A Highly Fluorescent Metallosalalen‐Based Chiral Cage for Enantioselective Recognition and Sensing

Abstract

A highly fluorescent coordination cage [Zn8L4I8] has been constructed by treating enantiopure pyridyl-functionalized metallosalalen units (L) with zinc(II) iodide and characterized by a variety of techniques including microanalysis, thermogravimetric analysis (TGA), circular dichroism (CD) spectroscopy, and single-crystal and powder X-ray diffraction. Strong intermolecular π-π, CH⋅⋅⋅π, and CH⋅⋅⋅I interactions direct packing of the cage molecules to generate a 3D polycage network interconnected by pentahedral cages formed by adjacent pentamers. The cage has an amphiphilic helical cavity decorated with chiral NH functionalities capable of interactions with guest species such as saccharides. The fluorescence of the cage was greatly enhanced by five enantiomeric saccharides in solution, with enantioselectivity factors of 2.480-4.943, and by five enantiomeric amines in the solid state, with enantioselective fluorescence enhancement ratios of 1.30-3.60. This remarkable chiral sensing of both saccharides and amines with impressive enantioselectivity may result from the steric confinement of the cavity as well as its conformational rigidity. It holds great promise for the development of novel chiral cage materials for sensing applications.

Ultrathin two-dimensional porous organic nanosheets with molecular rotors for chemical sensing

“…29 ), respectively. The quenching constant K SV represents the quenching sensitivity 62 , 63 , and the K SV values were calculated to be 27,214, 4387, 3242, and 1984 M −1 for Fe 3+ , Co 2+ , Cu 2+ , and Mn 2+ , respectively. The quenching percentage of other metal ions are 2–30% and the K SV are 30–1200 M −1 (Fig.…”

Homochiral D4-symmetric metal–organic cages from stereogenic Ru(II) metalloligands for effective enantioseparation of atropisomeric molecules

“…The design and synthesis of discrete nanoscale metal–organic cages/containers (MOCs) with specific configurations and cavities applying directional bridging ligands and geometrically prefixed metals is emerging as an appealing topic in recent supramolecular coordination chemistry 1 2 3 . Among this, the controlled assembly of enantiopure chiral cages is of special importance because of their potential applications in stereoselective recognition, catalysis and enzyme mimics 4 5 6 7 8 9 10 11 . Since the chiral space in regular polyhedra only rarely presents in snub dodecahedron and snub cube (all other Platonic, Archimedean, prismatic and antiprismatic solids are achiral) 12 13 , assembly of chiral polyhedral MOCs is usually achieved by introducing stereogenic centres into the faces, edges or vertices of a polyhedron to remove inversion and mirror symmetries.…”

Water-mediated deracemization of a bisporphyrin helicate assisted by diastereoselective encapsulation of chiral guests

“…Among the double helices prepared so far, helicates, a class of metal-directed self-assembled helical complexes, are the most popular structural motifs since the seminal work by Lehn and co-workers 7–11 . The control of its handedness is of key importance for developing one-handed helicates with a specific functionality that involves separation 12 and sensing enantiomers 12–14 and asymmetric catalysis 15 as well as antimicrobial materials 16 . However, double-stranded helicates composed of achiral molecular strands assembled with labile metal ions, such as Cu(I) ions, mostly exist in an equal mixture of interconvertible right- ( P ) and left-handed ( M ) helices and their resolution into the enantiomers remains difficult except for one example 17 .…”