the complexes increase with increase in the number of planar aromatic rings in the co-ligand, and on replacing both the py moieties in pdto complexes (1-3) by bzim moieties to give bbdo complexes (4-6). Upon interaction with CT DNA the complexes 1, 2, 5 and 6 show a decrease in anodic current in the cyclic voltammograms. On the other hand, interestingly, 3 and 4 show an increase in anodic current suggesting their involvement in electrocatalytic guanine oxidation. Interestingly, of all the complexes, only 6 alters the superhelicity of DNA upon binding with supercoiled pBR322 DNA. The cytotoxicities of the dppz complexes 3 and 6, which avidly bind to DNA, have been examined by screening them against cell lines of different cancer origins. It is noteworthy that 6 exhibits selectivity with higher cytotoxicity against the melanoma cancer cell line (A375) than other cell lines, potency approximately twice that of cisplatin and toxicity to normal cells 3 and 90 times less than cisplatin and adriamycin respectively.