Substituent dependent dimensionalities in cobalt isophthalate supramolecular complexes and coordination polymers containing dipyridylamine ligands

Hydrothermal synthesis has afforded cobalt 5-substituted isophthalate complexes with 4,4′-dipyridylamine (dpa) ligands, showing different dimensionalities depending on the steric bulk and hydrogen-bonding facility of the substituent. [Co(tBuip)(dpa)(H₂O)]_n (1, tBuip = 5-tert-butylisophthalate) is a (4,4) grid two-dimensional coordination polymer featuring 2-fold parallel interpenetration. [Co(MeOip)₂(Hdpa)₂] (2, MeOip = 5-methoxyisophthalate) is organized into 3-fold parallel interpenetrated (4,4) grids through strong N-H⁺?O⁻ hydrogen bonding. {([Co(OHip)(dpa)(H₂O)₃])₃·2H₂O}_n (3, OHip = 5-hydroxyisophthalate) possesses 1-D chain motifs. The 5-methyl derivative {[Co(mip)(dpa)]·3H₂O}_n (4, mip = 5-methylisophthalate) has a 3-D 6⁵8 cds topology. {[Co(H₂O)₄(Hdpa)₂](nip)₂·2H₂O} (5, nip = 5-nitroisophthalate) and {[Co(sip)(Hdpa)(H₂O)₄]·2H₂O} (6, sip = 5-sulfoisophthalate) are coordination complexes. Antiferromagnetic superexchange is observed in 1 and 4, with concomitant zero-field splitting. Thermal decomposition behavior of the higher dimensionality complexes is also discussed.     

Acid dissociation of 2,2′-dipyridylamine in non-aqueous medium when chelated to some Ru(II)N4 cores

[Ru(2,2′-bipyridine)₂(Hdpa)](BF₄)₂ · 2H₂O (1), [Ru(1,10-phenanthroline)₂(Hdpa)] (PF₆)₂ · CH₂Cl₂ (2) and [Ru(4,4,4′,4′-tetramethyl-2,2′- bisoxazoline)₂(Hdpa)] (PF₆)₂ (3) are synthesized where Hdpa is 2,2′-dipyridylamine. The X-ray crystal structures of 1 and 2 have been determined. Hdpa in 1 and 2 is found to bind the metal via the two pyridyl N ends. Comparing the NMR spectra in DMSO-d₆, it is concluded that 3 has a similar structure. The pK_a values (for the dissociation of the NH proton in Hdpa) of free Hdpa and its complexes are determined in acetonitrile by exploiting molar conductance. These correlate linearly with the chemical shift of the NH proton in the respective entities.     

fac-/mer-[RuCl3(NO)(P-N)] (P-N = [o-(N,N-dimethylamino)phenyl]diphenylphosphine): Synthesis, characterization and DFT calculations

