Effects of Ionic Liquid [bmim][PF₆] on Absorption Spectra and Reaction Kinetics of the Duroquinone Triplet State in Acetonitrile

Abstract

The transient absorption spectra and photoinduced electron-transfer process of duroquinone (DQ) in mixed binary solutions of ionic liquid (IL) [bmim][PF6] and acetonitrile (MeCN) have been investigated by laser photolysis at an excitation wavelength of 355 nm. A spectral blue shift of 3DQ* was observed in the IL/MeCN mixtures compared to MeCN. At lower VIL(volume fraction of IL), the interaction between DQ and the solvent is dominant, and the decay rate constant (kobs) of 3DQ* increases steadily with the increasing of VIL; to the contrary, at higher VIL, the network structures due to the hydrogen bond and viscosity are dominant, and the decay rate constant decreases obviously with increasing VIL. A critical point (turnover) was observed at VIL = approximately 0.30. The dependence of the observed growth rate (kgr) of the photoinduced electron-transfer (PET) products on VIL is complex and shows a special change; kgr first decreases with increasing VIL, then increases, and finally decreases slowly with further increasing of VIL. It is speculated that the PET process in the mixture can be affected by factors including the local structure and the reorganization energy of the solvent and salt and cage effects. The change of local structure of [bmim][PF6]/MeCN is supported by following the steady-state fluorescence behavior of the mixture, in combination with the molecular dynamics simulation of the thermodynamic property. The results revealed that the degree of self-aggregation of monomeric cations (bmim+) to associated forms increases with increasing VIL. This is in good agreement with the laser photolysis results for the same solutions.

Assembly of quinone-based renewable biobattery using redox molecules from Lawsonia inermis

“…The peaks under the range 293 nm-295 nm corresponded with 4-t-butyl-1,2-benzoquinone [27]. Various other peaks around 420 nm, 370 nm and 390 nm suggested the presence of duroquinone [28], 2-hydroxy-1,4-naphthoquinone [29] and 1,4-naphthoquinone [25], respectively. The hennaethyl acetate extract absorption spectrum was observed to have maximum wavelengths at 295 nm and 410 nm.…”

Towards Understanding the Solvent‐Dynamic Control of the Transport and Heterogeneous Electron‐Transfer Processes in Ionic Liquids

“…Experimentally and through simulation studies, it has been established that imidazolium‐based ILs exist as supramolecular associates, and the introduction of small molecules and macromolecules leads to variation in the structural organisation of their constituents. Absorption and emission characteristics of imidazolium‐based ILs in the UV/Vis range have proven to be very informative in this regard . Since the solute‐induced structural variations in [BMIM][PF 6 ] are expected to be responsible for the observed dependence of the diffusion coefficient on concentration, EFc solutions of varying concentration were probed for their absorbance and fluorescence characteristics.…”

“…Absorption and emission characteristics of imidazolium-basedI Ls in the UV/Vis range have proven to be very informativei nt his regard. [16,51,52] Since the solute-in- Absorption in the low-wavelength range is attributed to the monomeric form of the imidazolium cation, and the higherwavelength features, which appear as an unusually long tail, are attributed to excitation of aggregates of the imidazolium cation and anion with various energies. [16,[50][51] The emission spectrum of pure [BMIM][PF 6 ]( Figure 7B)a lso establishes its supramolecular character.T he band in the low-wavelength regionh as been attributedt ot he monomeric imidazolium cation, while the emissive features in the longer-wavelength regiona re attributed to the relaxation of photoexcited supramolecular associates of IL constituents with various energies.…”

Laser photolysis studies of quaternary ammonium ionic liquids aqueous solution

“…The analyzing light was transformed into the electronic signal after entering a monochromator followed by an R955 photomultiplier. Detailed descriptions of the setup of laser photolysis equipment and experimental conditions have been described elsewhere [17].…”

“…Several elementary processes such as solvated and ''dry'' electrons reactions, charge and H transfer have been studied by time-resolved techniques, for example pulse radiolysis, laser photolysis, and steady-state and time-resolved fluorescence [11][12][13][14][15][16][17][18][19][20][21]. These studies mainly focused on solvent relaxation dynamics [11][12][13], and electron and energy transfer kinetics [14][15][16][17][18][19][20][21]. Effects of ILs on transient absorption spectra and bimolecular reaction rate constants of solutes have been partly revealed.…”