Department of Chemistry, College of Natural Sciences, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
Center for Soft and Living Matter, Institute for Basic Science (IBS), Ulsan 44919, Republic of Korea.
J Phys Chem B. 2022 Feb 17;126(6):1275-1283. doi: 10.1021/acs.jpcb.1c09070. Epub 2022 Feb 4.
The excited-state proton transfer (ESPT) of a cationic superphotoacid, -methyl-7-hydroxyquinolium, was studied within the water pool of an anionic aerosol-OT (AOT), bis(2-ethylhexyl) sulfosuccinate, reverse micelle (RM). Previously, we had found that the cationic photoacid residing at the anionic AOT interface was conducive to ESPT to the bound water having concentric heterogeneity on the time scale of hundreds of picoseconds to nanoseconds. In our present study, on the time scale of hundreds of femtoseconds to a few tens of picoseconds, the photoacid underwent an ultrafast ESPT influenced by mobile water constituting the core of the RM. The two subpopulations of the core water molecules that determine the ultrafast biphasic deprotonation of the photoacid on time scales differing by an order of magnitude were identified. The core water molecules solvating the counteranion of the photoacid showed a higher basicity than typical water clusters in bulk resulting in ESPT on a subpicosecond time scale. Bare water clusters sensed by the photoacid showed a slower ESPT, over several picoseconds, as typically limited by the rotational motion of water molecules for similar types of the photoacid.
研究了阳离子超酸 - 甲基-7-羟基喹啉鎓在阴离子气溶胶-OT（AOT），双（2-乙基己基）磺基琥珀酸钠反胶束（RM）水相中质子转移激发态（ESPT）。此前，我们发现，位于阴离子 AOT 界面的阳离子光酸有利于与同心异质的结合水在数百皮秒到纳秒的时间尺度上进行 ESPT。在我们目前的研究中，在数百飞秒到数十皮秒的时间尺度上，光酸经历了由构成 RM 核的可移动水影响的超快 ESPT。确定了决定光酸超快双相去质子化的两种核心水分子亚群，它们的时间尺度相差一个数量级。与体相中典型的水分子簇相比，光酸的抗衡阴离子溶剂化的核心水分子显示出更高的碱性，从而导致 ESPT 在亚皮秒时间尺度上发生。光酸感知到的裸露水簇的 ESPT 较慢，需要数皮秒，这通常受类似类型光酸的水分子旋转运动限制。