Complex fac-[RuCl₃(NO)(P-N)] (1) was synthesized from the reaction of [RuCl₃(H₂O)₂(NO)] and the P-N ligand, o-[(N,N-dimethylamino)phenyl]diphenylphosphine) in refluxing methanol solution, while complex mer,trans-[RuCl₃(NO)(P-N)] (2) was obtained by photochemical isomerization of (1) in dichloromethane solution. The third possible isomer mer,cis-[RuCl₃(NO)(P-N)] (3) was never observed in direct synthesis as well as in photo- or thermal-isomerization reactions. When refluxing a methanol solution of complex (2) a thermally induced isomerization occurs and complex (1) is regenerated.The complexes were characterized by NMR (³¹P{¹H}, ¹⁵N{¹H} and ¹H), cyclic voltammetry, FTIR, UV-Vis, elemental analysis and X-ray diffraction structure determination. The ³¹P{¹H} NMR revealed the presence of singlet at 35.6 for (1) and 28.3 ppm for (2). The ¹H NMR spectrum for (1) presented two singlets for the methyl hydrogens at 3.81 and 3.13 ppm, while for (2) was observed only one singlet at 3.29 ppm. FTIR Ru-NO stretching in KBr pellets or CH₂Cl₂ solution presented 1866 and 1872 cm⁻¹ for (1) and 1841 and 1860 cm⁻¹ for (2). Electrochemical analysis revealed a irreversible reduction attributed to Ru^II-NO⁺ → Ru^II-NO⁰ at −0.81 V and −0.62 V, for (1) and (2), respectively; the process Ru^II → Ru^III, as expected, is only observed around 2.0 V, for both complexes.Studies were conducted using ¹⁵NO and both complexes were isolated with ¹⁵N-enriched NO. Upon irradiation, the complex fac-[RuCl₃(NO)(P-N)] (1) does not exchange ¹⁴NO by ¹⁵NO, while complex mer,trans-[RuCl₃(NO)(P-N)] (2) does. Complex mer,trans-[RuCl₃(¹⁵NO)(P-N)] (2′) was obtained by direct reaction of mer,trans-[RuCl₃(NO)(P-N)] (2) with ¹⁵NO and the complex fac-[RuCl₃(¹⁵NO)(P-N)] (1′) was obtained by thermal-isomerization of mer,trans-[RuCl₃(¹⁵NO)(P-N)] (2′).DFT calculation on isomer energies, electronic spectra and electronic configuration were done. For complex (1) the HOMO orbital is essentially Ru (46.6%) and Cl (42.5%), for (2) Ru (57.4%) and Cl (39.0%) while LUMO orbital for (1) is based on NO (52.9%) and is less extent on Ru (38.4%), for (2) NO (58.2%) and Ru (31.5%).     

Synthesis, structure and reactivity of complexes containing [M(S2)2] fragments (M=Ru, Os; (S2)=1,2-benzenedithiolate (2−))

Subsequent addition of 1,2-benzenedithiol (S₂-H₂) and nBuLi to a solution of [Ru(NO)Cl₃ · xMeOH] in THF afforded exclusively the monomeric species NBu₄[Ru^II(NO)(S₂)₂] (1). Formation of dimeric (NBu₄)₂[Ru^II(NO)(S₂)₂]₂ (2) has been confirmed when the deprotonated ligand S₂-Li₂ was added to [Ru(NO)Cl₃ · xMeOH] and allowed to stir for 30 h. The monomer 1 undergoes aerial oxidation to give (NBu₄)₂[Ru^IV(S₂)₃] (3). The reaction between RuCl₃ · xH₂O and S₂-H₂ in the presence of NaOMe, afforded the dinulear Ru^III species (NMe₄)₂[Ru^III(S₂)₂]₂ (4). A modified method for the preparation of 1 is being employed to synthesize the osmium analogue NBu₄[Os(NO)(S₂)₂] (5) effectively. The solid state structures of 1, 2 and 3 were determined by X-ray crystal structure analysis. A comparison of relevant bond distance data suggests that 1,2-benzenedithiolate acts as an “innocent” ligand.     

Stepwise syntheses, structure and spectroscopic studies of ruthenium complexes of 2,6-bis(benzimidazol-2-yl)pyridine with o-iminoquinone ancillary ligand

The ruthenium complexes [Ru^II(bbp)(L)(Cl)] (1), [Ru^II(bbp)(L)(H₂O)] (2) and [Ru^II(bbp)(L)(DMSO)] (3) {bbp = 2,6-bis(benzimidazol-2-yl)pyridine, L = o-iminoquinone} have been synthesized in a stepwise manner starting from [Ru^III(bbp)Cl₃]. The single crystal X-ray structures, except for the complex 2, have been determined. All the complexes were characterized by UV-Vis, FT-IR, ¹H NMR, Mass spectroscopic techniques and cyclic voltammetry. The Ru^III/Ru^II couple for complexes 1, 2, and 3 appears at 0.63, 0.49, 0.55 V, respectively versus SCE. It is observed that complex 2, on refluxing in acetonitrile, results into [Ru^II(bbp)(L)(CH₃CN)], 4 which has been prepared earlier in a different method. The structural, spectral and electrochemical properties of complexes 1, 2 and 3 were compared to those of earlier reported complex 4, [Ru^II(bbp)(L)(CH₃CN)].     

