4 Considerations for Pump-Probe Photocrystallography
Section 2 highlighted the important role that research on linkage isomer systems has
played in developing modern photocrystallographic experiments. The detailed understanding of the isomerisation kinetics enabled by these measurements, outlined in
Sect. 3, further highlights their potential as model systems for developing TR crystallography experiments. Systems such as the [Pd(Bu 4 dien)(NO 2 )]BPh 4 complex can be
excited rapidly to high conversion levels, and the thermal decay can be adjusted to a
wide range of timescales simply by changing the measurement temperature.
Fig. 14 Steady-state measurements on the [Ni(Et 4 dien)(η
2
-O,ON)(η
1
-NO 2 )] linkage isomer system. The photoisomerisable NO 2 ligand can adopt the nitro (η
1 -NO 2 ) (a) and endo- and exo-nitrito
(η
1
-ONO) (b, c) binding modes. The steady-state occupation of the excited-state endo-nitrito isomer
falls from 100% to zero from ~140 to 180 K, and the transient exo-nitrito isomer is observed in
levels up to ~10% over this temperature window (d). Adapted with permission from Ref. [58]
Watching Photochemistry Happen: Recent Developments in Dynamic Single-Crystal. . .
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