Solvent-induced self-assembly of Naphthalenediimide conjugated to Tetraphenylethene through D- and L-Alanine

Abstract

Herein, the synthesis and supramolecular self-assembly of naphthalenediimide (NDI)-tetraphenylethene (TPE) conjugates with l-alanine (coded as: 1) and d-alanine (coded as: 2) was investigated. The pair stereoisomer molecules were designed to undergo self-assembly under solvophobic effects. Mixtures of THF-water was used to fine tune the solvophobic effect leading to microbelt for both 1 and 2 in 40 percent v/v of THF in H sub(2) O, while microbelt and particulate microsphere supramolecular structures were observed in 20 percent, v/v THF in H sub(2) O. When 10 percent THF in H sub(2) O was employed derivative 1 produces belt-like structures, however, 2 produces microsphere. Less uniformly defined microstructure morphologies of 1 and 2 were formed in THF/hexane and DCM/hexane. The solvophobic effect on self-assembly further evidenced using UV/Vis, fluorescence, circular dichroism, X-ray diffraction (XRD) spectroscopies. DLS used to evaluate formation of assembly in solution, DFT (density functional theory) and TD-DFT (time dependent density functional theory) molecular modelling support the hypothesis. Scanning electron microscopy used to visualise formation of supramolecular self-assembled nano- and micro-structures.