Mimicking the reduced, oxidized and azide inhibited form of manganese superoxide dismutase by mononuclear Mn compounds utilizing tridentate ligands

The manganese complexes [Mn^II(Hbmimpm)₂(NO₃)](NO₃) · Et₂O (1), [Mn^III(bmimpm)₂(OAc)] · 2CH₂Cl₂(2), and [Mn^III(bmiapm)₂(OAc)] · MeOH · H₂O · CH₂Cl₂(3) containing the new ligands Bis(1-methylimidazol-2-yl)-(4-methoxyphen-1-yl)methanol (Hbmimpm) and Bis[(1-methylimidazol-2-yl)](2-aminophenyl)methanol (Hbmiapm) were synthesized. They are good structural models for the reduced (1) and oxidized (2, 3) form of manganese superoxide dismutase. All complexes were characterized by spectroscopic methods and X-ray structure analysis. Compounds 1 and 2 crystallize in the monoclinic space group P2₁/c whereas complex 3 crystallizes in the monoclinic space group P2₁/n. The coordination sphere around the manganese cores is distorted octahedral with two corresponding tridentate ligands representing the protein ligands and one nitrate (1) or acetate (2, 3) ion occupying two cis positions. Similar to the enzyme the Mn(III) complex 2 reacts with sodium azide. The obtained microcrystalline azide adduct was characterized by UV-Vis and IR spectroscopy.     

Aerobic oxygenation of organic sulfides using diruthenium activators

Diruthenium compounds supported by carboxylate or mixed carboxylate/carbonate bridging ligands were found to be active catalysts for aerobic oxygenation of organic sulfides. Ru₂(OAc)₃(CO₃) (A), Ru₂(O₂CCF₃)₃(CO₃) (B) and Ru₂(OAc)₄Cl (C) promote the conversion of organic sulfide to sulfoxide, and subsequently sulfone in an oxygen atmosphere at ca. 90 °C. The order of catalytic activity is A > B ? C. Catalytic reactions are operative in a number of 1:1 co-solvent-H₂O combinations, and the highest reactivity was found in aqueous media.     

Synthesis, structure and luminescence behaviour of a mononuclear cadmium(II) dicyanamide and a coordination polymer of mercury(II) dicyanamide containing 2,2′-dipyridylamine (dpaH) as end-capping ligand/anion of dpaH as binucleating bridge. Variance in coordination numbers, nuclearities and architectures with metal ion templates

A mononuclear compound [Cd(dpaH)₂(dca)₂] (1) and a tetranuclear based 2D coordination polymer [Hg₄(dpa)₄(dca)₄]_n (2) [dpaH = 2,2′-dipyridylamine, dpa = anion of dpaH, dca = dicyanamide] have been synthesized and characterized. X-ray structural analyses reveal that cadmium(II) center in 1 has a distorted octahedral geometry with a CdN₆ chromophore ligated through two bidentate neutral dpaH units along with two nitrile N atoms of two terminally bound dca units in mutual cis orientation. Each of the four independent mercury(II) centers in 2 adopts a distorted trigonal bipyramidal environment coordinated by two pyridine N atoms of two different anionic dpa ligands, two nitrile N atoms of two μ_1,5 bridged dca units and the fifth position is occupied by the amide N of one dpa. Cooperative intermolecular N-H···N and C-H···N hydrogen bondings promote dimensionality in 1. The compounds display intraligand ¹(π-π^∗) fluorescence in DMF solutions at room temperature.     

