Effect of ligand congeniality on energy transfer reaction between photo-excited tris(bipyridine)ruthenium(II) and chromate(III) complexes in aqueous solutions

Energy-transfer rate-constants from photo-excited [Ru(N–N)₃]²⁺ (N–N = 2,2′-bipyridine (bpy), 4,4′-dimethyl-2,2′-bipyridine (4dmb), 5,5′-dimethyl-2,2′-bipyridine (5dmb)) to [Cr(O–O)₃]³⁻ (O–O²⁻ = ox²⁻ ((COO⁻)₂), mal²⁻ (CH₂(COO⁻)₂)) and [Cr(CN)₆]³⁻ in encounter complexes were evaluated in aqueous solutions containing alkali metal ion. The rate constant depends on the molecular size of the ruthenium(II) complex: 1.8 × 10⁸ s⁻¹ for [Ru(bpy)₃]²⁺ (molecular radius, r = 5.8 Å), 1.4 × 10⁸ s⁻¹ for [Ru(5dmb)₃]²⁺ (r = 6.1 Å) and 0.96 × 10⁸ s⁻¹ for [Ru(4dmb)₃]²⁺ (r = 6.7 Å) in the system of [Ru(N–N)₃]²⁺–[Cr(ox)₃]³⁻ in aqueous solution. However, the rate constant is much more sensitive to the chromate(III) complex than to ruthenium(II) complex; 1.8 × 10⁸ s⁻¹ and 0.43 × 10⁸ s⁻¹ for [Cr(ox)₃]³⁻ (r = 4.0 Å) and [Cr(mal)₃]³⁻ (r = 4.2 Å) in the [Ru(bpy)₃]²⁺–[Cr(O–O)₃]³⁻ systems, respectively. We conclude that the congeniality between the donor’s and acceptor’s ligands in encounter complex plays an important role in energy transfer in aqueous solution.     

Novel Ru(II) oximato complexes with silent oxygen atom: Synthesis,chemistry and biological activities

A series of octahedral complexes, [Ru(CO)(EPh₃)₂(bhmh)] (E = P or As; H₂bhmh = benzoic acid (2-hydroxyimino-1-methyl-propylidene)-hydrazide), [Ru(CO)(EPh₃)₂(ihmh)] (H₂ihmh = isonicotinic acid (2-hydroxyimino-1-methyl-propylidene)-hydrazide), [Ru(CO)(EPh₃)₂(hhmh)] (H₂hhmh = 2-hydroxy-benzoic acid (2-hydroxyimino-1-methyl-propylidene)-hydrazide) have been prepared by a facile procedure. X-ray structure determination of three of the complexes revealed that the hydrazone ligand coordinates through the imine and the oxime nitrogen and the amide oxygen atoms. In all the complexes, the N–OH moiety of the oxime is deprotonated to give an N–O^? species and this oxygen atom did not coordinate to the central metal atom. The oxidation–reduction processes for each of these complexes have been determined in CH₃CN by cyclic voltammetry. The complexes displayed two oxidation couples and one irreversible reduction response between +1.6 and ?1.6 V. The trend in the half wave potentials reflects the electronic nature of the hydrazone ligand. Antibacterial activity of the ligands and the complexes has been evaluated against five pathogenic bacteria. The binding of the complexes with herring sperm DNA has also been investigated by UV–Vis spectroscopy and cyclic voltammetry.     

