Excited‐State Double Proton Transfer in Model Base Pairs: The Stepwise Reaction on the Heterodimer of 7‐Azaindole Analogues |
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| Authors: | Wan‐Ting Hsieh Cheng‐Chih Hsieh Chin‐Hung Lai Dr Yi‐Ming Cheng Dr Mei‐Lin Ho Kung K Wang Prof Gene‐Hsiang Lee Pi‐Tai Chou Prof |
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| Institution: | 1. Department of Chemistry, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Da‐an District, Taipei 106, Taiwan, Fax: (+886)‐2‐2369?5208;2. Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506‐6045, USA |
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| Abstract: | A four fused‐ring system 11‐propyl‐6H‐indolo2,3‐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 ～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. |
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| Keywords: | excited‐state double proton transfer femtosecond dynamics fluorescence heterodimer photophysics |
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