The Syntheses and Spectroscopic Properties of the Styryl Quinoline Derivatives

The simple method of the syntheses of the styryl quinoline derivatives was developed. The intermediate of 2-methylquinoline was synthesized from 10 mmol aniline and 20 mmol (E)-2-Butenal dissolved in 8 mL methylbenzene refluxing at 100 ℃ for 3 hours with 10 mL 6 M hydrochloric acid as catalyst. Eight derivatives were obtained in 15 mL glacial acetic acid using 2-methylquinoline (10 mmol) and aromatic aldehyde (12 mmol) as materials refluxing for 8 hours with a yield of 71%～88%. The method is simple, high yield, easy purification and environment friendly. The structures of all derivatives were confirmed with MS, 1HNMR and IR. The vicinal coupling constant of olefinic carbon hydrogen in 1HNMR is 12～18 Hz, and moderate strength absorption peaks appeared at 960～980 cm-1 in IR indicate that carbon-carbon double bond is transconfiguration. Maximum absorption wavelengths of eight products in CH3OH, DMSO, THF and DMF were measured, and emission wavelengths were measured using maximum absorption wavelengths as excitation wavelengths. It turned out that maximum absorption wavelengths among different solvents were 325～376 nm, and emission wavelengths were 367～477 nm. The molar extinction coefficients were within the range of 1.738×104～4.578×104 L·mol-1·cm-1. The maximum absorption wavelengths and emission wavelengths of styryl quinoline derivatives with methoxyl, hydroxyl and benzyl group are greater than others. Among four solvents, the maximum absorption wavelengths almost unchanged, however, the emission wavelengths varies significantly in the following order DMSO>DMF>CH3OH>THF, which indicates the Stokes shift of one product at aprotic solvent is greater than protic solvent. 2-(3,4,5-trimethoxyphenyl)styryl quinolone (Product Ⅱ) which shows the best fluorescence property and the highest Stokes shift value worth further studying.