2H Solid-State NMR Spectroscopy Reveals the Dynamics of a Pyridine Probe Interacting with Coordinatively Unsaturated Metal Sites of MIL-100(Al) Metal–Organic Frameworks

Coordinatively unsaturated metal sites (CUS) play an important role in catalysis by metal-organic frameworks (MOF). Being an intrinsic part of the framework the CUS take the role of acidic sites active in industrially relevant processes such as condensation or oxidation reactions. The key step of such reactions represents the coordination of the reagents to CUS. In MOFs the mechanism of the reagent interaction with CUS is poorly understood. Herein, we characterize the interaction of a widely used acidity probe pyridine with CUS of MIL-100(Al) MOF by means of the ²H solid-state NMR spectroscopy. ²H NMR reveals that pyridine species, which are interacting with CUS and the ones which are coordinated to the Al−OH site, exhibit different motional behavior. ²H NMR line shape as well as T₁, T₂ relaxation analyses for [D₅]pyridine adsorbed in MIL-100(Al) allowed us to perform a detailed characterization of pyridine dynamics in both states including the kinetics of the exchange process between these adsorption states.     

Isolation and Densitometric HPTLC Analysis of Rutin,Narcissin, Nicotiflorin,and Isoquercitrin in Caragana spinosa Shoots

JPC – Journal of Planar Chromatography – Modern TLC - Athin-layer chromatographic (TLC) method was used for the quantification of four dominant flavonoids (rutin, narcissin,...     

Raman imaging and photodegradation study of phthalocyanine containing microcapsules and coated particles

We present the results of using Raman molecular imaging and atomic force microscopy (AFM) investigation of the composition, stability, and photodegradation of polyelectrolyte multilayer microcapsules and coated microparticles containing copper–phthalocyanine and iron–phthalocyanine. The influence of laser light on degradation of these phthalocyanine dyes embedded in the walls of polyelectrolyte multilayer capsules and shells of microparticles was studied by both AFM and Raman molecular imaging, but only the latter technique gave information on dynamics of photodegradation. Raman peak assignment was performed according to theoretical calculations. The degradation rate of phthalocyanine dyes is estimated from Raman signal measurements and a model is proposed to account for the degradation rate. Practical applications of our approach are outlined. Copyright © 2011 John Wiley & Sons, Ltd.     

Using data compressors to construct order tests for homogeneity and component independence

Nonparametric order tests for homogeneity and component independence are proposed, which are based on data compressors. For homogeneity testing the idea is to compress the word obtained by ordering the combined samples and writing the number of the sample in the place of each element. H₀ should be rejected if the string is compressed to a certain degree and accepted otherwise. We show that such a test obtained from an ideal data compressor is valid against all alternatives. Component independence is reduced to homogeneity testing.     

Unbounded Representations of q-Deformation of Cuntz Algebra

We study a deformation of the Cuntz–Toeplitz C ^*-algebra determined by the relations ${a_i^*a_i=1+q a_ia_i^*,\, a_i^*a_j=0}$ . We define its well-behaved unbounded *-representations and classify all irreducible ones up to unitary equivalence.     

Reactions of 3-R-5-nitropyridines with nucleophiles: Nucleophilic substitution vs conjugate addition

A number of 3-R-5-nitropyridines were synthesized and their reactions with various types of nucleophiles were investigated. The reaction outcome depends on the nature of a nucleophile: in case of anionic O-, N- and S-nucleophiles the previously unreported substitution of non-activated nitro group occurred while carbon nucleophiles underwent dearomatization of the pyridine ring with the formation of products of 1,2- and 1,4-addition.