Helical self-assembled polymers from cooperative stacking of hydrogen-bonded pairs

Abstract

The double helix of DNA epitomizes this molecule's ability to self-assemble in aqueous solutions into a complex chiral structure using hydrogen bonding and hydrophobic interactions. Non-covalently interacting molecules in organic solvents are used to design systems that similarly form controlled architectures. Peripheral chiral centres in assemblies and chiral side chains attached to a polymer backbone, have been shown to induce chirality at the supramolecular level, and highly ordered structures stable in water are also known. However, it remains difficult to rationally exploit non-covalent interactions for the formation of chiral assemblies that are stable in water, where solvent molecules can compete effectively for hydrogen bonds. Here we describe a general strategy for the design of functionalized monomer units and their association in either water or alkanes into non-covalently linked polymeric structures with controlled helicity and chain length. The monomers consist of bifunctionalized ureidotriazine units connected by a spacer and carrying solubilizing chains at the periphery. This design allows for dimerization through self-complementary quadruple hydrogen bonding between the units and solvophobically induced stacking of the dimers into columnar polymeric architectures, whose structure and helicity can be adjusted by tuning the nature of the solubilizing side chains.

Shape‐Switchable Azo‐Macrocycles

“…This requires an accurate control of the molecular arrangements over a wide range of length scales, from micrometers down to the molecular level. Covalent, but more often non covalent intermolecular forces have been used to engineer highly ordered three dimensional supramolecular architectures where the single building blocks are held together by specific interactions, such as metal ligand bonding, [85]- [87] hydrogen bonding [88]- [91] and stacking. [92] On the other hand, self assembly at the solid liquid interface has been successfully used to control the molecular arrangement in two dimensions.…”

“…[92] On the other hand, self assembly at the solid liquid interface has been successfully used to control the molecular arrangement in two dimensions. [91][93]…”

Hierarchical formation of helical supramolecular polymers via stacking of hydrogen-bonded pairs in water

“…To ensure water solubility molecules, 1 and 2 were modified by providing them with penta(ethylene oxide) monomethyl ether side chains. Compounds 3 and 4 were accordingly designed and synthesized in an enantiomerically pure form and subsequently studied in aqueous solutions (26). In this paper, we present optical studies on these molecules in solution, revealing a hierarchical assembly process in water (Scheme 1).…”

“…The formation of helical self-assembled polymers in solution by both stacking and hydrogen bonding has recently been demonstrated by us (26,27). Self-complementary apolar molecules 1 and 2 dimerize via strong cooperative 4-fold hydrogen bonding (ADAD) in chloroform (28), giving rise to the formation of a dimer by 1 and a random coil polymer by 2, the latter featuring viscous solutions at higher concentrations.…”

Ureidobenzotriazine Multiple H-Bonding Arrays: The Importance of Geometrical Details on the Stability of H-Bonds

“…[13][14][15][16][17] In particular, strongly associating self-complementary molecules developed by our group have been of † eminent importance for the development of main-chain supramolecular polymers. [18][19][20][21][22] However, the self-complementarity of these units imposes restrictions to the self-assembly of copolymers and the construction of supramolecular architectures consisting of more than one compound. Given our research interest in multiple hydrogen-bonding units as well as the recent use of complementary recognition motifs in supramolecular polymers, there is a clear need for strong complementary binding motifs.…”