對位與間位二苯乙烯胺衍生物的光誘導分子內電荷轉移行為之研究; Photoinduced Intramolecular Charge Transfer Behavior of meta and para- Aminostilbene Derivatives

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题名:	對位與間位二苯乙烯胺衍生物的光誘導分子內電荷轉移行為之研究;Photoinduced Intramolecular Charge Transfer Behavior of meta and para- Aminostilbene Derivatives
作者:	廖康廩;Kang-Ling Liau
贡献者:	化學研究所
关键词:	螢光;共軛;分子內電荷轉移;異構化作用;異構物;扭轉分子內電荷轉移;反式二苯乙烯;胺基;取代基;激發態;isomers;twisted intramolecular charge transfer;isomerization;conjugation;photochemistry;ICT;amino group;intramolecular charge transfer;TICT;fluorescence;trans-stilbene;excited state;substituent
日期:	2007-07-23
上传时间:	2009-09-22 10:14:44 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	含有強的電子予體（D）與受體（A）的共軛系統，其激發態都具有光誘導之分子內電荷轉移（ICT）行為存在，此ICT態的構形常被探討。在非極性溶劑中的ICT態，通常因電子未定域化效應而形成平面ICT（PICT）結構；可是在極性溶劑中，有些D-A系列的化合物，則是會扭轉連結D與A的單鍵，形成電荷分離的扭轉ICT（TICT）態。　　本論文的研究對象為反式二苯乙烯胺的衍生物，研究方法係運用「胺基共軛效應」—在激發態時，N-苯基取代的反式-4-二苯乙烯胺之螢光強弱，對分子構形的平面性相當敏感。就系列化合物p1R而言，我們發現它們的ICT結構與取代基間具有關鍵性的影響—當R為甲氧基、甲氧甲酯基與氰基時，在氰甲烷中會產生TICT行為，雖然扭轉的C—N單鍵不盡相同，但其共同的現象就是有Φf + 2Φtc << 1的行為。　　我們也研究反式-3-二苯乙烯胺的系列化合物m1R（p1R的間位異構物）的相關行為。結果發現1CN與1Me的對位和間位異構物的TICT形成過程都屬於放熱反應，但它們形成TICT態的傾向並不相同，顯示PICT至TICT態的能量障礙扮演重要角色。我們首先提出新的觀點：「熱力學上允許的TICT態不一定會生成，因為其反應動力學可能是不利生成的。」　　除了p1R和m1R外，兩個胺基取代的二苯乙烯衍生物，如3DDS等的ICT行為，也在本論文中有所討論。 Photoinduced intramolecular charge transfer (ICT) often dictates the excited-state behavior of strong electron donor (D)-acceptor (A) substituted conjugated systems. One important issue associated with ICT is the D-A conformation. In nonpolar solvents, it is conceivable that the ICT state is dominated by D-A mesomeric interactions and thus favors a planar geometry (PICT). However, in polar solvents, some D-A systems undergo torsional motion about the D-A bond and lead to a charge-separated twisted ICT (TICT) state. In this thesis, we have studied the ICT states of a series of trans-aminostilbenes on the basis of the “amino conjugation effect”, where the fluorescence intensity of N-phenyl substituted trans-4-aminostilbenes is sensitive to the planarity of molecules in the excited state. For the compound series p1R, we found that the ICT structure of p1R depends on the substituent in the N-phenyl group. When the R group is a methoxy, methoxycarbonyl, or cyano group, the TICT state could be formed in acetonitrile. Although the position for C-N bond twisting is not necessarily the same for all the TICT-forming species, the phenomenon of Φf + 2Φtc << 1 is one thing in common. We have also designed a series of trans-3-N-arylaminostilbenes, m1R, the meta isomers of p1R. The results show that the meta and para isomers of 1CN and 1Me have different propensity of TICT formation. Although the TICT forming processes are all exothermic, the absence of TICT formation indicates that the energy barrier from PICT state to TICT state plays an important role. We have shown that a “thermodynamically allowed TICT formation is insufficient to argue for its formation, because it could be kinetically inhibited.” Besides p1R and m1R, the ICT behavior of other related diamino stilbenes such as 3DDS were also discussed in this thesis.
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