Acetato, formato and chloride copper(II) complexes with 2-(aminomethyl)pyridine: Synthesis, crystal structure, magnetic properties and EPR results

By the reactions of Cu(OAc)₂ · H₂O and Cu(HCOO)₂ · 4H₂O with 2-(aminomethyl)pyridine in different proportions, the compounds Cu(OAc)₂(2-amp) (1), Cu(HCOO)₂(2-amp) (2), Cu(HCOO)₂(2-amp)_1/2 (5), Cu(OAc)₂(2-amp)₂ · H₂O (6) and Cu(HCOO)₂(2-amp)₂ · H₂O (7) were obtained. In 1 the copper shows an elongated rhombic octahedral stereochemistry determined by a 2-amp molecule and two asymmetrical bidentate acetate groups. The hydrogen bonds between the NH₂ groups and O atoms yield to the formation of a double chain. Compound 2 instead consists in monodimensional chains of Cu(2-amp)(HCOO) units, with monodentate formate groups, linked by syn-anti bridging formate groups. Sheets are formed by hydrogen bonds between the chains. By crystallization of a solution of 6 in chloroform, CuCl₂(2-amp)₂ (3) was obtained. It presents a highly distorted square pyramidal geometry around the copper atom. The sheets, formed by the hydrogen bonds between NH₂ and Cl, are interpenetrated and shows π stacking. Magnetic properties and EPR spectra for these new compounds have been studied. Also the magnetic behaviour of Cu(OAc)₂(2-amp)_1/2 (4) is described.     

[Molybdenum(VI)/aminopyridinium] system as catalyst for the epoxidation of cyclooctene with H2O2

A new inorganic-organic supramolecular polymer, i.e. [MoO₂Cl₂(H₂O)₂]·Hdpa·Cl·H₂O (1) (where Hdpa stands for 2,2′-dipyridylammonium), has been synthesised and characterized, including by single-crystal X-ray diffraction studies. 1 is constituted of inorganic [MoO₂Cl₂(H₂O)₂] moieties associated to organic Hdpa units via hydrogen bonds. The combination of hydrogen-bonding and π-π stacking interactions gives rise to a remarkable 3D framework. Compound 1 is an effective catalyst for the H₂O₂-mediated epoxidation of cyclooctene at 50 °C.     

Dinuclear iron, ruthenium and cobalt complexes containing 1,4-dimethyl-1,4,7-triazacyclononane ligands as well as carboxylato and oxo or hydroxo bridges

The reaction of 1,4-dimethyl-1,4,7-triazacyclononane (L-Me₂) with FeSO₄ · 7H₂O in aqueous ethanol gives, in the presence of sodium carboxylates, hydrogen peroxide, sodium hydroxide and KPF₆, the dinuclear Fe(III)-Fe(III) complex cations [(L-Me₂)₂Fe₂(O)(OOCR)₂]²⁺ (R = H: 1, R = CH₃: 2, R = C₆H₅: 3), which crystallise as the hexafluorophosphate salts. The corresponding reaction with RuCl₃ · nH₂O does not work, however, the analogous Ru(III)-Ru(III) complex [(L-Me₂)₂Ru₂(O)(OOCCH₃)₂]²⁺ (5) can be synthesised by reacting Ru(dmso)₄Cl₂ with L-Me₂, HCl and air in refluxing ethanol, followed by addition of sodium acetate, the mononuclear intermediate (L-Me₂)RuCl₃ · H₂O (4) being also isolated and characterised. The reaction of L-Me₂, sodium acetate, hydrogen peroxide and triethylamine with CoCl₂ · 6H₂O in acetonitrile yields, however, the hydroxo-bridged Co(III)-Co(III) complex [(L-Me₂)₂Co₂(OH)(OOCCH₃)₂]³⁺ (6). The molecular structures of 2, 5 and 6, solved by single-crystal X-ray structure analyses of the hexafluorophosphate salts, reveal for the orange crystals of [2][PF₆]₂ a Fe-Fe distance of 3.104(1) Å, for the purple crystals of [5][PF₆]₂ a Ru-Ru distance of 3.230(1) Å, and for the violet crystals of [6][PF₆]₃ · (CH₃)₂CO a Co-Co distance of 3.358(1) Å. All six complexes show catalytic activity for the oxidation of isopropanol with hydrogen peroxide in water to give acetone in the presence of ascorbic acid as co-catalyst.     