EPR and H NMR spectroscopy and DFT study of pentaammineruthenium(III)phenylcyanamide complexes

The EPR and ¹H NMR spectroscopy of seven [Ru(NH₃)₅L]²⁺ complexes, where L = 3,5-dimethoxyphenylcyanamide (MeO₂pcyd), 3,4,5-trimethoxyphenylcyanamide (MeO₃pcyd), 4-nitrophenylcyanamide (NO₂pcyd), 2,3-dichlorophenylcyanamide (Cl₂pcyd), 2,4,6-trichlorophenylcyanamide (Cl₃pcyd), 2,3,5,6-tetrachlorophenylcyanamide (Cl₄pcyd) and pentachlorophenylcyanamide (Cl₅pcyd), was performed. EPR spectra of the complexes showed an axial signal with g_|| and g_⊥ at high and low field, respectively. The g_|| axis is suggested to lie along the Ru-cyanamide bond. Gas-phase DFT calculations of [Ru(NH₃)₅ phenylcyanamide]²⁺ showed spin density localized mostly on the phenylcyanamide ligand, in disagreement with EPR data. DFT/polarizable continuum model (PCM, water solvation) calculations shifted spin density towards ruthenium so that spin density was shared between ruthenium and phenylcyanamide ligand. Proton contact shifts were determined from NMR and EPR data and were used to estimate spin density distributions on phenyl ring carbons. The results showed that the DFT/PCM calculation overestimated spin density on phenyl ring carbons by approximately one order of magnitude. Donor-acceptor interactions between the solute and solvent that are not fully accounted for in the DFT/PCM method are suggested to stabilize the Ru(III) oxidation state.     

Photochemical NO release from nitrosyl RuII complexes with C-bound imidazoles

The series of nitrosyl complexes trans-[Ru(NH₃)₄L(NO)]Cl₃, L = caffeine, theophylline, imidazole and benzoimidazole in position trans to NO were prepared and their photochemical properties studied. All complexes showed nitric oxide (NO) release under light irradiation at 330–440 nm. Quantum yields for [Ru(NH₃)₄L(H₂O)]³⁺ formation (?_Ru(III)) were sensitive to the natures of L, λ_irr and pH. The major product of the irradiation of trans-[Ru(NH₃)₄L(NO⁺)]³⁺ is the trans-[Ru^III(NH₃)₄L(Cl)]²⁺ and NO as suggested by UV–Vis, electrochemical, and FTIR techniques.     

Synthesis and characterization of tetraphenylporphyrin manganese(III) complexes of phenylcyanamide ligands

Several complexes of TPPMn-L, where TPP is the dianion of tetraphenylporphyrin and L is monoanion of 4-methylphenylcyanamide (4-Mepcyd) (1), 2,4-dimethylphenylcyanamide (2,4-Me₂pcyd) (2), 3,5-dimethylphenylcyanamide (3,5-Me₂pcyd) (3), 4-methoxyphenylcyanamide (4-MeOpcyd) (4), phenylcyanamide (pcyd) (5), 2-chlorophenylcyanamide (2-Clpcyd) (6), 2,5-dichlorophenylcyanamide (2,5-Cl₂pcyd) (7), 2,6-dichlorophenylcyanamide (2,6-Cl₂pcyd) (8), 4-bromophenylcyanamide (4-Brpcyd) (9), and 2,3,4,5-tetrachlorophenylcyanamide (2,3,4,5-Cl₄pcyd) (10), have been prepared from the reaction of TPPMnCl and thallium salt of related phenylcyanamide. Each of the complexes has been characterized by IR, UV-Vis and ¹H NMR spectroscopies.4-Methylphenylcyanamidotetraphenylporphyrin manganese(III) crystallized with one molecule of solvent CHCl₃ in the triclinic crystal system and space group with the following unit cell parameters of: a = 11.596(6) Å; b = 11.768(9) Å; c = 17.81(2) Å; and α, β, γ are 88.91(9)°, 88.16(7)°, 67.90(5)°, respectively; V = 2251(3) Å³; Z = 2. A total of 4234 reflections with I > 2σ(I) were used to refine the structure to R = 0.0680 and R_w = 0.2297. The Mn(III) shows slightly distorted square pyramidal coordination with the 4-methylphenylcyanamide in the axial position, coordinated from nitrile nitrogen. The reduction of each of the TPPMn-L complexes was also examined in dichloromethane and spectroelectrochemical behavior of (1) was investigated and compared to TPPMnCl.     

