Interaction studies of DNA binding of ruthenium(II) mixed-ligand complexes: [Ru(phen)2(dtmi)]2+ and [Ru(phen)2(dtni)]2+

Two new ligands, 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-methoxylisatin (dtmi), 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-nitroisatin (dtni) and their ruthenium(II) complexes [Ru(phen)2(dtmi)](ClO4)2 (1) and [Ru(phen)2(dtni)](ClO4)2 (2) have been prepared and characterized by elemental analysis, FAB-MS, ES-MS and 1H NMR. The DNA-binding behaviors of complexes have been studied by spectroscopic titration, viscosity measurements, thermal denaturation and circular dichromism (CD). The results indicate that the complexes 1 and 2 interact with calf thymus DNA (CT-DNA) by intercalative mode. The DNA-binding affinity of the complexes 2 is larger than that complex 1 does.     

Effect of the ancillary ligands on the binding of ruthenium(II) complexes [Ru(dmp)2(MCMIP)]2+ and [Ru(dmb)2(MCMIP)]2+ with DNA

Two polypyridine ruthenium(II) complexes, [Ru(dmp)₂(MCMIP)]²⁺ (1) (MCMIP = 2-(6-methyl-3-chromonyl)imidazo[4,5-f][1,10]-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline) and [Ru(dmb)₂(MCMIP)]²⁺ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized by elemental analysis, ES-MS and ¹H NMR. The DNA-binding behaviors of these complexes were investigated by electronic absorption titration, fluorescence spectroscopy, viscosity measurements and thermal denaturation. The results show that 1 and 2 effectively bind to CT-DNA; the DNA-binding affinities are closely related to the ancillary ligand.     

Effect of substituents on DNA-binding behaviors of ruthenium(II) complexes: [Ru(dmb)2(dtmi)]2+ and [Ru(dmb)2(dtni)]2+

Two Ru(II) complexes [Ru(dmb)₂(dtmi)](ClO₄)₂ (1) (dmb = 4, 4′-dimethyl-2, 2′-bipyridine, dtmi = 3-(pyrazin-2-yl)-as-triazino[5, 6-f]-5-methoxylisatin) and [Ru(dmb)₂(dtni)](ClO₄)₂ (2) (dtni = 3-(pyrazin-2-yl)-as-triazino[5, 6-f]-5-nitroisatin) have been synthesized and characterized by elemental analysis, ES-MS, and ¹H NMR. DNA-binding behaviors of these complexes have been investigated by spectroscopic titration, viscosity measurements, and thermal denaturation. The results indicate that the two complexes interact with calf thymus DNA by intercalation.     

Symmetrical dinuclear complexes with high DNA affinity based on [Ru(dpq)2(phen)]2+

Symmetrical homometallic dinuclear complexes of the type [(Ru(dpq)2)2(phen-SOS-phen)]4+, with a flexible 2-mercaptoethyl ether linker joining the two [Ru(dpq)2(phen)]2+-based sub-units, have DNA dissociation constants (Kd) in the nM range.     

Synthesis and spectroscopic DNA binding studies of [Ru(phen)2(tbtc)]2+ and [Ru(2,9-dmp)2(tbtc)]2+

A new polypyridyl ligand tbtc (tbtc=4,5,9,14-tetraaza-benzo[b]triphenylene-11-carboxylic acid methyl ester) and its complexes [Ru(phen)2(tbtc)]2+ (1) (phen=1,10-phenanthroline) and [Ru(2,9-dmp)2(tbtc)]2+ (2) (2,9-dmp=2,9-dimethyl-1,10-phenanthroline) were synthesized and characterized by element analysis, MS, and 1H NMR. The DNA binding properties of both complexes to calf thymus DNA (CT-DNA) were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that both complexes bind to DNA via an intercalative mode, and the DNA binding affinity of complex 1 is much greater than that of complex 2. This difference in binding affinity probably was caused by the different ancillary ligands. Also, when irradiated at 365 nm, complex 1 was found to be a more-effective DNA-cleaving agent than complex 2.     

