Synthesis and characterization of rigid +2 and +3 heteroleptic dinuclear ruthenium(II) complexes

Synthesis and characterization of the dinuclear ruthenium coordination complexes with heteroleptic ligand sets, [Cl(terpy)Ru(tpphz)Ru(terpy)Cl](PF₆)₂(7) and [(phen)₂Ru(tpphz)Ru(terpy)Cl](PF₆)₃(8), are reported. Both structures contain a tetrapyrido[3,2-α:2′,3′-c:3′′,2′′-h:2′′,3′′-j]phenazine (tpphz) (6) ligand bridging the two metal centers. Complex 7 was obtained via ligand exchange between, RuCl₂(terpy)DMSO (5) and a tpphz bridge. Complex 8 was obtained via ligand exchange between, [Ru(phen)₂tpphz](PF₆)₂(4) and RuCl₂(terpy)DMSO (5). Metal-to-ligand-charge-transfer (MLCT) absorptions are sensitive to ligand set composition and are significantly red-shifted due to more electron donating ligands. Complexes 7–9 have been characterized by analytical, spectroscopic (IR, NMR, and UV–Vis), and mass spectrometric techniques. The electronic spectral properties of 7, 8, and [(phen)₂Ru(tpphz)Ru(phen)₂](PF₆)₄(9), a previously reported +4 analog, are presented together. The different terminal ligands of 7, 8, and 9 shift the energy of the MLCT and the π–π* transition of the bridging ligand. These shifts in the spectra are discussed in the context of density functional theory (DFT). A model is proposed suggesting that low-lying orbitals of the bridging ligand accept electron density from the metal center which can facilitate electron transfer to nanoparticles like single walled carbon nanotubes and colloidal gold.     

NO donors cis-[Ru(bpy)2(L)NO] and [Fe(CN)4(L)NO] complexes immobilized on modified mesoporous silica spheres

The reaction of [Ru(bpy)₂Cl₂] and Na₂[Fe(CN)₄(dmso)₂] complexes with isonicotinic acid immobilized on silica spheres (Si-ATPS-ISN) followed by a NO bubbling produced Si-ATPS-ISN-[Ru(bpy)₂(NO)] (system I) and Si-ATPS-ISN-[Fe(CN)₄(NO)] (system II). The characterization of these systems was carried out by UV–Vis, FTIR spectroscopy and electrochemical techniques. As judged by the FTIR data, the nitric oxide ligand has an NO⁺ character in both systems (ν(NO⁺): 1938 cm⁻¹). The NO release, which was monitored by means of FTIR, electrochemistry, and NO sensor electrode, was observed for both systems upon white light irradiation and chemical reduction by cysteine. These results indicated that the system (II) presents a higher potential for controlled NO release. The characterization (FTIR and UV–Vis) of the systems after the NO release suggested the formation of the aqua systems ATPS-ISN-[Ru(bpy)₂(OH₂)] and ATPS-ISN-[Ru(bpy)₂(OH₂)].     

Synthesis of tridentate 2,6-bis(imino)pyridyl aminechlorohydro ruthenium(II) complexes: The convenient use of amine hydrochlorides to generate metal-hydride

The reaction of low-valent ruthenium complexes with 2,6-bis(imino)pyridine ligand, [η²-N₃]Ru(η⁶-Ar) (1) or {[N₃]Ru}₂(μ-N₂) (2) with amine hydrochlorides generates six-coordinate chlorohydro ruthenium (II) complexes with amine ligands, [N₃]Ru(H)(Cl)(amine) (4). Either complex 1 or 2 activates amine hydrochlorides 3, and the amines coordinate to the ruthenium center to give complex 4. This is a convenient and useful synthetic approach to form ruthenium complexes with amine and hydride ligands using amine hydrochloride.     