Vanadium complexes with 2-pyridineformamide thiosemicarbazones: In vitro studies of insulin-like activity

Reaction of VOCl₂ with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives in ethanol gave as products [VO(H2Am4DH)Cl₂] (1), [VO(H2Am4Me)Cl₂] · 1/2HCl (2), [VO(H2Am4Et)Cl₂] · HCl (3) and [VO(2Am4Ph)Cl] (4). Upon the dissolution of 1-4 in water, oxidation immediately occurs with the formation of [VO₂(2Am4DH)] (5), [VO₂(2Am4Me)] (6), [VO₂(2Am4Et)] (7) and [VO₂(2Am4Ph)] (8). The crystal and molecular structures of 5 and 6 were determined. Complexes 5-8 inhibited glycerol release in a similar way to that observed with insulin but showed a low enhancing effect on glucose uptake by rat adipocytes.     

Synthesis, characterization and antibacterial activity of Fe, Co, Cu and Zn complexes probed by transmission electron microscopy

We synthesized iron(III), cobalt(II), copper(II) and zinc(II) complexes [Fe^III(HBPClNOL)Cl₂]·H₂O (1), [Co^II(H₂BPClNOL)Cl₂] (2), [Cu^II(H₂BPClNOL)Cl]Cl·H₂O (3), and [Zn^II(HBPClNOL)Cl] (4), where H₂BPClNOL is the ligand (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)]propylamine). The complexes obtained were characterized by elemental analysis, IR and UV-visible spectroscopies, electrospray ionization mass spectrometry (ESI-MS), tandem mass spectrometry (MS/MS), and cyclic voltammetry. X-ray diffraction studies were performed for complexes (3) and (4) revealing the presence of mononuclear and dinuclear structures in solid state for (3). However, the zinc complex is mononuclear in solid state. Biological studies of complexes (1)-(4) were carried out in vitro for antimicrobial activity against nine Gram-positive bacteria (Staphylococcus aureus strains RN 6390B, COL, ATCC 25923, Smith Diffuse, Wood 46, enterotoxigenic S. aureus FRI-100 (SEA+), FRI S-6 (SEB+) and SEC FRI-361) and animal strain S. aureus LSA 88 (SEC/SED/TSST-1+). The following sequence of inhibition promoted by the complexes was observed: (4) > (2) > (3) > (1), showing the effect of the metal on the biological activity. To directly observe the morphological changes of the internal structure of bacterial cells after the treatment, transmission electron microscopy (TEM) was employed. For the most active complex [Zn^II(HBPClNOL)Cl] (4), granulation deposits around the genetic material and internal material leaking were clearly detected.     

Synthesis and exploratory coordination chemistry of the new ditertiary carbinamine ligand 2,6-bis(α-aminoisopropyl)pyridine