The DNA-binding behavior and DFT calculation of ruthenium(II) complexes [Ru(phen)2L](ClO4)2 (L = HMOPIP and MOHPIP)

Two ruthenium(II) complexes, [Ru(phen)₂HMPIP]²⁺ (1) and [Ru(phen)₂MHPIP]²⁺ (2), have been synthesized and characterized by elemental analysis, ESI-MS, and ¹H NMR spectroscopy. The DNA-binding properties of 1 and 2 have been investigated by electronic and emission spectra and viscosity experiments. The results show that both 1 and 2 can bind to DNA in intercalating mode, with 1 exhibiting stronger binding affinity. These were confirmed by the strong hypochromism at IL and MLCT absorption bands in both complexes when DNA was added into solution, and the increase in relative viscosity of CT-DNA in the presence of both complexes. Moreover, the calculated intrinsic binding constant for 1 and 2 from the decay of electronic spectra is 3.82 × 10⁵ and 2.06 × 10⁵ M^?1, respectively. Finally, the effects of the substituent groups on the DNA-binding behavior of ruthenium(II) complexes have also been rationally discussed by computer calculation of density functional theory (DFT) methods.     

Synthesis,characterization, duplex-DNA interactions,and anticancer activities of novel octahedral [Ni(phen)2(dppz-idzo)]2+ and [Co(phen)2(dppz-idzo)]3+ complexes

Two new octahedral [Ni(phen)₂(dppz-idzo)]²⁺ and [Co(phen)₂(dppz-idzo)]³⁺ complexes have been synthesized and characterized by CHN analysis, electrospray ionization-MS, nuclear magnetic resonance, and UV–Vis spectra. The DNA-binding ability of these complexes was spectrophotometrically, hydrodynamically, and electrophoretically evaluated which indicated that they strongly intercalate into the DNA double helix, and that both induced severe DNA damage in the presence of peroxide. The complexes also showed strong antiproliferative effect against HepG2 and MDA-MB-231 cells. By contrast, they were found to be inactive against the MCF-7 cell line. The ligand itself was found to be inactive against the cells tested.     

Synthesis,characterization, and DNA-binding of [Co(phen)2(CPIA)]3+, [Co(phen)2(BIP)]3+, and [Co(phen)2(CIP)]3+

Three ligands, 2-(3-(carboxymethyl)-1,10-phenanthroline-[5,6-d]imidazole-1-yl)acetate (CPIA), 2-(benzo[d][1,3]dioxol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (BIP), and 2-(9H-carbazol-3-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (CIP), and their complexes, [Co(phen)₂(CPIA)]³⁺ (1) (phen = 1,10-phenanthroline), [Co(phen)₂(BIP)]³⁺ (2), and [Co(phen)₂(CIP)]³⁺ (3), have been synthesized and characterized. Binding of the three complexes with calf thymus DNA (CT-DNA) has been investigated by spectroscopic methods, cyclic voltammetry, and viscosity measurements. The three complexes bind to DNA through an intercalative mode, and the size and shape of the intercalative ligands have significant effects on the binding affinity of complexes to CT-DNA.     

Light-driven expulsion of the sterically hindering ligand L in tris-diimine ruthenium(II) complexes of the Ru(phen)2(L)2+ family: a pronounced ring effect

Three new ruthenium(II) complexes have been prepared which contain two 1,10-phenanthroline units and a third sterically hindering chelate. In one case, the hindering ligand is a disubstituted 2,2'-bipyridine (bpy) attached to two very bulky manisyl groups. The two other systems are similar in terms of size of the hindering groups (anisyl substituents) located close to the central metal. The complexes investigated in the Present Report are aimed at providing building blocks of future light-driven molecular machines. The photochemical expulsion of the sterically hindering chelate has thus been studied by UV-vis spectroscopy and 1H NMR. Surprisingly, the manisyl-containing complex turned out to be photochemically inert, indicating that a too bulky group acts as a protecting function versus decomplexation rather than as a destabilizing group. For the two other systems, a pronounced ring effect was observed: whereas the acyclic systems undergo fast photochemical expulsion of the bipy-based ligand, in the cyclic complex, the bipy-incorporating ring is decoordinated about 5 times less efficiently than the acyclic ligand of the previous case. These observations on the strong dependence of the photochemical behavior of the ruthenium(II) complexes on their structural properties are corroborated by X-ray diffraction studies on the three compounds investigated.     

