Excited state structural dynamics of 4-cyano-4′-hydroxystilbene: deciphering the signatures of proton-coupled electron transfer using ultrafast Raman loss spectroscopy

Mathew, Reshma; Kayal, Surajit; Lakshmanna, Yapamanu Adithya

doi:10.1039/c9cp02923k

Cited by 5 publications

(3 citation statements)

References 68 publications

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“…Photoinduced PCET processes among various photoacids have been widely reported; − however, analysis of such processes involving photobases is relatively less explored. Photobases are molecules that exhibit enhanced basicity in electronically excited states as compared to their ground states .…”

Section: Introductionmentioning

confidence: 99%

Excited-State Dynamics in 4-[4′(Dimethylamino)styryl]pyridine, a Photobase: Role of Photoinitiated Proton-Coupled Electron Transfer

Mathew,

Verma,

Barak

et al. 2023

J. Phys. Chem. A

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The photoinitiated proton-coupled electron transfer (PCET) process in photoacid-based adducts is predominantly governed by the evolution of the electron–proton transfer state. However, such a process is underexplored in the case of photobases as the excited states evolve through multiple competitive channels. Here, we elucidate the excited-state dynamics of a photobase, 4-[4′-(dimethylamino)styryl]pyridine (DMASP), in the presence of hexafluoroisopropanol (HFIP) that enables PCET. Transient absorption measurements show the evolution of a protonated species in the excited state with a time constant of ∼2.5 ps. Fluorescence upconversion measurements reveal the signatures of an emissive intramolecular charge transfer state and a protonated state. The role of such states is further confirmed by time-resolved measurements in the presence of trifluoroacetic acid and computational analysis. Furthermore, the proton-abstraction dynamics of DMASP is analyzed in bulk methanol and butanol solvents. The extent of proton abstraction by DMASP is found to be higher in the presence of HFIP when compared with the normal alcohols over a time period of a few picoseconds.

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Section: Introductionmentioning

confidence: 99%

Excited-State Dynamics in 4-[4′(Dimethylamino)styryl]pyridine, a Photobase: Role of Photoinitiated Proton-Coupled Electron Transfer

Mathew,

Verma,

Barak

et al. 2023

J. Phys. Chem. A

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“…Mechanistic understanding of interfacial PCET is often derived from current–voltage measurements. ,, While such techniques can be quite powerful, spectroscopic measurements can provide additional mechanistic details of electrochemical reactions − For example, electrochemical impedance spectroscopy is sensitive to capacitance but averages the behavior over the entire double layer and is not sensitive to the molecular details near the electrode.…”

Section: Introductionmentioning

confidence: 99%

“…3,12,14 While such techniques can be quite powerful, spectroscopic measurements can provide additional mechanistic details of electrochemical reactions. 15 Operando spectroscopy, in particular, can aid in the detection of chemical or physical changes near the electrode prior to the onset potential; such insights cannot be obtained from current−voltage relationships alone. 16−18 For example, electrochemical impedance spectroscopy is sensitive to capacitance but averages the behavior over the entire double layer and is not sensitive to the molecular details near the electrode.…”

Section: ■ Introductionmentioning

confidence: 99%

Mechanistic Insights about Electrochemical Proton-Coupled Electron Transfer Derived from a Vibrational Probe

et al. 2021

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Proton-coupled electron transfer (PCET) is a fundamental step in a wide range of electrochemical processes, including those of interest in energy conversion and storage. Despite its importance, several mechanistic details of such reactions remain unclear. Here, we have combined a proton donor (tertiary ammonium) with a vibrational Stark-shift probe (benzonitrile), to track the process from the entry of the reactants into the electrical double layer (EDL), to the PCET reaction associated with proton donation to the electrode, and the formation of products. We have used operando vibrational spectroscopy and periodic density functional theory under electrochemical bias to assign the reactant and product peaks and their Stark shifts. We have identified three main stages for the progress of the PCET reaction as a function of applied potential. First, we have determined the potential necessary for desolvation of the reactants and their entry into the polarizing environment of the EDL. Second, we have observed the appearance of product peaks prior to the onset of steady state electrochemical current, indicating formation of a stationary population of products that does not turn over. Finally, more negative of the onset potential, the electrode attracts additional reactants, displacing the stationary products and enabling steady state current. This work shows that the integration of a vibrational Stark-shift probe with a proton donor provides critical insight into the interplay between interfacial electrostatics and heterogeneous chemical reactions. Such insights cannot be obtained from electrochemical measurements alone.

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Photoacid as ICT probe for ground state proton transfer process from solute to solvents

Panja

2020

Journal of Molecular Liquids

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Excited state structural dynamics of 4-cyano-4′-hydroxystilbene: deciphering the signatures of proton-coupled electron transfer using ultrafast Raman loss spectroscopy

Abstract: The photo-initiated proton-coupled electron transfer process in the 4-cyano-4′-hydroxystilbene–tert-butylamine adduct strongly affects the excited-state structural dynamics of CHSB.

Cited by 5 publications

References 68 publications

Excited-State Dynamics in 4-[4′(Dimethylamino)styryl]pyridine, a Photobase: Role of Photoinitiated Proton-Coupled Electron Transfer

Excited-State Dynamics in 4-[4′(Dimethylamino)styryl]pyridine, a Photobase: Role of Photoinitiated Proton-Coupled Electron Transfer

Mechanistic Insights about Electrochemical Proton-Coupled Electron Transfer Derived from a Vibrational Probe

Photoacid as ICT probe for ground state proton transfer process from solute to solvents

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