Yan Liwei, Wang Zhen, Chen Ming-Tsz, Wu Ningjie, Lan Jingbo, Gao Xin, You Jingsong, Gau Han-Mou, Chen Chi-Tien
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, and State Key Laboratory of Biotherapy, West China Medical School, Sichuan University, Chengdu 610064, China.
Chemistry. 2008;14(36):11601-9. doi: 10.1002/chem.200801154.
A novel type of chiral tris-monodentate imidazolinyl ligands ((S,S,S)-4 and (R,R,R)-4) has been achieved in good yields. The ligands show a strong tendency to induce the generation of the discrete sandwich-shaped M(3)L(2) architectures with programmed helicity through the edge-directed complexation with a series of d(3)-d(10) transition-metal ions, while taking advantage of the steric hindrance of the bulky substituents of the imidazoline rings to avoid the formation of extended metal-organic frameworks (MOFs). In spite of different coordination geometries, monovalent metal ions (e.g. Ag(+)), divalent metal ions (e.g. Pd(2+), Cu(2+), Cd(2+), Zn(2+), Co(2+), Mn(2+), and Ni(2+)), and even trivalent metal ions (e.g. Fe(3+) and Cr(3+)) exhibit isostructural coordination. Installation of stereocenters fused onto the imidazoline rings results in favored handedness of the self-assemblies through the expression of molecular chirality into supramolecular helicity. In the crystal structures of [M(3){(S,S,S)-4}(2)], the self-assembly has to adopt the M form to relax the van der Waals repulsions of the phenyl and isopropyl groups. The replacement of (S,S,S)-4 with (R,R,R)-4 exclusively affords the opposite helicity (P). These results should provide important insights for the design of chiral helical capsule-like assemblies.
一种新型的手性三单齿咪唑啉基配体（(S,S,S)-4 和 (R,R,R)-4）已以良好的产率合成出来。这些配体通过与一系列 d(3)-d(10) 过渡金属离子进行边导向络合，表现出强烈的诱导生成具有特定螺旋性的离散夹心状 M(3)L(2) 结构的倾向，同时利用咪唑啉环上庞大取代基的空间位阻来避免形成扩展的金属有机框架（MOF）。尽管配位几何结构不同，但一价金属离子（如 Ag(+)）、二价金属离子（如 Pd(2+)、Cu(2+)、Cd(2+)、Zn(2+)、Co(2+)、Mn(2+) 和 Ni(2+)），甚至三价金属离子（如 Fe(3+) 和 Cr(3+)）都表现出同构配位。连接到咪唑啉环上的立体中心的引入通过将分子手性表达为超分子螺旋性，导致自组装具有偏好的手性。在 [M(3){(S,S,S)-4}(2)] 的晶体结构中，自组装必须采用 M 型以缓解苯基和异丙基的范德华排斥作用。用 (R,R,R)-4 完全取代 (S,S,S)-4 仅产生相反的螺旋性（P）。这些结果应为手性螺旋胶囊状组装体的设计提供重要的见解。
