Flower-like supramolecular self-assembly of phosphonic acid appended naphthalene diimide and melamine

Abstract

Diverse supramolecular assemblies ranging from nanometres to micrometers of small aromatic π-conjugated functional molecules have attracted enormous research interest in light of their applications in optoelectronics, chemosensors, nanotechnology, biotechnology and biomedicines. Here we study the mechanism of the formation of a flower-shaped supramolecular structure of phosphonic acid appended naphthalene diimide with melamine. The flower-shaped assembly formation was visualised by scanning electron microscope (SEM) and transmission electron microscopy (TEM) imaging, furthermore, XRD and DLS used to determined mode of aggregation. Characteristically, phosphonic acid-substituted at imide position of NDIs possess two important properties resulting in the formation of controlled flower-like nanostructures: (i) the aromatic core of the NDI which is designed to optimize the dispersive interactions (π-π stacking and van der Waals interactions) between the cores within a construct and (ii) phosphonic acid of NDI interact with malamine through molecular recognition i.e. strong hydrogen-bonding (H-bonding). We believe such arrangements prevent crystallization and favour the directional growth of flower-like nanostructure in 3D fashion. These works demonstrate that complex self-assembly can indeed be attained through hierarchical non-covalent interactions of two components. Furthermore, flower-like structures built from molecular recognition by these molecules indicate their potential in other fields if combined with other chemical entities.

Supramolecular Flower-Like Microarchitectures Self-Assembly from Naphthalenediimide Amphiphile Bearing Melamine Functionality

“…reported the first flower‐like morphology based on organic molecules such as C 60 . In this line of research, we recently reported the formation of flower‐like assemblies by mixing naphthalene diimide (NDI) with melamine via self‐organisation . However, it still remains a challenging task to design bio‐inspired building blocks that assemble into controlled complex hierarchical flower‐like nanostructures from a single molecule.…”

A new approach on improving the fire resistance of polyamide 11 by incorporating sulfur‐based flame retardant

“…In the FTIR spectrum of MEL (Figure ), some distinct characteristic peaks at 3468, 3418, and 3131 cm −1 can be observed, which are assigned to amino groups in MEL. However, the locations of these peaks in SA‐M are slightly shifted because of the ionic bonds between ─NH 2 groups from MEL and ─OH groups from SA . Another characteristic peak of ─NH 2 in MEL is located at 1651 cm −1 .…”

Strong Color Tuning of Self‐Assembled Azo‐Derived Phosphonic Acids upon Hydrogen Bonding

“…Recent studies have reported the use of polar azo materials with terminal phosphonic acid moieties to create acentric layers for non‐linear optical applications and polarizing dielectric layers in organic thin‐film transistors . Another report investigated the combination between melamine and naphthalene dimiide, tetrafold functionalized with phosphonic acid, that formed flower‐like self‐assemblies . However, for all these works, the phosphonic acid moieties were electronically disconnected from the π‐conjugated structure.…”

“…[12] Another report investigated the combination between melamine and naphthalened imiide, tetrafold functionalized with phosphonic acid, that formed flower-like self-assemblies. [13] However, for all these works, the phosphonic acid moieties were electronically disconnected from the p-conjugated structure.T herefore, no specific color change occurred upon H-bonding interactions, which limits their use as tunable optical materials. We want to show herein that the conjugatedi nsertion of phosphonic acid units in aromaticd yes with strong molar absorption coefficient like azo compounds leads to unprecedented optical changes upon H-bonding interactions.…”