本論文利用實驗室自行架設的光學克爾光閘超快時間解析螢光光譜系統(time-resolved optical Kerr gating fluorescence spectroscopy)及超快瞬態吸收光譜儀研究一系列電子給體-受體(electron donor-acceptor, EDA)錯合物的電荷轉移動力學(Charge transfer , CT)。本論文主要研究四種具單一雙鍵但不同游離能之烯烴類(olefin)電子給體與四氰基乙烯(TCNE)形成之錯合物溶於二氯甲烷及四氯甲烷溶劑中的電子轉移動力學，並結合實驗室前人對一系列芳香類(arene)-四氰基乙烯錯合物的研究結果做討論，比較此兩種類型的電子給體與TCNE形成之錯合物之動力學過程。研究之烯烴分子為1-hexene, 2-hexene, 1-methylcyclohexene, 2,3-dimethyl-2-butene。吾人藉由測量靜態吸收光譜與螢光光譜來測量錯合物的電荷轉移吸收譜帶(CT band)與放光波長，並根據測量結果選擇適當的激發波長及偵測範圍，來觀察錯合物激發態的時間解析螢光光譜。經由總體放光強度隨時間變化函數P(t)分析，吾人認為錯合物激發態的淬息途徑有兩步驟，錯合物被雷射激發至激發態後，經由快速的solvation、能量緩解至較低的結構(此為次皮秒的過程)，接著以電荷再結合的方式回到基態(數個皮秒以內)。在極性溶劑二氯甲烷中，電荷再結合的時間約2~3 ps，而在非極性的四氯化碳中電荷再結合的時間約10~20 ps。由olefin-TCNE與arene-TCNE的結果比較，吾人發現，此系列之olefin-TCNE錯合物的電荷再結合速率比同能隙(energy gap)之arene-TCNE錯合物約快一個數量級，且皆屬於非平衡電子轉移行為，超快時間尺度的淬息會與其他能量鬆弛途徑做競爭，因此在靜態螢光光譜中，吾人發現olefin-TCNE錯合物的Stokes shift比arene-TCNE的還要小許多。吾人認為這兩種系統最大的差別在於電子耦合強度的大小，olefin-TCNE錯合物之電子耦合的強度較大，能增快其電子轉移速率，且電荷再結合速率似乎已接近極(<3ps)，因此對-∆G0之依賴性較小。

We studied the charge-transfer (CT) state relaxation dynamics of a series of electron donor-acceptor (EDA) complexes with broadband ultrafast time-resolved fluorescence spectroscopy implemented by optical Kerr gating and transient absorption spectroscopy. The EDA complexes studied here are those containing various olefins (1-hexene, 2-hexene, 1-methylcyclohexene, 2,3-dimethyl-2-butene) as the donor and tetracyanoethylene (TCNE) as the acceptor. In our experiments, the CT state of the EDA complexes are directly reached by femtosecond laser excitation in either CH2Cl2 or CCl4 solutions, and the subsequent temporal evolution of the fluorescence spectra were measured to explore the charge recombination (CR) dynamics. EDA complexes with various arenes, including methyl substituted and non-methyl substituted benzenes, as the donor have been studied previously in our laboratory. We used the total fluorescence intensity function P(t) to analyze CT state relaxation and CR dynamics of EDA complexes. We found two different decay behaviors in these olefin-TCNE complexes. The faster component (<1 ps) was assigned to vibrational relaxation and solvation , the slower component was attributed to CR. We concluded that the most important difference between the olefin-TCNE and arene-TCNE complexes was the electronic coupling strength. The greater electronic coupling strength in the olefin-TCNE complexes extremely accelerates CR reactions and result in a weak dependence of ET rate on the driving-force.

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