Derivatives of the [Ru(bipy)(CN)4]2- chromophore with pendant pyridyl-based binding sites:: synthesis, pH dependent-luminescence, and time-resolved infrared spectroscopic studies
Derivatives of the [Ru(bipy)(CN)4]2- chromophore with pendant pyridyl-based binding sites:: synthesis, pH dependent-luminescence, and time-resolved infrared spectroscopic studies
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DOI：
10.1039/b105864a
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发表时间：
2001-01-01
期刊：
影响因子：
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通讯作者：
George, MW
中科院分区：
文献类型：
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作者：
Encinas, S;Morales, AF;George, MW
K-4[Ru(CN)(6)]与2,2':4',4 '-三吡啶（L-1）或2,2':3',2 ':6 ',2 '-季吡啶（L-2）在酸性甲醇水溶液中反应，分别得到配合物K-2[Ru(L-1)(CN)(4)]和K-2[Ru(L-2)(CN)(4)]，它们都含有{Ru(bipy)(CN)(4)}（2-）发色团，但分别具有悬置的吡啶或联吡啶单位。对MeCN-D2O中K-2[Ru(CN)(4) (L-2)]的时间分辨红外分析表明，在激光激发后，最强烈的CN拉伸振动向高能量转移了约50 cm(-1)，与Ru(III)/(L-2)的形成一致。-) MLCT激发态，其寿命测量值（38 +/- 5ns，由TRIR测量）与发光方法测量值（30 +/- 2ns）相当吻合。对这两种配合物的吸收和发射光谱的pH依赖性的研究表明，存在两种不同的效应，分别是由垂链吡啶基/联吡啶基位点的质子化（在每种情况下，pK(a)近似为3.1）和氰化物配体的质子化（在每种情况下，pK(a)近似为2）引起的。对于K-2[Ru(L-1)(CN)(4)]，悬垂吡啶基单元的质子化导致(MLCT)-M-1激发态能量降低约1000 cm(-1)，而在较低的pH值（2.5-1）下，氰化物配体的质子化使(MLCT)-M-1激发态能量提高超过2000 cm（-1）。相比之下，对于K-2[Ru(L-2)(CN)(4)]，悬垂联吡啶基单元的质子化对(MLCT)-M-1能量没有可检测到的影响，因为悬垂位点通过L-2的自由和配位联吡啶组分之间的大量扭曲与配合物核心电子解耦；然而，氰化物在较低pH值下的质子化使(MLCT)-M-1激发态不稳定。悬垂吡啶基位的质子化导致发光完全(对于[Ru(L-1)(CN)（4)](2-)）或接近完全(对于[Ru(L-2)(CN)（4)](2-)）猝灭；讨论了这种行为的可能原因。本文还描述了两种相关配合物[Ru((t)Bu(2)bipy)(2)(L-1)][PF6](2)和[Cl2Pt(mu -L-2)Ru(bipy)(2)][PF6](2)的晶体结构，以说明关于L-1和L-2构象的争论。
Reaction of K-4[Ru(CN)(6)] with 2,2':4',4 " -terpyridine (L-1) or 2,2':3',2 " :6 " ,2'''-quaterpyridine (L-2) in acidic aqueous methanol affords the complexes K-2[Ru(L-1)(CN)(4)] and K-2[Ru(L-2)(CN)(4)] respectively, both containing the {Ru(bipy)(CN)(4)}(2-) chromophore but with pendant pyridyl or bipyridyl units, respectively. Time-resolved IR analysis of K-2[Ru(CN)(4) (L-2)] in MeCN-D2O showed that the most intense CN stretching vibration shifted to higher energy by ca. 50 cm(-1) after laser excitation, consistent with formation of a Ru(III)/(L-2)(.-) MLCT excited state for which the lifetime measurement (38 +/- 5 ns, measured by TRIR) agrees reasonably well with the value measured by luminescence methods (30 +/- 2 ns). Study of the pH dependence of the absorption and emission spectra of the two complexes revealed the presence of two different effects arising from protonation of the pendant pyridyl/bipyridyl site (which occurs with pK(a) approximate to 3.1 in each case) and protonation of the cyanide ligands (which occurs with pK(a) approximate to 2 in each case). For K-2[Ru(L-1)(CN)(4)], protonation of the pendant pyridyl unit results in the (MLCT)-M-1 excited state being lowered in energy by ca. 1000 cm(-1), whereas at lower pH values (2.5-1), protonation of the cyanide ligands raises the (MLCT)-M-1 excited state energy by over 2000 cm(-1). For K-2[Ru(L-2)(CN)(4)] in contrast, protonation of the pendant bipyridyl unit has no detectable effect on the (MLCT)-M-1 energy, as the pendant site is electronically decoupled from the complex core by a substantial twist between the free and coordinated bipy components of L-2; protonation of the cyanides at lower pH values however destabilises the (MLCT)-M-1 excited state. Protonation of the pendant pyridyl sites results in complete (for [Ru(L-1)(CN)(4)](2-)) or near-complete (for [Ru(L-2)(CN)(4)](2-)) quenching of the luminescence; possible reasons for this behaviour are discussed. The crystal structures of the two related complexes [Ru((t)Bu(2)bipy)(2)(L-1)][PF6](2) and [Cl2Pt(mu -L-2)Ru(bipy)(2)][PF6](2) are also described to illustrate arguments about the conformations of L-1 and L-2.