釕聯吡啶錯合物與過硫酸鹽之光化學反應機制與其應用
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2020
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本論文設計了五個釕聯吡啶錯合物 [Ru(deebpy)3]2+ (1)、[Ru(deeb)2(dm)]2+ (2)、[Ru(bpy)3]2+ (3)、[Ru(dmbpy)3]2+ (4)、[Ru(tmbpy)3]2+ (5)，藉由修飾聯吡啶上的取代基，進而改變錯合物的氧化還原電位。接著利用雙分子淬熄反應來了解釕聯吡啶錯合物與 S2O82⎻ 和 SO4⎻ • 之間的電子傳遞速率，以便更進一步探討釕聯吡啶錯合物在合成水凝明膠中的反應機制。各錯合物皆使用電子吸收光譜、冷光光譜測量其基本性質，接著使用循環伏安法測得各別的氧化還原電位，再利用冷光光譜推算各錯合物激發態的位能 (E00) 後並用其計算出各錯合物對淬熄劑的電子傳遞驅動力。
將五個釕聯吡啶錯合物照光激發後與淬熄氧化劑 Na2S2O8 反應，經由 Stern-Volmer equation 得知各錯合物與 S2O82⎻ 間的淬熄反應速率 kq，其數值介於 9.7 x 107 M-1 s-1 至 1.5 x 109 M-1 s-1 之間，與電子傳遞驅動力 1.93 eV 至 2.64 eV 呈現正相關性。接著透過瞬時吸收光譜發現各錯合物與 S2O82⎻ 反應後，S2O82⎻ 會斷鍵並生成 SO4⎻ •，並且 SO4⎻ • 會再與基態的釕聯吡啶錯合物反應形成三價釕聯吡啶錯合物，其反應速率常數 kq2，由 2.0 x 109 M-1 s-1 至 6.9 x 109 M-1 s-1，同樣對應於其電子傳遞驅動力 0.88 eV 至 1.48 eV。
將各錯合物對 S2O82⎻ 和 SO4⎻ • 間的淬熄反應速率和電子傳遞驅動力，透過Marcus theory 計算後可得到激發態錯合物與 S2O82⎻ 反應的重組能量 4.41 eV 和基態錯合物與 SO4⎻ • 反應的重組能量 2.46 eV。由於S2O82⎻ 反應涉及斷鍵，因而重組能量較大。
在水凝明膠的應用上，使用 [Ru(bpy)3]2+ 作為主要錯合物，透過瞬時吸收光譜觀察 SO4⎻ • 與明膠之間的反應機制並與 I-2959 比較，藉由光譜證明 SO4⎻ • 與在合成水凝明膠的反應中並不受氧氣影響，並且發現三價的釕聯吡啶錯合物同時也會參與反應，這或許是釕聯吡啶錯合物在合成水凝明膠的效率非常好的原因。
In this study, five ruthenium (Ru) complexes were synthesized, namely [Ru(deeb)3]2+, [Ru(deeb)2(dm)]2+, [Ru(bpy)3]2+, [Ru(dm)3]2+, and [Ru(tm)3]2+, by changing the substituents on bipyridine, the redox potentials of the complexes were thereby changed. Subsequently, the complexes were used to investigate electron treansfer with persulfate. The oxidation potentials for complexes 1–5 were 1.41, 1.18, 1.06, 0.86, and 0.77 V vs SCE, respectively. Furthermore, the bimolecular quenching rate constants (kq) of complexes 1–5 using the quencher S2O82⎻ were between 9.7 × 107 M−1 s−1 and 1.5 × 109 M−1 s−1. The reaction between the excited state of a Ru complex and S2O82⎻ broke the O-O band in S2O82⎻ and produced SO4⎻ •. Then, SO4⎻ • reacted with the ground state of the Ru complex and produced more Ru(III). The electron transfer rate constants (k2) of complexes 1–5 with SO4⎻ • were between 2.0 × 109 and 6.9 × 109 M−1 s−1, and these results were dependent on the driving force. The driving force between complexes 1–5 and S2O82⎻ were −1.93, −2.07, −2.56, −2.48 and −2.64 eV, respectively, whereas that between the complexes 1–5 and SO4⎻ • were −0.88, −1.10, −1.49, −1.40 and −1.45 eV, respectively. Subsequently, this study calculated the reorganization energy of the two reactions using Marcus theory, and that between the Ru complexes and S2O82⎻ was 4.41 eV. . This value was higher than the reorganization energy between the Ru complexes and SO4⎻ • (2.17 eV), which is because the reaction between Ru complexes and S2O82⎻ involves a broken bond. In addition, hydrogel gelatin was applied with [Ru(bpy)3]2+ as the main complex, and the reaction mechanism between SO4⎻ • and the gelatin was observed using transient absorption spectroscopy and compared with I-2959. This reaction was observed to be unaffected by oxygen. Furthermore, the final product Ru(III) was found to react with gelatin in the process of synthesizing hydrogel gelatin.
In this study, five ruthenium (Ru) complexes were synthesized, namely [Ru(deeb)3]2+, [Ru(deeb)2(dm)]2+, [Ru(bpy)3]2+, [Ru(dm)3]2+, and [Ru(tm)3]2+, by changing the substituents on bipyridine, the redox potentials of the complexes were thereby changed. Subsequently, the complexes were used to investigate electron treansfer with persulfate. The oxidation potentials for complexes 1–5 were 1.41, 1.18, 1.06, 0.86, and 0.77 V vs SCE, respectively. Furthermore, the bimolecular quenching rate constants (kq) of complexes 1–5 using the quencher S2O82⎻ were between 9.7 × 107 M−1 s−1 and 1.5 × 109 M−1 s−1. The reaction between the excited state of a Ru complex and S2O82⎻ broke the O-O band in S2O82⎻ and produced SO4⎻ •. Then, SO4⎻ • reacted with the ground state of the Ru complex and produced more Ru(III). The electron transfer rate constants (k2) of complexes 1–5 with SO4⎻ • were between 2.0 × 109 and 6.9 × 109 M−1 s−1, and these results were dependent on the driving force. The driving force between complexes 1–5 and S2O82⎻ were −1.93, −2.07, −2.56, −2.48 and −2.64 eV, respectively, whereas that between the complexes 1–5 and SO4⎻ • were −0.88, −1.10, −1.49, −1.40 and −1.45 eV, respectively. Subsequently, this study calculated the reorganization energy of the two reactions using Marcus theory, and that between the Ru complexes and S2O82⎻ was 4.41 eV. . This value was higher than the reorganization energy between the Ru complexes and SO4⎻ • (2.17 eV), which is because the reaction between Ru complexes and S2O82⎻ involves a broken bond. In addition, hydrogel gelatin was applied with [Ru(bpy)3]2+ as the main complex, and the reaction mechanism between SO4⎻ • and the gelatin was observed using transient absorption spectroscopy and compared with I-2959. This reaction was observed to be unaffected by oxygen. Furthermore, the final product Ru(III) was found to react with gelatin in the process of synthesizing hydrogel gelatin.
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釕聯吡啶錯合物, 過硫酸鹽, 光化學反應, Photoreaction, Ruthenium, Persulfate