具推拉電子基之三苯荑與五苯荑之合成與光物理性質之研究

Synthesis and Photophysical Properties of Donor-Acceptor Substituted Triptycenes and Pentiptycenes

陳維翔(Wei-Shyang Tan)

指導教授 ： 楊吉水

國立臺灣大學/理學院/化學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.00266

摘要

4-(N,N-二甲胺基苯甲腈) (DMABN) 在極性溶劑中的雙重螢光放射性質在文獻中引起了極多的討論，目前認為是電子予體與受體之間的扭轉造成，也與La和Lb兩個狀態之間的相對能量有關。為了了解苯荑結構對於雙重螢光放射之影響，我們設計了一系列甲胺基及苯胺基取代之三苯荑腈與五苯荑腈化合物，並比較其與相同電子予體的苯甲腈化合物之光化學行為。結果我們發現化合物DMACT與DMACP在極性溶劑下具有雙重螢光放射。

本論文從三個角度來探討苯荑結構對DMABN類型分子的影響：
(一) 超共軛作用
在吸收光譜中發現苯荑結構中的側環能與中間苯環進行超共軛作用 (除苯胺基取代之化合物PACT和PACP外)。這樣的超共軛作用也使到五苯荑系列化合物之S1態含有較高比例的Lb性質，且為較允許的吸收。

(二) 立體效應
苯荑結構中的側環提供很大的立體體積，使得電子予體與受體在固態下呈現預扭轉的現象。此效應使得ICT現象變得更容易，理論計算也發現取代基效應使 delta E(S1,S2) 變小。

(三) 溶劑合作用
三苯荑與五苯荑所造成的非極性環境程度有異。結果顯示，五苯荑的側環數目比三苯荑多，其與極性溶劑分子之間的作用力變小，故對CT態的穩定程度變差。

關鍵字

三苯荑 ； 五苯荑 ； 合成方法 ； 雙重螢光放射 ； 分子內電荷轉移 ； 超共軛作用

並列摘要

4-(N,N-dimethylamino)benzonitrile, abbreviated as DMABN, exhibits dual fluorescence in polar solvents. The origin of dual fluorescence is still controversial. However, the twist angle between donor and acceptor as well as the relative energy between La and Lb are related to such a phenomenon. In order to explore the effect of iptycene substituents on the dual fluorescence of this system, we have designed a series of donor-acceptor substituted triptycenes and pentiptycenes. The results show that compounds DMACT and DMACP exhibit dual fluorescence in polar solvents.
This thesis addresses the influence of the iptycene substituents to the behavior of DMABN systems in three aspects:
(1) Hyperconjugation
Interaction of pi-electrons between side rings and central ring of iptycenes except for N-phenyl substituted compounds (i.e. PACT and PACP) is significant based on the absorption spectra. Such interactions also account for the fact that S0 to S1 transition of the pentiptycenes possesses more Lb character and higher oscillator strength.
(2) Steric Effect
Steric congestion imposed by the iptycene substituents induces a large pretwist of the donor. This effect facilitates the CT state formation. Meanwhile, delta E(S1,S2) obtained from theoretical calculation tends to be reduced.
(3) Solvation Effect
Role of solvation in the excited states cannot be neglected. The photophysical data indicate that pentiptycene derivatives are less stablized than that of the triptycene derivatives.

並列關鍵字

triptycene ； pentiptycene ； synthetic method ； dual fluorescence ； intramolecular charge transfer ； hyperconjugation

參考文獻

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