| 摘要: | 隨著雷射在1960年的問世，有關雙光子材料的研究開始蓬勃發展，不論是在生醫領域或是軍武領域，皆對於雙光子材料產生博大的興趣。而為了能夠應用於各領域，我們實驗室致力於研究擁有在固態及溶液態皆有螢光之雙態發射的螢光染料並且探討其光物理性質。
本論文合成出條型分子並且使用Donor-π bridge-Acceptor (D-π-A)的結構為設計，以N,N-二甲基苯胺作為推電子基、噻吩為π-bridge、苯碸作為拉電子基的設計為第一系列模型分子，並以嗎啉單元及二乙二醇甲乙醚兩種烷鏈與推電子基進行烷化反應開發出化合物1及化合物2；另外，本論文亦合成多分歧型分子，其分子結構是以三唑及喹喔啉稠合作為核心、芴作為π-bridge並以二苯胺為推電子基團，如此形成的形成四叉結構作為第二系列模型分子。在連結核心與推電子基單元上，我們以C-C單鍵與C-C三鍵作為鍵結，企圖比較其產生的影響。比較此兩系列模型分子的光物理行為，可歸納出以下結論：
(1) 在第一系列模型分子中，可以從光學數據中觀察到不論嗎啉單元或二乙二醇甲乙醚作為烷鏈皆呈現相差無幾的數據，代表其發光性能不受烷鏈種類影響，唯一有明顯不同的僅有固態螢光量子產率，以嗎啉單元作為烷鏈的化合物1比以二乙二醇甲乙醚作為烷鏈的化合物2高出將近20%的固態螢光量子產率，我們推測嗎啉單元比二乙二醇甲乙醚能有更好的分子隔離效果，致使化合物1在固態螢光量子產率上有較好的表現。
(2) 由第二系列模型分子之光學數據，可觀察到以三鍵延長共軛的化合物4與以單鍵連接的化合物3相比有紅移的現象產生並且隨著溶劑極性的增加其紅移及強度下降的現象更為明顯，有一篇發表在Mater. Adv., 2023, 4, 6612–6620的文獻指出含有三鍵的化合物有前述現象發生，原因可能是分子內電荷轉移的效果因為三鍵而減弱所造成的現象，本論文的化合物4也出現相同行為。
(3) 在雙光子行為方面，若將本論文的第二系列模型分子與實驗室已畢業之研究生(蔡博凱)所開發之模型分子比較，可觀察到此類多分岐型分子若以三鍵作為共軛延長，相較於單鍵類似物，可以使雙光子截面值有大幅提升的效果。而本論文的第二系列模型分子的雙光子性質也有與此一致的行為。
;With the advent of lasers in 1960, research on two-photon processes began to flourish, garnering significant interest in both biomedical and military fields. To apply these processes across various fields, we have focused on studying fluorescent dyes with dual-state emission and exploring their photophysical properties.
In this thesis, we have synthesized linear molecules based on a Donor-π bridge-Acceptor (D-π-A) structure. The first series is designed with N, N-dialkyl aniline as the electron-donating group, thiophene as the π-bridge, and sulfone as the electron-withdrawing group. We have developed compounds 1 and 2 with different alkyl groups attached to the donor. For the multi-branched molecules, we have used fused triazole and quinoxaline as the core, fluorene as the π-bridge, and diphenylamine as the electron-donating group, forming a multi-branched structure as the second series model compounds. Compounds 3 and 4 use C-C single and C-C triple bonds as the linkages and are designed to compare the impact caused by this structural variation. From the photophysical properties of these two series of model compounds, some features should be noted:
1. For the model compounds of the first series, it is found that whether using morpholine unit or (2-methoxyethoxy)ethane as the alkyl chain, the model compounds show nearly identical optical properties, indicating that the emission properties are not significantly affected by the type of alkyl chain. The only noticeable difference is in the solid-state fluorescence quantum yields, that is compound 1 shows nearly 20% higher solid-state fluorescence quantum yields compared to that of compound 2. This suggests that the morpholine unit offers better molecular segregation in the solid-state, leading to improved solid-state fluorescence quantum yields.
2. In the second series, optical data show that the compound 4 with triple bond as the extension of π-conjugation exhibits red-shifted fluorescence emission compared to that of compound 3. The red-shifted fluorescence emission accompanied by a decrease in emission intensity become more pronounced with increasing the solvent polarity. Similar behavior was reported by a literature (Mater. Adv., 2023, 4, 6612–6620) and it was postulated that in C-C triple bond as the linkage may cause the decline of intramolecular charge transfer and lead to the observed emission behavior.
3. Using C-C triple bond as the linkage has a pronounced promotion of the molecular two-photon absorptivity compared to that of using C-C single bond as the linkage, which is consistent with the experimental results observed by our former lab member′s (Mr. Bo-Kai Tsai) model system. |
