Photophysics of heteroleptic iridium(III) complexes of current interest; a closer look on relaxation dynamics.
The excited-state dynamics of heteroleptic iridium(III) complexes have been investigated using femto-nanosecond time-resolved luminescence and transient absorption spectroscopy. Two prototypical examples illustrated here are iridium(III) bis[2-(2,4-difluorophenyl)pyridinato-N,C(2')] quinaldinate (1) and iridium(III) bis[2-(2,4-difluorophenyl)pyridinato-N,C(2')][2-(6-methylbenzoxazol-2-yl)phenolate] (2). Upon photoexcitation at, for example, 400 nm, the emission decay, monitored at the region of phosphorescence, for both 1 and 2 consists of a system response limited rise (<300 ps) and a single exponential decay. Further single wavelength as well as full spectrum of femto-picosecond transient absorption acquired in CH(2)Cl(2) at room temperature reveals an ultrafast S(1) --> T(n) intersystem crossing (<1 ps) and a rapid T(n) --> T(1) internal conversion/vibrational relaxation within a time period of <10 ps. The results lead us to conclude that following Franck-Condon excitation, the time scale required to populate the lowest triplet state should be <10 ps.
Duan
Hsin-Sheng
HS
Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan, ROC.
Chou
Pi-Tai
PT
Hsu
Cheng-Chih
CC
Hung
Jui-Yi
JY
Chi
Yun
Y