聯比啶二價釕錯化合物之光物理性質

Photophysical Properties Of Ruthenium(II) Polypyridyl Complexes

蘇建華(Chien-Hua Su)

指導教授 ： 張一知 博士

國立臺灣師範大學/理學院/化學系/博士(1999年)

摘要

中文摘要
含羧酸基聯比啶之二價釕錯化合物已成功的合成出，混合不同推拉電子基的聯比啶共合成六個錯化合物，分為下列兩類：[Ru(LL')(mcbpy)](PF6)2，(LL' = dmbpy, tmbpy, dnbpy), 及[Ru(bpy)3-x(mcbpy)x](PF6)2 (x=1,2,3，mcbpy=4'-methyl-2,2'-bipyridine-4-carboxylic acid)。
在吸收光譜中，二價釕聯比啶錯化合物的特徵吸收峰，金屬到配位基的電荷轉移吸收 (MLCT)，隨著聯比啶上拉電子基的增加而紅位移的現象愈明顯。其吸收最大值依序為：[Ru(bpy)2(mcbpy)](PF6)2，456 nm ；[Ru(bpy)(mcbpy)2](PF6)2 ，460 nm；[Ru(mcbpy)3](PF6)2，465 nm；[Ru(dmbpy)2(mcbpy)](PF6)2，463 nm；[Ru(tmbpy)2(mcbpy)](PF6)2，447 nm；[Ru(dnbpy)2(mcbpy)](PF6)2，475 nm。它們的冷光光譜亦有相同的趨勢，其冷光光譜最大值分別為：625 nm, 629 nm, 633 nm, 645 nm, 655 nm, 675 nm。
錯化合物在基態的酸解離平衡常數 (pKa)，經由吸收光譜實驗結果可得到：[Ru(bpy)2(mcbpy)](PF6)2，[Ru(bpy)(mcbpy)2](PF6)2 ，[Ru(mcbpy)3](PF6)2 及[Ru(dmbpy)2(mcbpy)](PF6)2，[Ru(tmbpy)2(mcbpy)](PF6)2，[Ru(dnbpy)2(mcbpy)](PF6)2 在基態的酸解離平衡常數分別為： 2.98, 2.10, 2.50, 2.30, 2.47 和 2.06。在激發態的酸解離平衡常數 (pKa*) 是以冷光光譜滴定曲線與對激發態的生命期做校正後，可得到這六個釕錯化合物之酸解離平衡常數分別為：3.25, 2.88, 3.99, 3.01, 3.4, 和 2.08。由實驗結果可知，所有的釕錯化合物在激發態的鹼度要比基態來得大些。
由二者的差值 (激發態的酸解離平衡常數-基態的酸解離平衡常數)可得 (DpKa)：0.27, 0.78, 1.49, 0.71, 0.93, 0.02。相差愈大的，代表含羧基聯比啶在激發態時有較多的電子密度。由此結果可知釕聯比啶錯化合物在激發態時定性上的電子密度分佈情形。

關鍵字

聯比啶二價釕錯化合物 ； 金屬到配位基的電子轉移 ； 基態的酸解離平衡常數 ； 激發態的酸解離平衡常數

並列摘要

Abstract
Ruthenium(II) tris(dipyridyl) complexes have been synthesized. By varying the electron-withdrawing and electron-donating abilities on each bipyridyl ligand, we have made six complexes that contain at least one 4-carboxyl-4'-methy,2'-bipyridine. These complexes are [Ru(bpy)2(mcbpy)](PF6)2, [Ru(bpy)(mcbpy)2](PF6)2, [Ru(mcbpy)3](PF6)2, [Ru(dmbpy)2(mcbpy)](PF6)2, [Ru(tmbpy)2(mcbpy)](PF6)2 and [Ru(dnbpy)2(mcbpy)](PF6)2.
The metal-to-ligand charge-transfer (MLCT) bands shift to red with the increasing electron-withdrawing ability of the ligands. Luminescence spectra results from the 3MLCT band have shown the similar behavior. The absorption maximums are 456, 460, 465, 463, 447, and 475 nm, and the luminescence maximums are 625, 629, 633, 645, 655, and 675 nm for [Ru(bpy)2(mcbpy)](PF6)2, [Ru(bpy)(mcbpy)2](PF6)2, [Ru(mcbpy)3](PF6)2, [Ru(dmbpy)2(mcbpy)](PF6)2, [Ru(tmbpy)2(mcbpy)](PF6)2 and [Ru(dnbpy)2(mcbpy)](PF6)2, respectively.
The ground-state acid dissociation constants (pka) were obtained from the titration curve of absorption changes. The excited-state acid dissociation constant (pka*) were obtained from the luminescence titration curve and lifetime calibration.
The pka are 2.98, 2.10, 2.50, 2.30, 2.47, and 2.06, and the pka* are 3.25, 2.88, 3.99, 3.01, 3.4, and 2.08 for [Ru(bpy)2(mcbpy)](PF6)2, [Ru(bpy)(mcbpy)2](PF6)2, [Ru(mcbpy)3](PF6)2, [Ru(dmbpy)2(mcbpy)](PF6)2, [Ru(tmbpy)2(mcbpy)](PF6)2, and [Ru(dnbpy)2(mcbpy)](PF6)2, respectively.
A large difference of the acid dissociation constant between the excited- and the ground state (Dpka = pka* - pka) indicates the electron density of the bipyridine that contains the carboxyl group has a higher electron density in the excited state than the ground state. From the acid dissociation constant studies, the electron density in the excited state of Ruthenium(II) tris(dipyridyl) complexes can be qualitatively mapped.

並列關鍵字

Ruthenium(II) Polypyridyl Complexes ； MLCT(metal-to-ligand charge-transfer) ； pKa ； pKa*

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