Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata 700032, India.
Inorg Chem. 2010 Mar 1;49(5):2334-48. doi: 10.1021/ic9022272.
Mixed-ligand monometallic and bimetallic ruthenium(II) complexes of compositions (bpy)(2)Ru(H(3)Imbzim)(2) x 2 H(2)O (1) and (bpy)(2)Ru(H(2)Imbzim)Ru(bpy)(2)(3) x CH(2)Cl(2) (2), where H(3)Imbzim = 4,5-bis(benzimidazol-2-yl)imidazole and bpy = 2,2'-bipyridine, have been synthesized and characterized using standard analytical and spectroscopic techniques. The X-ray crystal structures of both compounds have been determined and showed that 1 crystallized in the triclinic form with space group P1 and 2 is in the monoclinic form with space group P2(1)/m. The anion binding properties of complexes 1 and 2, as well as those of the parent H(3)Imbzim, were thoroughly investigated in an acetonitrile solution using absorption, emission, and (1)H NMR spectral studies, which revealed that both of the metalloreceptors act as sensors for F(-), for AcO(-), and, to some extent, for H(2)PO(4)(-). At a relatively lower concentration of anions, a 1:1 hydrogen-bonded adduct was formed; however, in the presence of an excess of anions, stepwise deprotonation of the two benzimidazole NH fragments occurred, an event that was signaled by the development of vivid colors visible with the naked eye. Double deprotonation was also observed in the presence of hydroxide. Less basic anions (AcO(-) and H(2)PO(4)(-)) induce deprotonation of only one NH. The effect of solvents on the absorption and emission spectral behavior has also been studied in detail. The binding affinities of different anions toward the receptors were evaluated and showed that the binding constants of 1 and 2 are substantially enhanced relative to free H(3)Imbzim because upon coordination to the Ru(II) center(s), H(3)Imbzim/H(2)Imbzim(-) becomes electron-deficient, thereby rendering the imidazole NH protons more available for hydrogen bonding to the anions. Cyclic voltammetry studies carried out in acetonitrile provided evidence of an anion-dependent electrochemical response with F(-) and AcO(-). Anion-induced lifetime shortening makes complex 2 a suitable lifetime-based sensor for anions.
(bpy)(2)Ru(H(3)Imbzim)(2) x 2 H(2)O 和 (bpy)(2)Ru(H(2)Imbzim)Ru(bpy)(2)(3) x CH(2)Cl(2) 的合成与表征：单核和双核钌（II）配合物的混合配体单金属和双金属
混合配体单核和双核钌（II）配合物(bpy)(2)Ru(H(3)Imbzim)(2) x 2 H(2)O（1）和(bpy)(2)Ru(H(2)Imbzim)Ru(bpy)(2)(3) x CH(2)Cl(2)（2）的合成与表征采用标准分析和光谱技术。通过 X 射线晶体结构分析确定了这两种化合物的结构，结果表明，1 以三斜晶系空间群 P1 结晶，而 2 以单斜晶系空间群 P2(1)/m 结晶。配合物 1 和 2 以及母体 H(3)Imbzim 的阴离子结合特性通过吸收、发射和（1）H NMR 光谱研究进行了深入研究，结果表明，这两种金属受体都可以作为 F(-)、AcO(-)的传感器，并且在一定程度上可以作为 H(2)PO(4)(-)的传感器。在相对较低的阴离子浓度下，形成了 1:1 的氢键加合物；然而，在过量阴离子存在下，两个苯并咪唑 NH 片段发生逐步去质子化，这一事件通过肉眼可见的鲜艳颜色的发展来指示。在存在氢氧根的情况下，也观察到双去质子化。碱性较弱的阴离子（AcO(-)和 H(2)PO(4)(-)）仅诱导一个 NH 去质子化。还详细研究了溶剂对吸收和发射光谱行为的影响。评估了不同阴离子与受体的结合亲和力，结果表明，1 和 2 的结合常数相对于游离 H(3)Imbzim 有显著提高，因为在与 Ru(II)中心配位后，H(3)Imbzim/H(2)Imbzim(-)变得缺电子，从而使咪唑 NH 质子更容易与阴离子形成氢键。在乙腈中进行的循环伏安研究提供了阴离子依赖性电化学响应的证据，其中包括 F(-)和 AcO(-)。阴离子诱导的寿命缩短使配合物 2 成为一种适用于阴离子的基于寿命的传感器。
