Synthesis and conversion of 2‐(pyrazol‐1‐yl)quinoxaline 4‐oxides

The reaction of 6‐chloro‐2‐hydrazinoquinoxaline 4‐oxide 1b with acetylacetone or benzoylacetone gave 6‐chloro‐2‐(3,5‐dimethylpyrazol‐i‐yl)quinoxaline 4‐oxide 5a or 6‐chloro‐2‐(3‐methyl‐5‐phenylpyrazol‐1‐yl)quinoxaline 4‐oxide 5b , respXectively. Compound 5a or 5b was converted into the pyrrolo[1,5‐a]quinoxaline 6a or 6b , triazolo[4,3‐a]quinoxaline 9a or 9b , and tetrazolo[1,5‐a]quinoxaline 10.     

Photoresponsive hyaluronate nanogel as an anticancer drug carrier

In this study, we introduced photolabile 4‐(4‐(1‐hydroxyethyl)‐2‐methoxy‐5‐nitrophenoxy)butyric acid (HMNB) to prepare photoresponsive nanogels. Hyaluronate (HA) grafted with 4‐(4‐(1‐hydroxyethyl)‐2‐methoxy‐5‐nitrophenoxy)butyric acid (HA‐g‐HMNB) was self organized in aqueous solution. Interestingly, HA‐g‐HMNB nanogels exhibited caging and photo‐uncaging properties for an encapsulated antitumor drug. Photoactivation allowed accelerated antitumor drug release from uncaged nanogels. We found a significant improvement in KB tumor‐cell‐killing efficacy when this system was associated with local light irradiation. Copyright © 2013 John Wiley & Sons, Ltd.     

A mechanophysical phase transition provides a dramatic example of colour polymorphism: the tribochromism of a substituted tri(methylene)tetrahydrofuran-2-one

Background

Derivatives of fulgides have been shown to have interesting photochromic properties. We have synthesised a number of such derivatives and have found, in some cases, that crystals can be made to change colour on crushing, a phenomenon we have termed “tribochromism”. We have studied a number of derivatives by X-ray crystallography, to see if the colour is linked to molecular structure or crystal packing, or both, and our structural results have been supported by calculation of molecular and lattice energies.

Results

A number of 5-dicyanomethylene-4-diphenylmethylene-3-disubstitutedmethylene-tetrahydrofuran-2-one compounds have been prepared and structurally characterised. The compounds are obtained as yellow or dark red crystals, or, in one case, both. In two cases where yellow crystals were obtained, we found that crushing the crystals gave a deep red powder. Structure determinations, including those of the one compound which gave both coloured forms, depending on crystallisation conditions, showed that the yellow crystals contained molecules in which the structure comprised a folded conformation at the diphenylmethylene site, whilst the red crystals contained molecules in a twisted conformation at this site. Lattice energy and molecular conformation energies were calculated for all molecules, and showed that the conformational energy of the molecule in structure IIIa (yellow) is marginally higher, and the conformation thus less stable, than that of the molecule in structure IIIb (red). However, the van der Waals energy for crystal structure IIIa, is slightly stronger than that of structure IIIb – which may be viewed as a hint of a metastable packing preference for IIIa, overcome by the contribution of a more stabilising Coulomb energy to the overall more favourable lattice energy of structure IIIb.

Conclusions

Our studies have shown that the crystal colour is correlated with one of two molecular conformations which are different in energy, but that the less stable conformation can be stabilised by its host crystal lattice.

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Graphical abstract Graphical representation of the structural and colour change in the tribochromic compound (III).

     

Facile synthesis of multimeric micelles

Bringing it all together: Synthesis of a dimeric micelle (see scheme) is shown to produce specifically linked Janus-like micelles. The reaction conditions for dimeric micelle formation were optimized and the resulting micelles characterized. Trimeric, tetrameric, and multimeric micelles were also synthesized using the same technique.     

螺旋波激发甲烷等离子体光谱诊断

利用螺旋波激发等离子体化学气相沉积(LPP-CVD)技术,以甲烷和氦气为反应气体产生等离子体.通过采集到甲烷的可见光到紫外发射光谱,对甲烷等离子体进行原位诊断,发现存在CH、Ha及Hβ等碎片粒子的光辐射,同时,分析了不同入射功率、气压下CH粒子以及Hβ、Hγ的相对强度变化情况.结果表明:CH粒子的相对强度随着射频功率是先增大而后减小,随工作气压的增大而逐渐减小;随气压及功率的增加,Hβ、Hγ相对强度变化的总体趋势都是先增加而后减小的.