Comparative reactivity studies of dppf-containing CpRu and (C6Me6)Ru complexes towards different donor ligands (dppf=1,1-bis(diphenylphosphino)ferrocene)

[CpRu(dppf)Cl] (Cp=η⁵-C₅H₅) (1) and [(HMB)Ru(dppf)Cl]PF₆ ((HMB)=η⁶-C₆Me₆) (3) react with different donor ligands to give rise to N-, P- and S-bonded complexes. The stoichiometric reactions of 1 and 3 with NaNCS give the mononuclear complexes [CpRu(dppf)(NCS)] (2) and [(HMB)Ru(dppf)(NCS)]PF₆ (4), respectively, in yields above 80%, while 3 also gives a dppf-bridged diruthenium complex [(HMB)Ru(NCS)₂]₂(μ-dppf) (5) in 67% yield from reaction with four molar equivalents of NaNCS. Compound 5 is also obtained in 70% yield from the reaction of 4 with excess NaNCS. With CH₃CN in the presence of salts, both 1 and 3 give their analogous solvento derivatives [CpRu(dppf)(CH₃CN)]BPh₄ (6) and [(HMB)Ru(dppf)(CH₃CN)] (PF₆)₂ (7). With phosphines, the reaction of 1 gives chloro-displaced complexes [(CpRu(dppf)L]PF₆ (L =PMe₃ (8), PMe₂Ph(9)), whereas the reaction of 3 with PMe₂Ph leads to substitution of dppf, giving [(HMB)Ru(PMe₂Ph)₂Cl] PF₆ (10). The reaction of 1 with NaS₂CNEt₂ gives a dinuclear dppf-bridged complex [{CpRu(S₂CNEt₂)}₂(μ-dppf)] (11), whereas that of 3 results in loss of the HMB ligand giving a mononuclear complex [Ru(dppf)(S₂CNEt₂)₂] (12). With elemental sulfur S₈, 1 is oxidized to give a dinuclear CpRu^III dppf-chelated complex [{CpRu(dppf)}₂(μ-S₂)](BPh₄)Cl (13), whereas 3 undergoes oxidation at the ligand, giving a dppf-displaced complex [(HMB)Ru(CH₃CN)₂Cl]PF₆ (14) and free dppfS₂. The structures of 1, 2, 5-9, 11, 13 and 14 were established by X-ray single crystal diffraction analyses. Of these, 5 and 11 both contain a dppf-bridge between Ru^II centers, while 13 is a dinuclear CpRu^III disulfide-bridged complex; all the others are mononuclear. All complexes obtained were also spectroscopically characterized.     

Preparation, characterization, and catalytic properties of ruthenium nitrosyl complexes with polypyrazolylmethane ligands

Ruthenium(II) nitrosyl complexes with polypyrazolylmethanes, [(Bpm)Ru(NO)Cl₃] [Bpm = bis(1-pyrazolyl)methane, 1], [(Bpm^∗)Ru(NO)Cl₃] [Bpm^∗ = bis(3,5-dimethyl-1-pyrazolyl)methane, 2], [(Tpm)Ru(NO)Cl₂][PF₆] [Tpm = tris(1-pyrazolyl)methane, 3], and [(Tpm^∗)Ru(NO)Cl₂][PF₆] [Tpm^∗ = tris(3,5-dimethyl-1-pyrazolyl)methane, 4], have been synthesized and characterized. The solid-state structures of [(Bpm^∗)Ru(NO)Cl₃] (2) and [(Tpm^∗)Ru(NO)Cl₂][PF₆] (4) were determined by single-crystal X-ray crystallographic analyses. These complexes have been tested as catalysts in the transfer hydrogenation of several ketones under mild conditions.     

Synthesis,characterization, DNA-binding and DNA-photocleavage studies of [Ru(bpy)2(pmip)] and [Ru(phen)2(pmip)] (pmip = 2-(2′-pyrimidyl)imidazo[4,5-f][1,10]phenanthroline

Two new Ru(II) complexes, [Ru(bpy)₂(pmip)]²⁺ (1) and [Ru(phen)₂(pmip)]²⁺ (2), have been synthesized and characterized by elemental analysis, ESI-MS and ¹H NMR spectra. Their DNA-binding properties were studied by means of UV–VIS, emission and CD spectra, thermal denaturation and viscosity measurements as well as their DNA-photocleavage properties. The experimental results show that both 1 and 2 can bind to DNA in an intercalative mode; the DNA-binding affinity of 2 is greater than that of 1, which suggests that the ancillary ligands have a significant effect on the spectroscopic properties and DNA-binding behavior of the Ru(II) complexes. Under irradiation with UV light, the Ru(II) complexes show excellent efficiency of cleaving DNA. This research may provide valuable insight into the interactions of metal complexes with DNA, knowledge that is an excellent backdrop for the rational design of promising drugs.     

