Annibaldi, Valeria and Yu, Tian and Breslin, Carmel B. (2020) Electrostatic interactions between viologens and a sulfated β-cyclodextrin; formation of insoluble aggregates with benzyl viologens. Journal of Inclusion Phenomena and Macrocyclic Chemistry, 96 (1-2). pp. 155-167. ISSN 1388-3127

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Abstract

Viologens are important compounds and are used in several applications. The interactions between viologens and a negatively charged cyclodextrin, sulfated β-cyclodextrin (sβ-CD), were studied using electrochemistry, 1H NMR and UV–Vis spectroscopy. Weak electrostatic interactions were found between the dicationic viologens (V2+) and the anionic cyclodextrin. The diffusion coefficient of ethyl viologen (EV2+) was reduced from 5.33 × 10−6 to 1.98 × 10−6 cm2 s−1 with an excess of sβ-CD. More significant electrostatic interactions were found between benzyl viologen (BV2+) and sβ-CD. The H atoms in the benzyl substituent, which appear as a singlet in the NMR experiment, were split into a multiplet in the presence of the sβ-CD, while the chemical shift of the H in the β position to the quaternary nitrogen, was shifted by 0.17 ppm in the presence of sβ-CD. Greater electrostatic interactions were evident between the benzyl radical cation (BV·+) and sβ-CD. Using cyclic voltammetry, reduction of the radical cation to the neutral benzyl viologen (BV0) was shifted by 230 mV to a lower potential, indicating that the reduction of the radical cation becomes considerably more difficult in the presence of sβ-CD. This was attributed to the formation of an insoluble BV·+:sβ-CD aggregate, which was also evident in rotating disc voltammetry, where the typical diffusion-limited currents were not observed and in spectroelectrochemistry experiments, where the deposition of the aggregate at the ITO electrode increased the absorbance of the radical species.

Item Type:	Article
Keywords:	Sulfated β-cyclodextrin; Viologens; Benzyl viologen; Insoluble aggregate;
Academic Unit:	Faculty of Science and Engineering > Chemistry
Item ID:	16204
Identification Number:	https://doi.org/10.1007/s10847-019-00961-3
Depositing User:	Dr. Carmel Breslin
Date Deposited:	29 Jun 2022 08:53
Journal or Publication Title:	Journal of Inclusion Phenomena and Macrocyclic Chemistry
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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