A series of Cu(II) complexes with cyclam-based ligands containing two N-(2,2,2-trifluoroethyl)-aminoalkyl pendant arms in 1,8-positions (L1: 1,2-ethylene spacer, L2: 1,3-propylene spacer; L3: 1,4-butylene spacer) was studied in respect to potential use as contrast agents for ¹⁹F magnetic resonance imaging (MRI). A number of structures of the complexes as well as of several organic precursors were determined by single-crystal X-ray diffraction analysis. Geometric parameters (especially distances between fluorine atoms and the central metal ion) were determined for each complex and the identity of isomeric complex species present in solution was established. The NMR longitudinal relaxation times (T₁) of ¹⁹F nuclei in the ligands at clinically relevant fields and temperatures (1–2 s) were significantly shortened upon Cu(II) binding to 7–10 ms for [Cu(L1)]²⁺, 20–30 ms for [Cu(L2)]²⁺ and 20–50 ms for [Cu(L3)]²⁺. The trend of the relaxation time shortening is in accordance with the distance and number of chemical bonds between fluorine atoms and the Cu(II) ion. The signals show promising T₂*/T₁ ratios in the range 0.25–0.55, assuring their good applicability to ¹⁹F NMR/MRI. The results show that even the Cu(II) ion, with a small magnetic moment, causes significant relaxation enhancement with a long-range effect and can be considered as a highly suitable metal ion for efficient ¹⁹F MRI contrast agents.

中文翻译：

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具有 N-(2,2,2-三氟乙基)-氨基烷基侧臂的环己胺铜 (II) 配合物作为 19F 磁共振成像的潜在探针

一系列 Cu( II ) 配合物，具有基于仙客来的配体，在 1,8 位包含两个N -(2,2,2-三氟乙基)-氨基烷基侧臂（ L1：1,2-乙烯间隔基，L2：1， 3-丙烯间隔基；L3：1,4-丁烯间隔基）作为^{19 的造影剂的潜在用途进行了研究}F磁共振成像（MRI）。通过单晶 X 射线衍射分析确定了复合物以及几种有机前体的许多结构。确定了每个复合物的几何参数（尤其是氟原子与中心金属离子之间的距离），并确定了溶液中存在的同分异构复合物种类。^配体中19 F 核的NMR 纵向弛豫时间 ( T ₁ )在临床相关场和温度下 (1–2 s) 在 Cu( II )结合后显着缩短[Cu( L1 )] ²至 7–10 ms ⁺ , [Cu( L2 )] ²⁺为 20–30 ms，[Cu( L3)为 20–50 ms)] ²⁺。弛豫时间缩短的趋势与氟原子与Cu( II )离子之间的化学键距离和数量有关。信号显示有希望的T ₂ */ T ₁比率在 0.25–0.55 范围内，确保它们对¹⁹ F NMR/MRI 具有良好的适用性。结果表明，即使是具有小磁矩的 Cu( II ) 离子，也会引起具有长程效应的显着弛豫增强，可以被认为是一种非常适合用于高效¹⁹ F MRI 造影剂的金属离子。