Desymmetrized Vertex Design toward a Molecular Cage with Unusual Topology.

Abstract

A novel low-symmetry organic molecular cage with distinctive geometry was successfully synthesized from 5,5'-(propane-2,2-diyl)bis(2-hydroxyisophthalaldehyde) and 1,2-cyclohexanediamine building blocks, through the desymmetrized vertex design strategy. Single-crystal X-ray crystallographic analysis shows that the cage contains asymmetrical and nonplanar windows, exhibiting an unprecedented C2 symmetry and an efficient packing. The molecular cage structure was also characterized by FTIR, NMR, and MALDI-TOF. Quantum chemistry studies show that the cage structure contains rare intramolecular hydrogen-hydrogen (C-H⋅⋅⋅H-C) bonding interactions. The cage crystals exhibit high iodine vapor uptake (3.78 g g-1 ), which is among the highest for porous molecular materials. The knowledge gained in this study would open new possibilities for the design and synthesis of molecular cages with novel topologies targeting a broad range of applications.