The monomeric (PdL·2H₂O) and dimeric (Pd₂L₂·7H₂O) palladium(II) complexes of N,N′-bis(2-aminoethyl)oxamide (H₂L) were isolated, and their structures were established by single-crystal X-ray diffraction. Both compounds display identical cis-(2N_amide + 2N_amine) coordination environments of the metal ion. The dimer, representing a combination of two PdL species with an open lateral chelate ring, has an “open clamshell”-like structure. The intramolecular metal–metal separation in Pd₂L₂ (3.215 Å) is slightly shorter than the sum of the van der Waals radii of the palladium(II) atoms. The dimeric complex is relatively stable to dissociation, and its spectral features in aqueous solutions have been compared to those of the monomeric complex. A ¹H NMR spectroscopic study revealed the presence of the dynamic conformational exchange process assigned to a turning of the dimeric molecule “inside out” with an activation energy of 65 kJ/mol. Cyclic voltammetry of PdL in perchlorate-, chloride-, and sulfate-containing electrolytes revealed two-electron oxidation of the palladium center. For the dimeric complex similar, though irreversible, oxidation to the palladium(IV) state was observed in NaCl electrolyte. At the same time, in NaClO₄ or Na₂SO₄ solutions oxidation of Pd₂L₂ occurs in two distinct steps. The first step is quasi-reversible and can be assigned to the formation of species in an intermediate Pd^IIIPd^III state. Monomeric palladium(IV) complex Pd^IVLCl₂ was generated via chemical oxidation of Pd^IIL by peroxodisulfate in the presence of chloride ions and structurally characterized. The related M^IIL complexes (M = Pd, Ni, Cu) showed low cytotoxicity in human cancer cell lines AGS (gastric adenocarcinoma) and HCT116 (colorectal carcinoma) with IC₅₀ values from 204 to 525 μM, while the proligand H₂L was devoid of antiproliferative activity (IC₅₀ > 1000 μM).

中文翻译：

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N，N'-双（2-氨基乙基）乙酰胺的钯配合物（H ₂ L）：结构式（Pd ^II L，Pd ^II ₂ L ₂和Pd ^IV LCl ₂），电化学，动态¹ H NMR和细胞毒性研究

分离出N，N'-双（2-氨基乙基）乙酰胺（H ₂ L）的单体（PdL·2H ₂ O）和二聚体（Pd ₂ L ₂ ·7H ₂ O）钯（II）配合物通过单晶X射线衍射确定。两种化合物都显示出相同的金属离子顺式（（2N_酰胺+ 2N_胺）配位环境。代表两个PdL种类与一个开放的侧面螯合环的组合的二聚体具有“开放的翻盖”状结构。Pd ₂ L _2中的分子内金属-金属分离（3.215Å）稍短于钯（II）原子的范德华半径之和。二聚配合物对解离相对稳定，并且已将其在水溶液中的光谱特征与单体配合物的光谱特征进行了比较。阿¹ 1 H NMR光谱研究表明分配给该二聚体分子的转动“内向外”与65千焦/摩尔的活化能动态构象交换过程的存在。含高氯酸盐，氯化物和硫酸盐的电解质中PdL的循环伏安法揭示了钯中心的两电子氧化。对于二聚体类似物，尽管不可逆，但在NaCl电解质中观察到氧化为钯（IV）态。同时，在NaClO ₄或Na ₂ SO中_4种溶液中Pd ₂ L _2的氧化分两个不同的步骤进行。第一步是准可逆的，可以指定为中间Pd ^III Pd ^III状态的物质形成。单体钯（IV）络合物Pd ^IV LCl ₂是在氯离子存在下，通过过二硫酸盐对Pd ^II L进行化学氧化而生成的，并进行了结构表征。相关的M ^II L配合物（M = Pd，Ni，Cu）在人类癌细胞系AGS（胃腺癌）和HCT116（结肠直肠癌）中显示出低细胞毒性，IC ₅₀值为204-525μM，而配体H ₂L缺乏抗增殖活性（IC ₅₀ > 1000μM）。