Cy3B™: Improving the Performance of Cyanine Dyes

The spectral properties of a rigidified trimethine cyanine dye, Cy3B have been characterised. This probe has excellent fluorescent properties, good water solubility and can be bioconjugated. The emission properties of this fluorophore have also been investigated upon conjugation to an antibody. This study compared the conjugated emission properties of Cy3B with other commercially available fluorophores emitting at similar wavelengths.     

Interactions between hairy rod anionic conjugated polyelectrolytes and nonionic alkyloxyethylene surfactants in aqueous solution: observations from cloud point behaviour

The effect of three anionic, hairy-rod fluorene based conjugated polyelectrolytes on the cloud points of the alkyloxyethylene surfactants C10E3, C12E4, C12E5, and C12E6 has been studied in aqueous solution. Although the association behaviour of these rigid polymers with surfactants is different from that of more flexible polyelectrolytes, both types of polymers are seen to increase the cloud points, probably as a consequence of associative interactions. The possible importance of Coulombic interactions is suggested by the decrease in cloud points with these systems in the presence of NaCl. With the conjugated polyelectrolytes, the effect appears to be most pronounced with poly[9,9-bis(4-phenoxybutylsulfonate)fluorene-co-2,5-thienylene], which may result from specific interactions between oxyethylene groups and the thiophene ring. The value of cloud point behaviour in designing water based formulations for preparation of devices of these conjugated polyelectrolytes is discussed.     

Kinetic and mechanistic studies of the I(2)/O(3) photochemistry

The atmospherically relevant chemistry generated by photolysis of I2/O3 mixtures has been studied at 298 K in the pressure range from 10 to 400 hPa by using a laboratory flash photolysis setup combining atomic resonance and molecular absorption spectroscopy. The temporal behaviors of I, I(2), IO, and OIO have been retrieved. Conventional kinetic methods and numerical modeling have been applied to investigate the IO self-reaction and the secondary chemistry. A pressure independent value of k(IO + IO) = (7.6 +/- 1.1) x 10(-11) cm(3) molecule-1 s(-1) has been determined. The pressure dependence of the branching ratios for the I + OIO and IOIO product channels in the IO + IO reaction have been determined and have values of 0.45 +/- 0.10 and 0.44 +/- 0.13 at 400 hPa, respectively. The branching ratios for the 2I + O(2) and I(2) + O(2) product channels are pressure independent with values of 0.09 +/- 0.06 and 0.05 +/- 0.03, respectively. The sensitivity analysis indicates that the isomer IOIO is more thermally stable than predicted by theoretical calculations. A reaction scheme comprising OIO polymerization steps has been shown to be consistent with the temporal behaviors recorded in this study. For simplicity, the rate coefficient has been assumed to be the same for each reaction (OIO)(n) + IO --> (OIO)(n+1), n = 1, 2, 3, 4. The lower limit obtained for this rate coefficient is (1.2 +/- 0.3) x 10(-10) cm(3) molecule(-1) s(-1) at 400 hPa. Evidence for the participation of IO in the polymerization mechanism also has been found. The rate coefficient for IO attachment to OIO and to small polymers has been determined to be larger than (5 +/- 2) x 10(-11) cm(3) molecule(-1) s(-1) at 400 hPa. These results provide supporting evidence for atmospheric particle formation induced by polymerization of iodine oxides.     

Rhodium-Promoted Linear Tetramerization and Cyclization of 3,3-Dimethylbut-l-yne

With tetrahydrofuran as the solvent [Rh(thf)₂(cod)]⁺ promotes the selective coupling of tBuC₂H to form triene-yne 1 ; at high alkyne concentrations, however, an unusual C−H activation process intervenes, leading to the formation of complex 2 , which contains two linked five-membered rings. cod=1,5-cyclooctadiene.     

Reaction pathways and mechanisms of photodegradation of pesticides

The photodegradation of pesticides is reviewed, with particular reference to the studies that describe the mechanisms of the processes involved, the nature of reactive intermediates and final products. Potential use of photochemical processes in advanced oxidation methods for water treatment is also discussed. Processes considered include direct photolysis leading to homolysis or heterolysis of the pesticide, photosensitized photodegradation by singlet oxygen and a variety of metal complexes, photolysis in heterogeneous media and degradation by reaction with intermediates generated by photolytic or radiolytic means.     

