Some observations on the systems Co2(CO)8/sodium amalgam and Hg[Co(CO)4]2/sodium amalgam,and the effect of added LiBr

Co₂(CO)₈ and Hg[Co(CO)₄]₂ react sodium amalgam and/or mercury in ethereal solvents to give a variety of products. On treatment with aqueous M(o-phen)₃Cl₂(M  Fe, Ni), the anions [Co(CO)₄^?, [Co₃(CO)₁₀]^?, {Hg[Co(CO)₄]₃}^? and {Hg[Co(CO)₄]₂Cl}^? could be isolated as their [M(o-phen)₃]²⁺ salts. The effect of LiBr on the reacting systems was also investigated and the anion {Hg[Co(CO)₄]₂Br}^? isolated.     

Bis[pyrrolyl Ru(ii)] triads: a new class of photosensitizers for metal–organic photodynamic therapy

A new family of ten dinuclear Ru(ii) complexes based on the bis[pyrrolyl Ru(ii)] triad scaffold, where two Ru(bpy)₂ centers are separated by a variety of organic linkers, was prepared to evaluate the influence of the organic chromophore on the spectroscopic and in vitro photodynamic therapy (PDT) properties of the compounds. The bis[pyrrolyl Ru(ii)] triads absorbed strongly throughout the visible region, with several members having molar extinction coefficients (ε) ≥ 10⁴ at 600–620 nm and longer. Phosphorescence quantum yields (Φ_p) were generally less than 0.1% and in some cases undetectable. The singlet oxygen quantum yields (Φ_Δ) ranged from 5% to 77% and generally correlated with their photocytotoxicities toward human leukemia (HL-60) cells regardless of the wavelength of light used. Dark cytotoxicities varied ten-fold, with EC₅₀ values in the range of 10–100 μM and phototherapeutic indices (PIs) as large as 5400 and 260 with broadband visible (28 J cm^–2, 7.8 mW cm^–2) and 625 nm red (100 J cm^–2, 42 mW cm^–2) light, respectively. The bis[pyrrolyl Ru(ii)] triad with a pyrenyl linker (5h) was especially potent, with an EC₅₀ value of 1 nM and PI > 27 000 with visible light and subnanomolar activity with 625 nm light (100 J cm^–2, 28 mW cm^–2). The lead compound 5h was also tested in a tumor spheroid assay using the HL60 cell line and exhibited greater photocytotoxicity in this more resistant model (EC₅₀ = 60 nM and PI > 1200 with 625 nm light) despite a lower dark cytotoxicity. The in vitro PDT effects of 5h extended to bacteria, where submicromolar EC₅₀ values and PIs >300 against S. mutans and S. aureus were obtained with visible light. This activity was attenuated with 625 nm red light, but PIs were still near 50. The ligand-localized ³ππ* state contributed by the pyrenyl linker of 5h likely plays a key role in its phototoxic effects toward cancer cells and bacteria.     

Methodological approaches for the study of GABA<Subscript>A</Subscript> receptor pharmacology and functional responses

Inhibitory GABA_A receptor ion channels are the target for a wide range of clinically-used therapeutic agents. The complex structural diversity of these ligand-gated channels, revealed by molecular cloning studies, together with increasing requirements for higher-throughput functional assays in drug discovery, has led to the development of a wide range of techniques to examine GABA_A receptor pharmacology and function. In the current article we review some of the methodologies which have contributed to the expansion of knowledge in this field. The techniques include: molecular approaches, immunoprecipitation, and immunopurification to study receptor assembly, structure, and functional expression; in situ hybridization, immunocytochemistry, and autoradiography to examine receptor distribution in native tissues; radioligand binding, site-directed mutagenesis, and electrophysiology to examine pharmacology and allosteric modulation; and patch clamp, ion flux, microphysiometry, and a variety of novel fluorescence-based technologies to examine ion-channel function. The use of gene targetting approaches in transgenic mice has also provided important insights into the role of specific GABA_A receptor subtypes in vivo. The continuing evolution of novel technologies and assay approaches with appropriate sensitivity and resolution to measure subtle modulation of GABA_A ion channels will facilitate ongoing investigation of the physiological functions of these important inhibitory receptors.     

