o-Amino analogs of green fluorescence protein chromophore: Photoisomerization, photodimerization and aggregation-induced emission
Journal
Photochemistry and Photobiology
Journal Volume
91
Journal Issue
3
Pages
714-722
Date Issued
2015
Author(s)
Abstract
Abstract The photochemical properties of three o ‐amino analogs of the green fluorescence protein chromophore O0, O1 and O8 ( o ‐ ABDI s) have been investigated and compared with those of the m ‐ and p ‐amino isomers ( m ‐ ABDI s and p ‐ ABDI s) in solutions, aggregates, and the solid state. In aprotic solvents, the fluorescence competes with the Z → E photoisomerization for all cases, and the o ‐ ABDI s display a fluorescence quantum efficiency of 1–6%, lying between the m ‐ ABDI s of 5–48% and the p ‐ ABDI s of < 0.1%. The fluorescence of both the o ‐ and m ‐ ABDI s is nearly quenched in protic solvents, attributable to the solvent–solute hydrogen bonding ( SSHB ) interactions. The phenomenon of aggregation‐induced emission observed for O8 in poor solvents resembles the behavior of M8 as a consequence of exclusion of the SSHB interactions and restriction of internal rotation for molecules located inside the aggregates. The occurrence of [2 + 2] photodimerization for O0 in the solid state is unique among the ABDI s, and the X‐ray crystal structures of O0 and the photodimer OD reveal the head‐to‐tail syn ‐oriented stereochemistry. Analysis on the X‐ray crystal structures of O0, O1, M0, M1 and P0 shows that not only the pairwise topochemical geometry but also the columnar packing mode is important in determining the photodimerization reactivity.
Type
journal article