A new oxamato-bridged heterotrinuclear NiCuNi complex with irregular spin state structure: Synthesis, spectroscopy, crystal structure and magnetism

A new oxamato-bridged Ni^IICu^IINi^II species, [Ni(tacn)(H₂O)]₂[μ-Cu(pba)](ClO₄)₂·6H₂O 1, (tacn=1,4,7-triazacyclononane; pba=1,3-propylenebis(oxamato)) has been synthesized and structurally as well as magnetically characterized. Complex 1 has a discrete trinuclear Ni^IICu^IINi^II structure: Two nickel(II) ions are bridged by [Cu(pba)]²⁻ anion, macrocyclic ligand tacn works as terminal ligand of the nickel(II) center. The magnetic data of compound 1 was analyzed by means of

leading to g_Cu=2.19, g_Ni=2.18, J=−112.8 cm⁻¹, D=±4.31 cm⁻¹. The parameters are compared with the similar complexes and the irregular spin state structure of complex 1 is also described here.     

Influences of permeation of vanadium ions through PVDF-g-PSSA membranes on performances of vanadium redox flow batteries

The preparation and physical characterization of a poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid) (PVDF-g-PSSA) membrane prepared by a solution-grafting method were described. These membranes exhibited high conductivity with a value 3.22 x 10(-2) S/cm at 30 degrees C. ICP studies revealed that the PVDF-g-PSSA membrane showed dramatically lower vanadium ion permeability compared to Nafion 117. Trivalent vanadium ions had the highest permeability through all these membranes in contrast to pentavalent vanadium ions with the lowest. The VRB with the low-cost PVDF-g-PSSA membrane exhibited a higher performance than that with Nafion 117 under the same operating conditions, and its energy efficiency reached 75.8% at 30 mA/cm(2). The performance of VRB with the PVDF-g-PSSA membrane can be maintained after more than 200 cycles at a current density of 60 mA/cm(2).     

Surface tension effect on transmembrane channel stability in a model membrane

The effect of surface tension on the lipid bilayer membrane is a question that has drawn considerable research effort. This interest has been driven both by the desire to determine the surface tension effects on the lipid bilayer and from the suggestion that adding finite surface tension to a small membrane system may provide more realistic lipid properties in molecular dynamics simulations. Here, the effect of surface tension on a palmitololelylphosphatidylcholine (POPC) bilayer membrane containing a four-helix transmembrane alamethicin peptide bundle is investigated. Simulations of 10 ns were undertaken for two different ensembles, NPT and NP(z)gammaT with a surface tension, gamma, of 20 mN m(-1) per interface, which is near the pore-forming region. The significance of differences between the tension-free and surface tension simulations was determined using nonparametric statistical analysis on replicate simulations with different initial conditions. The results suggest that, when the membrane is under surface tension, the peptide helical structure is perturbed from that in the tension-free state but that the bundle conformation is more stable than that in the tension-free state, with hydrogen bonding playing an important stabilizing role. Surface tension counteracts the influence of the transmembrane helix bundle on nearby lipid order, making the lipid order more uniform throughout the membrane in the tension state. Conversely, the lipid mobility was less uniform in the tension state, with lipids far from the bundle being significantly more mobile than those near the bundle. One general implication of the results is that surface tension can affect the membrane nonuniformly, in that the properties of lipids near the peptide are different from those further away.     

Marine Metabolites and Metal Ion Chelation: The Facts and the Fantasies

The marine environment is a seemingly inexhaustible treasury of organisms whose secondary metabolites bear witness to the lavishness and inventiveness with which nature is able to manipulate molecular architecture. But to what purpose are these diverse and often grotesque compounds produced? This review is founded on the premise that some of them may be involved in the uptake and transport of metal ions present in the aquatic milieu. Many metabolites produced by terrestrial organisms are known to act as ionophores, but the case for similar behavior by their marine counterparts is far hazier. Notwithstanding the relative abundance of certain metal ions in the oceans, and of metabolite structures possessing features that should facilitate the chelation of metal ions, few attempts to establish a connection between these two phenomena have been reported. We have whittled down the voluminous literature of natural products derived from marine sources to expose a core of observations and speculations germane to our premise. These facts and fantasies are evaluated in this review. A mere handful of metal-containing complexes has actually been isolated; furthermore, attempts to prepare such complexes in vitro are rare, and spectroscopic evidence for metal–metabolite interactions, whether in vivo or in vitro, is not common. Only with the vanadium-sequestering tunichromes does a logical (but by no means complete) picture begin to emerge. In several other cases, the plausibility of metal chelation, though mooted by authors, remains unsupported by experimental evidence. However, continuing efforts to obtain structural, and particularly conformational, information on the metabolites by means of X-ray crystallography, nuclear magnetic resonance spectroscopy, and molecular mechanics calculations would seem to provide the key to a rational approach to this neglected topic. On the basis of recent studies dealing with such structural aspects, we present a selection of candidate compounds, some of which are the targets of our own synthetic attentions, whose potential for binding to metal cations merits further research.     