The new pyridine-based N∩N∩N tridentate ligand 2,6-C₅H₃N(CMe₂NH₂)₂ (1) was synthesized by the treatment of 2,6-pyridinedicarbonitrile with an excess of the organocerium reagent in situ generated from CeCl₃ and methyllithium in THF. The reaction of 1 with [RuCl₂(PPh₃)₃] in THF at ambient conditions afforded (OC-6-23)-[RuCl{2,6-C₅H₃N(CMe₂NH₂)₂}(PPh₃)₂]Cl (2). The corresponding dimethyl sulfoxide complex [RuCl{2,6-C₅H₃N(CMe₂NH₂)₂}{S(O)Me₂}₂]Cl (3) was isolated as a mixture of the (OC-6-23) and (OC-6-32) stereoisomers 3a and 3b from the reaction between 1 and (OC-6-22)-[RuCl₂{S(O)Me₂}₃(OSMe₂)] in toluene at 80 °C. A prolonged interaction in toluene at reflux temperature gave isomerically pure 3a. The metal trichloride hydrates MCl₃ · xH₂O (M = Ru, Rh, Ir; x ≅ 2-4) produced mer-[RuCl₃{2,6-C₅H₃N(CMe₂NH₂)₂}] (M = Ru: 4; Rh: 5; Ir: 6), when combined with 1 in refluxing ethanol. The crystal structures of the following compounds were determined: ligand 1 and complexes 2-5 as addition compounds 2 · CH₂Cl₂, 3a · C₇H₈, 4 · EtOH and .     

6-Halogenopyridin-2-olato complexes with the diruthenium(2+) core: Equilibria between head-to-head and head-to-tail structures

The dinuclear bis(6-X-pyridin-2-olato) ruthenium complexes [Ru₂(μ-XpyO)₂(CO)₄(PPh₃)₂] (X = Cl (4B) and Br (5B)), [Ru₂(μ-XpyO)₂(CO)₄(CH₃CN)₂] (X = Cl (6B), Br (7B) and F (8B)) and [Ru₂(μ-ClpyO)₂(CO)₄(PhCN)₂] (9B) were prepared from the corresponding tetranuclear coordination dimers [Ru₂(μ-XpyO)₂(CO)₄]₂ (1: X = Cl; 2: X = Br) and [Ru₂(μ-FpyO)₂(CO)₆]₂ (3) by treatment with an excess of triphenylphosphane, acetonitrile and benzonitrile, respectively. In the solid state, complexes 4B-9B all have a head-to-tail arrangement of the two pyridonate ligands, as evidenced by X-ray crystal structure analyses of 4B, 6B and 9B, in contrast to the head-to-head arrangement in the precursors 1-3. A temperature- and solvent-dependent equilibrium between the yellow head-to-tail complexes and the red head-to-head complexes 4A-7A and 9A, bearing an axial ligand only at the O,O-substituted ruthenium atom, exists in solution and was studied by NMR spectroscopy. Full ¹H and ¹³C NMR assignments were made in each case. Treatment of 1 and 2 with the N-heterocyclic carbene (NHC) 1-butyl-3-methylimidazolin-2-ylidene provided the complexes [Ru₂(μ-XpyO)₂(CO)₄(NHC)], X = Cl (11A) or Br (12A). An XRD analysis revealed the head-to-head arrangement of the pyridonate ligands and axial coordination of the carbene ligand at the O,O-substituted ruthenium atom. The conversion of 11A and 12A into the corresponding head-to-tail complexes was not possible.     

Versatile coordination behaviour of Ph2AsCH2AsPh2 with Ru(II)

Treatment of ‘RuCl₃ · 3H₂O’ with Ph₂AsCH₂AsPh₂ (dpam) in hot EtOH gives either trans-[RuCl₂(dpam-As,As′)(dpam-As)₂] (1), or cis-[RuCl₂(dpam-As,As′)₂] (2), depending on the mole ratio. On exposure to light, solutions of 2 isomerise to trans-[RuCl₂(dpam-As,As′)₂] (3). Treatment of [RuCl₂(PPh₃)₃] with two equivalents of dpam in CH₂Cl₂ gave a mixture of two products, from which trans-[RuCl₂(PPh₃) (dpam-As,As′)(dpam-As)] (4) was isolated by recrystallisation. The crystal structures of 1-4 are reported. Complexes 1-3 in CH₂Cl₂ undergo electrochemical oxidation to Ru(III), and the Ru(III) form of 2 undergoes isomerisation on the voltammetric timescale to the Ru(III) form of 3.     

