Dipole moments of selenophene analogs of the chalcones

The dipole moments of 24 selenophene analogs of the chalcones have been measured and have been compared with the data calculated by a vectorial additive scheme and also with their chemical structures. Considerations are expressed on the conformational state of the molecules of the compounds investigated. The existence of a correlation between the dipole moments the intramolecular distances, and the Hammett's -parameters has been shown. The applicability of Higashi's equation to the calculation of for , -unsaturated ketones is pointed out.     

Carbolithiation of aromatic rings: cyclohexadienes from N-aroyl-2,2,6,6-tetramethylpiperidines

Benzamides whose nitrogen atom is part of a 2,2,6,6-tetramethylpiperidine ring are dearomatised by alkyllithiums, which attack them regioselectively to yield, after electrophilic quench, substituted cyclohexadienes.     

Synthesis of SBA-15/carbon composite with an ink-bottle-like pore structure by a novel pulse CVD technique

A novel and easy post modification method, pulse chemical vapor deposition (pulse CVD), was developed to tailor the pore-opening of SBA-15 while largely keeping its surface area and pore volume. By using acetylene as carbon precursor and nitrogen as carrier gas, the pore-mouth of SBA-15 was effectively reduced from 8.1 nm to 5.1 nm within 5 min while maintaining the pore body at 8.1 nm. This ink-bottle-structured SBA-15/carbon composite only losses 12% BET specific surface area and 16% total pore volume, respectively. The SBA-15/carbon composite is highly hexagonally ordered and has similar particle morphology as the original SBA-15. The effect of three pore modification factors—the number of cycles of pulse CVD, the ratio of acetylene/nitrogen and the feeding time of carbon precursor, on the final pore structure of the SBA-15/carbon composite is also studied.     

Control synthesis of isocyanate and alkoxy-silane terminated macromers

The kinetics of the reactions in bulk of 4,4′-dicyclohexyl methane diisocyanate (H₁₂ MDI) and 5-isocyanato-1,3,3-trimethylcyclohexylmethyl isocyanate or isophorone diisocyanate (IPDI) with benzylic alcohol (BZA) and α-hydroxy-ω-methyl ether-terminated polyethylene oxide PEO (M?_w = 350) were studied by size exclusion chromatography (SEC) and ¹³C nuclear magnetic resonance (¹³C-NMR). The substitution effect is exhibited in the case of H₁₂ MDI reactivity. The kinetic constants were calculated by a numerical method. The second-order kinetic mechanism was shown to be valid. In the IPDI case, the cycloaliphatic isocyanate group is shown to be more reactive than the aliphatic group in our conditions, without catalysis, in agreement with previous results from the literature, in our obtained by ¹H-and ¹³C-NMR without any catalyst. The reactivity ratio is found to be on the order of 3. This difference in reactivity of the two isocyanate groups is used for the control synthesis of isocyanate and alkoxy-silane-terminated macromers.     

High-performance liquid affinity chromatography for the purification of immunoglobulin A from human serum using jacalin

A high-performance liquid affinity chromatographic method for the purification of serum immunoglobulin A (IgA) using a jacalin column is described. The automated procedure takes about 2 with minimal manipulation. The yields of the isolated IgA and of its IgG and IgM contamination were studied by enzyme-linked immunosorbent assay (ELISA) of 30 sera. Purity was assured by immunoelectrophoresis. The ratio of IgA1 to total IgA was unchanged after purification, as verified by ELISA. The results showed that greater than 90% IgA could be recovered with less than 0.5% total IgG and greater than 2.0% total IgM remaining in the fractions containing purified IgA.     

Spectrophotometric method for the determination of sorbic acid in various food samples with iron(III) and 2-thiobarbituric acid as reagents

A simple, rapid and accurate spectrophotometric method has been developed for the determination of sorbic acid in various food samples based on the oxidation of sorbic acid by iron(III) at 100 degrees C to malonaldehyde, which then reacts with 2-thiobarbituric acid to form a reddish brown product. The optimum experimental conditions for colour development have been assessed. Absorbance measurements were made at 529 nm in the presence of 0.4% m/V citric acid. The calibration graph was linear for 0-6 micrograms ml-1 of sorbic acid with a slope of 0.131 A micrograms-1 ml. The recoveries of sorbic acid at concentrations of 164-557 micrograms ml-1 ranged from 96 to 103%. The relative standard deviations of ten replicate determinations of sorbic acid in a synthetic cream soda sample spiked with 573 micrograms ml-1 of sorbic acid and in an onion juice sample containing 82 micrograms ml-1 of sorbic acid were 1.6 and 1.9%, respectively. Interferences from several common food additives can be minimised by extracting sorbic acid with diethyl ether and then back-extracting the acid with sodium hydrogen carbonate. The method has been applied successfully to the determination of sorbic acid in a wide range of food samples including beverages, cake, cake mate, garlic bread sprinkle, onion juice, oyster flavoured sauce and grenadine syrup.     

