One molecule, two switches: Synthesis and DFT studies of Oxalohydrazide-based photoswitches

Abstract

In organic chemistry, compounds with hydrazone moiety have the potential for application in various fields. Many hydrazone compounds with different functional groups, which can be converted from one state or isomer to another by light or heat, are used as molecular photoswitches. The research on these intriguing functional molecules is rapidly advancing.

Herein, N¹, N²-bis(-naphthalen-1-ylmethylene) oxalohydrazide (2) containing the –CO–NH-N=CH– moiety as a photoswitch linker was designed and synthesized. The structures of the synthesized compound were characterized by proton nuclear magnetic resonance (1H NMR), carbon nuclear magnetic resonance (13C NMR), Mass spectrometry (MS), and the Fourier-transform infrared spectroscopy (FT-IR) spectra. Photoswitching of the obtained compound was carried out under UV–light (300–400 nm). As far as we know, this is the first study of photoswitching of oxalohydrazide compounds.

As a result of Ultraviolet-visible spectroscopy (UV–vis), 1H NMR spectra, and density functional theory calculations (DFT), it was found that compound 2 undergoes a characteristic E to Z photoisomerization after light irradiation. Fast E/Z response under UV–light illumination was observed. The thermally unstable Z isomer was found to be recovered to the E isomer by temperature, which refers to T–type photochromic switches. It is envisaged that the compound can be used as a possible photoswitch after further studies are completed.