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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Properties of a new 4-imidazolyl derivative of a 14-membered tetraazamacrocyclic chelating agent
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Properties of a new 4-imidazolyl derivative of a 14-membered tetraazamacrocyclic chelating agent

机译：14元四氮杂大环螯合剂的新型4-咪唑基衍生物的性质

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摘要

A new bis-N,N'-(5-methylimidazol-4-ylmethyl) derivative of a 14-membered tetraazamacrocycle, L1, has been synthesized. The protonation constants of this compound and the stability constants of its complexes with divalent first-row transition metal ions and Fe~(3+) were determined at 298.2 K in aqueous 0.10 mol dm~(3-) KNO3. Compound L1 exhibits high overall basicity, which is mainly conferred by the imidazolyl groups. The complexes of the divalent first row-transition metal ions of L1 follow the Irving-Williams order of stability with the maximum for Cu~(2+) as expected, but a steep fall of constants is verified for the Mn~(2+), Fe~(2+) and Co~(2+), in one side, and for the Zn~(2+) complexes, in the other side. Additionally, L1 shows a large affinity for Fe~(3+), and the relative stability constants for its Cd~(2+) and Pb~(2+) complexes indicate that L1 may be useful for the complexometric determination of these two toxic metal ions in solutions containing both metal ions. These studies together with NMR, UV-vis and EPR spectroscopic data indicated the presence of mononuclear complexes, which adopt distorted pyramidal or octahedral geometries depending on the metal centre. The X-ray crystal structure of [Cu(HL1)](PF6)2(NO3)-H2O showed that the coordination sphere of the copper centre can be described as a distorted square pyramid with the basal plane defined by three nitrogen donors of the macrocycle backbone and one nitrogen atom from one imidazolyl pendant arm. The apical position is occupied by the nitrogen atom of the macrocycle trans to the pyridine ring. To achieve this coordination environment, the macrocycle is folded along the axis defined by the two N atoms contiguous to the pyridine ring. The free methylimidazolyl arm points away from the metal centre leading to an intramolecular Cu···N distance of 5.155(1) A.
机译：合成了一种新的14元四氮杂大环L1的双-N，N'-（5-甲基咪唑-4-基甲基）衍生物。在0.10 mol dm〜（3-）KNO3水溶液中，该化合物的质子化常数及其与二价第一行过渡金属离子和Fe〜（3+）的配合物的稳定常数在298.2 K下测定。化合物L1显示出高的总体碱性，这主要是由咪唑基基团赋予的。 L1的二价第一行跃迁金属离子的配合物遵循Irving-Williams稳定性顺序，如预期的那样，Cu〜（2+）的最大值最大，但已证明Mn〜（2+）的常数急剧下降，一侧为Fe〜（2+）和Co〜（2+），另一侧为Zn〜（2+）配合物。此外，L1对Fe〜（3+）表现出较大的亲和力，其Cd〜（2+）和Pb〜（2+）配合物的相对稳定性常数表明L1可以用于络合测定这两种有毒物质包含两种金属离子的溶液中的金属离子。这些研究与NMR，UV-vis和EPR光谱数据一起表明存在单核络合物，根据金属中心的不同，它们会采用扭曲的棱锥或八面体几何形状。 [Cu（HL1）]（PF6）2（NO3）-H2O的X射线晶体结构表明，铜中心的配位球可描述为扭曲的四棱锥，其基面由三氮供体定义。大环骨架和一个咪唑基悬垂臂上的一个氮原子。顶位被大环的氮原子反式至吡啶环占据。为了实现这种配位环境，大环沿着由两个与吡啶环相邻的N原子限定的轴折叠。游离甲基咪唑基臂指向远离金属中心的位置，导致分子内Cu··N距离为5.155（1）A。

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