An oxamato bridged trinuclear copper(II) complex: Synthesis, crystal structure, reactivity, DNA binding study and magnetic properties

A linear tri-nuclear oxamato bridged copper(II) complex [Cu₃(pba)(dpa)₂(H₂O)(ClO₄)](ClO₄)·H₂O (1) (pbaH₄ = 1,3-propanediylbis(oxamic acid), dpa = 2,2′-dipyridylamine) was isolated from the reaction mixture of Na₂[Cu(pba)]·3H₂O, copper perchlorate hexahydrate and dipyridylamine in methanol. On reaction with dpa or DMF in basic medium (KOH) at ambient temperature complex 1 changed to dinuclear oxalate bridged copper(II) derivatives, [Cu₂(μ-C₂O₄)(dpa)₄](ClO₄)₂ (2) and [Cu₂(μ-C₂O₄)(dpa)₂(DMF)₂](ClO₄)₂ (3), respectively. The complexes 1, 2 and 3 have been characterized by physicochemical and spectroscopic tools, and also by the X-ray single crystal analysis. The hydrolysis of 1 in basic medium and thermo-gravimetric analysis has been studied. Absorption and emission spectral studies showed that complex 1 interacts with calf thymus-DNA (CT-DNA) with a binding constant (K_b) of 4.01 × 10⁴ M⁻¹ and linear Stern-Volmer quenching constant (K_sv) of 6.9 × 10⁴. A strong anti-ferromagnetic interaction with a coupling constant J_CuCu of 320.0 ± 0.3 cm⁻¹ was observed from the study of magnetic behavior of complex 1 in the temperature range of 2-300 K. Electrochemical equivalency of three copper(II) ions in 1 was identified by getting only one quasi reversible cyclic voltammogram.     

Synthesis, isolation and spectroscopic characterization of Dawson polyoxotungstate-supported, organometallic complex, [{(C6H6)Ru}P2W15V3O62]: The two positional isomers

The Dawson polyoxotungstate (POM)-based, organometallic ruthenium(II) complex, [{(C₆H₆)Ru}P₂W₁₅V₃O₆₂]⁷⁻, was synthesized as two materials, i.e. 1 · 2Bu₄NCl and 1 · 1Bu₄NCl (1 = (Bu₄N)₇[{(C₆H₆)Ru}P₂W₁₅V₃O₆₂]), which contained two positional isomers a and b as major or minor species. In isomer a with the overall C_s symmetry, the (C₆H₆)Ru²⁺ group was supported on one vanadium(V) octahedral site (two V-O-V bridging oxygens and one OV terminal oxygen) of the three edge-shared vanadium(V) octahedra (V₃ site, B-site) in the Dawson POM-support [1,2,3-P₂W₁₅V₃O₆₂]⁹⁻, whereas in the other isomer b with the overall C_3v symmetry, the (C₆H₆)Ru²⁺ group was supported on the center of the V₃ site in the Dawson POM-support. Material 1 · 2Bu₄NCl was prepared by a stoichiometric reaction in CH₂Cl₂ at ambient temperature of the Dawson POM-support (Bu₄N)₉[1,2,3-P₂W₁₅V₃O₆₂] with the precursor [(C₆H₆)RuCl₂]₂, whereas material 1 · 1Bu₄NCl was prepared by a stoichiometric reaction in CH₃CN under refluxing conditions. The temperature-varied ³¹P NMR spectra revealed that b was thermodynamically more stable thana.     