Structures,magnetic properties,and XPS of cyanide-bridged NdIII/SmIII/GdIII–CrIII complexes

Synthesis, structural characterization, and spectroscopic and magnetic properties of three new cyano-bridged 3d–4f bimetallic complexes, Ln^III(DMF)₄(H₂O)₃Cr^III (CN)₆ · nH₂O (Ln = Nd, Sm, Gd), have been described. The Nd–Cr complex crystallizes in the monoclinic P2₁/n space group with the following unit cell parameters: a = 20.063(7) Å, b = 8.967(4) Å, c = 18.023(6) Å, b = 96.12(3)°, V = 3224(2) Å³, and Z = 4. The neodymium (III) ion, which adopts anti-prism eight-coordination environment, is linked to the [Cr^III(CN)₆]³⁻ moiety through a bridging cyanide ligand with Nd–N = 2.550(4) Å and Nd–N–C = 164.4(4)°. The variable-temperature (0.5 T at 2–300 K) and variable-field (0–5 T at 2 and 5 K) magnetic measurements reveal that the weak interaction of Gd–Cr complexes differs from that of Nd–Cr and Sm–Cr ones mainly because of the lack of orbital angular momentum. The XPS and diffuse reflectance electronic spectra were also measured to discuss charge transfer transitions concerning π-backdonation from the viewpoint of magneto-optical functions.     

Synthesis,EPR, electrochemistry and EXAFS studies of ruthenium(III) complexes with a symmetrical tetradentate N2O2 Schiff base

A series of new hexa-coordinated ruthenium(III) complexes of the type [RuX(Nap-o-phd)(EPh₃)] (where, H₂-Nap-o-phd = N,N′-bis(2-hydroxy-1-naphthaldehyde) o-phenylene diamine; X = Cl or Br; E = P or As) have been prepared by reacting [RuX₃(EPh₃)₃] and [RuBr₃(PPh₃)₂(MeOH)] (where X = Cl or Br; E = P or As) with tetradentate Schiff base ligand (H₂-Nap-o-phd) in 1:1 molar ratio. The complexes have been characterized by elemental analyses, infra red, electronic, electron paramagnetic resonance spectroscopy and cyclic voltammetry. The coordination geometry and structure of the complexes have been investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy and an octahedral structure has been proposed.     

Synthesis,characterization and magnetic properties of six new copper(II) complexes with aminoacids as bridging ligand,exhibiting ferromagnetic coupling

The synthesis, crystallographic analysis and magnetic studies of six new copper(II) complexes of formulae [Cu(μ-ala)(im)(H₂O)]_n(ClO₄)_n (1), [Cu(μ-ala)(pz)(μ-ClO₄)] (2), [Cu(μ-phe)(im)(H₂O)]_n(ClO₄)_n (3), [Cu(μ-gly)(H₂O)(ClO₄)]_n (4), [Cu(μ-gly)(pz)(ClO₄)]_n(5) and [Cu(μ-pro)(pz)(ClO₄)]_n (6) have been carried out (ala = alanine; phe = phenylalanine; gly = glycine; pro = proline; im = imidazole; pz = pyrazole). In all cases, the deprotonated aminoacid ligand acts as chelate through the N(amine) and one O(carboxylato), whereas the second O atom of the same carboxylato acts as a bridge to the neighbouring copper(II) ion. The coordination of copper(II) ions is square-pyramidal in all complexes but 2 (elongated O_h). All complexes (1–6) are uniform chains with syn–anti (equatorial–equatorial) coordination mode of the carboxylato bridging ligand, exhibiting intrachain ferromagnetic interactions.     

