Effects of Supramolecular Encapsulation on Photophysics
and Photostability of a 9,10-Bis(arylethynyl)anthracene-Based Chromophore
Revealed by Single-Molecule Fluorescence Spectroscopy
posted on 2016-10-18, 15:49authored byMasaaki Mitsui, Koji Higashi, Yohei Hirumi, Kenji Kobayashi
The effects of supramolecular encapsulation
on the photophysics
and photostability of a highly fluorescent dimeric derivative of 2,6-diacetoxy-9,10-bis(arylethynyl)anthracene
(G2) were investigated by single-molecule fluorescence spectroscopy
(SMFS). The fluorescence properties of free-G2 and its self-assembled
boronic ester encapsulation complex, G2@(Cap)2, were compared
in solution and a glassy polymer film. The fluorescence spectral characteristics
and theoretical calculations suggest that the environment affects
the excited-state conformation and subsequent fluorescence emission
of G2@(Cap)2. In particular, in the liquid and polymer
environments, G2@(Cap)2 emits a fluorescence photon in
the planar and twist conformation, respectively, whereas the fluorescence-emitting
conformation of free-G2 is planar in both environments. The luminous
conformation differences between free-G2 and G2@(Cap)2 in
polymer are reflected in the intersystem crossing (ISC) parameters
(the ISC quantum yield and triplet lifetime), as determined by fluorescence
autocorrelation analysis. The photobleaching yield revealed a 3-fold
enhancement in the photostability of encapsulated G2 (relative to
free-G2). Under the SMFS measurement conditions, the photostability
of the encapsulation complex was independent of the guest’s
photostability and appeared to be dominated by the thermal stability
of the Cap host molecule.