New fluorescent dipolar pyrazine derivatives for non-doped red organic light-emitting diodes

Dipolar fluorescent compounds containing electron-accepting pyrazine-2,3-dicarbonitrile and electron-donating arylamine moiety have been designed and synthesized. The optical and electrochemical properties of these compounds can be adjusted by changing pi-bridge length and the donor (D) strength. Organic light-emitting devices based on these compounds are fabricated. Saturated red emission of (0.67, 0.33) and the external quantum efficiency as high as 1.41% have been demonstrated for one of these compounds.

Polymer light-emitting diodes based on a bipolar transporting luminescent polymer

A soluble electroluminescent polymer containing hole-deficient triphenylamine and electron-deficient oxadiazole units in the main chains has been designed and studied. The design is based on the consideration that the triphenylamine group possesses good hole-transporting property and the oxadiazole unit is known to be of electron-transporting character. Because of the good bipolar transporting performance, the brightness and electroluminescent efficiency are significantly improved and the turn-on voltage is reduced compared with a similar polymer without the electron-deficient oxadiazole units in the main chains. For a device with configuration ITO/PEDOT/polymer/CsF/Al, a maximum brightness of 3600 cd m(-2) and a maximum luminescent efficiency of 0.65 cd A(-1) (quantum efficiency of 0.3%) were obtained in the polymer with oxadiazole units, about 15 times brighter and 15 times more efficient than the corresponding polymer without oxadiazole units.

The research of cellulose derivatives as chiral stationary phases and high performance liquid chromatography with polarimeter as on-line detector

Three cellulose derivatives were synthesized and used as chiral stationary phases based on silica gel. The effects of adsorbances on the column numbers and stabilities have been investigated. These stationary phases exhibited high chiral recognition for various racemates. At the same time, the on-line curves of polarimeter were obtained by high performance liquid chromatography with polarimeter as on-line detector.

Study of the effect of hydrogen bonding on the phase behaviour of p-nitro azobenzene derivatives with hydrophilic tails

The infrared spect ra of N-n-(4-nitrophenyl)azophenyloxyalkyldiethanolamines (Cn) are examined in the range of 4000-400 cm(-1) at different temperatures and the assignment of the fundamental vibrations given. Based on (1) the localization of the broad absorption band at 3456 cm(-1), and (2) attribution of the associated OH bands centred at 1410-1390, 1100, and 650-634 cm(-1) to, respectively delta OH deformation, nu C-O stretching and gamma OH out-of-plane bending, intermolecular hydrogen bonding between OH groups in the crystalline, liquid crystalline and isotropic states is proposed. By considering the results of FTIR, WAXD and DSC measurements, the molecular arrangement of C10 in its smectic A phase as consisting of hydrogen bonding and strong interaction between dipolar groups (NO,) is proposed. This may explain the high stability and high orientational ordering property of Cn compounds in the liquid crystalline state compared with that of n-bromo-1-[4-(4-nitrophenyl)azophenyl]oxyalkanes (Bn).

Studies on quantitative structure-activity relationship between the structures of derivatives of benzamide and their antiallergic activities

Molecular connectivity index and comparative molecular field analysis (CoMFA) have been applied to the studies of the correlation of the derivatives of benzamide and their antiallergic activities. The results achieved by using CoMFA based on 3D factors are much better than that obtained by using multiple regression analysis based on majorly 2D structural information. The CoMFA results show that the dominant factor which affects activity is steric, whereas electrostatic effect only plays an unimportant role.

