Reactions of a carbene stabilised indium trihydride complex, [InH3{CN(Mes)C2H2N(Mes)}] Mes = mesityl,with transition metal complexes

The reactivity of the carbene stabilised indium trihydride complex, [InH₃(IMes)] IMes = 1,3-dimesitylimidazol-2-ylidene, toward a variety of transition metal complexes has been investigated. The study has shown that the InH₃ complex can act as a carbene and/or hydride transfer reagent to transition metal centres but does not yield heterobimetallic materials. Two new complexes, [Cp₂Ti(-Cl)₂Zn(IMes)Cl] and [CpNi(H)(IMes)], have resulted from this work, both of which have been spectroscopically and structurally characterised.     

Dual-column GC analysis of mediterranean fish for ten organochlorine pesticides and sixty two chlorobiphenyls

The simultaneous analysis of α-HCH, β-HCH, γ-HCH, HCB, p,p′-DDD, p,p′-DDT, p,p′-DDE, o,p′-DDT, mirex, dieldrin and 62 chlorobiphenyl congeners on two parallel capillary GC columns of different polarity is described for nine Mediterranean fish species. Ten commercially available columns with stationary phases completely characterized in respect of their PCB elution patterns were considered for dual-column GC-ECD analysis. The combination of a 60 m × 0.25 mm i.d. column coated with a 0.25 μm film of 50% diphenyl dimethylsiloxane and a series combination of a 25 m × 0.25 mm i.d. column coated with a 0.25 μm film of 5% diphenyl dimethylsiloxane with a 25 m × 0.22 mm i.d. column coated with a 0.10 μm film of 1, 10-dicarba-closo-dodecarborane dimethylpolysiloxane furnished the highest number of separated chlorobiphenyl congeners (104). The dual-column GC system performed with high stability and reproducibility over a broad concentration range (1–3000 ng/g lipid) of the organochlorine compounds in the investigated fish.     

Reactive dications: the superacid-catalyzed reactions of alkynes bearing adjacent N-heterocycles or amine groups

A variety of aminoalkynes and related heterocycles are reacted in the Bronsted superacid CF(3)SO(3)H (triflic acid), and products are obtained in generally good yields (69-99%) from Friedel-Crafts-type reactions. The reactions are consistent with the formation of novel dicationic intermediates having a vinyl cationic site and an adjacent protonated N-heterocycle or ammonium cation.     

Synthesis, characterization, and preliminary intramolecular energy transfer studies of rigid, emissive, rhenium-linked porphyrin dimers

The reaction of pyridyl functionalized porphyrins with Re(CO)(5)Cl in THF results in the formation of porphyrin dimers which, despite incorporation of rhenium into the assemblies, remain fluorescent. The rigid compounds provide an efficient geometry and/or orbital pathway for singlet energy transfer, rendering these compounds suitable, in principle, for the study of both through-bond and through-space energy transfer. Derivatives containing both metallated and freebase porphyrins connected via the metal corners display efficient porphyrin-porphyrin energy transfer. The photophysical properties of the assemblies have been studied by both steady-state and time-resolved fluorescence techniques, yielding approximate rates and efficiencies for porphyrin-porphyrin energy transfer.     

Oscillatory dynamics protect enzymes and possibly cells against toxic substances

We have used the oscillating peroxidase-oxidase (PO) reaction as a model system to study how oscillatory dynamics may affect the influence of toxic reaction intermediates on enzyme stability. In the peroxidase-oxidase reaction reactive intermediates, such as hydrogen peroxide, superoxide, and hydroxyl radical are formed. Such intermediates inactivate many cellular macromolecules such as proteins and nucleic acids. These reaction intermediates also react with peroxidase itself to form an inactive enzyme. The fact that the PO reaction shows bistability between an oscillatory and a steady state gives us a unique possibility to compare such inactivation when the system is in one of these two states. We show that inactivation of peroxidase is slower when the system is in an oscillatory state, and using numerical simulations we provide evidence that oscillatory dynamics lower the average concentration of the reactive intermediates.     

222RN at Bermuda and Mauna Loa: Local and distant sources

Continuous measurements of atmospheric²²²Rn were made for the past three years by the Environmental Measurements Laboratory (EML) at the Atmosphere/Ocean Chemistry Experiment site located at Tudor Hill, Bermuda and at the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Mauna Loa Observatory. The²²²Rn analyzer is based on the two-filter tube method. At the Bermuda site, monthly median²²²Rn concentration range from 50 to 700 mBq m^–3, and the concentrations vary seasonally, with a maximum in the winter and a minimum in the summer. The concentrations are significantly elevated when local winds traverse the island. At MLO, monthly median²²²Rn concentrations range from 100 mBq m^–3 during the fall months to 400 mBq m^–3 during the spring months. The springtime maximum values correspond to periods of rapid transport in the free troposphere from the Asian continent, corroborated by backward air mass trajectories. The²²²Rn data are also used to help decipher local daily upslope/downslope conditions present at MLO. This study illustrates the value of atmospheric²²²Rn monitoring, when screened through the filter of local meteorology, in studying the transport of continental air to the oceans, as well as the dynamics of local meteorological effects.