The initial photocrystallographic studies were carried out on molecular complexes that either underwent irreversible photoactivated processes where the conversion took hours or days. Structural snapshots were taken during the process.
Materials that achieved a metastable state under photoactivation and the excited
(metastable) state had a long enough lifetime for the data from the crystal to be
collected and the structure solved. For systems with shorter lifetimes, the first timeresolved results were obtained for macromolecular structures, where pulsed lasers
were used to pump up the short lifetime excited state species and their structures
were probed by using synchronised X-ray pulses from a high-intensity source.
Developments in molecular crystallography soon followed, initially with monochromatic X-ray radiation, and pump-probe techniques were used to establish the
structures of photoactivated molecules with lifetimes in the micro- to millisecond
range. For molecules with even shorter lifetimes in the sub-microsecond range, Laue
diffraction methods (rather than using monochromatic radiation) were employed to
speed up the data collections and reduce crystal damage. Future developments in
time-resolved crystallography are likely to involve the use of XFELs to complete
“single-shot” time-resolved diffraction studies that are already proving successful in
the macromolecular crystallographic field.
Keywords Excited state lifetimes · Lasers · Macromolecules · Metastable states ·
Photochemistry · Photocrystallography · Solid-state · Synchrotron radiation · Timeresolved crystallography · XFELs · X-rays
Abbreviations
CCD
Charge coupled device
DFT
Density functional theory
ES
Excited state
ESRF
European Synchrotron Radiation Facility
EXAFS Extended X-ray absorption fine structure
FWHM
Full width at half maximum
GS
Ground state
HATRX Hadamard time-resolved crystallographic experiment
LIESST Light-induced excited spin-state trapping experiment
PES
Photoelectron spectrum
RATIO
Method for collecting sequential laser-on and laser-off X-ray data
XAFS
X-ray absorption fine structure
XFEL
X-ray free-electron laser
240
P. R. Raithby
Materials that achieved a metastable state under photoactivation and the excited
(metastable) state had a long enough lifetime for the data from the crystal to be
collected and the structure solved. For systems with shorter lifetimes, the first timeresolved results were obtained for macromolecular structures, where pulsed lasers
were used to pump up the short lifetime excited state species and their structures
were probed by using synchronised X-ray pulses from a high-intensity source.
Developments in molecular crystallography soon followed, initially with monochromatic X-ray radiation, and pump-probe techniques were used to establish the
structures of photoactivated molecules with lifetimes in the micro- to millisecond
range. For molecules with even shorter lifetimes in the sub-microsecond range, Laue
diffraction methods (rather than using monochromatic radiation) were employed to
speed up the data collections and reduce crystal damage. Future developments in
time-resolved crystallography are likely to involve the use of XFELs to complete
“single-shot” time-resolved diffraction studies that are already proving successful in
the macromolecular crystallographic field.
Keywords Excited state lifetimes · Lasers · Macromolecules · Metastable states ·
Photochemistry · Photocrystallography · Solid-state · Synchrotron radiation · Timeresolved crystallography · XFELs · X-rays
Abbreviations
CCD
Charge coupled device
DFT
Density functional theory
ES
Excited state
ESRF
European Synchrotron Radiation Facility
EXAFS Extended X-ray absorption fine structure
FWHM
Full width at half maximum
GS
Ground state
HATRX Hadamard time-resolved crystallographic experiment
LIESST Light-induced excited spin-state trapping experiment
PES
Photoelectron spectrum
RATIO
Method for collecting sequential laser-on and laser-off X-ray data
XAFS
X-ray absorption fine structure
XFEL
X-ray free-electron laser
240
P. R. Raithby