含芘之聯吡啶釕錯合物光物理與光化學性質研究

Abstract

本實驗調控 Ru-bpy 類錯合物的配位基，將 pyrene 和 2,2’-Dimethyl pyridine (dmb) 鍵結在一起，合成出配位基 pyr-dmb 後，再進一步合成錯合物 [Ru(bpy)2(pyr-dmb)]2+ 和 Ru(pyr-dmb)2(SCN)2 並研究其光物理與光化學性質。 從吸收光譜中可看出 [Ru(bpy)2(pyr-dmb)]2+ 在 pyrene 和 [Ru(bpy)3]2+ 間的電子耦合能力非常微弱。由於 3pyrene 的能階和 Ru 錯合物的 3MLCT 能階非常接近，因而推論 3MLCT 會和 3pyrene 形成平衡，使生命期被延長至約為 2.5 s。 將 [Ru(bpy)2(pyr-dmb)]2+ 和 [Ru(bpy)3]2+ 與淬息物進行雙分子淬息反應。當以 Ru(NH3)63+ 為淬息物時，[Ru(bpy)2(pyr-dmb)]2+ 和 [Ru(bpy)3]2+ 之淬息速率常數分別為 5.79 × 108 M-1s-1 和 1.24 × 109 M-1s-1。在 Ru(NH3)63+ 濃度為 5 mM 時，反應產率約 87.9 % 和 77.4 %。以 MV2+ 為淬息物時，[Ru(bpy)2(pyr-dmb)]2+ 和 [Ru(bpy)3]2+ 之淬息速率常數則分別為 8.68 × 108 M-1s-1 和 6.81 × 108 M-1s-1，MV2+ 濃度為 5 mM 時，產率約 91.6 % 和 65.3 %。由於 [Ru(bpy)2(pyr-dmb)]2+ 之生命期較長，故反應產率優於 [Ru(bpy)3]2+。 以 N3 dye 為模型錯合物，並和 Ru(pyr-dmb)2(SCN)2 比較。從吸收光譜可得知 pyrene 和 Ru 金屬中心的電子耦合能力很微弱，此結果與第一部分一致。N3 dye 沒有放光和生命期，修飾上 pyrene 後的Ru(pyr-dmb)2(SCN)2 則有了放光的現象，生命期約為 30 ns。將 MV2+ 與 Ru(pyr-dmb)2(SCN)2 進行雙分子淬息反應，可求得淬息速率常數 5.52 × 109 M-1s-1，反應產率 8.5 %。而與 N3 dye 反應之產率則為 5.8 %。可知修飾上 pyrene 的錯合物進行雙分子淬息反應之產率較佳，此結果也與第一部分相同。 本實驗藉由在 Ru 錯合物的配位基 bpy 上修飾能階與錯合物 3MLCT接近的有機化合物，讓原本無放光現象的 SCN－ 錯合物也具有放光行為，且成功延長錯合物之生命期，進而提高雙分子淬息反應之產率。The lifetime of ruthenium tris-bipyridine type of complexes are greatly extended by incorporating an energetically close organic triplet state. In this work, pyrenyl unit was utilized to construct a new ligand pyr-dmb (pyr-dmb = 4-methyl-4- (2-hydroxyethylpyrenyl)-2,2’-bipyridine). Two ruthenium complexes have been prepared by using this ligand, Ru(bpy)2(pyr-dmb)2+ and Ru(pyr-dmb)2(SCN)2. Absorption spectrum ofRu(bpy)2(pyr-dmb)2+ indicates a poor electronic coupling between pyrene and Ru(bpy)32+ moiety. However, the potential of the 3pyrene is in close proximity with the 3MLCT of Ru-bpy type complexes. The lifetime of the 3MLCT was determined as 2.5 s, which is much longer than the Ru-bpy type complexes (0.6 s). Bimolecular quenching rate constant with electron acceptor Ru(NH3)63+ are 5.79 × 108 and 1.24 × 109 M-1s-1 for Ru(bpy)2(pyr-dmb)2+ and Ru(bpy)32+; respectively, and with methyl viologen are 8.68 × 108 and 6.81 × 108 M-1s-1; respectively. Though the quenching rate constant for Ru(bpy)2(pyr-dmb)2+ are slightly smaller than Ru(bpy)32+ (or roughly the same), due to its long lifetime, the products (Rua62+ and MV＋‧) yield (87.9 % and 91.6 %) are much higher than Ru(bpy)32+ (77.4% and 65.3 %) at the same quencher concentration (5 mM). Complex Ru(pyr-dmb)2(SCN)2 has an emission that centered around 705 nm and lifetime of 30 ns. The bimolecular reaction with MV2+ gives quenching rate constant of 5.52 × 109 M-1s-1 and electron transfered product yield of 8.5 % at 5 mM MV2+. These results help to understand there action of Ru(bpy)2(SCN)2 in dye-sensitized solar cells.