Structural and process controls of AIEgens for NIR-II theranostics

Aggregation-induced emission (AIE) is a cutting-edge fluorescence technology, giving highly-efficient solid-state photoluminescence. Particularly, AIE luminogens (AIEgens) with emission in the range of second near-infrared window (NIR-II, 1000–1700 nm) have displayed salient advantages for biomedical imaging and therapy. However, the molecular design strategy and underlying mechanism for regulating the balance between fluorescence (radiative pathway) and photothermal effect (non-radiative pathway) in these narrow bandgap materials remain obscure. In this review, we outline the latest achievements in the molecular guidelines and photophysical process control for developing highly efficient NIR-II emitters or photothermal agents with aggregation-induced emission (AIE) attributes. We provide insights to optimize fluorescence efficiency by regulating multi-hierarchical structures from single molecules (flexibilization) to molecular aggregates (rigidification). We also discuss the crucial role of intramolecular motions in molecular aggregates for balancing the functions of fluorescence imaging and photothermal therapy. The superiority of the NIR-II region is demonstrated by fluorescence/photoacoustic imaging of blood vessels and the brain as well as photothermal ablation of the tumor. Finally, a summary of the challenges and perspectives of NIR-II AIEgens for in vivo theranostics is given.

Structural and process controls of NIR-II AIEgens realize manipulating of radiative (R) and nonradiative (NR) decay for precise theranostics.     

NMR and monte carlo simulation studies of water adsorption dynamics

Nuclear magnetic resonance water proton spin-spin relaxation time T(2) was measured in wood samples with moisture contents ranging from 0.50 to 26.4%. The experimental results are discussed in terms of Monte Carlo simulations, which determine the correlation times tau for reorientation of the water molecule proton-proton vectors. We demonstrate that 1/T(2) and tau qualitatively follow the same behavior with surface hydration. The common application of the multisite exchange model to hydrated systems is discussed in light of the new results.     

Reversible OH-bond activation and amphoterism by metal–ligand cooperativity of calix[4]pyrrolato aluminate

Most p-block metal amides irreversibly react with metal alkoxides when subjected to alcohols, making reversible transformations with OH-substrates a challenging task. Herein, we describe how the combination of a Lewis acidic square-planar-coordinated aluminum(iii) center with metal–ligand cooperativity leverages unconventional reactivity toward protic substrates. Calix[4]pyrrolato aluminate performs OH-bond activation of primary, secondary, and tertiary aliphatic and aromatic alcohols, which can be fully reversed under reduced pressure. The products exhibit a new form of metal–ligand cooperative amphoterism and undergo counterintuitive substitution reactions of a polar covalent Al–O bond by a dative Al–N bond. A comprehensive mechanistic picture of all processes is buttressed by isolation of intermediates, spectroscopy, and computation. This study delineates how structural constraints can invert thermodynamics for seemingly simple addition reactions and invert common trends in bond energies.

The combination of structural constraint and metal–ligand cooperativity in calix[4]pyrrolato aluminate inverts common trends of bond energies and enables reversible OH-bond activation.     

Encoding method for OBOC small molecule libraries using a biphasic approach for ladder-synthesis of coding tags

In the "one-bead one-compound" (OBOC) combinatorial library method, each compound bead displays only one compound entity. Hundreds of thousands to millions of compound beads can be synthesized rapidly and screened simultaneously. Positive compound beads are then isolated for structural analysis. To fully exploit the power of OBOC combinatorial small molecule libraries, a robust and high throughput encoding method is needed to decode the positive compound beads. In this paper, we report on the development of a novel encoding strategy that combines the concepts of ladder-synthesis and chemical encoding on bilayer beads. In these encoded libraries, small molecule compounds are displayed on the bead surface, and cleavable coding tags consisting of a series of truncated molecules reside in the bead interior. Such a library can be easily constructed using the biphasic approach (J. Am. Chem. Soc.2002, 124, 7678) to topologically segregate the functionalities of the beads during library synthesis. The ladder members and coding tags are then released for MALDI-TOF-MS analysis. To simplify the interpretation of the mass spectra, we purposely add bromine into the cleavable linker so that the cleavage products generate a characteristic isotope fingerprint. The chemical structure of library compounds can be determined by analyzing the mass differences between adjacent peaks on the mass spectra. This encoding strategy also provides valuable information on the quality of the testing compound on the surface of the bead. To validate this methodology, a model OBOC small molecule library with 12,288 members was synthesized on TentaGel beads and screened against streptavidin. The chemical structures of the compound on each positive bead were unambiguously identified.