TY - JOUR
T1 - Dormant acceptor activation of 10-hydroxybenzoquinline derivatives by excited-state intramolecular proton transfer
AU - Kisin-Finfer, Einat
AU - Simkovitch, Ron
AU - Shabat, Doron
AU - Huppert, Dan
N1 - Publisher Copyright:
© 2016 Elsevier B.V. All rights reserved.
PY - 2016/7/15
Y1 - 2016/7/15
N2 - We studied the excited-state intramolecular proton transfer (ESIPT) of two derivatives of hydroxybenzo[h]quinoline (10-HBQ). We used time-resolved and steady-state techniques for this purpose. These two compounds are water soluble and can be excited by visible light, thus they have a potential use in in vitro and in vivo imaging applications. We found that the ESIPT rate of ortho-indolium-10-hydroxybenzo[h]quinoline is greater than 1013 s-1, whereas for ortho-picolinium-10-hydroxybenzo[h]quinoline the rate constant is rather low (kPT = 7 × 1012 s-1, τPT = 140 ± 20 fs). We also found a kinetic isotope effect of 1.5 ± 0.2 for ortho-picolinium-10-hydroxybenzo[h]quinoline. We observe in both compounds, a slower time component of 300 ± 50 fs with low amplitude of 0.05 ± 0.02 for the enol form decay. This slower component is also observed in the fluorescence-signal rise of the keto form, but with a higher amplitude of 0.2 ± 0.04. The fluorescence-signal rise of the keto forms of both compounds shows a third long-time component of several picoseconds. This time component in ortho-indolium-10-hydroxybenzo[h]quinoline is solvent-dependent and is assigned to solvation dynamics in protic solvents. We explain the relatively slow ESIPT rate of ortho-picolinium-10-hydroxybenzo[h]quinoline by the smaller enol-keto energy gap of this compound.
AB - We studied the excited-state intramolecular proton transfer (ESIPT) of two derivatives of hydroxybenzo[h]quinoline (10-HBQ). We used time-resolved and steady-state techniques for this purpose. These two compounds are water soluble and can be excited by visible light, thus they have a potential use in in vitro and in vivo imaging applications. We found that the ESIPT rate of ortho-indolium-10-hydroxybenzo[h]quinoline is greater than 1013 s-1, whereas for ortho-picolinium-10-hydroxybenzo[h]quinoline the rate constant is rather low (kPT = 7 × 1012 s-1, τPT = 140 ± 20 fs). We also found a kinetic isotope effect of 1.5 ± 0.2 for ortho-picolinium-10-hydroxybenzo[h]quinoline. We observe in both compounds, a slower time component of 300 ± 50 fs with low amplitude of 0.05 ± 0.02 for the enol form decay. This slower component is also observed in the fluorescence-signal rise of the keto form, but with a higher amplitude of 0.2 ± 0.04. The fluorescence-signal rise of the keto forms of both compounds shows a third long-time component of several picoseconds. This time component in ortho-indolium-10-hydroxybenzo[h]quinoline is solvent-dependent and is assigned to solvation dynamics in protic solvents. We explain the relatively slow ESIPT rate of ortho-picolinium-10-hydroxybenzo[h]quinoline by the smaller enol-keto energy gap of this compound.
KW - 10-HBQ
KW - ESIPT
KW - Fluorogenic-dye
KW - Photoacids
UR - http://www.scopus.com/inward/record.url?scp=84966322365&partnerID=8YFLogxK
U2 - 10.1016/j.jphotochem.2016.04.021
DO - 10.1016/j.jphotochem.2016.04.021
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AN - SCOPUS:84966322365
SN - 1010-6030
VL - 326
SP - 89
EP - 99
JO - Journal of Photochemistry and Photobiology A: Chemistry
JF - Journal of Photochemistry and Photobiology A: Chemistry
ER -