Temperature dependence of the excited-state proton-transfer reaction of quinone-cyanine-7

Ron Simkovitch; Shay Shomer; Rinat Gepshtein; Doron Shabat; Dan Huppert

doi:10.1021/jp3128669

Temperature dependence of the excited-state proton-transfer reaction of quinone-cyanine-7

Ron Simkovitch, Shay Shomer, Rinat Gepshtein, Doron Shabat, Dan Huppert

School of Chemistry

Tel Aviv University

Research output: Contribution to journal › Article › peer-review

Abstract

Steady-state and time-resolved fluorescence techniques were used to study the temperature dependence of the photoprotolytic process of quinone-cyanine-7 (QCy7), a very strong photoacid, in H₂O and D₂O ice, over a wide temperature range, 85-270 K. We found that the excited-state proton-transfer (ESPT) rate to the solvent decreases as the temperature is lowered with a very low activation energy of 10.5 ± 1 kJ/mol. The low activation energy is in accord with free-energy-correlation theories that predict correlation between ΔG of reaction and the activation energy. At very low temperatures (T < 150 K), we find that the emission band of the RO^-, the deprotonated form of QCy7, is blue-shifted by ∼1000 cm^-1. We attributed this band to the RO ^-···H₃O⁺ ion pair that was suggested to be an intermediate in the photoprotolytic process but has not yet been identified spectroscopically.

Original language	English
Pages (from-to)	3925-3934
Number of pages	10
Journal	Journal of Physical Chemistry A
Volume	117
Issue number	19
DOIs	https://doi.org/10.1021/jp3128669
State	Published - 16 May 2013

All Science Journal Classification (ASJC) codes

Physical and Theoretical Chemistry

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10.1021/jp3128669

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title = "Temperature dependence of the excited-state proton-transfer reaction of quinone-cyanine-7",

abstract = "Steady-state and time-resolved fluorescence techniques were used to study the temperature dependence of the photoprotolytic process of quinone-cyanine-7 (QCy7), a very strong photoacid, in H2O and D2O ice, over a wide temperature range, 85-270 K. We found that the excited-state proton-transfer (ESPT) rate to the solvent decreases as the temperature is lowered with a very low activation energy of 10.5 ± 1 kJ/mol. The low activation energy is in accord with free-energy-correlation theories that predict correlation between ΔG of reaction and the activation energy. At very low temperatures (T < 150 K), we find that the emission band of the RO-, the deprotonated form of QCy7, is blue-shifted by ∼1000 cm-1. We attributed this band to the RO -···H3O+ ion pair that was suggested to be an intermediate in the photoprotolytic process but has not yet been identified spectroscopically.",

author = "Ron Simkovitch and Shay Shomer and Rinat Gepshtein and Doron Shabat and Dan Huppert",

year = "2013",

month = may,

day = "16",

doi = "10.1021/jp3128669",

language = "الإنجليزيّة",

volume = "117",

pages = "3925--3934",

journal = "Journal of Physical Chemistry A",

issn = "1089-5639",

publisher = "American Chemical Society",

number = "19",

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TY - JOUR

T1 - Temperature dependence of the excited-state proton-transfer reaction of quinone-cyanine-7

AU - Simkovitch, Ron

AU - Shomer, Shay

AU - Gepshtein, Rinat

AU - Shabat, Doron

AU - Huppert, Dan

PY - 2013/5/16

Y1 - 2013/5/16

N2 - Steady-state and time-resolved fluorescence techniques were used to study the temperature dependence of the photoprotolytic process of quinone-cyanine-7 (QCy7), a very strong photoacid, in H2O and D2O ice, over a wide temperature range, 85-270 K. We found that the excited-state proton-transfer (ESPT) rate to the solvent decreases as the temperature is lowered with a very low activation energy of 10.5 ± 1 kJ/mol. The low activation energy is in accord with free-energy-correlation theories that predict correlation between ΔG of reaction and the activation energy. At very low temperatures (T < 150 K), we find that the emission band of the RO-, the deprotonated form of QCy7, is blue-shifted by ∼1000 cm-1. We attributed this band to the RO -···H3O+ ion pair that was suggested to be an intermediate in the photoprotolytic process but has not yet been identified spectroscopically.

AB - Steady-state and time-resolved fluorescence techniques were used to study the temperature dependence of the photoprotolytic process of quinone-cyanine-7 (QCy7), a very strong photoacid, in H2O and D2O ice, over a wide temperature range, 85-270 K. We found that the excited-state proton-transfer (ESPT) rate to the solvent decreases as the temperature is lowered with a very low activation energy of 10.5 ± 1 kJ/mol. The low activation energy is in accord with free-energy-correlation theories that predict correlation between ΔG of reaction and the activation energy. At very low temperatures (T < 150 K), we find that the emission band of the RO-, the deprotonated form of QCy7, is blue-shifted by ∼1000 cm-1. We attributed this band to the RO -···H3O+ ion pair that was suggested to be an intermediate in the photoprotolytic process but has not yet been identified spectroscopically.

UR - http://www.scopus.com/inward/record.url?scp=84878050297&partnerID=8YFLogxK

U2 - 10.1021/jp3128669

DO - 10.1021/jp3128669

M3 - مقالة

SN - 1089-5639

VL - 117

SP - 3925

EP - 3934

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

IS - 19

ER -

Temperature dependence of the excited-state proton-transfer reaction of quinone-cyanine-7

Abstract

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