Stability constants and multinuclear NMR measurements of phosphonic acid derivatives with aluminum in aqueous solutions

We are reporting the stability constants of the different complexes between phosphonoacetic acid (PAA), phosphonoformic acid (PFA), aminomethylphosphonic acid (AMPA), aminoethylphosphonic acid (AEPA) and methylenediphosphonic acid (MDP) with the aluminum metal ion in aqueous solutions. (In this study the term aluminum is reserved for the 3+ ion.) The affinity of the phosphonic acid derivatives to chelate aluminum has been tested by potentiometric titrations with I = 0.10 M KNO₃ at 25 ± 0.1 °C. The proposed aluminum–ligand complex structures have been confirmed by ³¹P NMR, ¹³C NMR, and ²⁷Al NMR experiments. Both PAA and PFA formed simple one to one complexes. The respective values for PAA are log β₁₁₁ = 13.57, log β₁₁₀ = 10.58, and log β₁₁₋₁ = 5.84. The respective values for PFA are log β₁₁₂ = 15.24, log β₁₁₁ = 13.11, and log β₁₁₀ = 6.88. In contrast to PAA and PFA, the major species formed with AMPA and AEPA consist of a series of dimeric complexes. The ³¹P NMR spectra of these complexes indicate that the amine groups do not co-ordinate to aluminum and remain protonated. In addition to these dimeric complexes, a monoprotonated monomer of Al–AMPA also has been detected. The ²⁷Al NMR experiments indicated that the aluminum is hexacoordinated in all the complexes in this study and the hydroxide ion did not remove aluminium from its complexes. Among the ligands studied, PAA and PFA were able to solubilize aluminum at physiological pH. A comparison between the acidities and the chelating properties of the ligands used is presented.     

Crystal structure,magnetic and thermal properties of the one-dimensional complex [Nd(pzam)3(H2O)Mo(CN)8] · H2O

The new d–f cyanido-bridged 1D assembly [Nd(pzam)₃(H₂O)Mo(CN)₈] · H₂O was prepared by self-assembly of pyrazine-2-carboxamide (pzam), Nd(NO₃) · nH₂O and (Bu₃NH)₃[Mo(CN)₈] · 4H₂O in acetonitrile. X-ray crystallographic studies indicate that the complex comprises chains of alternating, cyanido-bridged [Nd(pzam)₃(H₂O)]³⁺ and Mo(CN)₈]^3? fragments. The magneto-structural properties have been studied by field-dependent magnetization and specific heat measurements at low temperatures (?0.3 K). Below ≈10 K the Nd(III) moment is well approximated by an effective spin S = 1/2, with anisotropic g-tensor. The exchange coupling between the Nd(III) and the Mo(V) spins S = 1/2 along the structural chains is found to be ferromagnetic, with J/k_B = 1.8 ± 0.2 K and approximately XY (planar) anisotropy. No evidence for 3D interchain magnetic ordering is found. A comparison with magneto-structural data of other cyanido-bridged complexes involving the Nd(III) ion is presented.     

Synthesis,electrochemistry and spectroscopy of lanthanide(III) homodinuclear complexes bridged by polyazine ligands

Six new complexes [Eu(tta)₃]₂bpm, [Er(tta)₃]₂bpm, [Tb(tta)₃]₂bpm, [Er(tta)₃]₂dpp, Pr(tta)₃bpm and Nd(tta)₃bpm (tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, bpm = 2,2′-bipyrimidine, dpp = 2,3-bis(2-pyridyl)pyrazine) were prepared and studied. The electronic absorption spectra of the complexes display tta π → π* transitions in the UV region. Cyclic voltammetry of the complexes show an irreversible reduction followed by a reversible reduction both associated with the tta ligand. Eu(III) reduction in the homodinuclear [Eu(tta)₃]₂bpm complex occurs as an irreversible reduction at less negative potentials than the tta-based reductions. Emission spectra of the Eu(III) and Tb(III) bimetallics are typical of this type of bonding motif with ligand centered (tta) absorptions resulting in 4f–4f transitions in the visible and near infrared region.     

