The separation of americium(III) from europium(III) by two new 6,6'-bistriazinyl-2,2'-bipyridines in different diluents

The synthesis and extraction of americium(III) and europium(III) from aqueous nitric acid solutions by the new BTBP ligands 6,6’-bis(5,5,7,7- tetramethyl-5,7-dihydrofuro[3,4-e]-1,2,4-triazin-3-yl)-2,2’-bipyridine (Cy5-O-Me4-BTBP), and 6,6’-bis(5,5,7,7-tetramethyl-5,7-dihydrothieno[3,4-e]-1,2,4-triazin-3-yl)- 2,2’-bipyridine (Cy5-S-Me4-BTBP) is described. The affinity for Am(III) and the selectivity for Am(III) over Eu(III) of Cy5-S-Me4-BTBP were generally higher than for Cy5-O-Me4-BTBP. For both ligands, the extraction of Am(III) and Eu(III) from 3 M HNO3 into 3 mM organic solutions varied with the diluent used. The highest distribution ratios and separation factors observed were in cyclohexanone and 2-methylcyclohexanone, respectively. For Cy5-S-Me4-BTBP, there is a strong correlation between the distribution ratio for Am(III) and the permittivity of the diluent used. With 1-octanol as the diluent, low distribution ratios (D(Am) < 1) were observed for Cy5-S-Me4-BTBP although this ligand extracts Am(III) selectively (SFAm/Eu = 16-46 from 1-4 M HNO3). For Cy5-S-Me4-BTBP, Am(III) is extracted as the disolvate. The distribution ratios for Am(III), and the separation factors for Am(III) over Eu(III) are both significantly higher for CyMe4-BTBP than they are for Cy5-O-Me4-BTBP and Cy5-S-Me4-BTBP in cyclohexanone. Changing the diluent from cyclohexanone to 2-methylcyclohexanone leads to a decrease in D(Am) but an increase in SFAm/Eu for Cy5-S-Me4-BTBP.

Conformational studies of mixed-ligand copper(II) chelates. Crystal and molecular structure of (N,N-dimethyl-N′-ethyl-1,2-diaminoethane-(1-phenyl-1,3,-butanedionato)copper(II) perchlorate

The IR and ligand field spectra and the structure of the mixed-ligand compound [N,N-dimethyl-N′-ethyl-1,2-diaminoethane(1-phenyl-1,3-butanedionato)(perchlorato)copper(II)]), [Cu(dmeen)bzac(OClO3)], are reported. The structure was determined by single crystal X-ray diffraction analysis (triclinic, space group ). The structure is square pyramidal with the apical position occupied by one oxygen of the tetrahedral perchlorato group (distance from copper 2.452(5) Å). The plane of the phenyl ring is tilted forming an angle of 16.72(14)° with the plane of the β-dionato moiety. The nitrogenous base adopts the gauche conformation with torsional angle of 108.72(14)°. The ethyl group is cis oriented relative to the phenyl group, occupying the equatorial position with the vector of the carbon-nitrogen bond forming an angle of 143.9(3)° with the CuNN plane. The interactions of the adjacent axial hydrogen with an oxygen of the perchlorato group result in hydrogen bond formation. The IR spectra reveal that in the solid state the Br− or Cl− displace easily the ClO4− group. The shifts in the ligand field spectra indicate that polar solvents participate in donor-acceptor interactions with the metal centre along an axis perpendicular to the CuN2O2 plane.

Synthesis, X-ray crystal structure and reactivity of the polymeric copper(II) dicarboxylic acid complex {Cu2(η1η1μ2-oda)2(py)4(H2O)2}n(odaH2 = octanedioic acid, PY = pyridine)

An aqueous solution of the α-ω-dicarboxylic acid octanedioic acid (odaH2) reacts with [Cu2(μ-O2CCH3)4(H2O)2] in the presence of an excess of pyridine (py) to give the crystalline copper(II) complex {Cu2(η1η1μ2-oda)2(py)4(H2O)2}n (1). structure of 1, as determined by X-ray crystallography, consists of polymeric chains in which bridging oda2− anions link two crystallographically identical copper atoms. The copper atoms are also ligated by two transoidal pyridine nitrogens and an oxygen atom from an apical water molecule, giving the metals an overall N2O3 square-pyramidal geometry. If the blue solid 1 is gently heated, or if it is left to stand in its mother liquor for prolonged periods, it loses one molecule of pyridine and half a molecule of water and the green complex {Cu (oda)(py)(H2O)0.5}n (2) is formed. Spectroscopic and magnetic data for both complexes are given, together with the electrochemical and thermogravimetric measurements for 1.

