Physical Properties of 8‐Substituted 5,7‐Dichloro‐2‐Styrylquinolines as Potential Light Emitting Materials

Derivatives of 5,7‐dichloro‐2‐styrylquinoline ( 1 ), modified at position 8 of quinoline moiety with a methyl ether ( 4 , DCSQM) or acetate ( 5 , DCSQA), were synthesized and investigated. Both compounds exhibited high thermal stability ( Td > 320 °C). The UV‐vis absorption of DCSQM and DCSQA varied only slightly in different solvents, whereas the emission spectra showed pronounced red shifts with increasing solvent polarity, suggesting the intramolecular charge transfer character of the emission state. Compounds 4 and 5 can emit lights from blue to green color in different solvents. The solvent polarity dependent electronic transitions are attributed to efficient intramolecular charge transfer (ICT) processes, in which the HOMOs and LUMOs are localized on the styrene‐based ring and the quinoline‐based moiety, respectively. The quinoline‐based LUMO provides compelling evidence that the first reduction site occurs on the electron‐deficient quinoline moiety.