Conformation of Novel Azo-Dyes Bearing End-Capped Oligo(ethylene glycol) Studied by UV–vis and NMR Spectroscopy

Abstract

Two novel azo-dyes bearing an end-capped oligo(ethylene glycol) chain were synthesized and then studied by UV-visible and NMR spectroscopy. For both azobenzenes, the end-capped oligo(ethylene glycol) segment is on the para position of the first phenyl ring. On the second phenyl ring, a methoxy group is added on the para position for one azo-dye and no substitution group on the other, which made them electronically a push-push and a push system, respectively. The presence of the methoxy group changes significantly the absorption and the photoisomerization behaviors and results in a much less intense absorbance for the trans isomer and a shift from 350 to 360 nm. In the kinetic studies the azobenzene bearing a methoxy group shows a zero-order and a first-order kinetics as a function of the time scale of the study as well as an aggregation phenomenon. This azo-dye in different solvents has been studied by (1)H NMR and pulsed gradient NMR experiments to understand the effects of the photoisomerization and the aggregation on the self-diffusion of these molecules in solutions.

Biobased Magnetic Microspheres Containing Aldehyde Groups: Constructed by Vanillin-Derived Polymethacrylate/Fe3O4 and Recycled in Adsorbing Amine

“…To justify our expectation, we took paraanisidine as a model of amines to examine the adsorption and the recycled uses’ capacity of the microspheres. The reason for using paraanisidine is because it is extensively used for preparing dyes, pharmaceuticals, etc . The processes are illustratively described in Figure .…”

“…The reason for using paraanisidine is because it is extensively used for preparing dyes, pharmaceuticals, etc. 40 The processes are illustratively described in Figure 5. In the adsorption process, the amino groups of absorbate react with aldehyde groups in the microspheres to form Schiff base bonds via forming a transition state through nucleophilic addition and then dehydration.…”