| Summary: | 碩士 === 國立中央大學 === 化學研究所 === 95 === In this study, we demonstrated the reaction between ionic liquid bmimPF6 and acetophenone derivatives. Upon heating constantly, the PF6- anion of bmimPF6 decomposes to fluoride anion and PF5. The strong Lewis acid PF5 then activates acetophenone derivatives easily to proceed with the aldol condensation to yield dimer(A2-D2), cyclic trimer(A3-D3) and strongly fluorescent pyrilium salt(A4-D4). The more electron-releasing substituent on aryl ring of acetophenone produces more pyrilium salt.
The structure of A3-D3, a 1,3,5-triarylbenzene, allows the ring current on the peripheral phenyl rings to affect de-shielding by the inner phenyl ring protons. Hence, the chemical shifts of inner phenyl protons are down-field to those of peripheral phenyl protons. The chemical shifts of protons on 2,4,6-triarylpyrylium core (A4-D4) are further down-field, attributed to the positive charge of pyrylium ring. For the series of A4, B4, and C4, the electron-releasing substituent on peripheral phenyl ring also leads to the down-field shift on the 13C signals of phenyl ring, whereas, with the increase of electron density on the pyrylium ring, the 13C chemical shifts move up-field. Moreover, the stronger electron-releasing substituent on peripheral phenyl ring, the higher red-shift for UV-visible and PL spectra, with also greater quantum yield.
|
|---|
