Dao-Hang He

Synthesis and optical properties of two novel stilbene derivatives containing 1,3,4-oxadiazole moiety.

Two novel stilbene derivatives containing 1,3,4-oxadiazole moiety were synthesized and characterized by elemental analyses, (1)H NMR, MS. The photophysical processes of the title compounds were investigated by UV-vis absorption and fluorescence emission spectra in different solutions. The fluorescence quantum yield (Phi) of 1a and 1b in THF is 0.65 and 0.69, respectively. The influence of the solution on the fluorescence intensities was also discussed. Under ultraviolet light excitation, the two compounds exhibit strong blue fluorescence emission. They may serve as potential applications in organic electroluminescent materials.

Synthesis, fluorescence properties and applications of two novel oxadiazole-based stilbene optical brighteners as UV protectants for insect baculovirus.

Two novel symmetrical stilbene optical brighteners based on 1,3,4-oxadiazole bearing sodium sulfonate unit were synthesized. The two target compounds were characterized by NMR and elemental analysis. The photophysical processes of the target compounds were investigated by UV-Vis absorption and fluorescence emission spectra in different solutions. The two optical brighteners were tested as radiation protectants for the Spodoptera litura nuclear polyhedrosis virus (SINPV) against 2nd-instar S. litura larvae. The results indicate that the two compounds exhibit strong blue fluorescence emission, and the fluorescence quantum yield in DMF is 0.86 and 0.75, respectively. The insecticidal effect of SINPV is increased by the addition of the two compounds and especially the compound 3b shows more obvious synergy effect.

Asymmetric 1,3,4-oxadiazole derivatives containing naphthalene and stilbene units: synthesis, optical and electrochemical properties.

Six novel asymmetric 1,3,4-oxadiazole derivatives containing naphthalene and stilbene units have been efficiently synthesized and characterized by FT-IR, (1)H NMR, (13)C NMR, mass spectrometry and elemental analysis. The UV-vis absorption maximum wavelength, fluorescence excitation wavelength, fluorescence emission wavelength and fluorescence quantum yield were measured in dilute tetrahydrofuran solution. The solvent effect was also studied. The HOMO and LUMO levels of these compounds were calculated by density functional theory (DFT) (B3LYP, 6-31G(*)) method and cyclic voltammetry. They emit bright violet to blue emission with high fluorescence quantum yields (0.23-0.94) and large Stokes shifts (53-102 nm). These compounds possess high HOMO levels (-5.03 to -5.17 eV) and suitable band gaps, indicating that they could be benefit for hole injection. The results show that they have a potential for application in optoelectronic materials.

Characterization and optical properties of novel unsymmetrical stilbene-based 1,3,4-oxadiazole derivatives.

A series of novel unsymmetrical stilbene-based 1,3,4-oxadiazole derivatives were efficiently synthesized by a four-pots reaction sequence. All of the title compounds were characterized by MS, (1)H-NMR and elemental analysis. UV-Vis absorption and fluorescence emission spectra of the compounds were investigated in dilute chloroform solution; the compounds exhibit strong blue-green fluorescence ranged from 397 to 499 nm and show potential for application in organic optical materials.

1-[2-(3,4-Dichloro­phen­yl)-5-(3,4,5-trimethoxy­phen­yl)-2,3-dihydro-1,3,4-oxadiazol-3-yl]ethanone

The title compound, C19H18Cl2N2O5, was synthesized by the reaction of N′-(3,4-dichlorobenzylidene)-3,4,5-trimethoxybenzohydrazide and acetic anhydride. The oxadiazole ring makes dihedral angles of 82.82 (7) and 9.92 (7)° with the 3,4-dichlorobenzene and the 3,4,5-trimethoxybenzene ring planes, respectively. The crystal structure is stabilized by intermolecular C—H⋯ O and C—H⋯ N hydrogen bonds. Intramolecular C—H⋯O and C—H⋯N hydrogen bonds are also present.

N'-(4-Fluoro-benzyl-idene)-3,4,5-trimethoxy-benzohydrazide.

The title compound, C17H17FN2O4, is of interest due to its potential pharmaceutical and agrochemical activity. All three methoxy groups are twisted with respect to the attached aromatic ring [C—C—O—C torsion angles = 10.43 (18), 97.38 (14), −19.34 (17)°] and the phenyl ring makes a dihedral angle of 40.6 (2)° with the plane through the remaining atoms in the molecule. Intermolecular N—H⋯O hydrogen bonds link the molecules into chains running along the c axis.

N′-(2-Chloro­benzyl­idene)-3,4,5-tri­methoxy­benzohydrazide methanol solvate

In the title compound, C17H17ClN2O4·CH4O, the dihedral angle between the benzene ring planes is 5.29 (6)°. Intermolecular N—H⋯O and O—H⋯O hydrogen bonds link the molecules into a chain along the a axis.