本論文乃針對具有架橋之反式-4-(N-芳基)二苯乙烯胺衍生物 (B2)於溶劑中螢光量子產率大幅降低及照光後發生[1,3]氫轉移(去共軛)反應的原因作深入的研究。 為了暸解化合物B2在不同溶劑中照光後的光化學行為，我們將架橋取代為甲基並改變架橋位置設計了化合物B1、M1、M2、M3來做比較。其於正己烷及二氯甲烷溶劑中的光化學行為，絕大部份都為順反異構化，而[1,3]氫轉移(去共軛)反應具有位置效應：只有當化合物為B2且在二氯甲烷中時才會發生。因此，限制雙鍵旁的單鍵旋轉造成B2於正己烷中的螢光量子產率大為降低是因其雙鍵扭轉能障變小使得進行異構化的速率變的很快。由於二氯甲烷中含有少量的酸造成化合物B2於酸性的溶劑系統中會發生[1,3]氫轉移(去共軛)反應。其於照光後會先進行異構化產生順式化合物，雙鍵發生質子化產生三級的氫化茆碳陽離子(indanyl cation)後，再發生去質子化得到[1,3]氫轉移(去共軛)後的產物。此外，測量異構化量子產率所加入的內標物(1,4-二辛氧基苯，DOB)會抑制化合物M1、M2的異構化行為且造成了B2在二氯甲烷中具有波長效應的光化學行為會發生光誘導電子轉移使其產生[1,3]氫轉移(去共軛)反應。 This thesis reports the photophysical and photochemical properties of a series of trans-4-aminostilbenes (B1, B2, M1-M3) in order to gain insights into the origins of low fluorescence quantum yields and the occurrence of the [1,3] hydrogen shift (deconjugation) reaction observed for the ring- bridged derivative B2. Except for B2 in dichloromethane, the photochemistry of B1, B2, and M1-M3 in hexane and dichloromethane is merely the trans -> cis photoisomerization. The reason responsible for the low fluorescence quantum yield for B2 in hexane is the low double-bond torsional barrier in the singlet excited state. The presence of a trace amount of acid in dichloromethane accounts for the deconjugation reaction for B2 in dichloromethane. The deconjugation reaction results from the protonation of the cis isomer of B2, which forms a tertiary carbocation intermediate. Deprotonation of the bridged methylene carbon leads to the deconjugated product. In the presence of 1,4-dioctyloxybenzene (DOB), the quantum yield for trans -> cis photoisomerization for M1 and M2 is reduced, presumably due to the occurrence of photoinduced electron transfer (PET) from the excited DOB to M1 and M2. The PET between DOB and B2 is also responsible for the wavelength-dependent photochemical behavior of B2 in dichloromethane.