Copper(II) complexes of benzene-1,2-dioxyacetic acid (bdoaH2): X-ray crystal structure of [Cu2(bdoa)(phen)4]bdoa·13H2O (phen = 1,10-phenanthroline)

Copper(II) acetate reacts with benzene-1,2-dioxyacetic acid (bdoaH2) in aqueous media to give [Cu(bdoa)(H2O)2] (1). Complex 1 reacts with the N-donor ligands pyridine (py), ammonia and 1,10-phenanthroline (phen) to give [Cu(bdoa)(NH3)2]·H2O (2), [Cu(bdoa)(py)2]·H2O (3) and [Cu2(bdoa)(phen)4]bdoa·13H2O (4), respectively. The X-ray crystal structure of the dicopper(II,II) complex 4 shows each copper atom at the centre of a distorted trigonal bipyramid comprising four nitrogen atoms from two chelating phen ligands and a single oxygen atom from one of the carboxylate moieties of the bridging bdoa2− ligand. The cyclic voltammogram of 4 shows a single reversible wave for the Cu2+/Cu+ couple at E = + 115 mV (vs Ag/AgCl). Spectroscopic and magnetic data for the complexes are given.

Synthesis and properties of tetra-μ-acetatodiruthenium(II,III) phenylphosphinate and phenylphosphonate complexes: X-ray crystal structures of [Ru2(μ-O2CCH3)4(HPhPO2)2]H and [Ru2(μ-O2CCH3)4(PhPO3H)2]H·H2O

Phenylphosphinic acid (HPhPO2H) and phenylphosphonic acid (PhPO3H2) react with a methanolic solution of [Ru2(μ-O2CCH3)4(O2CCH3)2]H·0.7H2O at room temperature to give [Ru2(μ-O2CCH3)4(HPhPO2)2H (1) and [Ru2(μ-O2CCH3)4 (PhPO3H)2]H·H2O (2), respectively. The X-ray crystal structures of 1 and 2 each show the RuRu core to be ligated by four bridging bidentate acetate ligands [RuRu distances: 1 = 2.272(1) Å; 2 = 2.267(2) Å] and two axial phenylphosphinate and phenylphosphonate ligands, respectively. In each complex the individual bimetallic molecules are linked together by a hydrogen ion which bridges the oxygen atoms of neighbouring axial ligands. In 2 the water molecule is also hydrogen-bonded to one of the axial phenylphosphonate groups. Spectroscopic, magnetic and cyclic voltammetric data for the complexes are given.

Reaction of (±)-1,1′-binaphthyl-2,2′-diyl hydrogen phosphate {(±)-phosH} with copper(II), cobalt(II) and iron(II) compounds; Identification by x-ray diffraction of [Co(CH3OH)4(H2O)2][(+)-phos][(−)-phos]. 2CH3OH·H2O

[Cu2(μO2CCH3)4(H2O)2], [CuCO3·Cu(OH)2], [CoSO4·7H2O], [Co((+)-tartrate)], and [FeSO4·7H2O] react with excess racemic (±)- 1,1′-binaphthyl-2,2′-diyl hydrogen phosphate {(±)-PhosH} to give mononuclear CuII, CoII and FeII products. The cobalt product, [Co(CH3OH)4(H2O)2]((+)-Phos)((−)-Phos) ·2CH3OH·H2O (7), has been identified by X-ray diffraction. The high-spin, octahedral CoII atom is ligated by four equatorial methanol molecules and two axial water molecules. A (+)- and a (−)-Phos− ion are associated with each molecule of the complex but are not coordinated to the metal centre. For the other CoII, CuII and FeII samples of similar formulation to (7) it is also thought that the Phos− ions are not bonded directly to the metal. When some of the CuII and CoII samples are heated under high vacuum there is evidence that the Phos− ions are coordinated directly to the metals in the products.

Complete Experimental Structure Determination of the p(3x2)pg Phase of Glycine on Cu{110}

We present a quantitative low energy electron diffraction (LEED) surface-crystallograpic study of the complete adsorption geometry of glycine adsorbed on Cu{110} in the ordered p(3×2) phase. The glycine molecules form bonds to the surface through the N atoms of the amino group and the two O atoms of the de-protonated carboxylate group, each with separate Cu atoms such that every Cu atom in the first layer is involved in a bond. Laterally, N atoms are nearest to the atop site (displacement 0.41 Å). The O atoms are asymmetrically displaced from the atop site by 0.54 Å and 1.18 Å with two very different O-Cu bond lengths of 1.93 Å and 2.18 Å. The atom positions of the upper-most Cu layers show small relaxations within 0.07 Å of the bulk-truncated surface geometry. The unit cell of the adsorbate layer consists of two glycine molecules, which are related by a glide-line symmetry operation. This study clearly shows that a significant coverage of adsorbate structures without this glide-line symmetry must be rejected, both on the grounds of the energy dependence of the spot intensities (LEED-IV curves) and of systematic absences in the LEED pattern.