Synthesis, photochemistry, and electrochemistry of ruthenium(II) polypyridyl complexes anchored by dicobalt carbonyl units

A novel hybrid complex system of ruthenium polypyridyl complexes anchored by dicobalt carbonyl units, [Ru(bpy)₂{phen-C{Co₂(CO)₄(dppm)}C-tolyl}](PF₆)₂ (1) and [Ru(bpy)₂{tolyl-C{Co₂(CO)₄(dppm)}C-phen-C{Co₂(CO)₄(dppm)}C-tolyl}](PF₆)₂ (2), has been prepared from the dicobalt carbonyl complex Co₂(CO)₆(dppm) (dppm = bis(diphenylphosphino)methane) and the ruthenium complex [Ru(bpy)₂(phen--tolyl)](PF₆)₂ (3) or [Ru(bpy)₂(tolyl--phen--tolyl)](PF₆)₂ (4).The present Ru-Co₂ hybrid complexes 1 and 2 are nonluminescent at room temperature, although precursor ruthenium polypyridyl complexes, such as 3 and 4, clearly show phosphorescence from the ³MLCT excited state. The emission quenching of these hybrid complexes indicates the intramolecular energy transfer from the ruthenium polypyridyl unit to the dicobalt carbonyl unit(s) and then to the ground state by a radiationless deactivation process accompanied by a vibrational relaxation of the dicobalt carbonyl unit(s). This interpretation is supported by spectral change measurements along with constant potential electrolysis and electrochemical data.     

Synthesis and characterisation of new pyrazole-phosphinite ligands and their ruthenium(II) arene complexes

The new potentially bidentate pyrazole-phosphinite ligands [(3,5-dimethyl-1H-pyrazol-1-yl)methyl diphenylphosphinite] (L¹) and [2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl diphenylphosphinite] (L²) were synthesised and characterised. The reaction of L¹ and L² with the dimeric complexes [Ru(η⁶-arene)Cl₂]₂ (arene = p-cymene, benzene) led to the formation of neutral complexes [Ru(η⁶-arene)Cl₂(L)] (L = L¹, L²) where the pyrazole-phosphinite ligand is κ¹-P coordinated to the metal. The subsequent reaction of these complexes with NaBPh₄ or NaBF₄ produced the [Ru(η⁶-p-cymene)Cl(L²)][BPh₄] and [Ru(η⁶-benzene)Cl(L²)][BF₄] compounds which contain the pyrazole-phosphinite ligand κ²-P,N bonded to ruthenium. All the complexes were fully characterised by analytical and spectroscopic methods. The structure of the complex [Ru(η⁶-p-cymene)Cl(L²)][BPh₄] was also determined by a X-ray single crystal diffraction study.     

Bio-catalysts and catalysts based on ruthenium(II) polypyridyl complexes imparting diphenyl-(2-pyridyl)-phosphine as a co-ligand

