Probing the Dynamic Environment-Associated Conformational Conversion from Secondary to Supersecondary Structures in Oligo(phenanthroline dicarboxamide)s

Soft 2D Covalent Organic Framework with Compacted Honeycomb Topology

In this contribution, we report the synthesis of an imine-based soft 2D covalent organic framework (S-COF) with compacted honeycomb topology via inveterately selecting a helically folded ditopic flexible linker and a trigonal building block. In contrast to various topological structures of rigid monomer-based COFs (R-COFs) reported so far, owing to the presence of flexible skeleton S-COF can spontaneously form a compacted and nonporous topological structure via intramolecular π stacking of presupposed honeycomb-like topology. Such S-COFs with a compacted honeycomb topology have neither been proposed theoretically nor been achieved experimentally. The compacted topological structure of 2D S-COF was clearly characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and circular dichroism (CD) measurements. This study opens a new window to the development of S-COFs and will significantly expand the scope of COF materials.

Artificial supersecondary structures based on aromatic oligoamides

With an intelligent design of the monomers, considerable effort has so far focused on the creation of aromatic oligoamide foldamers which are able to mimic the secondary structures of biopolymers. Supersecondary structure is a growing set of known and classifiable protein folding patterns that provides an important organizational context to this complex endeavor. In this article, we highlight the design, chemical synthesis, and structural studies of artificial supersecondary structures based on aromatic oligoamide foldamers in recent years.

Encapsulation of conventional and unconventional water dimers by water-binding foldamers

Water-binding foldamers have been rarely studied. By orienting both H-bond donors and acceptors toward their interior, two pyridine-derived crescent-shaped folding oligoamides were found to be capable of trapping both conventional and unconventional water dimer clusters in their cavity (∼2.5 Å radius). In the unconventional water dimer cluster, the two water molecules stay in contact via an unusual H-H interaction (2.25 Å) rather than the typical H-bond.

Minimalist end groups for control of absolute helicity in salen- and salophen-based metallofoldamers

(S)-1-Methylindan end groups are effective controllers of absolute helicity in Ni-salen- and Ni-salophen-based foldamers derived from (R,R)-trans-1,2-cyclohexanediamine and 1,2-phenylenediamine, respectively. Evidence for the helicity of the described complexes was provided through X-ray crystallography and study of chiroptical properties in solution. The chiral end groups control the absolute sense of helicity for the salen complexes, even in a case where the helical bias of the end group is mismatched relative to that of the internal diamine.