Theoretical study on photooxidation mechanism of ruthenium complex [Ru(II)‐(bpy)2(TMBiimH2)]2+ with molecular oxygen

Photoinduced reactions of ruthenium complexes with molecular oxygen have attracted a lot of experimental attention; however, the reaction mechanism remains elusive. In this work, we have used the density functional theory method to scrutinize the visible‐light induced photooxidation mechanism of the ruthenium complex [Ru(II)‐(bpy)₂(TMBiimH₂)]²⁺ (bpy: 2, 2‐bipyridine and TMBiimH₂: 4, 5, 4, 5‐tetramethyl‐2, 2‐biimidazole) initiated by the attack of molecular oxygen. The present computational results not only explain very well recent experiments, also provide new mechanistic insights. We found that: (1) the triplet energy transfer process between the triplet molecular oxygen and the metal‐ligand charge transfer triplet state of the ruthenium complex, which leads to singlet molecular oxygen, is thermodynamically favorable; (2) the singlet oxygen addition process to the S₀ ruthenium complex is facile in energy; (3) the chemical transformation from endoperoxide to epidioxetane intermediates can be either two‐ or one‐step reaction (the latter is energetically favored). These findings contribute important mechanistic information to photooxidation reactions of ruthenium complexes with molecular oxygen. © 2016 Wiley Periodicals, Inc.     

[Ru(bpy)2(phen)]^2+主配体上双取代效应DFT法研究

对钌联吡啶菲咯啉配合物[Ru(bpy)2(phen)]^2+及其主配体(phen)上5,6-双取代衍生物,用密度泛函(DFT)法在B3LYP/LanL2DZ水平上进行理论计算研究。探讨供电子基团(OH)和拉电子基团(F)在主配体上的取代对配合物的电子结构及相关性质,如配合物前沿分子轨道的能量、组成、光谱性质、原子的净电荷布居及配位键长键角等的影响规律。计算结果表明,取代基对该系列取代衍生物的电子结构,特别是第一激发态的电子云分布影响较大,拉电子基团(F)能活化主配体,钝化辅助配体;而代电子基团(OH)则相反。无认是供电子基团(OH),还是拉电子基团(F)都导致取代衍生物的电子基谱带红移。此外,用基于极性交替规律及极性叠加概念的多系列箭头的图示方法对主配体上的原子净电荷布居的特征作了讨论。计算结果能较好地解释有关的实验现象与规律。     

Photophysical properties of [Ru(phen)2(dppz)]2+ intercalated into DNA: an integrated Car-Parrinello and TDDFT study

Combined Car-Parrinello and time-dependent DFT calculations performed on [Ru(phen)2dppz]2+ intercalated into an adenine-thymine tetramer reveal a remarkable influence of the base pairs in determining the electronic structure and the character of the excited states involved in the absorption and emission processes.     

Controlling substitution chemistry in ruthenium(II) systems. Synthesis of heteroleptic complexes incorporating the [Ru([9]aneS3)]2+ metal center

