T. Stensitzki, Y. Yang, A. Berg, A. Mahammed, Z. Gross, and K. Heyne
STRUCTURAL DYANMICS 3, 043210 (2016); doi: 10.1063/1.4949363
View online: http://dx.doi.org/10.1063/1.4949363
We combined femtosecond (fs) VIS pump–IR probe spectroscopy with fs VIS
pump–supercontinuum probe spectroscopy to characterize the photoreaction of the
hexacoordinated Al(tpfc-Br8)(py)2 in a comprehensive way. Upon fs excitation at 400 nm
in the Soret band, the excitation energy relaxes with a time constant of 250 +- 80 fs to the S2
and S1 electronic excited states. This is evident from the rise
time of the stimulated emission signal in the visible spectral range.On the same time scale,
narrowing of broad infrared signals in the C=C stretching region around 1500 cm-1 is observed.
Energy redistribution processes are visible in the vibrational and electronic dynamics with time
constants between about 2 ps and 20 ps. Triplet formation is detected with a time constant 95 +- 3 ps. This
is tracked by the complete loss of stimulated emission. Electronic transition of the emerging triplet absorption
band overlaps considerably with the singlet excited state absorption. In contrast, two well separated vibrational
marker bands for triplet formation were identified at 1477 cm-1 and at 1508 cm-1. These marker bands allow
a precise identification of triplet dynamics in corrole systems.