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4NPOH.pdf (948.6 kB)

Time-Resolved Study of Light-Induced Ground State Proton Transfer from Acid Medium to 4-Nitrophenolate

submitted on 12.09.2020 and posted on 14.09.2020 by Leandro Scorsin, Leticia Martins, Haidi Fiedler, Faruk Nome, RENE NOME
In the present work, we study the transient laser-induced formation of 4-nitrophenolate (4-NPO-) in the ground electronic state and subsequent proton transfer reaction with acetic acid and water with numerical calculations and laser flash photolysis. We employ the Debye-Smoluchowski spherically-symmetric diffusion model of photoacid proton transfer to determine experimental conditions for studying thermally activated chemical reactions in the ground electronic state. Numerically calculated protonation and deprotonation probabilities for 4-NPO- and 4-nitrophenol (4-NPOH) in both ground and excited states showed the feasibility of efficiently producing the ground state anion in the photoacid cycle. We performed laser flash photolysis measurements of 4-NPOH to characterize the photo-initiated ground state protonation and deprotonation rate constants of 4-NPO-/4-NPOH as a function of acetic acid, pH, temperature and viscosity. Overall, the work presented here shows a simple way to study fast competing bimolecular proton transfer reactions in non-equilibrium conditions in the ground electronic state (GSPT).


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