Dataset Information

Kinetics and Energetics of Thermal Cis-Trans Isomerization of a Resonance-Activated Azobenzene in BMIM-Based Ionic Liquids for PF₆-/Tf₂N- Comparison.

ABSTRACT: BMIM PF₆ (1-butyl-3-methylimidazolium hexafluorophosphate) and BMIM Tf₂N (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) are two conventional room-temperature ionic liquids widely employed and investigated as reaction media. Despite the presence of the same imidazolium ring in their structure they are different in many chemical and physical properties due to the nature of the anions. The thermal cis-trans isomerization of an electronically activated azobenzene have been used as reaction model to compare the behavior of PF₆- and Tf₂N-. Rotation is the mechanism by which the investigated azobenzene is converted into the trans isomer spontaneously in the dark both in BMIM PF₆ and in BMIM Tf₂N. The kinetic rate constants of the process have been determined at different temperatures and the activation energies of the reaction have been calculated according to the Arrhenius and Eyring equations. The results presented herein highlight different solute-solvent interactions involving the PF₆- and Tf₂N- anions during the cis-trans isomerization.

SUBMITTER: Angelini G

PROVIDER: S-EPMC6152290 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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Publications

Kinetics and Energetics of Thermal Cis-Trans Isomerization of a Resonance-Activated Azobenzene in BMIM-Based Ionic Liquids for PF₆-/Tf₂N- Comparison.

Angelini Guido G Campestre Cristina C Scotti Luca L Gasbarri Carla C

Molecules (Basel, Switzerland) 20170729 8

BMIM PF₆ (1-butyl-3-methylimidazolium hexafluorophosphate) and BMIM Tf₂N (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) are two conventional room-temperature ionic liquids widely employed and investigated as reaction media. Despite the presence of the same imidazolium ring in their structure they are different in many chemical and physical properties due to the nature of the anions. The thermal cis-trans isomerization of an electronically activated azobenzene have ...[more]

PMID: 28758922

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Project description:The light-modulated isomerization and aggregation behavior of ionic liquids (ILs) in aqueous solutions holds fundamental and technological significance. Although several azobenzene-based photoresponsive ILs have been synthesized, there is still a lack of understanding regarding the aggregation mechanism, regularity of the alkyl chain length, and the position of the azobenzene (cis- and trans-) in these photoresponsive ILs. To elucidate the structure-property relationship of photoresponsive ILs, four types of azobenzene groups photosensitive ILs ([AzoCnDMEA]Br, n = 2,4,6,10) in both trans- and cis- configurations were investigated by density functional theory (DFT) calculations. We investigated the geometric properties of cations, H-bonds interactions of ionic pairs, microstructures of clusters, and the interactions between ILs and water molecules. It was found that the molecular volume of cis- is smaller than that of trans- cation structures. Despite multiple H-bonds between the anions and the ammonium group of cations, longer alkyl chains weaken anion-cation interactions. The interaction energies of trans- n[AzoC2DMEA]Br (1 ≤ n ≤ 4) clusters are stronger than those of cis-. Moreover, the interaction energy between trans-structures of photoresponsive ILs and water molecules is smaller than that of cis- structures based on the DFT calculations. The interaction energies per water molecule in the ILs-water clusters tend to saturation as the number of water molecules increases. The electrostatic interaction plays a crucial role in the stabilization of ILs and water systems. The structure-property relationship of photoresponsive ILs including the regularity of the alkyl chain length and the azobenzene position as well as the microscopic interaction mechanism of ILs and ILs-water clusters had been studied from theoretical calculation perspective. This work can contribute to an in-depth understanding of the microcosmic interactions of azobenzene-based photoresponsive ILs and aid in designing them in a "task-specific" way.

Dataset Information

Kinetics and Energetics of Thermal Cis-Trans Isomerization of a Resonance-Activated Azobenzene in BMIM-Based Ionic Liquids for PF₆-/Tf₂N- Comparison.

Publications

Kinetics and Energetics of Thermal Cis-Trans Isomerization of a Resonance-Activated Azobenzene in BMIM-Based Ionic Liquids for PF₆<sup>-</sup>/Tf₂N<sup>-</sup> Comparison.

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