含羧基聯吡啶釕錯合物之性質研究

王茲嶸

指導教授 ： 張一知

國立臺灣師範大學/理學院/化學系/碩士(2010年)

摘要

在光敏性染料電池的實驗中合成了兩系列釕錯合物，分別為含兩個 -NCS- 配位基與單一個 -NCS- 配位基以及 NCS 僅為吡啶取代基之錯合物。配位基上的推拉電子基團對氧化還原之影響可由 UV-vis 光譜與氧化還原電位測知。
此類錯合物在 I-/I3- + BMII 環境下 Ru(dcbpy)2(NCS)(im)+ 有最好的光電轉換效率，值最大為 5.93%。在 2Br-/Br2 + BMIBr 的環境下，新合成之錯合物 Ru(dcbpy)2(phenNCS)2+ 具有最好的光電轉換效率，值最高為 0.4%。
利用氧化端還原電位配合其光電轉換效率，發現錯合物之 HOMO 與電解質氧化電位兩者之間的能階差必須大於 0.32 V (v.s. SCE)，才能提供足夠的 driving force 使電子從電解質傳遞到 HOMO，光電轉換效率才有辦法提高。
三個含羧基取代之吡啶之錯合物亦在此研究中合成，為Ru(dpa)2(mcbpy)2+、Ru(dpk)2(mcbpy)2+ 與 Ru(bpz)2(mcbpy)2+。在酸鹼性質的研究中，透過吸收度和冷光光譜強度對酸鹼值作圖可得基態和激發態解離平衡常數 pKa、pKa*’，再以錯合物質子化與去質子化之生命期校正，可得真正激發態平衡常數 pKa*。激發態與基態平衡常數的差值 pKa (pKa*- pKa)，能顯示錯合物電子分布受到推拉電子基的影響。
這三個錯合物中，Ru(dpa)2(mcbpy)2+ 之 pKa 為 0.78，代表錯
合物激發態有較多電子轉移到含羧基聯吡啶上。而 Ru(dpk)2(mcbpy)2+
之 pKa 為 -0.07，顯示錯合物激發態電子轉移到含羧基聯吡啶的效果
最差。

關鍵字

釕錯合物 ； 聯吡啶 ； 羧基

並列摘要

Two series of Ru(dcbpy)(LL1)(NCS)2 and Ru(dcbpy)2(NCS)(L2)+ complexes, where LL1 = dabpy, dMeObpy, bpy and dcbpy, L2 = Me-im, im, and COOH-im, and Ru(dcbpy)2(phenNCS)2+ have been synthesized. UV-vis spectra and redox potentials have been measured for all complexes in order to understand their photophysical and electrochemical properties.
These complexes were assembled to solar cell as the dye. When I-/I3- and BMII (1-Butyl-3-methylimidazolium iodine) were utilized as electrolyte, Ru(dcbpy)2(NCS)(im)+ gave the highest efficiency of 5.93%, whereas with 2Br-/Br2 and BMIBr (1-Butyl-3-methylimidazolium bromide), Ru(dcbpy)2(phenNCS)2+ had highest efficiency of 0.4%.
Redox potentials of these complexes did not show direct correlation to solar cell efficiency. However, it showed that the energy gap between the HOMO of complexes and electrolyte must greater than 0.32 V (v.s. SCE). It is the minimum driving force to transfer electron from electrolyte to the HOMO of the complexes, and therefore, gives reasonable conversion.
Three Ruthenium(II) complexes with mcbpy were synthesized. (mcbpy = 4’-Methyl-2.2’-bipyridine-4-carboxylic acid). Titration curves were plotted from absorption and emission intensity changes versus the solution pH values. The acid dissociation constants of pKa and pKa*’ were obtained from the inflation points of the titration curves. True excited state acid dissociation constant, pKa* was obtained from pKa*’ and lifetime calibration. The difference of dissociation constants, pKa (pKa*- pKa), reveals the electron-withdrawing and electron-donating abilities of ligands in the complexes.
The most positive pKa of 0.78 for Ru(dpa)2(mcbpy)2+ indicates the MLCT excited state has more electron density on mcbpy ligand. The most negative pKa of -0.07 for Ru(dpk)2(mcbpy)2+ indicates the excited state has slightly less electron density on mcbpy ligand.

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