Design and synthesis of biphenyl derivatives as mushroom tyrosinase inhibitors

Two new series of biphenyls, analogs of aglycone of natural product fortuneanoside E, were prepared using Suzuki–Miyaura cross-coupling and selective magnesium iodide demethylation/debenzylation, and their mushroom tyrosinase inhibitory activity was evaluated. Most of the 4-hydroxy-3,5-dimethoxyphenyl biphenyl compounds (series II, 20–36) were in general more active than 3,4,5-trimethoxyphenyl biphenyl compounds (series I, 1–19). Structure–activity relationships study showed that monosaccharide substituents, such as glucose, were not necessary and the presence of 4-hydroxy-3,5-dimethoxyphenyl moiety was crucial for inhibitory activity. Among the compounds synthesised, compound 21 (IC₅₀ = 0.02 mM) was found to be the most active one, which exhibited an activity that was 7 times higher than that of fortuneanoside E (IC₅₀ = 0.14 mM) and 10 times higher than that of arbutin (IC₅₀ = 0.21 mM), known as potent tyrosinase inhibitors. The inhibition kinetics analyzed by Lineweaver–Burk plots revealed that compound 21 was a competitive inhibitor (K_i = 0.015 mM).     

[RuIII(medtra)(H2O)] (medtra = N-methylethylenediaminetriacetate) complex – A highly efficient NO inhibitor with low toxicity

Stopped-flow kinetic measurements were used to compare the reactivities of [Ru(medtra)(H₂O)] (medtra³⁻ = N-methylethylenediaminetriacetate) (1) and [Ru(hedtra)(H₂O)] (2) (hedtra³⁻ = N-hydroxyethylethylenediaminetriacetate) with NO in aqueous solution at 15 °C, pH 7.2 (phosphate buffer). The measured second-order rate constants (3 × 10³ and 6 × 10⁴ M⁻¹ s⁻¹ for 1 and 2, respectively) are three to four order of magnitudes lower than that for the reaction between [Ru^III(edta)(H₂O)]⁻ (3) with NO. However, NO scavenging studies of complexes 1–3, conducted by measuring the difference in nitrite production between treated and untreated murine macrophage cells, revealed that despite being less kinetically reactive toward NO, the [Ru(medtra)(H₂O)] complex exhibited the highest NO scavenging ability and lowest toxicity of compounds 1–3.     

Syntheses,structures, and magnetic properties of heterobimetallic complexes based on tetracyanometallic building blocks

Two tetracyanometalate building blocks, [Fe(5,5′-dmbipy)(CN)₄]^? (2) and [Fe(4,4′-dmbipy)(CN)₄]^? (3) (5,5′-dmbipy = 5,5′-dimethyl-2,2′-bipyridine; 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine), and two cyano-bridged heterobimetallic complexes, [Cu₂(bpca)₂(H₂O)₂Fe₂(5,5′-dmbipy)₂(CN)₈] · 2[Cu(bpca)Fe(5,5′-dmbipy)(CN)₄] · 4H₂O (4) and [Cu(bpca)Fe(4,4′-dmbipy)(CN)₄]_n (5) (bpca = bis(2-pyridylcarbonyl)amidate), have been synthesized and structurally characterized. Complex 4 contains two dinuclear and one tetranuclear heterobimetallic clusters in an asymmetric unit whereas the structure of complex 5 features a one-dimensional heterobimetallic zigzag chain. The Cu(II) ion is penta-coordinated in the form of a distorted square-based pyramid. Magnetic studies show ferromagnetic coupling between Cu(II) and Fe(III) ions with g = 2.28, J₁ = 2.64 cm^?1, J₂ = 5.40 cm^?1 and TIP = ?2.36 × 10^?3 for complex 4, and g = 2.17, J = 4.82 cm^?1 and zJ′ = 0.029 cm^?1 for complex 5.     

