Preferential formation of homochiral helical sandwich-shaped architectures through the metal-mediated assembly of tris(imidazoline) ligands with a set of d(3)-d(10) transition-metal ions.
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.
Yan
Liwei
L
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.
Wang
Zhen
Z
Chen
Ming-Tsz
MT
Wu
Ningjie
N
Lan
Jingbo
J
Gao
Xin
X
You
Jingsong
J
Gau
Han-Mou
HM
Chen
Chi-Tien
CT
D000838:Anions / Q000737:chemistry; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D048288:Imidazolines / Q000138:chemical synthesis / Q000737:chemistry*; D017705:Lignans; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013237:Stereoisomerism; D028561:Transition Elements / Q000737:chemistry*; D014961:X-Ray Diffraction
D000838:Anions; D048288:Imidazolines; D017705:Lignans; D028561:Transition Elements