間位-二苯乙烯胺衍生物之合成與光誘導分子內電荷轉移性質之研究

Abstract

本論文之目的為合成一系列間位-二苯乙烯胺化合物，並用以研究其光誘導分子內電荷轉移之行為。根據我們先前的研究，反式-4-二苯乙烯胺化合物在激發態時會有分子內電荷轉移（ICT）的現象，且其ICT的可能構形有兩種，平面ICT（PICT）與扭轉ICT（TICT）（圖1-35），由N-苯基上的取代基來決定。例如，取代基為 -OMe 或 -CN 時，在極性溶劑中屬TICT構形，具低螢光量子產率。PICT具有較大之電子非定域化作用，TICT具有較大之分子偶極矩，需在極性溶劑中才能與PICT競爭。 為了了解間位效應對於ICT性質之影響，我們設計一系列不同取代基的反式-3-(N-苯基)二苯乙烯胺的化合物。比較其與對位化合物的光化學行為。我們發現化合物m1OM和m1Me有TICT的行為，m1CN則無，其中m1Me和m1CN在激發態的光化學行為，分別與p1Me和p1CN有明顯的不同。相較於對位N-苯基取代，間位的化合物因共軛性質較差，由ICT往TICT能階活化能的大小也有所差異。同樣的，我們也可以藉由限制C-N鍵的旋轉（m1MeB3和m1OMB3），來證明m1OM與m1Me的TICT的行為。 我們也針對3,4’-DDS的衍生物其光化學行為做探討。由文獻資料顯示，3,4’-DDS可能具有TICT的行為。但經由我們重新量測並配合化合物34DDSB3與34DDSB4，我們發現此類化合物均無TICT的行為。但當我們引入強推電子基 –OMe 分別在間位與對位胺基時，化合物便具有TICT的行為。 另外，我們也成功的合成了化合物DNSB2，此化合物的合成相較於其他二苯乙烯胺衍生物有較高的困難度。雖然我們限制了在styryl-anilino C-C鍵的旋轉，此化合物在極性溶劑中仍然呈現TICT的行為。

This thesis is about the synthesis and the photoinduced intramolecular charge transfer (ICT) behavior of a series of trans-3-aminostilbenes. We recently reported that trans-4-(N-aryl-amino)stilbenes undergo ICT in the excited state. The ICT state of trans-4-(N-arylamino)-stilbenes could be planar (PICT) or twisted (TICT), depending on the substituent in the N-phenyl group. For instance, when the substituent is 4-OMe or 4-CN, a TICT state is present. The TICT state formation leads to low fluorescence quantum yields. Whereas a PICT state is favored by the electron delocalization effect, a TICT state possesses a larger dipole moment and gains better solvation in polar solvents. We have designed a series of trans-3-(N-arylamino)stilbenes to investigate the meta effect on ICT properties and compare with the corresponding para isomers. The results show that m1OM and m1Me undergo TICT formation, but m1CN doesn’t. The distinct propensity of torsional motion toward TICT between the para and meta isomers of 1CN and 1Me are due to the difference in intramolecular charge delocalization ability. On the basis of the ring-bridged model compounds m1MeB3 and m1OMB3, the TICT state for m1OM and m1Me results from the twisting of the stilbenyl-anilino C-N bond. We have also investigated the photochemical behavior of 3,4’-DDS and its derivatives. According to the data in literature, 3,4’-DDS might have a TICT state. However, through the reexamination of the data and investigation of the related compounds 34DDSB3 and 34DDSB4, we conclude that these diaminostilbenes do not undergo TICT state formation. However, those having the N-(4-methoxy)phenyl group (D3AAS and AA3DS) display the TICT behavior. Moreover, we have synthesized compound DNSB2. The synthesis of DNSB2 is more difficult compared to that of the other aminostilbenes. The results show that restriction of the twisting of the styryl-anilino C-C bond does not inhibit TICT formation in polar solvents.