In vitro and in vivo biological activity screening of Ru(III) complexes involving 6-benzylaminopurine derivatives with higher pro-apoptotic activity than NAMI-A

A series of novel octahedral ruthenium(III) complexes involving 6-benzylaminopurine (L) derivatives as N-donor ligands has been prepared by the reaction of [(DMSO)₂H][trans-RuCl₄(DMSO)₂] with the corresponding L derivative. The complexes 1-12 have the general compositions trans-[RuCl₄(DMSO)(n-Cl-LH)] ⋅ xSol (1-3), trans-[RuCl₄(DMSO)(n-Br-LH)] · xSol (4-6), trans-[RuCl₄(DMSO)(n-OMe-LH)] · xSol (7-9) and trans-[RuCl₄(DMSO)(n-OH-LH)] · xSol (10-12); n = 2, 3, and 4, x = 0-1.5; and Sol = H₂O, DMSO, EtOH and/or (Me)₂CO. The complexes have been thoroughly characterized by elemental analysis, UV-visible, FTIR, Raman, and EPR spectroscopy, ES + (positive ionization electrospray) mass spectrometry, thermal analysis, cyclic voltammetry, magnetic and conductivity measurements. The X-ray molecular structure of trans-[RuCl₄(DMSO)(3-Br-LH)] ⋅ (Me)₂CO (5) revealed the distorted octahedral coordination in the vicinity of the central atom, and also confirmed that the 3-Br-L ligand is present as the N3-protonated N7-H tautomer and is coordinated to Ru(III) through the N9 atom of the purine moiety. The tested complexes have been found to be in vitro non-cytotoxic against K562, G361, HOS and MCF7 human cancer cell lines with IC₅₀ > 100 μM in contrast to the moderate results regarding the antiradical activity with IC₅₀ ≈ 10^− 3 M. On the contrary, in vivo antitumor activity screening showed that the prepared Ru(III) complexes possess higher pro-apoptotic activity than NAMI-A. The reduction of Ru(III) to Ru(II) and Ru(II)-species formation in tumor tissues was confirmed by means of a simple method of detection and visualization of intracellular Ru(II) by fluorescence microscopy. The originality of this method is based on the preparation of a Ru(II)-bipyridine complex in situ.     

New pyridyl modified phosphines: Synthesis and late transition-metal coordination studies

Using a phosphorus based Mannich condensation reaction the new pyridylphosphines {5-Ph₂PCH₂N(H)}C₅H₃(2-Cl)N (1-Cl) and {2-Ph₂PCH₂N(H)}C₅H₃(5-Br)N (1-Br) have been synthesised in good yields (60% and 88%, respectively) from Ph₂PCH₂OH and the appropriate aminopyridine. The ligands 1-Cl and 1-Br display variable coordination modes depending on the choice of late transition-metal complex used. Hence P-monodentate coordination has been observed for the mononuclear complexes AuCl(1-Cl) (2), AuCl(1-Br) (3), RuCl₂(p-cymene)(1-Cl) (4), RuCl₂(p-cymene)(1-Br) (5), RhCl₂(Cp^∗)(1-Cl) (6), RhCl₂(Cp^∗)(1-Br) (7), IrCl₂(Cp^∗)(1-Cl) (8), IrCl₂(Cp^∗)(1′-Cl) (8′), IrCl₂(Cp^∗)(1-Br) (9), cis-/trans-PdCl₂(1-Cl)₂ (10), cis-/trans-PdCl₂(1-Br)₂ (11), cis-PtCl₂(1-Cl)₂ (12) and cis-PtCl₂(1-Br)₂ (13). Reaction of Pd(Me)Cl(cod) (cod = cycloocta-1,5-diene) with either 1 equiv. of 1-Br or the known pyridylphosphines 1′-Cl, 1-OH or 1-H gave the P/N-chelate complexes Pd(Me)Cl(1-Br-1-H) (14)-(17). All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 4, 5, 10 and 16 · (CH₃)₂SO have been elucidated by single crystal X-ray crystallography. A crystal structure of the dinuclear metallocycle trans,trans-[PdCl₂{μ-P/N-{Ph₂PCH₂N(H)}C₅H₄N}]₂ · CHCl₃, 18 · CHCl₃, has also been determined. Here 1-H bridges, using both P and pyridyl N donors, two dichloropalladium centres affording a 12-membered ring with the PdCl₂ units adopting a head-to-tail arrangement.