The compound 2-[1,4,7,10-tetraazacyclododecan-1-yl]-ethanethiol (L2) has been synthesized and characterized by multinuclear NMR spectroscopy and mass spectrometry. Its thiol-protected precursor L1 has also been isolated and characterized, including by X-ray structural analysis. The protonation constants of L2 were determined by potentiometric methods at 25.0 °C and 0.10 mol dm⁻³ KNO₃ ionic strength. ¹³C NMR studies and 2D NMR spectra recorded at different pD values have been used to analyse its protonation scheme. Stability constants of L2 with Cu²⁺, Zn²⁺ and Cd²⁺ were also determined by potentiometry, and the Zn(II) and Cu(II) complexes were studied in solution by NMR, UV–Vis, and EPR spectroscopies. The pM values (pH 7.4) calculated for the metal complexes of L2 are higher than the corresponding values found for cyclen and cyclam, but the selectivity of L2 for Cu²⁺ is low.

中文翻译：

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环己基衍生物2- [1,4,7,10-四氮杂环十二烷-1-基]-乙硫醇及其对d-过渡金属离子的络合行为的研究

合成了化合物2- [1,4,7,10-四氮杂环十二烷-1-基]-乙硫醇（L2），并通过多核NMR光谱法和质谱法对其进行了表征。还对其硫醇保护的前体L1进行了分离和表征，包括通过X射线结构分析。通过电势法在25.0°C和0.10 mol dm ^-3 KNO ₃离子强度下测定L2的质子化常数。在不同pD值下记录的¹³ C NMR研究和2D NMR光谱已用于分析其质子化方案。L2与Cu 2 ⁺，Zn ²⁺和Cd ^2+的稳定性常数还可以通过电位测定法测定，并通过NMR，UV-Vis和EPR光谱研究溶液中的Zn（II）和Cu（II）配合物。为L2的金属络合物计算的pM值（pH 7.4）高于相应的cycln和cyclam值，但L2对Cu ²⁺的选择性低。