Solid-state self-assembly of polymeric double helicates leading to linear arrays of silver(I) ions and reversible strand/double helix interconversion in solution

Reaction of a bent py-hyz-pym-hyz-pym 1 and of a linear py-hyz-py-hyz-pym 3 (py=pyridine; pym=pyrimidine; hyz=hydrazone) ligand strands with silver(I) tetrafluoroborate in CH(3)NO(2) generates double-helical dinuclear 2 and trinuclear 4 complexes. These complexes form polymeric, highly ordered solid-state structures, with wirelike, linear continuous or discontinuous polycationic Ag(n) (+) arrays with Ag--Ag distances of 2.78 to 4.42 A. Ligand 5, an isomer of 1, is found to yield a [2x2] grid-type complex 6. Titration experiments reveal the formation of linear rack-type dinuclear species from 1 and 5. Acid-base modulated, reversible interconversion between strand 1 and double helicate 2 may be achieved by using tren as a competing complexing agent (tren=N(CH(2)CH(2)NH(2))(3)). Progressive addition of silver(I) ions to a 1:1 mixture of 1 and 5 leads to the preferential formation of the double helicate 2 over the grid complex 6, illustrating a process of self-organisation with selection of the correct ligand.     

Dispirofluorene-indenofluorene derivatives as new building blocks for blue organic electroluminescent devices and electroactive polymers

A series of new dispiro[fluorene-9',6,9',12-indeno[1,2b]fluorenes] (DSF-IFs) has been synthesised. These new building blocks for blue-light-emitting devices and electroactive polymers combine indenofluorene (IF) and spirobifluorene (SBF) properties. We report here our synthetic investigations towards these new structures and their thermal, structural, photophysical and electrochemical properties. These properties have been compared to those of IF and SBF. We also report the anodic oxidation of DSF-IFs that leads to the formation of non-soluble transparent three-dimensional polymers. The structural and electrochemical behaviour of these polymers has been studied. The first application of these building blocks as new blue-light-emitting materials in organic light-emitting diodes (OLED) is also reported.     

Arranging up to six ferrocene carboxamides around metal centres

Ferrocene carboxamide, FcCONH(2), forms homo- and heteroleptic complexes with Co(II), Ni(II) and Cu(II) via coordination of its carbonyl group. Whereas for both Co(II) and Ni(II), hexaferrocenyl complexes are obtained in the presence of BF(4)(-) anion, in the case of Cu(II) a tetraferrocenyl species is observed in the presence of triflate anion.     

Frequency-modulation Fourier transform spectroscopy: a broadband method for measuring weak absorptions and dispersions

A new method, FM-FTS, combining frequency modulation heterodyne laser spectroscopy and Fourier transform spectroscopy is presented. It provides simultaneous sensitive measurement of absorption and dispersion profiles with broadband spectral coverage capabilities. Experimental demonstration of the overtone spectrum of C(2)H(2) in the 1.5 microm region is presented.     

Beam breakup integral measurement on high-power laser chains

We experimentally demonstrate the efficiency of a single-shot method to measure the beam breakup integral (B) accumulated across a high power chain. The technique uses spectrally shaped strongly chirped femtosecond pulses and takes advantage of time-to-spectral coupling generated by nonlinear effects. We performed B measurements on regenerative amplifiers (Ti:sapphire) and on the ALISE 200 J facility currently installed at CEA-CESTA (France).     

Cyclic Ti9 keggin trimers with tetrahedral (PO4) or octahedral (TiO6) capping groups

We have synthesized the cyclic Ti 9 Keggin trimers [(alpha-Ti 3PW 9O 38) 3(PO 4)] (18-) ( 1) and [(alpha-Ti 3SiW 9O 37OH) 3(TiO 3(OH 2) 3)] (17-) ( 2), which are both composed of three (Ti 3XW 9O 37) units (X = P or Si) linked via three Ti-O-Ti bridges and a capping group, which is either tetrahedral PO 4 ( 1) or octahedral TiO 6 ( 2). Polyanions 1 and 2 were fully characterized in the solid state (IR, X-ray diffraction, thermogravimetric and elemental analyses) and in solution ( (31)P or (183)W NMR).     

Effect of particle size and natural organic matter on the migration of nano- and microscale latex particles in saturated porous media

In the interest of fully assessing the potential environmental risks linked to "nanolitter," we need to be able to predict the persistence, toxicity, and mobility of engineered nanomaterials in the natural subsurface environment. To examine the effects of particle size and natural organic matter on nanoparticle mobility, laboratory-scale filtration experiments were performed using different sized model nanomaterials (i.e., latex colloids having diameters of 50, 110, and 1500 nm) in the presence and absence of 5.0 mg/L Suwannee River humic acid (SRHA). At low ionic strengths (1-10 mM KCl), an increase in attachment efficiency (alpha) with increasing particle size was observed. This result contrasts with predictions of particle filtration based on attachment in the primary energy minimum of the particle-grain interaction energy profile evaluated using Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The presence of SRHA generally resulted in a decrease in alpha over the range of experimental conditions investigated. Results of particle transport experiments combined with particle characterization measurements suggest that the decrease in colloid attachment in the presence of SRHA is related to the combined influence of the mechanisms of charge stabilization and steric stabilization.