Synthesis, Optical Properties And Antibacterial Activities Of Unsymmetric Stilbene Derivatives

In recent years, heterocyclic compounds, especially fused heterocyclic compound, play avery important role in the development of pharmaceuticals, pesticides and materials.1,3,4-oxadiazoles is a class of heterocyclic compounds with a wide range of biologicalactivities, such as insecticide, antibacterial, anticancer, anti-inflammatory and antivirus, whichhas attracted much attention. Stilbene derivatives are well known for their considerablebiological activities, such as antimicrobial, insecticidal activity, anticancer, vasodilatingactivity and synergistic activity of baculovirus. In this paper, novel unsymmetric styrenederivatives containing1,3,4-oxadiazole with specific molecular structure and special naturewere mainly designed and synthesized. In order to investigate the molecular structure, opticalproperties and antibacterial activity of target compound, the computer simulation,fluorescence and in vitro antibacterial experiments were performed. The details are asfollows:1.4-Methylbenzohydrazide and1-naphthaldehyde as the simple starting materials, viaahydrazone reaction, chloramine T cyclization, bromination, esterification and Wittig-Hornerreaction in high yield to synthesize23novel stilbene derivatives containing naphthalene and1,3,4-oxadiazole. All new synthesized compounds were characterized by melting point,elemental analysis, IR, NMR and MS to determine their structure.2. The optimized structure and the frontier molecular orbital of the target compoundswere calculated with Gaussian09software using density functional theory(DFT) at the(B3LYP)/6-31G*level to obtain the structural parameters and electron density maps.3. The UV-vis absorption and fluorescence spectra of the target compounds in DMSO,THF and CHCl3have been studied, and the fluorescence quantum yields Φfhave also beenmeasured. The maximum absorption wavelengths of target compounds are range from328nm to403nm. The compounds exhibit strong violet, blue and green fluorescence with themaximum emission wavelength varying from382nm to522nm. The fluorescence quantumyields are in the range of0.05-0.94and the Stokes shifts are48-118nm. The maximumabsorption wavelength and fluorescence emission wavelength are red shift with electrondonor groups and the increasing polarity of the solvent. The electron-withdrawing groups andspace steric make the fluorescence weakened.4. Using the disk diffusion method and the growth rate method to test eight targetcompounds against Escherichia coli, Staphylococcus aureus and Candida albicans in vitroantibacterial activity. The results showed that the tested compounds exhibited significant antibacterial avtivities against the tested strains. With the increasing concentration, theinhibitory effect was enhanced. Different substituents have some effects on the inbibitoryeffect of compounds. Especially s exhibited greater performance.