Synthesis,X-ray structures,and magnetic properties of heterometal dinuclear Cr(III)–M(II) complexes

New 3,5-bis(2-pyridyl)pyrazolato (bpypz) bridged heterometal dinuclear complexes [(nta)Cr(μ-bpypz)M^II(picen)]⁺ (M = Mn(II), Ni(II)) and [(acac)₂Cr(μ-bpypz)Ni^II(picen)]²⁺ (nta = nitrilotriacetate, picen = N,N′-bis(2-pyridylmethyl)ethylenediamine, acac = acetylacetate) were synthesized and characterized by the X-ray analysis, ESI-MS and the magnetic measurements, and/or ²H NMR spectra. The molecular structures were compared from a viewpoint of the conformation of the picen depending on M^II ionic radii or different modes of hydrogen bonds. The picen in [(nta)Cr(μ-bpypz)Mn^II(picen)]BF₄ takes an abnormal conformation with intramolecular bifurcated three-center hydrogen bonds between two carboxylate oxygens of nta and an amine proton of the picen as found for the previously reported corresponding Fe(II) complex [K. Ni-iya, A. Fuyuhiro, T. Yagi, S. Nasu, K. Kuzushita, S. Morimoto, S. Kaizaki, Bull. Chem. Soc. Jpn. 74 (2001) 1891]. On the other hand, for both Ni(II)-nta and Ni(II)-acac complexes, the picen takes a normal conformation with only a two-center hydrogen bond between non-bridging ligands. The magneto-structural relation is discussed for the Cr(III)–Ni(II) complexes in connection with the orthogonality or orbital overlap arising from the difference in distortion around Cr(III) moiety.     

Association of urinary 15-F2t-isoprostane level with oxygen desaturation and carotid intima–media thickness in nonobese sleep apnea patients

Obstructive sleep apnea (OSA) is characterized by recurrent apnea during sleep that may unbalance oxidative stress, increasing atherosclerosis. Among oxidative stress markers, 15-F_2t-isoprostane is considered one of the most sensitive and specific metabolites of lipid peroxidation. To explore the relationship between urinary 15-F_2t-isoprostane with sleep apnea severity and carotid modifications in nonobese OSA patients, 31 nonobese sleep apnea patients were studied, along with 10 lean subjects without OSA. Patients were assessed by polysomnography, blood pressure measurement, and ultrasonography to determine the carotid intima–media thickness (IMT). Urinary 15-F_2t-isoprostanes were measured by liquid chromatography–tandem mass spectrometry. Urinary 15-F_2t-isoprostane concentrations were increased in severe OSA patients compared to control subjects (20.2 ± 7.3 vs 12.3 ± 2.8 ng/mmol creatinine; P = 0.020). Mean carotid IMT was correlated with 15-F_2t-isoprostane (r = 0.532; P < 0.001) and with the apnea–hypopnea index (r = 0.345; P = 0.029). 15-F_2t-Isoprostane level was related to the night time spent at SaO₂ < 90% (r = 0.478; P = 0.002), the apnea–hypopnea index (r = 0.465; P = 0.003), and the mean nocturnal SaO₂ (r = ? 0.424; P = 0.007). These results showed a relationship between lipid peroxidation, carotid intima–media thickness, and intermittent hypoxia in nonobese OSA patients, thus reinforcing the hypothesis that oxidative stress could be involved in the early atherosclerotic process.     

Synthesis and characterization of tetraphenylporphyrin iron(III) complexes with substituted phenylcyanamide ligands