Synthesis and antifungal properties of sulfanilamide derivatives of chitosan

Sulfanilamide derivatives of chitosan (2-(4-acetamido-2-sulfanimide)-chitosan (HSACS, LSACS), 2-(4-acetamido-2-sulfanimide)-6-sulfo-chitosan (HSACSS, LSACSS) and 2-(4-acetamido-2-sulfanimide)-6-carboxymethyl-chitosan (HSACMCS, LSACMCS)) were prepared using different molecular weights of chitosan (CS), carboxymethyl chitosan (CMCS) and chitosan sulfates (CSS) reacted with 4-acetamidobenzene sulfonyl chloride in dimethylsulfoxide solution. The structures of the derivatives were characterized by FT-IR spectroscopy and elemental analysis, which showed that the substitution degree of sulfanilamide group of HSACS, HSACSS, HSACMCS, LSACS, LSACSS and LSACMCS were 0.623, 0.492, 0.515, 0.576, 0.463 and 0.477, respectively. The solubility of the derivatives (pH < 7.5) was higher than that of chitosan (pH < 6.5). The antifungal activities of the derivatives against Aiternaria solani and Phomopsis asparagi were evaluated based on the method of Jasso et al. in the experiment. The results indicated that all the prepared sulfanilamide derivatives had a significant inhibiting effect on the investigated fungi in the polymer concentration range from 50 to 500 mu g mL(-1). The antifungal activities of the derivatives increased with increasing the molecular weight, concentration or the substitution degree. The sulfanilamide derivatives of CS, CMCS and CSS show stronger antifungal activities than CS, CMCS and CSS. (C) 2007 Elsevier Ltd. All rights reserved.

Identification of phenolics and nucleoside derivatives in Gastrodia elata by HPLC-UV-MS

An HPLC-UV-MS method for simultaneous identification of predominant phenolics and minor nucleoside derivatives in Gastrodia elata was developed, which was based on their UV and MS characteristics summarized through a series of homemade reference standard experiments. Phenolics showed characteristic UV lambda(max) at 267 nm, [M + NH4](+) base peak in positive mode and [M - H](-) base peak in negative mode while nucleosides exhibited UV lambda(max) at 255 nm, [M + H](+), [M - H + 2H(2)O](-) or [M - H + CH3COOH](-). Phenolics conjugates mainly underwent the consecutive loss of gastrodin residue (- 268 U) and the combined loss of H2O and CO2 from the citric acid unit under negative MS/MS conditions whereas nucleosides simply lost the ribose (- 132 U) under positive MS/MS conditions. According to these characteristics, a special pattern under MS/MS conditions and reported compound data for G. elata in the literature, not only 15 phenolics were identified but also 6 nucleoside derivatives were identified. Among these compounds, seven phenolics and three nucleoside derivatives have not been reported yet from G. elata.

Determination of alcohols by high-performance liquid chromatography with fluorimetric detection after pre-column derivatisation with carbazole-9-N-acetic acid and chromatographic behaviour of alcoholic derivatives

Alcohols were derivatised to their carbazole-9-N-acetic acid (CRA) esters with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC . HCl) as the dehydrating agent. Studies on derivatisation conditions indicated that the coupling reaction proceeded rapidly and smoothly in the presence of a base catalyst in acetonitrile to give the corresponding sensitively fluorescent derivatives. The retention behaviour of alcohol derivatives was investigated by varying mobile phase compositions (ACN-water and MeOH-water). The parameters from the equation log k'=A-BX were evaluated by retention data of derivatives using an isocratic elution with different mobile phases. The results indicated that the parameters derived allowed computation of retention factors in good agreement with experiments. At the same time, a general equation was derived that makes possible predictions of partition coefficient in binary mobile phases with different proportions of organic solvent to water based on some simple regression analysis. The LC separation for the derivatised alcohols containing higher carbon alcohols showed good reproducibility on a reversed-phase C-18 column with gradient elution. The detection limits (excitation at 335 nm, emission at 360 nm) for derivatised alcohols (signal-to-noise ratio=3:1) were in the range of 0.1-0.4 pg per injection. (C) 2001 Elsevier Science B.V. All rights reserved.

Lewis acid assisted ring-closing metathesis of chiral diallylamines: An efficient approach to enantiopure pyrrolidine derivatives

Lewis acid assisted ring-closing olefin metathesis (RCM) of chiral diallylamines, using the second generation RCM ruthenium-based catalyst, leads to enantiopure pyrrolidine derivatives in 79-93% yields under very mild conditions. The scope of the olefin metathesis has been expanded.