Effects of Hydrogen Bonding on Internal Conversion of GFP-like Chromophores. I. The para-Amino Systems

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• 作者：Guan-Jhih Huang ; Chi-Wen Cheng ; Hung-Yu Hsu ; Ch. Prabhakar ; Yuan-Pern Lee ; Eric Wei-Guang Diau ; Jye-Shane Yang
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：March 7, 2013
• 年：2013
• 卷：117
• 期：9
• 页码：2695-2704
• 全文大小：542K
• 年卷期：v.117,no.9(March 7, 2013)
• ISSN：1520-5207

文摘

To understand the effects of solvent鈥搒olute hydrogen bonding (SSHB) on the excited-state dynamics of two GFP-like chromophores, p-ABDI and p-CFABDI, we have determined the quantum yields for fluorescence (桅_f) and the isomerization Z 鈫?E (桅_ZE) and the femtosecond fluorescence and transient infrared absorption in selected solvents. The behavior that 桅_ZE 0.50 in aprotic solvents, such as CH₃CN, indicates that the E鈥揨 photoisomerization adopts a one-bond-flip mechanism through the torsion of the exocyclic C鈺怌 bond (the 蟿 torsion) to form a perpendicular species (蟿 90掳) in the singlet excited state followed by internal conversion (IC) to the ground state and partition to form the E and Z isomers with equal probabilities. The observed 桅_ZE decreased from 0.50 to 0.15鈥?.28 when CH₃CN was replaced with the protic solvents CH₃OH and CF₃CH₂OH. In conjunction with the solvent-independent rapid (<1 ps) kinetics for the fluorescence decay and the solvent-dependent slow (7鈥?0 ps) kinetics for the ground-state recovery, we conclude that the SSHB modifies the potential energy surface for the 蟿 torsion in a way that the IC occurs also for the twisted intermediates with a 蟿-torsion angle smaller than 90掳, which favors the formation of the Z isomers. The possibility of IC induced by torsion of the exocyclic C鈥揅 bond (the 蠁 torsion) is also considered but excluded.