Several five coordinate complexes of [(TPP)Fe^III(L)] in which TPP is the dianion of tetraphenylporphyrin and L is the monoanion of phenylcyanamide (pcyd) (1), 2,5-dichlorophenylcyanamide (2,5-Cl₂pcyd) (2), 2,6-dichlorophenylcyanamide (2,6-Cl₂pcyd) (3), and 2,3,4,6-tetrachlorophenylcyanamide (2,3,4,6-Cl₄pcyd) (4) have been prepared by the reaction of [(TPP)Fe^IIICl] with appropriate thallium salt of phenylcyanamide. Each of the complexes has been characterized by IR, UV-Vis and ¹H NMR spectroscopic data. Dark red-brown needles of [(TPP)Fe^III(2,6-Cl₂pcyd)] (C₅₁H₃₁Cl₂FeN₆ · CHCl₃) crystallize in the triclinic system. The crystal structure of Fe(III) compound shows a slight distortion from square pyramidal coordination with the 2,6-dichlorophenylcyanamide anion in the axial position through nitrile nitrogen atom. Iron atom is 0.47(1) Å out of plane of the porphyrin toward phenylcyanamide ligand. In non-coordinating solvents, such as benzene or chloroform, these complexes exhibit ¹H NMR spectra that are characteristic of high-spin (S = 5/2) species. The X-ray crystal structure parameters are also consistent with high-spin iron(III) complexes. The iron(III) phenylcyanamide complexes are not reactive toward molecular oxygen; however, these complexes react with HCl and produce TPPFe^IIICl.     

Electrochemical studies of a series of antimetastatic mono- and di-ruthenium complexes [Na][trans-RuIIICl4(DMSO)(L)] and [Na]2[{trans-RuIIICl4(DMSO)}2(μ-L)] (L = N-donor heterocyclic bridging ligand)

A study of the electrochemical behavior of a series of antimetastatic mono- and di-ruthenium complexes, namely [Na][trans-Ru^IIICl₄(DMSO)(L)] and [Na]₂[{trans-Ru^IIICl₄(DMSO)}₂(μ-L)], L = pyrazine (pyz), pyrimidine (pym), 4,4′-bipyridine (bipy), and 1,2-bis-(4-pyridyl)ethylene (etbipy), is reported. The results obtained show that in all dimeric Ru(III) complexes linked by heterocyclic non-chelating N-donor bridges, the two redox centers behave independently (with no remarkable electrochemical interaction), thus conferring no advantage in the likely hypothesis they act as pro-drugs (activation by reduction). Moreover, electrochemical evaluation of interaction between albumin and the title complexes confirms that this protein can act as the vehicle for drugs of this type in blood.     

Synthesis and biological evaluation of fluoro analogues of antimitotic phenstatin

With the aim of investigating the influence of fluorine, in particular on the A-ring, a new series of fluoro analogues (7a–l) of phenstatin (3) was synthesized and tested for interactions with tubulin polymerization and evaluated for cytotoxicity on an NCI-60 human cancer cell lines panel. We have shown that the replacement of 3,4,5-trimethoxyphenyl A-ring of phenstatin with 2,4,5-trifluoro-3-methoxyphenyl unit, results in the conservation of both antitubulin and cytotoxic effect. Fluoro isocombretastatin 7k was the most effective anticancer agent in the present study and demonstrated the highest antiproliferative potential on leukemia cell lines SR (GI₅₀ = 15 nM) and HL-60(TB) (GI₅₀ = 23 nM) and on melanoma cell line MDA-MB-435 (GI₅₀ = 19 nM).     

Expanding the 4,4′-bipyridine ligand: Structural variation in {M(pytpy)2}2+ complexes (pytpy = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine,M = Fe,Ni, Ru) and assembly of the hydrogen-bonded,one-dimensional polymer {[Ru(pytpy)(Hpytpy)]}n3n+

The solid state structures of [Ni(1)₂][NO₃]₂ · 2MeOH · 2H₂O, [Fe(1)₂][ClO₄]₂ · 2MeOH · 0.5H₂O, [Ru(1)₂][PF₆]₂ and [Ru(1)₂][PF₆][NO₃] (1 = 4′-(4-pyridyl)-2,2′:6′,2″-terpyridine) are presented and the structural variation observed for the {M(1)₂}²⁺ unit is discussed. Protonation of the pendant pyridine group in [Ru(1)₂]²⁺ leads to the formation of a hydrogen-bonded, one-dimensional polymer [{Ru(1)(H1)}_n]³ⁿ⁺ exemplifed by the solid-state structure of [{Ru(1)(H1)}{Fe(NCS)₆} · 1.25H₂O]_n.