title: Excited-state double proton transfer in model base pairs: the stepwise reaction on the heterodimer of 7-azaindole analogues.
abstract: 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.
authors.affiliation: Department of Chemistry, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Da-an District, Taipei 106, Taiwan.
authors.forename: Wan-Ting
authors.initials: WT
authors.lastname: Hsieh
authors.forename: Cheng-Chih
authors.initials: CC
authors.lastname: Hsieh
authors.forename: Chin-Hung
authors.initials: CH
authors.lastname: Lai
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Cheng
authors.forename: Mei-Lin
authors.initials: ML
authors.lastname: Ho
authors.forename: Kung K
authors.initials: KK
authors.lastname: Wang
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Pi-Tai
authors.initials: PT
authors.lastname: Chou
mesh_terms: 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
chemical_list: C527816:11-propyl-6H-indole(2,3-b)quinoline; C023422:7-azaindole dimer; D007211:Indoles; D011522:Protons; D011804:Quinolines