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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Effect of pH on the photophysical and redox properties of a ruthenium(II) mixed chelate derived from imidazole-4,5-dicarboxylic acid and 2,2′-bipyridine: An experimental and theoretical investigation
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Effect of pH on the photophysical and redox properties of a ruthenium(II) mixed chelate derived from imidazole-4,5-dicarboxylic acid and 2,2′-bipyridine: An experimental and theoretical investigation

机译：pH值对咪唑-4,5-二羧酸和2,2'-联吡啶衍生的钌（II）混合螯合物的光物理和氧化还原特性的影响：实验和理论研究

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摘要

Combined experimental and DFT-TD-DFT computational studies were utilized to investigate the structural and electronic properties of mixed-ligand monometallic ruthenium(II) complexes of compositions [(bpy) _2Ru(H _2Imdc)] ~+ (1 ~+), its N-H deprotonated form [(bpy) _2Ru(HImdc)] (1), and COOH deprotonated form [(bpy) 2Ru(Imdc)] - (1 -), where H _3Imdc = imidazole-4,5-dicarboxylic acid and bpy = 2,2′-bipyridine. The optimized geometrical parameters for the complexes computed both in the gas phase and in solution are reported and compared with the previously reported X-ray data. The influence of pH on the absorption, emission, and redox properties of [(bpy) _2Ru(H _2Imdc)] ~+ (1 ~+) has been thoroughly investigated. The absorption titration data were used to determine the ground state pK values, whereas the luminescence data were utilized for the determination of excited state acid dissociation constants. The proton-coupled redox activity of 1 ~+ has been studied over the pH range 2-12 in acetonitrile-water (3:2). From the E _(1/2) versus pH profile, the equilibrium constants of the variously deprotonated complex species in Ru ~(II) and Ru ~(III) oxidation states have been determined. As compared to the protonated complex (1 ~+), which undergoes reversible oxidation at 0.96 V (vs Ag/AgCl) in acetonitrile, the redox potential of the fully deprotonated complex (1 ~-) is shifted to a much lower value, viz., 0.52 V. Density functional theory (DFT) and time-dependent DFT (TD-DFT) study provides insight into the nature of the ground and excited states with resulting detailed assignments of the orbitals involved in absorption and emission transitions. In particular, the red-shifts of the absorption and emission bands and the cathodic shift in the oxidation potential of 1 ~+ compared to 1 and 1 ~- are also reproduced by our calculations.
机译：结合实验和DFT-TD-DFT计算研究来研究组成[[bpy）_2Ru（H _2Imdc）]〜+（1〜+）的混合配体单金属钌（II）配合物的结构和电子性质。 NH去质子化形式[（bpy）_2Ru（HImdc）]（1）和COOH去质子化形式[（bpy）2Ru（Imdc）]-（1--），其中H _3Imdc =咪唑-4,5-二羧酸，bpy = 2,2'-联吡啶。报告了在气相和溶液中计算出的配合物的最佳几何参数，并将其与先前报告的X射线数据进行了比较。彻底研究了pH对[（bpy）_2Ru（H _2Imdc）]〜+（1〜+）的吸收，发射和氧化还原特性的影响。吸收滴定数据用于确定基态pK值，而发光数据用于确定激发态酸解离常数。在乙腈-水（3：2）中，在2-12的pH范围内，已研究了1〜+的质子偶联氧化还原活性。从E _（1/2）与pH的关系曲线，可以确定Ru〜（II）和Ru〜（III）氧化态下各种去质子化的复合物种类的平衡常数。与质子化的络合物（1〜+）在乙腈中于0.96 V（vs Ag / AgCl）进行可逆氧化相比，完全去质子化的络合物（1〜-）的氧化还原电势转移到更低的值，即0.52V。密度泛函理论（DFT）和时变DFT（TD-DFT）研究提供了对基态和激发态性质的洞察力，从而得出了涉及吸收和发射跃迁的轨道的详细分配。特别地，通过我们的计算，还再现了吸收带和发射带的红移以及与1和1〜-相比1〜+的氧化电势的阴极移位。

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