Reactions of the ruthenium complexes [Ru(κ³-tpy)(PPh₃)Cl₂], [Ru(κ³-tptz)(PPh₃)Cl₂] and [Ru(κ³-tpy)Cl₃] [tpy = 2,2′:6′,2′′-terpyridine; tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine] with diphenyl-(2-pyridyl)-phosphine (PPh₂Py) have been investigated. The complexes [Ru(κ³-tpy)(PPh₃)Cl₂] and [Ru(κ³-tptz)(PPh₃)Cl₂] reacted with PPh₂Py to afford [Ru(κ³-tpy)(κ¹-P-PPh₂Py)₂Cl]⁺ (1) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py)₂Cl]⁺ (2), which were isolated as their tetrafluoroborate salts. Under analogous conditions, [Ru(κ³-tpy)Cl₃] gave a neutral complex [Ru(κ³-tpy)(κ¹-PPh₂Py)Cl₂] (3). Upon treatment with an excess of NH₄PF₆ in methanol, 1 and 2 gave [Ru(κ³-tpy)(κ¹-P-PPh₂Py)(κ²-P,N-PPh₂Py)](PF₆)₂ (4) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py)(κ²-P,N-PPh₂Py)](PF₆)₂ (5) containing both monodentate and chelated PPh₂Py. Further, 4 and 5 reacted with an excess of NaCN and CH₃CN to afford [Ru(κ³-tpy)(κ¹-P-PPh₂Py)₂(CN)](PF₆) (6), [Ru(κ³-tpy)(κ¹-P-PPh₂Py)₂(NCCH₃)](PF₆)₂ (7), [Ru(κ³-tptz)(κ¹-P-PPh₂Py)₂(CN)]PF₆ (8) and [Ru(κ³-tptz)(κ¹-P-PPh₂Py)₂(NCCH₃)](PF₆)₂ (9) supporting hemi labile nature of the coordinated PPh₂Py. The complexes have been characterized by elemental analyses, spectral (IR, NMR, electronic absorption, FAB-MS), electrochemical studies and structures of 1, 2 and 3 determined by X-ray single crystal analyses. At higher concentration level (40 μM) the complexes under investigation exhibit inhibitory activity against DNA-Topo II of the filarial parasite S. cervi and 3 catalyses rearrangement of aldoximes to amide under aerobic conditions.     

Synthesis and properties of novel crown ether-annelated 4′,5′-diaza-9′-(1,3-dithiole-2-ylidene)-fluorenes and their ruthenium(II) complexes

Two novel redox-active 1,3-dithiole (DT) ring-fused 4,5-diazafluorene ligands with crown ether moieties (L1 and L2) were synthesized and characterized. The crystal structure of L1 was studied. The electrochemical and spectroscopic properties of these new ligands, as well as the corresponding bis(bipyridine)ruthenium(II) complexes [4: Ru L1(bpy)₂ and 5: Ru L2(bpy)₂], were also been investigated.     

Synthesis and structural characterization of novel ruthenium(II) complexes featuring an N,N,O-scorpionate ligand: A versatile synthetic precursor for open-face scorpionatoruthenium(II) complexes

The syntheses and characterization of novel ruthenium(II) complexes containing bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza), a new class of scorpionate ligands, are reported herein. [RuCl(bdmpza)(η⁴-1,5-cyclooctadiene)] (1) was found to be a versatile precursor to synthesize a wide range of new ruthenium(II) complexes with the bdmpza ligand. The treatment of 1 with pyridine (py), diphenylphosphinoethane (dppe), 2,2′-bipyridyl (bpy), 1,10-phenanethroline (phen), or bispicolylamine (Hbpica) in refluxing N,N-dimethylformamide resulted in displacement of the 1,5-cyclooctadiene ligand to afford [RuCl(bdmpza)(py)₂] (2), [RuCl(bdmpza)(dppe)] (3), [RuCl(bdmpza)(bpy)] (4), [RuCl(bdmpza)(phen)] (5), and [Ru(bdmpza)(Hbpica)]Cl (6Cl) in good yields, respectively. The structures of 1–4, and 6 were determined by X-ray structure analyses.     

Synthesis,characterization, DNA-binding and DNA-photocleavage studies of [Ru(bpy)2(BPIP)] and [Ru(phen)2(BPIP)] (BPIP = 2-(4′-biphenyl)imidazo[4,5-f][1,10]phenanthroline)

New ligand 2-(4′-biphenyl)imidazo[4,5-f][1,10]phenanthroline (BPIP) and its complexes [Ru(bpy)₂(BPIP)]²⁺ (1) (bpy = 2,2′-bipyridine) and [Ru(phen)₂(BPIP)]²⁺ (2) (phen = 1,10-phenanthroline) have been synthesized and characterized by mass spectroscopy, ¹H NMR and cyclic voltammetry. The interaction of two Ru(II) complexes with calf thymus DNA (CT-DNA) was investigated by spectroscopic and viscosity measurements. Results indicate that both complexes bind to DNA via an intercalative mode and the DNA-binding affinity of complex 2 is much greater than that of complex 1. Furthermore, when irradiated at 365 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA.     

