Excited-state double proton transfer in model base pairs: the stepwise reaction on the heterodimer of 7-azaindole analogues.
A four fused-ring system 11-propyl-6H-indolo[2,3-b]quinoline (6 HIQ) is strategically designed and synthesized; it possesses a central moiety of 7-azaindole (7AI) and undergoes excited-state double proton transfer (ESDPT). Despite a barrierless type of ESDPT in the 6 HIQ dimer, femtosecond dynamics and a kinetic isotope effect provide indications for a stepwise ESDPT process in the 6 HIQ/7AI heterodimer, in which 6 HIQ (deuterated 6 HIQ) delivers the pyrrolyl proton (deuteron) to 7AI (deuterated 7AI) in less than 150 fs, forming an intermediate with a charge-transfer-like ion pair, followed by the transfer of a pyrrolyl proton (deuteron) from cation-like 7AI (deuterated 7AI) to the pyridinyl nitrogen of the anion-like 6 HIQ (deuterated 6 HIQ) in approximately 1.5+/-0.3 ps (3.5+/-0.3 ps). The barrier of second proton transfer is estimated to be 2.86 kcal mol(-1) for the 6 HIQ/7AI heterodimer.
Hsieh
Wan-Ting
WT
Department of Chemistry, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Da-an District, Taipei 106, Taiwan.
Hsieh
Cheng-Chih
CC
Lai
Chin-Hung
CH
Cheng
Yi-Ming
YM
Ho
Mei-Lin
ML
Wang
Kung K
KK
Lee
Gene-Hsiang
GH
Chou
Pi-Tai
PT
D020029:Base Pairing; D019281:Dimerization; D006860:Hydrogen Bonding; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects; D008956:Models, Chemical; D015394:Molecular Structure; D011522:Protons; D011789:Quantum Theory; D011804:Quinolines / Q000138:chemical synthesis / Q000737:chemistry* / Q000528:radiation effects
C527816:11-propyl-6H-indole(2,3-b)quinoline; C023422:7-azaindole dimer; D007211:Indoles; D011522:Protons; D011804:Quinolines