Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes
The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N′-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox...
Saved in:
Main Author: | |
---|---|
Other Authors: | |
Format: | Article |
Published: |
2023
|
Subjects: | |
Online Access: | https://repository.li.mahidol.ac.th/handle/123456789/87956 |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Institution: | Mahidol University |
id |
th-mahidol.87956 |
---|---|
record_format |
dspace |
spelling |
th-mahidol.879562023-07-20T01:01:10Z Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes Nguyen H.M. Mahidol University Chemistry The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N′-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ϵ) (acetonitrile, ϵ = 37.5; N,N-dimethylformamide, ϵ = 36.7; and dichloromethane, ϵ = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N′-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field. 2023-07-19T18:01:10Z 2023-07-19T18:01:10Z 2023-01-01 Article Journal of Physical Chemistry A (2023) 10.1021/acs.jpca.3c00827 15205215 10895639 2-s2.0-85163473215 https://repository.li.mahidol.ac.th/handle/123456789/87956 SCOPUS |
institution |
Mahidol University |
building |
Mahidol University Library |
continent |
Asia |
country |
Thailand Thailand |
content_provider |
Mahidol University Library |
collection |
Mahidol University Institutional Repository |
topic |
Chemistry |
spellingShingle |
Chemistry Nguyen H.M. Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes |
description |
The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N′-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ϵ) (acetonitrile, ϵ = 37.5; N,N-dimethylformamide, ϵ = 36.7; and dichloromethane, ϵ = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(KDMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N′-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field. |
author2 |
Mahidol University |
author_facet |
Mahidol University Nguyen H.M. |
format |
Article |
author |
Nguyen H.M. |
author_sort |
Nguyen H.M. |
title |
Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes |
title_short |
Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes |
title_full |
Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes |
title_fullStr |
Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes |
title_full_unstemmed |
Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes |
title_sort |
charge and solvent effects on the redox behavior of vanadyl salen-crown complexes |
publishDate |
2023 |
url |
https://repository.li.mahidol.ac.th/handle/123456789/87956 |
_version_ |
1781414589376757760 |