Synthesis and structures of metallocene complexes of iron(II) and ruthenium(II) derived from 9,9′-spirobifluorene

Reaction between 9,9′-spirobifluorene and [CpM]⁺ (where M = Fe and Ru) equivalents gives the complexes [CpRu(η⁶-SBF)][PF₆] (1), [(CpRu)₂(η⁶,η⁶-SBF)][PF₆]₂ (2) and [(CpFe)₂(η⁶,η⁶-SBF)][PF₆]₂ (3), respectively. Single crystal X-ray structures of 1 and 3 show that the metal atoms exhibit distorted η⁶-coordination to SBF phenyl moieties primarily as a consequence of steric interactions between Cp and SBF. The structure of 3 contains each of the possible C₂ enantiomers whereas NMR spectroscopy shows signals consistent with a 1:1 mixture of C₂ and C₁ stereoisomers for both 2 and 3. In conjunction with electrochemical data the observations are consistent with SBF acting as a molecule containing two independent biphenyl moieties.     

Synthesis and characterization of some novel ruthenium(II) complexes containing thiolate ligands

Reactions of the ruthenium complexes [RuH(CO)Cl(PPh₃)₃] and [RuCl₂(PPh₃)₃] with hetero-difunctional S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL¹), 2-mercapto-4-methyl-5-thiazoleacetic acid (HL²), and 2-mercaptobenzothiazole (HL³) have been investigated. Neutral complexes [RuCl(CO)(PPh₃)₂(HL¹)] (1), [RuCl(CO)(PPh₃)₂(HL²)] (2), [RuCl(CO)(PPh₃)₂(HL³)] (3), [Ru(PPh₃)₂(HL¹)₂] (4), [RuCl(PPh₃)₃(HL²)] (5), and [RuCl(PPh₃)₃(HL³)] (6) imparting κ²-S,N-bonded ligands have been isolated from these reactions. Complexes 1 and 4 reacted with diphenyl-2-pyridylphosphine (PPh₂Py) to give neutral κ¹-P bonded complexes [RuCl(CO)(κ¹-P-PPh₂Py)₂(HL¹)] (7), and [Ru(κ¹-P-PPh₂Py)₂(HL¹)₂] (8). Complexes 1-8 have been characterized by analytical, spectral (IR, NMR, and electronic absorption) and electrochemical studies. Molecular structures of 1, 2, 4, and 7 have been determined crystallographically. Crystal structure determination revealed coordination of the mercapto-thiadiazole ligands (HL¹-HL³) to ruthenium as κ²-N,S-thiolates and presence of rare intermolecular S-S weak bonding interaction in complex 1.     

Syntheses and characterization of cyano-bridged homo and hetero bimetallic complexes containing η and η-cyclic hydrocarbons

The reactions of [(ind)Ru(PPh₃)₂CN] (ind = η⁵-C₉H₇) (1) and [CpRu(PPh₃)₂CN] (Cp = η⁵-C₅H₅) (2) with [(η⁶-p-cymene)Ru(bipy)Cl]Cl (bipy = 2,2′-bipyridine) (3) in the presence of AgNO₃/NH₄BF₄ in methanol, respectively, yielded dicationic cyano-bridged complexes of the type [(ind)(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (4) and [Cp(PPh₃)₂Ru(μ-CN)Ru(bipy)(η⁶-p-cymene)](BF₄)₂ (5). The reaction of [CpRu(PPh₃)₂CN] (2), [CpOs(PPh₃)₂CN] (6) and [CpRu(dppe)CN] (7) with the corresponding halide complexes and [(η⁶-p-cymene)RuCl₂]₂ formed the monocationic cyano-bridge complexes [Cp(PPh₃)₂Ru(μ-CN)Os(PPh₃)₂Cp](BF₄) (8), [Cp(PPh₃)₂Os(μ- CN)Ru(PPh₃)₂Cp](BF₄) (9) and [Cp(dppe)Ru(μ-CN)Os(PPh₃)₂Cp](BF₄) (10) along with the neutral complexes [Cp(PPh₃)₂Ru(μ-CN)Ru (η⁶-p-cymene)Cl₂] (11), [Cp(PPh₃)₂Os(μ-CN)Ru(η⁶-p-cymene)Cl₂] (12), and [Cp(dppe) Ru(μ-CN)Ru(η⁶-p-cymene)Cl₂] (13). These complexes were characterized by FT IR, ¹H NMR, ³¹P{¹H} NMR spectroscopy and the molecular structures of complexes 4, 8 and 11 were solved by X-ray diffraction studies.     

