title: 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.
abstract: 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.
authors.affiliation: 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.
authors.forename: Liwei
authors.initials: L
authors.lastname: Yan
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.forename: Ming-Tsz
authors.initials: MT
authors.lastname: Chen
authors.forename: Ningjie
authors.initials: N
authors.lastname: Wu
authors.forename: Jingbo
authors.initials: J
authors.lastname: Lan
authors.forename: Xin
authors.initials: X
authors.lastname: Gao
authors.forename: Jingsong
authors.initials: J
authors.lastname: You
authors.forename: Han-Mou
authors.initials: HM
authors.lastname: Gau
authors.forename: Chi-Tien
authors.initials: CT
authors.lastname: Chen
mesh_terms: 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
chemical_list: D000838:Anions; D048288:Imidazolines; D017705:Lignans; D028561:Transition Elements