Spies Christian, Shomer Shay, Finkler Björn, Pines Dina, Pines Ehud, Jung Gregor, Huppert Dan
Biophysical Chemistry, Saarland University, Campus, Building B2 2, D-66123 Saarbrücken, Germany.
Phys Chem Chem Phys. 2014 May 21;16(19):9104-14. doi: 10.1039/c3cp55292f.
Steady-state and time-resolved techniques were employed to study the excited-state proton-transfer (ESPT) rate of two newly synthesized 8-hydroxy-1,3,6-pyrenetrisulfonate (pyranine, HPTS) derived photoacids in three protic solvents, water, methanol and ethanol. The ESPT rate constant k(PT) of tris(1,1,1,3,3,3-hexafluoropropan-2-yl)-8-hydroxypyrene-1,3,6-trisulfonate, 1a, whose pK(a)* ~ -4, in water, methanol and ethanol is 3 × 10(11) s(-1), 8 × 10(9) s(-1) and 5 × 10(9) s(-1) respectively. (8-Hydroxy-N1,N3,N6-tris(2-hydroxyethyl)-N1,N3,N6-trimethylpyrene-1,3,6 trisulfonamide, 1b) is a weaker acid than 1a but still a strong photoacid with pK(a)* ~ -1 and the ESPT rate in water, methanol and ethanol is 7 × 10(10) s(-1), 4 × 10(8) s(-1) and 2 × 10(8) s(-1). We qualitatively explain our kinetic results by a Marcus-like free-energy correlation which was found to have a general form suitable for describing proton transfer reactions in both the proton-adiabatic and the proton-non-adiabatic limits.
采用稳态和时间分辨技术研究了两种新合成的8-羟基-1,3,6-芘三磺酸盐（吡喃荧光素，HPTS）衍生的光酸在三种质子溶剂（水、甲醇和乙醇）中的激发态质子转移（ESPT）速率。三（1,1,1,3,3,3-六氟丙-2-基）-8-羟基芘-1,3,6-三磺酸盐（1a）的pK(a)*约为 -4，其在水、甲醇和乙醇中的ESPT速率常数k(PT)分别为3×10(11) s(-1)、8×10(9) s(-1)和5×10(9) s(-1)。（8-羟基-N1,N3,N6-三（2-羟乙基）-N1,N3,N6-三甲基芘-1,3,6-三磺酰胺，1b）是比1a弱的酸，但仍是一种强的光酸，其pK(a)*约为 -1，在水、甲醇和乙醇中的ESPT速率分别为7×10(10) s(-1)、4×10(8) s(-1)和2×10(8) s(-1)。我们通过类似Marcus的自由能相关性对动力学结果进行了定性解释，发现其具有适用于描述质子绝热和质子非绝热极限下质子转移反应的一般形式。