Preparation and reactivity of osmium(II) hydride complexes with phosphites and polypyridyls

Chloro-complexes [OsCl(N-N)P₃]BPh₄ (1, 2) [N-N=2,2^′-bipyridine (bpy) and 1,10-phenanthroline (phen); P=P(OEt)₃ and PPh(OEt)₂] were prepared by allowing OsCl₄(N-N) to react with zinc dust in the presence of phosphites. Treatment of the chloro-complexes 1, 2 with NaBH₄ yielded, in the case of bpy, the hydride [OsH(bpy)P₃]BPh₄ (4) derivatives. Mono-phosphite [OsCl(bpy)₂P]BPh₄ (3) complexes were also prepared by reacting the [OsCl₂(bpy)₂]Cl compound with zinc dust in the presence of phosphite. Protonation reaction of the hydride [OsH(bpy)P₃]⁺ (4) cations with Brønsted acid was studied and led to thermally unstable (above 0 °C) dihydrogen [Os(η²-H₂)(bpy)P₃]²⁺ (4*) derivatives. The presence of the H₂ ligand is supported by variable-temperature NMR spectra and T_1min measurements. Carbonyl [Os(CO)(bpy){P(OEt)₃}₃](BPh₄)₂ (5), nitrile [Os(CH₃CN)(bpy){P(OEt)₃}₃](BPh₄)₂ (6), and hydrazine [Os(bpy)(NH₂NH₂){P(OEt)₃}₃](BPh₄)₂ (7) complexes were prepared by substituting the H₂ ligand in the η²-H₂ (4*) derivatives. Aryldiazene complex [Os(C₆H₅NNH)(bpy){P(OEt)₃}₃](BPh₄)₂ (8) was also obtained by allowing the hydride [OsH(bpy)P₃]BPh₄ to react with phenyldiazonium cation.     

Ferrocene bridged and substituted tetramethylcyclopentadienyl (or indenyl) carbonyl complexes of iron, ruthenium, and molybdenum

Reactions of ferrocene bridged and substituted tetramethylcyclopentadiene ligands 1,1′-Fc(C₅Me₄H)₂ (1) (Fc = 1,1′-ferrocenediyl) and (C₅H₅FeC₅H₄)C₅Me₄H (5) with Ru₃(CO)₁₂, Fe(CO)₅, and Mo(CO)₃(CH₃CN)₃ in refluxing xylene gave the corresponding trinuclear and tetranuclear complexes Fc[(C₅Me₄)M(CO)]₂(μ-CO)]₂ [M = Ru (2), Fe (3)], Fc[(C₅Me₄)Mo(CO)₃]₂ (4) and [(C₅H₅ FeC₅H₄)C₅Me₄M(CO)]₂(μ-CO)₂ [M = Ru (6), Fe (7)], [(C₅H₅FeC₅H₄)C₅Me₄Mo(CO)₃]₂ (8). Reactions of (3-indenyl)ferrocene (9) with Ru₃(CO)₁₂ or Fe(CO)₅ in refluxing xylene or heptane, also gave the corresponding tetranuclear metal complexes [(C₅H₅FeC₅H₄)C₉H₆M(CO)]₂(μ-CO)₂ [M = Ru (10), Fe (11)]. The molecular structures of 2 and 3 were determined by X-ray diffraction analysis.     

Cationic arene ruthenium complexes containing chelating 1,10-phenanthroline ligands