The complex [Ru(py)3([9]aneS3)][PF6]2, 1 (py = pyridine), has proved to be a suitable starting material for the synthesis of heteroleptic Ru(II) complexes. By exploiting unfavorable steric interactions between 2-H and 6-H hydrogens of coordinated pyridyl ligands, we have synthesized half-sandwich complexes incorporating the thiocrown [9]aneS3 and a variety of facially coordinated N-donor ligands. Such complexes are easily prepared: Stirring 1 at room temperature in the presence of a suitable nitrile ligand leads to the exclusive substitution of one py ligand to produce complexes such as [([9]aneS3)Ru(py)2(NCMe)][PF6]2, 2. However, if the same reaction is carried out at higher temperatures, two py ligands are substituted, leading to complexes such as [([9]aneS3)Ru(py)(NCMe)2][PF6]2, 3. An alternative approach to such heteroleptic species has also been developed which exploits the restricted ability of thioethers to neutralize positive charges through sigma-donation. This phenomenon allows the synthesis of heteroleptic complexes in a two-step procedure via monocationic species. By variation of the donor/acceptor properties of ligands incorporated into the [Ru([9]aneS3)]2+ metal center, it is possible to tune the Ru(III)/Ru(II) redox couple over a range of > 700 mV. The solid-state structures of 1-3 were confirmed by X-ray crystallography studies. Crystal data: C22H30F12N4O2P2RuS3 (1.CH3NO2), monoclinic, Cc, a = 23.267(5) A, b = 11.5457(18) A, c = 26.192(5) A, alpha = 90 degrees, beta = 114.836(10) degrees, gamma = 90 degrees, Z = 8; C18H25F12N3P2RuS3 (2), triclinic, P1, a = 11.3958(19) A, b = 11.4280(19) A, c = 11.930(2) A, alpha = 100.518(3) degrees, beta = 100.542(3) degrees, gamma = 112,493(3) degrees, Z = 2; C15H23F12N3P2RuS3 (3), orthorhombic, Pna2(1)), a = 14.748(5) A, b = 18.037(18) A, c = 10.341(5) A, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, Z = 4.     

New organometallic Ru(II) and Fe(II) complexes with tetrathia-[7]-helicene derivative ligands

A series of organometallic complexes possessing new tetrathia-[7]-helicene nitrile derivative ligands [TH-7] as chromophores, of general formula [MCp(P–P)(NC{TH-[7]-Y}Z)][PF₆] (M = Ru, Fe, P–P = DPPE, Y = H, NO₂, Z = H, C≡N; M = Ru, L–L = 2PPh₃, Y = H, Z = H) has been synthesized and fully characterized. ¹H NMR, FT-IR and UV–Vis. spectroscopic data were analyzed with in order to evaluate the existence of electronic delocalization from the metal centre to the coordinated ligand to have some insight on the potentialities of these new compounds as non-linear optical molecular materials. Slow crystallization of compound [RuCp(PPh₃)₂(NC{TH-[7]-H}H)][PF₆] 2Ru revealed an interesting isomerization of the helical ligand with formation of two carbon-carbon bonds between the two terminal thiophenes, leading to the total closure of the helix (2*Ru).     

Synthesis,characterization and DNA binding and photocleavage studies of [Ru(bpy)2BDPPZ]2+, [Ru(dmb)2BDPPZ]2+ and [Ru(phen)2BDPPZ]2+ complexes and their antimicrobial activity

Polypyridyl ligand 9a,13a‐dihydro‐4,5,9,14‐tetraaza‐benzo[b]triphenylene‐11‐yl)‐phenyl‐methanone (BDPPZ) and its complexes [Ru(bpy)₂BDPPZ]²⁺, [Ru(dmb)₂BDPPZ]²⁺ and [Ru(phen)₂BDPPZ]²⁺ (where bpy = 2,2′‐bipyridine, dmb = 4,4′‐dimethyl‐2,2′‐bipyridine, phen = 1,10‐phenanthroline) have been synthesized and characterized by elemental analysis, IR, UV–vis, ¹H‐NMR, ¹³C‐NMR and mass spectra. The DNA‐binding properties of the complexes were investigated by absorption, emission, melting temperature and viscosity measurements. Experimental results indicate that the three complexes can intercalate into DNA base pairs. Photo activated cleavage of pBR‐322 DNA by the three complexes was also studied. Further, all three Ru(II) complexes synthesized were screened for their antimicrobial activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Schiff base complexes of ruthenium(II) with tridentateN-methyl-S-methyldithiocarbazate ligands

