取代基效應對反式-4-(N-苯基)二苯乙烯胺之光化學行為影響之研究; Studies on the Substituent Effects on the Photochemical Behavior of trans-4-(N-Phenylamino)stilbenes

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题名:	取代基效應對反式-4-(N-苯基)二苯乙烯胺之光化學行為影響之研究;Studies on the Substituent Effects on the Photochemical Behavior of trans-4-(N-Phenylamino)stilbenes
作者:	廖康廩;Kang-ling Liau
贡献者:	化學研究所
关键词:	光化學行為;反式-4-(N-苯基)二苯乙烯胺;取代基效應;Substituent Effects;Photochemical Behavior;trans-4-(N-Phenylamino)stilbenes
日期:	2002-06-24
上传时间:	2009-09-22 10:10:03 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	本論文乃針對「胺基共軛效應」對反式-4-二苯乙烯胺光化學行為的影響，作更深入的探討。「胺基共軛效應」主要在探討反式-4-(N-苯基)二苯乙烯胺。由於N-苯基取代導致反式-4-二苯乙烯上胺的胺基構形趨於平面，使其在激發態電荷轉移能力增加，光異構化反應速率變慢，因而造成高螢光量子產率的特性。　　為了瞭解取代基效應對反式-4-(N-苯基)二苯乙烯胺光化學行為的影響，我們以反式-4-胺基二苯乙烯為主體，設計了在N-苯基上含取代基的化合物2~6，以及在二苯乙烯4’位置上含強拉電子基的化合物7~8，並以化合物2與7為主軸，作一系列光化學性質的研究與比較。　　化合物2在各種不同的溶劑中，會隨著取代基推電子性增加，其吸收光譜與螢光光譜有紅位移的現象。螢光的強弱則視溶劑與取代基的推拉電子性而定。在正己烷中，螢光隨著取代基的拉電子性增加而增強；在極性較高的溶劑中，螢光強弱與取代基的推拉電子性則無類似關係。當取代基是甲氧甲酯基與腈基時，可能有分子扭轉電荷轉移結構（TICT），使螢光量子產率下降。　　此外，化合物7因同時含有強推與強拉電子基，其吸收光譜與螢光光譜隨著溶劑極性改變，有更明顯的紅位移的現象。在極性較高的溶劑中，可能因具有分子扭轉電荷轉移結構，其螢光與異構化量子產率比相同取代的反式-4-(N-苯基)二苯乙烯胺為低。 This thesis is a follow-up study on the “amino conjugation effect” of trans-4-aminostilbenes. N-phenyl substitution of trans-4-aminostilbene leads to a more planar ground-state geometry about the amino nitrogen atom, a larger charge-transfer character, a slower rate constant for photoisomerization, and thus a higher fluorescence quantum yield. To investigate the substituent effect on the photochemical behavior of trans-4-N-phenylaminostilbene, we have synthesized compound series 2-6, which have substituents on the N-phenylamino group, and compound series 7 and 8, which contain strong electron-withdrawing groups at the 4’ position of the stilbene group. More detained photochemical studies were performed on compound series 2 and 7. Electron-donating groups result in red-shifted absorption and emission spectra for compounds 2, which is valid in a variety of solvents. In hexane, the fluorescence quantum yield of compound 2 is larger for substituents with a stronger electron-withdrawing ability. Such a behavior is however not observed in other solvents. When the substituent in 2 is an ester or a cyano group, the fluorescence quantum yield is particular low in medium or polar solvents, which can be attributed to the formation of twisted internal charge-transfer (TICT) states. In the case of compounds 7, a significant solvent-dependent fluorescence spectra were recorded as a result of the presence of both strong electron-donating and electron-withdrawing groups. In polar solvents, both fluorescence and photoisomerization quantum yields are low, which might be a consequence of TICT formation.
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