Potentiometric and 1H NMR studies have been performed on the interaction of [Pd(en)(H2O)2]2+ and [Pd(pic)(H2O)2]2+ (pic = 2-picolylamine) with N-alkyl nucleobases and N-acetyl amino acids. The ligands 1-methylthymine, 1-methyluracil and uridine formed only mono and bis(ligand) complexes in the whole pH range (2 to 10) via the co-ordination of N(3) donor atoms of pyrimidine rings. In the case of 1-methylcytosine (MeC), N-acetyl-L-histidine (AcHis) and N-acetylhistamine (AcHm) polynuclear complexes containing a deprotonated exocyclic amino group of MeC or a fully deprotonated imidazole of AcHis or AcHm were also formed. In the [Pd(pic)(H2O)2]2+–MeC and AcHis/AcHm systems various isomeric species including the cis–trans and linkage isomers were detected by NMR measurements. The thermodynamic equilibrium constants of the complexes of [Pd(pic)(H2O)2]2+ with nitrogen donors were generally higher than those of [Pd(en)(H2O)2]2+. The differences in the complex formation reactions of [Pd(en)(H2O)2]2+ and [Pd(pic)(H2O)2]2+ were especially high for N-acetyl-L-methionine. The high trans-effect of the thioether donor function of AcMet resulted in the liberation of free ethylenediamine in the [Pd(en)(H2O)2]2+–AcMet system, while bidentate (S,O) co-ordination of AcMet was proposed for [Pd(pic)(H2O)2]2+ in acidic solutions. The hydrolytic reactions of the complexes were also followed. The formation of dihydroxo complexes [Pd(en)(OH)2] and [Pd(pic)(OH)2] was characteristic in alkaline solutions, while the existence of a dimeric–trimeric and monomeric–dimeric equilibrium was suggested in the neutral pH range for the monohydroxo complexes of [Pd(en)(H2O)2]2+ and [Pd(pic)(H2O)2]2+, respectively.
对 [Pd(en)(
H2O)2]2+ 和 [Pd(pic)( )2]2+ (pic = 2-picolylamine) 与 N-烷基核碱基和N-乙酰
氨基酸。
配体1-甲基胸腺
嘧啶、1-甲基尿
嘧啶和
尿苷通过
嘧啶环的N(3)供体原子的配位在整个pH范围(2至10)中仅形成单(
配体)配合物和双(
配体)配合物。在 1-甲基
胞嘧啶 (MeC)、N-乙酰基-
L-组氨酸 (AcHis) 和 N-乙酰
组胺 (AcHm) 的情况下,还形成含有去质子化的 MeC 环外
氨基或完全去质子化的 AcHis 或 AcHm
咪唑的多核复合物。在 [Pd(pic)( )2]2+–MeC 和 AcHis/AcHm 系统中,通过 NMR 测量检测到各种异构体,包括顺反异构体和连接异构体。 [Pd(pic)( )2]2+与氮供体配合物的热力学平衡常数普遍高于[Pd(en)( )2]2+。对于 N-乙酰基-
L-蛋氨酸,[Pd(en)( )2]2+ 和 [Pd(pic)( )2]2+ 络合物形成反应的差异特别大。 AcMet
硫醚供体功能的高反式效应导致 [Pd(en)( )2]2+–AcMet 体系中游离
乙二胺的释放,而 AcMet 的二齿 (S,O) 配位则被释放。建议用于酸性溶液中的 [Pd(pic)( )2]2+。还跟踪了配合物的
水解反应。二羟基配合物 [Pd(en)(OH)2] 和 [Pd(pic)(OH)2] 的形成是碱性溶液中的特征,而在中性溶液中则表明存在二聚体-三聚体和单体-二聚体平衡。分别为 [Pd(en)( )2]2+ 和 [Pd(pic)( )2]2+ 的单羟基络合物的 pH 范围。