A Brønsted‐Ligand‐Based Iron Complex as a Molecular Switch with Five Accessible States

A mononuclear Fe^II complex, prepared with a Brønsted diacid ligand, H₂L (H₂L=2‐[5‐phenyl‐1H‐pyrazole‐3‐yl] 6‐benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [Fe^II(H₂L)₂](BF₄)₂ ( 1_A ), exhibits abrupt spin transition at T_1/2=258 K, and treatment with base yields a deprotonated analogue [Fe^II(HL)₂] ( 1_B ), which shows gradual SCO above 350 K. A range of Fe^III analogues were also characterized. [Fe^III(HL)(H₂L)](BF₄)Cl ( 1_C ) has an S=5/2 spin state, while the deprotonated complexes [Fe^III(L)(HL)], ( 1_D ), and (TEA)[Fe^III(L)₂], ( 1_E ) exist in the low‐spin S=1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid‐state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.     

The colorimetric micro-determination of nickel as triphenylmethylarsonium bis-dithio-oxalato nickelate(II)

The colorimetric micro-determination of nickel described involves the formation of [Ph₃MeAs]₂ [Ni(C₂S₂O₂)₂] and ita extraction into an organic solvent. As the extracted compound is strongly coloured, its concentration is measured without furthcr treatment. The procedure given is suitable within a range of 25 to 250 μg of nickel -with an average error no greater than 1%. Iron, cobalt and copper interfere seriously, and a simple method is suggested for their removal.     

Copolymerization of styrene and butadiene in emulsion. III. Crosslinking studies by partial conversion properties

Crosslinking in the styrene–butadiene emulsion copolymerization (21 parts styrene:79 parts butadiene) prior to gelation has been studied by means of partial conversion number-average molecular weights at 5, 15, and 25°C. It is shown that the macromolecular population begins to diminish at progressively lower conversions as the reaction temperature is increased. This is attributed to the relative increase in crosslinking over propagation as the reaction temperature is increased and also to the decrease in mercaptan regulating index with increasing temperature.     

Decomposition of snarks

There are several methods for constructing snarks (cubic graphs with chromatic index 4). We study the reverse process of splitting a snark into smaller snarks which compose it. We also introduce the notion of a “prime” snark.     

Plasmachemical surface functionalised beads: versatile tailored supports for polymer assisted organic synthesis

Plasmachemical surface modification of porous polystyrene beads with allylamine or diaminopropane provides reactive amine functionality exclusively at accessible surface sites, allowing faster reactions than classically prepared materials.     

Phase-referenced Doppler optical coherence tomography in scattering media

We present a fiber-based, low-coherence interferometer that significantly reduces phase noise by incorporating a second, narrowband, continuous-wave light source as a phase reference. By incorporating this interferometer into a Doppler OCT system, we demonstrate significant velocity noise reduction in reflective and scattering samples using processing techniques amenable to real-time implementation. We also demonstrate 90% suppression of velocity noise in a flow phantom.