| 摘要: | 在甲基芳香基酮衍生物(A1-D1)存在下，離子液體bmimPF6與相關含PF6-陰離子的鹽類，長時間維持在>90℃，PF6-陰離子會解離出氟陰離子及強路易士酸PF5，進而催化A1-D1的醛醇反應，產生雙聚體(A2-D2)、成環三聚體(A3-D3)與氧鎓鹽化合物(A4-D4)，其中芳香基為苯基(A)、p-甲苯基(B)、p-甲氧基苯基(C)、p-溴苯基(D)。苯環上不同取代基的電子效應會影響到產物的產率比。 A3-D3為1,3,5-三芳香基苯，中間之苯環上的質子受到外圍苯環環電流影響，總感應磁場增加，使得去遮蔽效應增大，故1H-NMR光譜中間苯環質子的吸收訊號會較外圍苯環質子的吸收訊號低場；A4-D4為2,4,6-三芳香基氧鎓鹽，因含有帶正電荷的氧鎓鹽使得去遮蔽效應更大，故氧鎓環上質子的吸收峰訊號位置在更低場的地方。對於氧鎓鹽A4、B4與C4的13C-NMR光譜碳的吸收訊號而言，如果外圍苯環對位碳所接的取代基推電子性質愈強，則外圍苯環碳的化學位移會往低場偏移，而氧鎓環電子密度增加，其上碳的吸收峰訊號會往高場偏移；相同的，外圍苯環上取代基推電子性質愈強，氧鎓鹽的還原半電位愈高、吸收放射峰愈往紅移且量子產率愈大。 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. |