Boomerang‐Type Substitution Reaction: Reactivity of Fullerene Epoxides and a Halofullerenol

The C_s‐symmetric fullerene chlorohydrin C₆₀(Cl)(OH)(OOtBu)₄ reacts with 4‐dimethylaminopyridine (DMAP) and 1,4‐diazabicyclo[2.2.2]octane (DABCO) to yield two isomers with the formula C₆₀(O)(OOtBu)₄ in good yields. These isomers differ with respect to the location of the epoxy functionality. The one from DMAP is C_s symmetric, whereas that from DABCO is C₁ symmetric with the epoxy group on the central pentagon. Two different mechanisms are proposed to explain the chemoselectivity of these reactions. The reaction with DMAP involves single‐electron transfer as the key step; DMAP acts as the electron donor. A combination of an oxygen‐atom shift and S_N2′′ processes (boomerang substitution) are responsible for the formation of isomer with DACBO. Various related reactions support the proposed mechanisms. The structures of new fullerene derivatives were determined by spectroscopy, single‐crystal X‐ray analysis, and chemical correlation experiments.     

The Structure of Tetrakis(pentafluorophenyl)tellurium(IV), Te(C6F5)4

Tetrakis(pentafluorophenyl)tellurium(IV), Te(C₆F₅)₄, was prepared from the reaction of TeCl₄ and Mg(C₆F₅)Br. Crystallization of the crude product from n‐pentane at ?25 °C gave suitable single crystals. The title compound crystallizes in the monoclinic space group P2₁/c (Z = 8) with two independent molecules per unit cell.     

Synthesis,structures and properties of two novel copper(II) complexes with hydrogen bonding supramolecular networks

Two novel complexes, [Cu(HL)₂(H₂O)]₂(OH)₂(ClO₄)₂·1.5H₂O (1) and [Cu(HL)₂]Cl₂·4H₂O (2), have been prepared by reacting copper salts with the 4-amino-3-ethyl-1,2,4-triazole-5-thione (HL) ligand in neutral solution and in HCl (6 mol L^–1) medium, respectively. They were characterized by FT-IR and u.v.–vis. spectra, and the structures were determined by single crystal X-ray diffraction techniques. In both complexes, the triazole ligand chelated the metal ions through the amine and thione substituents on the five-membered ring. Complex (1) has a square-pyramidal copper(II) ion coordinated by two triazole ligands and one water molecule. Unlike (1), the Cu²⁺ ion in (2) displays its characteristic Jahn–Teller distortion with the distance of the Cl^– anions to metal ion further away than that of the triazole ligands. The most intriguing structural features of the title complexes are that the HL ligands chelate copper(II) ions through the N(1) and S(1) atoms, in a cis mode in (1) and a trans mode in (2). In both cases, self-assembled crystals, by supramolecular contacts simultaneously, form two multi-dimensional frameworks.     

Synthesis and Characterization of Ag2S Nanocrystals in Hyperbranched Polyurethane at Room Temperature

Ag₂S nanoparticles in hyperbranched polyurethane matrix were prepared through the in situ reaction with thioacetamide as the sulfur source at room temperature. Transmission electron microscopic analysis revealed a uniform spherical shape for Ag₂S nanoparticles, with an average size of about 4-10 nm and a narrow size distribution. X-ray powder diffraction and UV-vis spectroscopy were also used to characterize the obtained nanoparticles     

三烃基锡肟类化合物的合成及生物活性

共合成了１３个未见文献报道的三烃基锡肟衍生物，测定了它们的＾１ｈ，（＾１３Ｃ，＾１１９Ｓｎ）ＮＭＲ，ＩＲ和ＭＳ。结果表明此类化合物为四配位锡单体结构，生物活性测定结果表明部分化合物同时兼有杀菌、杀螨、除草多种活性。     

Optical properties of human prostate at 732 nm measured in mediated photodynamic therapy

Characterization of the tissue light penetration in prostate photodynamic therapy (PDT) is important to plan the arrangement and weighting of light sources so that sufficient light fluence is delivered to the treatment volume. The optical properties (absorption [mu(a)], transport scattering [mu(s)'] and effective attenuation [mu(eff)] coefficients) of 13 patients with locally recurrent prostate cancer were measured in situ using interstitial isotropic detectors. Measurements were made at 732 nm before and after motexafin lutetium (MLu)-mediated PDT in four quadrants. Optical properties were derived by applying the diffusion theory to the fluence rates measured at several distances (0.5-5 cm) from a point source. mu(a) and mu(s)' varied between 0.07 and 1.62 cm(-1) (mean 0.37 +/- 0.24 cm(-1)) and 1.1 and 44 cm(-1) (mean 14 +/- 11 cm(-1)), respectively. mu(a) was proportional to the concentration of MLu measured by an ex vivo fluorescence assay. We have observed, on average, a reduction of the MLu concentration after PDT, presumably due to the PDT consumption of MLu. mu(eff) varied between 0.91 and 6.7 cm(-1) (mean 2.9 +/- 0.7 cm(-1)), corresponding to an optical penetration depth (delta = 1/micro(eff)) of 0.1-1.1 cm (mean 0.4 +/- 0.1 cm). The mean penetration depth at 732 nm in human prostate is at least two times smaller than that found in normal canine prostates, which can be explained by a four times increase of the mean value of mu(s)' in human prostates. The mean light fluence rate per unit source strength at 0.5 cm from a point source was 1.5 +/- 1.1 cm(-2), excluding situations when bleeding occurs. The total number of measurements was N = 121 for all mean quantities listed above. This study showed significant inter- and intraprostatic differences in the optical properties, suggesting that a real-time dosimetry measurement and feedback system for monitoring light fluences during treatment should be considered for future PDT studies.