五苯荑衍生之π共軛系統之烷基鏈長效應對蒸氣誘導螢光變色行為之探究

Abstract

有機分子的螢光性質可受許多外界刺激調控，如熱致螢光變色 (Thermofluorochromism, TFC)、力致螢光變色 (mechanofluorochromism, MFC) 與薰致螢光變色 (vapofluorochromism, VFC)，這些特性讓有機分子具有成為溫度、壓力與有機蒸氣之螢光偵測材料之潛力。本實驗室曾發表由蒽發光團接上兩個五苯荑基團之9,10-An-C8分子，其具有MFC與VFC性質，來自於固態下之放光行為會因為受力研磨與否而由分子單體或激發雙體主導，或者在苯胺蒸氣下會與苯胺分子形成激發錯體進行放光。這些性質與分子在固態中之排列方式有高度相關，而在分子上修飾長短不同之烷基碳鏈，能影響分子在固態下之排列情形，於是本研究中改變9,10-An-Cn (n = 4,8,12,16) 之鏈長，探討鏈長效應對於MFC與VFC之影響。此外，為了增強發光團π-π作用力或促使發光團更易形成激發雙體，我們將中間發光團換成芘，設計一系列1,6-Py-Cn (n = 4,8,12,16) 分子，探討中間發光團之大小與鏈長效應之交互關係。本研究經由歸納分子MFC、VFC性質隨鏈長變化之趨勢，整理出一個理論模型來解釋此類固態分子螢光行為中之鏈長效應，期望能應用於有機螢光偵測材料之分子設計。

Stimuli-responsive fluorescence properties, such as thermofluorochromism (TFC), mechanofluorochromism (MFC) and vapofluorochromism (VFC), of organic molecules are attractive because of their potential application as fluorescent sensors toward temperature, pressure, and organic vapors. A pentiptycene-derived π-conjugated molecule 9,10-An-C8, which is composed of an anthracene group and two pentiptycene moieties, has been previously reported to exhibit MFC and VFC properties in its solid state. The MFC behavior of 9,10-An-C8 was induced by excimer/monomer transformation, while the VFC behavior resulted from the exciplex formation between aniline vapor and 9,10-An-C8. Both the MFC and VFC properties are highly associated with the molelcular packing in the solid state, which might be modified by alkyl chains of different lengths. In this work, we change the alkyl chain length of 9,10-An-Cn (n = 4, 8, 12, 16) to investigate the chain length effect on the MFC and VFC properties. This is also extended to the pyrene-based analogs, 1,6-Py-Cn (n = 4, 8, 12, 16) . A model is proposed to explain the observed chain-length effects. Our results would pave the way for rational design of novel organic materials for stimuli-responsive fluorescence properties.