3 research outputs found
Polyimide and Imide Compound Exhibiting Bright Red Fluorescence with Very Large Stokes Shifts via Excited-State Intramolecular Proton Transfer II. Ultrafast Proton Transfer Dynamics in the Excited State
A novel
polyimide (PI) and imide compound emitting prominent reddish-orange
fluorescence under excitation by UV light were prepared based on 3-hydroxypyromellitic
dianhydride (PHDA), and their fluorescence properties were examined.
The steady-state fluorescence spectrum of a PI film displayed an emission
band at 590 nm with a very large Stokes shift (ν = 10 448
cm<sup>–1</sup>) via the excited-state intramolecular proton
transfer (ESIPT), while the time-resolved fluorescence spectrum showed
a rapid decay of the emission band of the enol form at around 400
nm within 15 ps. Transient absorption measurements showed an induced
absorption and stimulated emission of the keto form with a time constant
of ca. 3.0 ps, implying that ESIPT occurs on this time scale. Consequently,
introduction of a hydroxy group into the pyromellitic moiety of PIs
and imide compounds led to the long-wavelength ESIPT emission applicable
to spectral converters having high thermal, mechanical, and environmental
stabilities