The importance of attractive three-point interaction in enantioselective surface chemistry: stereospecific adsorption of serine on the intrinsically chiral Cu{531} surface

Both enantiomers of serine adsorb on the intrinsically chiral Cu{531} surface in two different adsorption geometries, depending on the coverage. At saturation, substrate bonds are formed through the two oxygen atoms of the carboxylate group and the amino group (μ3 coordination), whereas at lower coverage, an additional bond is formed through the deprotonated β−OH group (μ4 coordination). The latter adsorption geometry involves substrate bonds through three side groups of the chiral center, respectively, which leads to significantly larger enantiomeric differences in adsorption geometries and energies compared to the μ3 coordination, which involves only two side groups. This relatively simple model system demonstrates, in direct comparison, that attractive interactions of three side groups with the substrate are much more effective in inducing strong enantiomeric differences in heterogeneous chiral catalyst systems than hydrogen bonds or repulsive interactions.

Protein kinase D isoforms are expressed in rat and mouse primary sensory neurons and are activated by agonists of protease-activated receptor 2

Serine proteases generated during injury and inflammation cleave protease-activated receptor 2 (PAR(2)) on primary sensory neurons to induce neurogenic inflammation and hyperalgesia. Hyperalgesia requires sensitization of transient receptor potential vanilloid (TRPV) ion channels by mechanisms involving phospholipase C and protein kinase C (PKC). The protein kinase D (PKD) serine/threonine kinases are activated by diacylglycerol and PKCs and can phosphorylate TRPV1. Thus, PKDs may participate in novel signal transduction pathways triggered by serine proteases during inflammation and pain. However, it is not known whether PAR(2) activates PKD, and the expression of PKD isoforms by nociceptive neurons is poorly characterized. By using HEK293 cells transfected with PKDs, we found that PAR(2) stimulation promoted plasma membrane translocation and phosphorylation of PKD1, PKD2, and PKD3, indicating activation. This effect was partially dependent on PKCepsilon. By immunofluorescence and confocal microscopy, with antibodies against PKD1/PKD2 and PKD3 and neuronal markers, we found that PKDs were expressed in rat and mouse dorsal root ganglia (DRG) neurons, including nociceptive neurons that expressed TRPV1, PAR(2), and neuropeptides. PAR(2) agonist induced phosphorylation of PKD in cultured DRG neurons, indicating PKD activation. Intraplantar injection of PAR(2) agonist also caused phosphorylation of PKD in neurons of lumbar DRG, confirming activation in vivo. Thus, PKD1, PKD2, and PKD3 are expressed in primary sensory neurons that mediate neurogenic inflammation and pain transmission, and PAR(2) agonists activate PKDs in HEK293 cells and DRG neurons in culture and in intact animals. PKD may be a novel component of a signal transduction pathway for protease-induced activation of nociceptive neurons and an important new target for antiinflammatory and analgesic therapies.

Hetero-metallic trinuclear nickel(II)–cadmium(II) complexes of a salicylaldimine ligand with thiocyanate, cyanate and azide ions: isolation of a pair of polymorphs with thiocyanate ion

Four new trinuclear hetero-metallic nickel(II)-cadmium(II) complexes [(NiL)(2)Cd(NCS)(2)] (1A and 1B), [(NiL)(2)Cd(NCO)(2)] (2) and [(NiL)(2)Cd(N-3)(2)] (3) have been synthesized using [NiL] as a so-called "ligand complex" (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine) and structurally characterized. Crystal structure analyses reveal that all four complexes contain a trinuclear moiety in which two square planar [NiL] units are bonded to a central cadmium(II) ion through double phenoxido bridges. The Cd(II) is in a six-coordinate distorted octahedral environment being bonded additionally to two mutually cis nitrogen atoms of terminal thiocyanate (in 1A and 1B), cyanate (in 2) and azide (in 3). Complexes 1A and 1B have the same molecular formula but crystallize in very different monoclinic unit cells and can be considered as polymorphs. On the other hand, the two isoelectronic complexes 2 and 3 are indeed isomorphous and crystallize only in one form. Their conformation is similar to that observed in 1A.

