Detection of nitroaromatics based on aggregation induced emission of barbituric acid derivatives.

Barbituric acid derivatives with typical aggregation induced emission (AIE) are reported. Their emission wavelengths varied with water fraction of their solution. UV-visible absorption spectroscopy and theoretical calculations revealed the intramolecular charge transfer (ICT) possibility from donor to acceptor and the mechanism was confirmed as a restriction of intramolecular motion (RIM). The AIE properties were affected by the different substituents on barbituric acid. When the molecular volume increased, the AIE effect decreased. Fluorescent quenching mechanism was applied to detect nitroaromatic explosives. For 2,4,6-trinitrophenol (PA), one of the derivatives 5-(4-diphenylamino styrene)-1,3-diphenyl-barbituric acid in THF/H2O mixture (1:9, v/v), showed amplified fluorescence quenching with a maximum Stern-Volmer quenching constant of 4.1 × 104 M-1. The solid phase paper test based on 5-(4-diphenylamino styrene)-1,3-diphenyl-barbituric acid also showed a superior sensitivity toward PA both in vapor and solution.

A series of phenyl sulfonate metal coordination polymers as catalysts for one-pot Biginelli reactions under solvent-free conditions.

Three new metal coordination polymers, namely, [Co(DPP)2(H2O)2]·(BS)2·2H2O (1), [Co(DPP)2(H2O)2]·(ABS)2·2H2O (2) and [Co(DPP)2(MBS)2] (3) [DPP = 1,3-di(pyridin-4-yl)propane, BS = phenyl sulfonic acid, ABS = p-aminobenzene sulfonic acid, MBS = p-methylbenzene sulfonic acid] were obtained under hydrothermal conditions. Complexes 1-3 were structurally characterized using X-ray single-crystal diffraction, XRD and IR spectroscopy. Both complexes 1 and 2 display a 1D tape structure. Meanwhile, complex 3 exhibits a 2D layer and further stacks via C-Hπ interactions to generate a three-dimensional supramolecular architecture. These three metal coordination polymers have been applied as catalysts for the green synthesis of a variety of 3,4-dihydropyrimidin-2(1H)-ones under solvent-free conditions through the Biginelli reaction. Interestingly, the catalysis products have been obtained in high yields under eco-friendly synthesis conditions.

New views on the reaction of primary amine and aldehyde from DFT study.

A general theoretical investigation on the reaction of primary amine with aldehyde was carried out by density functional theory. The calculation systems involve three kinds of primary amines (methylamine, vinylamine, and phenylamine) and three kinds of aldehydes (formaldehyde, acetaldehyde, and acrylaldehyde). The steric and electronic inductive effects on the reaction mechanism were studied. Results reveal that the nucleophilic attack of primary amine on aldehyde under neutral conditions leads to carbinolamines, rather than Schiff bases. The nucleophilic attack on the protonated aldehyde produces the protonated Schiff base. The steric hindrance of the aldehyde slows down the nucleophilic attack but allows enough time to abstract a H; consequently, the formation of the protonated Schiff base is preferred. During the carbinolamine protonation, the H(+) preferably locates on the amine nitrogen and then is abstracted by the hydroxyl oxygen over an energy barrier, leaving protonated Schiff base after timely water liberation. The formation of a prereaction potential energy well obviously softens the steric and electronic inductive effects on the active barrier for different reactants.

Dipolar Chromophore Facilitated Huisgen Cross-Linking Reactions for Highly Efficient and Thermally Stable Electrooptic Polymers.

Efficient thermal cross-linking protocol for an azide-alkyne-based Huisgen 1,3-dipolar cycloaddition reaction has been developed for making highly efficient electrooptic (EO) polymers. The material system is based on an azide-containing side-chain copolymer and cross-linkable dendronized chromophores that have two pairs of dendritic bispropargyl ether moiety on the periphery. The dendritic chromophore possesses a tetraene conjugating bridge and strong dialkylaminophenyl donor and CF3-TCF acceptor. This material system not only provides adequate accessibility for propargyl ether to react azido-containing moieties for efficient cross-linking but also gives the rotational freedom needed for electric field poling. The site isolation offered by the bispropargyl ether dendron effectively suppresses the unwanted side reactions that are usually associated with the decompositions of azides and chromophores. Due to these concerted efforts, it allows the Huisgen 1,3-dipolar cycloaddition reactions to be carried out at moderate temperatures in polar media that have a high concentration of dipolar polyene chromophores. Through sequential electric field poling and in situ cross-linking, the poled films exhibit very large EO activity (up to 147 pm/V at 1.31 µm) with a long-term alignment stability at 85 °C.

9-{4-[(E)-2-(4,6-Dimethyl-1,3,5-triazin-2-yl)ethen-yl]phen-yl}-9H-carbazole.

In the crystal structure of the title compound, C(25)H(20)N(4), the triazinyl ring is nearly coplanar with the planar (r.m.s. deviation = 0.028 Å) phenyl-ethenyl unit, the twist being only 5.8 (2)°; however, the planar carbazolyl unit (r.m.s. deviation = 0.008 Å) is twisted by 47.8 (1)° with respect to the phenyl-ethenyl unit. The nonplanar nature of the mol-ecule explains the phenomenon of light emission at short wavelengths in the solid state but at long wavelengths in solution.