Effects of hydrogen bonding on internal conversion of GFP-like chromophores. I. the para-amino systems

Guan Jhih Huang, Chi Wen Cheng, Hung Yu Hsu, Ch Prabhakar, Yuan-Pern Lee*, Wei-Guang Diau, Jye Shane Yang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

To understand the effects of solvent-solute 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 (Φf) and the isomerization Z → E (ΦZE) and the femtosecond fluorescence and transient infrared absorption in selected solvents. The behavior that ΦZE ≅ 0.50 in aprotic solvents, such as CH3CN, indicates that the E-Z photoisomerization adopts a one-bond-flip mechanism through the torsion of the exocyclic C=C bond (the τ torsion) to form a perpendicular species (τ ∼90) 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 ΦZE decreased from 0.50 to 0.15-0.28 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 (7-20 ps) kinetics for the ground-state recovery, we conclude that the SSHB modifies the potential energy surface for the τ torsion in a way that the IC occurs also for the twisted intermediates with a τ-torsion angle smaller than 90, which favors the formation of the Z isomers. The possibility of IC induced by torsion of the exocyclic C-C bond (the φ torsion) is also considered but excluded.

Original languageEnglish
Pages (from-to)2695-2704
Number of pages10
JournalJournal of Physical Chemistry B
Volume117
Issue number9
DOIs
StatePublished - 7 Mar 2013

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