The monocationic chloro complexes containing chelating 1,10-phenanthroline (phen) ligands [(arene)Ru(N∩N)Cl]⁺ (1: arene = C₆H₆, N∩N = phen; 2: arene = C₆H₆, N∩N = 5-NO₂-phen; 3: arene = p-MeC₆H₄Prⁱ, N∩N = phen; 4: arene = p-MeC₆H₄Prⁱ, N∩N = 5-NO₂-phen; 5: arene = C₆Me₆, N∩N = phen; 6: arene = C₆Me₆, N∩N = 5-NO₂-phen; 7: arene = C₆Me₆, N∩N = 5-NH₂-phen) have been prepared and characterised as the chloride salts. Hydrolysis of these chloro complexes in aqueous solution gave, upon precipitation of silver chloride, the corresponding dicationic aqua complexes [(arene)Ru(N∩N)(OH₂)]²⁺ (8: arene = C₆H₆, N∩N = phen; 9: arene = C₆H₆, N∩N = 5-NO₂-phen; 10: arene = p-MeC₆H₄Prⁱ, N∩N = phen; 11: arene = p-MeC₆H₄Prⁱ, N∩N = 5-NO₂-phen; 12: arene = C₆Me₆, N∩N = phen; 13: arene = C₆Me₆, N∩N = 5-NO₂-phen; 14: arene = C₆Me₆, N∩N = 5-NH₂-phen), which have been isolated and characterised as the tetrafluoroborate salts. The catalytic potential of the aqua complexes 8-14 for transfer hydrogenation reactions in aqueous solution has been studied: complexes 12 and 14 catalyse the reaction of acetophenone with formic acid to give phenylethanol and carbon dioxide with turnover numbers around 200 (80 °C, 7 h). In the case of 12, it was possible to observe the postulated hydrido complex [(C₆Me₆)Ru(phen)H]⁺ (15) in the reaction with sodium borohydride; 15 has been characterised as the tetrafluoroborate salt, the isolated product [15]BF₄, however, being impure. The molecular structures of [(C₆Me₆)Ru(phen)Cl]⁺ (1) and [(C₆Me₆)Ru(phen)(OH₂)]²⁺ (12) have been determined by single-crystal X-ray structure analysis of [1]Cl and [12](BF₄)₂.     

Cellular uptake, cytotoxicity, apoptosis, antioxidant activity and DNA binding of polypyridyl ruthenium(II) complexes

Ruthenium(II) polypyridyl complexes [Ru(phen)₂(APIP)](ClO₄)₂1 and [Ru(phen)₂(HAPIP)](ClO₄)₂2 have been synthesized and characterized. The DNA-binding behaviors were investigated by electronic absorption titration, luminescence spectra, viscosity measurements, thermal denaturation and photoactivated cleavage. The DNA-binding constants K_b for complexes 1 and 2 were determined to be 3.38 (±0.42) × 10⁵ M⁻¹ (s = 1.48) and 3.93 (±0.60) × 10⁵ M⁻¹ (s = 3.14), respectively. The studies on the photocleavage demonstrated that the effects of cleavage are concentration-dependent. The results showed that complexes 1 and 2 interact with CT-DNA by intercalative mode. The cytotoxicity of complexes 1 and 2 has been evaluated by MTT method. The apoptosis assay was carried out with acridine orange/ethidium bromide (AO/EB) staining methods. The cellular uptake showed that complexes can enter into the cytoplasm and accumulate in the nuclei. The antioxidant activity studies suggested that the ligands and complexes may be potential drugs to eliminate the radical.     

Synthesis,crystal structure and DNA-binding properties of ruthenium(II) polypyridyl complexes with dicationic 2,2′-dipyridyl derivatives as ligands

New Ru(II) complexes with dicationic ligand, [Ru(phen)₂L¹]⁴⁺(1) and [Ru(phen)₂L²]⁴⁺(2) (phen = 1,10-phenanthroline; L: L¹ = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L² = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation) have been synthesized and structurally characterized. The interaction of these complexes with calf thymus DNA (CT-DNA) has been investigated. The intrinsic binding constants (K_b: 1, 7.73 × 10⁴ M⁻¹; 2, 2.50 × 10⁴ M⁻¹) determined by absorption spectral titrations of these complexes with CT-DNA indicate the DNA-binding affinity of 1 is stronger than that of 2. Both complexes can display luminescence either alone in aqueous solution or in the presence of DNA. Equilibrium dialysis experiments monitored by CD spectroscopy reveal the preferential binding of the Δ-enantiomer to the right-handed CT-DNA. DNA-viscosity studies suggest that the binding modes are different, 1 may partially intercalate between DNA base-pairs while 2 most likely interact with DNA in an electrostatic binding mode.