Cationic polythiophene-surfactant self-assembly complexes: phase transitions, optical response, and sensing

The absorption and photoluminescence spectra of the cationic conjugated polyelectrolyte poly[3-(6-trimethylammoniumhexyl)thiophene] (P3TMAHT) were observed to be dramatically altered in the presence of anionic surfactants due to self-assembly through ionic complex formation. Small-angle neutron scattering (SANS), UV/vis, and photoluminescence spectroscopy were used to probe the relationship between the supramolecular complex organization and the photophysical response of P3TMAHT in the presence of industrially important anionic surfactants. Subtle differences in the surfactant mole fraction and chemical structure (e.g., chain length, headgroup charge density, perfluorination) result in marked variations in the range and type of complexes formed, which can be directly correlated to a unique colorimetric and fluorimetric fingerprint. Our results show that P3TMAHT has potential as an optical sensor for anionic surfactants capable of selectively identifying distinct structural subgroups through dual mode detection.     

Dipyridyl β-diketonate complexes and their use as metalloligands in the formation of mixed-metal coordination networks

The iron(III) and aluminium(III) complexes of 1,3-di(4-pyridyl)propane-1,3-dionato (dppd) and 1,3-di(3-pyridyl)propane-1,3-dionato (dmppd), [Fe(dppd)(3)] 1, [Fe(dmppd)(3)] 2, [Al(dppd)(3)] 3 and [Al(dmppd)(3)] 4 have been prepared. These complexes adopt molecular structures in which the metal centres contain distorted octahedral geometries. In contrast, the copper(II) and zinc(II) complexes [Cu(dppd)(2)] 5 and [Zn(dmppd)(2)] 6 both form polymeric structures in which coordination of the pyridyl groups into the axial positions of neighbouring metal centres links discrete square-planar complexes into two-dimensional networks. The europium complex [Eu(dmppd)(2)(H(2)O)(4)]Cl·2EtOH·0.5H(2)O 7 forms a structure containing discrete cations that are linked into sheets through hydrogen bonds, whereas the lanthanum complex [La(dmppd)(3)(H(2)O)]·2H(2)O 8 adopts a one-dimensional network structure, connected into sheets by hydrogen bonds. The iron complexes 1 and 2 act as metalloligands in reactions with silver(I) salts, with the nature of the product depending on the counter-ions present. Thus, the reaction between 1 and AgBF(4) gave [AgFe(dppd)(3)]BF(4)·DMSO 9, in which the silver centres link the metalloligands into discrete nanotubes, whereas reactions with AgPF(6) and AgSbF(6) gave [AgFe(dppd)(3)]PF(6)·3.28DMSO 10 and [AgFe(dppd)(3)]SbF(6)·1.25DMSO 11, in which the metalloligands are linked into sheets. In all three cases, only four of the six pyridyl groups present on the metalloligands are coordinated. The reaction between 2 and AgNO(3) gave [Ag(2)Fe(dmppd)(3)(ONO(2))]NO(3)·MeCN·CH(2)Cl(2)12. Compound 12 adopts a layer structure in which all pyridyl groups are coordinated to silver centres and, in addition, a nitrate ion bridges between two silver centres. A similar structure is adopted by [Ag(2)Fe(dmppd)(3)(O(2)CCF(3))]CF(3)CO(2)·2MeCN·0.25CH(2)Cl(2)13, with a bridging trifluoroacetate ion playing the same role as the nitrate ion in 12.     

Depth-dependent magnetism in epitaxial MnSb thin films: effects of surface passivation and cleaning

Depth-dependent magnetism in MnSb(0001) epitaxial films has been studied by combining experimental methods with different surface specificities: polarized neutron reflectivity, x-ray magnetic circular dichroism (XMCD), x-ray resonant magnetic scattering and spin-polarized low energy electron microscopy (SPLEEM). A native oxide ～4.5?nm thick covers air-exposed samples which increases the film's coercivity. HCl etching efficiently removes this oxide and in situ surface treatment of etched samples enables surface magnetic contrast to be observed in SPLEEM. A thin Sb capping layer prevents oxidation and preserves ferromagnetism throughout the MnSb film. The interpretation of Mn L(3,2) edge XMCD data is discussed.     

Does cation dehydration drive the binding of metal ions to polyelectrolytes in water? What we can learn from the behaviour of aluminium(III) and chromium(III)

Much stronger binding is seen in aqueous solutions between the anionic polyelectrolyte potassium poly(vinyl sulfate) and the substitution labile aluminium(III) than with the kinetically inert chromium(III). This strongly supports the idea that entropy driven water loss from the hydration sphere of the metal ion plays a major role in driving binding of the trivalent metal ion to the polyelectrolyte.