Harnessing Excited-State Intramolecular Proton-Transfer Reaction via a Series of Amino-Type Hydrogen-Bonding Molecules.
A series of new amino (NH)-type hydrogen-bonding (H-bonding) compounds comprising 2-(2'-aminophenyl)benzothiazole and its extensive derivatives were designed and synthesized. Unlike in the hydroxyl (OH)-type H-bonding systems, one of the amino hydrogens can be replaced with electron-donating/withdrawing groups. This, together with a versatile capability for modifying the parent moiety, makes feasible the comprehensive spectroscopy and dynamics studies of amino-type excited-state intramolecular proton transfer (ESIPT), which was previously inaccessible in the hydroxyl-type ESIPT systems. Empirical correlations were observed among the hydrogen-bonding strength (the N-H bond distances and proton acidity), ESIPT kinetics, and thermodynamics, demonstrating a trend that the stronger N-H···N hydrogen bond leads to a faster ESIPT, as experimentally observed, and a more exergonic reaction thermodynamics. Accordingly, ESIPT reaction can be harnessed for the first time from a highly endergonic type (i.e., prohibition) toward equilibrium with a measurable ESIPT rate and then to the highly exergonic, ultrafast ESIPT reaction within the same series of amino-type intramolecular H-bond system.
†Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Huan-Wei
HW
Tseng
‡School of Medical Applied Chemistry, Chung Shan Medical University, Taichung 40201, Taiwan.
Jun-Qi
JQ
Liu
†Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Yi-An
YA
Chen
‡School of Medical Applied Chemistry, Chung Shan Medical University, Taichung 40201, Taiwan.|§Department of Medical Education, Chung Shan Medical University Hospital, Taichung 40201, Taiwan.
Chi-Min
CM
Chao
‡School of Medical Applied Chemistry, Chung Shan Medical University, Taichung 40201, Taiwan.|§Department of Medical Education, Chung Shan Medical University Hospital, Taichung 40201, Taiwan.
Kuan-Miao
KM
Liu
†Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Chi-Lin
CL
Chen
†Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Tzu-Chieh
TC
Lin
‡School of Medical Applied Chemistry, Chung Shan Medical University, Taichung 40201, Taiwan.
Cheng-Hsien
CH
Hung
‡School of Medical Applied Chemistry, Chung Shan Medical University, Taichung 40201, Taiwan.
Yen-Lin
YL
Chou
‡School of Medical Applied Chemistry, Chung Shan Medical University, Taichung 40201, Taiwan.
Ta-Chun
TC
Lin
†Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Tian-Lin
TL
Wang
†Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Pi-Tai
PT
Chou
D000588:Amines / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D011522:Protons
D000588:Amines; D011522:Protons
dual emission; hydrogen bond; proton transfer