Modulation of ion channels by hydrogen sulfide

Increasing current awareness and understanding of the roles and mechanisms of action of ion channel regulation by H(2)S will open opportunities for therapeutic intervention with clear clinical benefits, and inform future therapies. In addition, more sensitive methods for detecting relevant physiological concentrations of H(2)S will allow for clarification of specific ion channel regulation with reference to physiological or pathophysiological settings.

Ion channels as effectors in carbon monoxide signaling

A wealth of recent studies has highlighted the diverse and important influences of carbon monoxide (CO) on cellular signaling pathways. Such studies have implicated CO, and the enzymes from which it is derived (heme oxygenases) as potential therapeutic targets, particularly (although not exclusively) in inflammation, immunity and cardiovascular disease.1 In a recent study,2 we demonstrated that CO inhibited cardiac L-type Ca(2+) channels. This effect arose due to the ability of CO to bind to mitochondria (presumably at complex IV of the electron transport chain) and so cause electron leak, which resulted in increased production of reactive oxygen species. These modulated the channel's activity through interactions with three cysteine residues in the cytosolic C-terminus of the channel's major, pore-forming subunit. Our study provided a potential mechanism for the cardioprotective effects of CO and also highlighted ion channels as a major potential target group for this gasotransmitter.

Steric effects on uranyl complexation: synthetic, structural, and theoretical studies of carbamoyl pyrazole compounds of the uranyl(VI) ion

New bifunctional pyrazole based ligands of the type [C3HR2N2CONR'] (where R = H or CH3; R' = CH3, C2H5, or (C3H7)-C-i) were prepared and characterized. The coordination chemistry of these ligands with uranyl nitrate and uranyl bis(dibenzoyl methanate) was studied with infrared (IR), H-1 NMR, electrospray-mass spectrometry (ES-MS), elemental analysis, and single crystal X-ray diffraction methods. The structure of compound [UO2(NO3)(2)(C3H3N2CON{C2H5}(2))] (2) shows that the uranium(VI) ion is surrounded by one nitrogen atom and seven oxygen atoms in a hexagonal bipyramidal geometry with the ligand acting as a bidentate chelating ligand and bonds through both the carbamoyl oxygen and pyrazolyl nitrogen atoms. In the structure of [UO2(NO3)(2)(H2O)(2)(C5H7N2CON {C2H5}(2))(2)], (5) the pyrazole figand acts as a second sphere ligand and hydrogen bonds to the water molecules through carbamoyl oxygen and pyrazolyl nitrogen atoms. The structure of [UO2(DBM)(2)C3H3N2CON{C2H5}(2)] (8) (where DBM = C6H5COCHCOC6H5) shows that the pyrazole ligand acts as a monodentate ligand and bonds through the carbamoyl oxygen to the uranyl group. The ES-MS spectra of 2 and 8 show that the ligand is similarly bonded to the metal ion in solution. Ab initio quantum chemical studies show that the steric effect plays the key role in complexation behavior.

Facile in situ copper(ii) mediated C–S bond activation transforming dithiocarbimate to carbamate and thiocarbamate generating Cu(ii) and Cu(i) complexes

Facile in situ Cu(II) mediated transformation of p-tolylsulfonyldithiocarbimate in conjunction with polypyridyl or phosphine ligands into corresponding carbamate and thiocarbamate led to the formation of new copper complexes with varying nuclearities and geometries, via C-S bond activation of the ligand within identical reaction systems.

Synthesis, crystal structures and magnetic properties of a phenoxo-bridged dinuclear Cu(II) complex and a dicyanamide bridged novel molecular rectangle based on it

The phenoxo-bridged dinuclear Cu-II complex [Cu2L2-(NCNCN)(2)] (1) and the dicyanamide-bridged molecular rectangle [Cu4L4{mu(1,5)-(NCNCN)(2)}]center dot(ClO4)(2)(H2O)(2) (2) were synthesized using the tridentate reduced Schiff-base ligand HL {2-[(2-dimethylamino-ethylamino) methyl] phenol}. The complexes were characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Complex 2 was formed through the joining of the phenoxo-bridged dinuclear Cu2O2 cores of 1 via the mu(1,5)-bridging mode of dicyanamide. The structural properties of the Cu2O2 cores in two complexes are significantly different. The geometry of the copper ions is distorted trigonal bipyramid in 1 but is nearly square-pyramidal in 2. These differences have a marked effect on the magnetic properties of two compounds. Although both are antiferromagnetically coupled, the coupling constants (J = -185.2 and -500.9 cm(-1) for 1 and 2, respectively) differ considerably.