Tu, Ting-HsunTing-HsunTuChen, Yi-TingYi-TingChenChen, Yi-AnYi-AnChenWEI-YU CHENChen, You-HuaYou-HuaChenChen, Chi-LinChi-LinChenShen, Jiun-YiJiun-YiShenChen, Yi-HanYi-HanChenHo, Ssu-YuSsu-YuHoCheng, Kum-YiKum-YiChengLee, Shern-LongShern-LongLeeCHUN-HSIEN CHENPI-TAI CHOU2019-02-192019-02-192018-04-23https://scholars.lib.ntu.edu.tw/handle/123456789/403578The compound 6-azaindole undergoes self-assembly by formation of N(1)-H⋅⋅⋅N(6) hydrogen bonds (H bonds), forming a cyclic, triply H-bonded trimer. The formation phenomenon is visualized by scanning tunneling microscopy. Remarkably, the H-bonded trimer undergoes excited-state triple proton transfer (ESTPT), resulting in a proton-transfer tautomer emission maximized at 435 nm (325 nm of the normal emission) in cyclohexane. Computational approaches affirm the thermodynamically favorable H-bonded trimer formation and the associated ESTPT reaction. Thus, nearly half a century after Michael Kasha discovered the double H-bonded dimer of 7-azaindole and its associated excited-state double-proton-transfer reaction, the triply H-bonded trimer formation of 6-azaindole and its ESTPT reaction are demonstrated.enH-bonded trimers; azaindole; excited-state triple proton transfer; hydrogen bonding; self-assembly[SDGs]SDG3journal article10.1002/anie.201800944294687882-s2.0-85044243401WOS:000432382800034