Summary Schiff bases (HL) produced by the condensation ofN-methyl-S-methyldithiocarbazate with -diketones and aromatic aldehydes or ketones react with [RuHClCO(PPh₃)₃] to yield hexacoordinated complexes of the type [RuClCO(PPh₃)₂(L)]. These Schiff bases react with [RuCl₂{P(OR)₃}₄] in 11 molar ratio to yield [RuCl{P(OR)₃}₂(L)] in which L is a tridentate. The chlorine atom in the complex can be removed in coordinating solvents in the presence of anions such as [BPh₄]^– to give cationic complexes. Bis chelate complexes, [Ru{P(OR)₃}₂(L)₂] are prepared from 12 molar proportions of the reactants. These complexes were characterised by elemental analyses, i.r.,¹H n.m.r., u.v. and conductivity studies.NCL Communication No. 4224.     

Photophysical study of a family of [Ru(phen)2(Me n dpq)]2+ complexes in different solvents and DNA: a specific water effect promoted by methyl substitution

The synthesis and spectroscopic characterisation of a family of ruthenium complexes [Ru(phen)(2)(Me(n)dpq)](2+)(n= 0, 1, 2) are reported and the photophysical effect of the progressive methyl substitution on the dpq ligand ascertained in a range of solvents and in the presence of DNA: [Ru(phen)(2)(dpq)](2+)(1), [Ru(phen)(2)(Medpq)](2+)(2) and [Ru(phen)(2)(Me(2)dpq)](2+)(3)(where dpq is dipyrido[3,2-f:2',3'-h]-quinoxaline; Medpq is 2-methyldipyrido[3,2-f:2',3'-h]-quinoxaline; Me(2)dpq is 2,3-dimethyldipyrido[3,2-f:2',3'-h]-quinoxaline and phen is 1,10-phenanthroline). The increase in electron density following substitution renders the quinoxaline nitrogen atoms more basic in the ground state to yield pK(a) values of -1.9, -2.3, and -2.7 for 3, 2, and 1, respectively. The methyl groups have a pronounced effect on the excited state photophysics of 1-3. In organic solvents, the non-radiative decay constant correlates well with the solvent polarity parameter pi*, with the effect being more pronounced with increasing methyl substitution. On the contrary, in aqueous solution there is a ca. four-fold decrease in the non-radiative decay constant upon methyl substitution. This "specific water effect" may be explained in terms of deactivation of the excited state by hydrogen bonding interactions between water and the quinoxaline nitrogen atoms, which is reduced on moving from 1 to 3. The excited state lifetimes and luminescence intensities for substantially increase when bound to DNA in aerated aqueous solutions, with a six-fold increase, compared to a more moderate three-fold increase for 2 and 3.     

Unusual sandwich platinum(II) complex: [Pt(phen)2]2+ cation between two Pt(phen)(OOCMe)2 molecules

New carboxylate platinum(II) complexes: syn and anti isomers of Pt(phen)(OOCMe)₂ molecular complex, [Pt(phen)(NCMe)₂](O₃SCF₃)₂, as well as unusual sandwich complex [Pt(phen)₂]²⁺ · 2syn-[Pt(phen)(OOCMe)₂] where [Pt(phen)₂]²⁺ cation is inserted between two syn-Pt(phen)(OOCMe)₂ molecules were synthesized and structurally characterized by X-ray diffraction analysis. As distinct from syn- and anti-Pt(phen)(OOCMe)₂ and [Pt(phen)(NCMe)₂](O₃SCF₃)₂ complexes with flat phenanthroline ligand, the phen ligands in [Pt(phen)₂]²⁺ cation have a curved configuration. Comparative DFT analysis of geometry of model structures phen, phen⁺, phenH⁺, and [Ptphen₂] ⁿ⁺ (n = 1, 2) showed that electron removal from phen molecule had no effect on its geometry in both free state and platinum(II) complexes.