A lanthanum macrocycle catalysed hydrolysis of 2,4-dinitrophenyl diethyl phosphate and O-isopropyl methylfluorophosphote (Sarin)

The lanthanum complex of a hexa-aza macrocycle is shown to be an effective catalyst for the hydrolysis of the water soluble phosphate triester 2,4-dinitrophenyl diethyl phosphate. At pH 9, using a catalyst concentration of 2.5 × 10⁻³ mol dm⁻³ at 25°C, the rate enhancement is ca 10³ fold. The reaction is shown to be catalytic rather than stoichiometric and possible mechanisms involving a metal-bound hydroxide nucleophile are considered to account for the catalysis. The macrocyclic complex is alswn to be an effective catalyst for the hydrolysis of the anticholinesterase agent O-isopropyl methylfluorophosphate (Sarin).     

Selective manganese(III) and vanadium(IV) catalysts for the oxidation of dialkyl sulfides in microemulsion media

The oxidation of n-Bu2S by t-BuOOH in the presence ofthe catalysts [Mn2L2(MeCO2)2 (-O)] (ClO4)2 (L= Me3tacn=1,4,7–trimethyl-1,4,7–triazacyclononane) and VO(acac)2 has been studied using microemulsion media (BRIJ 97 and SD2 microemulsions). In the presence of the MnIII complex oxidation to the sulfone occurs, while in the presence of the VIV complex the sulfide is oxidised to the sulfoxide. The oxidation of mustard gas, (ClCH2CH2)2S, has also been studied. The reactions have been monitored by total internal reflectance i.r. spectroscopy. The use of optically transparent microemulsions provides a useful method for carrying out oxidations involving inorganic reagents and water-insoluble substrates.     

Spatial dynamics of steady flames 2. Low-dimensional manifolds and the role of transport processes

The study of the spatial dynamics of steady one-dimensional H 2/O 2 flames is continued. Algorithms for generating low-dimensional manifolds for these systems are presented and used to find low-dimensional manifolds for the flames and the corresponding adiabatic, isobaric chemical-kinetic systems. It is demonstrated that these algorithms generate manifolds that are more accurate than the ILDM algorithm for two-dimensional manifolds of the flames. The manifolds are then employed to study the relationship between the manifolds of the flame and the manifolds of the chemical-kinetic system. It is shown that the one-dimensional manifolds of the flame match well with the composite manifolds of the chemical kinetics, but that for two-dimensional manifolds there are discrepancies between the flame manifolds and the chemical-kinetic manifolds.     

Anion-arene adducts: C-H hydrogen bonding, anion-pi interaction, and carbon bonding motifs

This article summarizes experimental and theoretical evidence for the existence of four distinct binding modes for complexes of anions with charge-neutral arenes. These include C-H hydrogen bonding and three motifs involving the arene-pi system-the noncovalent anion-pi interaction, weakly covalent sigma interaction, and strongly covalent sigma interaction.     

Exploration of variables in the fabrication of pyrolysed photoresist

The increased use of pyrolysed photoresist films (PPF) as electrode material intensifies the need to know what fabrication variables are important in the pyrolysis process. The main factor effects of seven variables (three time/temperature heating levels plus the position in the furnace tube) in the fabrication of PPF were investigated by a Plackett and Burman, eight-run, experimental design. In the three-step pyrolysis programme, gas flow had a large effect on the surface cleanliness and roughness. It was also observed that the position in the furnace affected the resistivity of the PPF. Fabrication parameters that give rapid electron transfer to redox species in solution, that provide low surface oxide and that lead to low surface roughness were identified. The guidelines on what fabrication conditions to employ to give a variety of different electrode characteristics are presented.