TY  - JOUR
AU  - Hallmann, J.
AU  - Morgenroth, W.
AU  - Paulmann, C.
AU  - Davaasambuu, J.
AU  - Kong, Q.
AU  - Wulff, M.
AU  - Techert, S.
AU  - DESY
TI  - Time-resolved x-ray diffraction of the photochromic alpha-styrylpyrylium Trifluoromethanesulfonate crystal films reveals ultrafast structural switching
JO  - Journal of the American Chemical Society
VL  - 131
SN  - 0002-7863
CY  - Washington, DC
PB  - American Chemical Society
M1  - PHPPUBDB-17382
SP  - 15018-15025
PY  - 2009
N1  - © American Chemical Society
AB  - The ultrafast structural dynamics of the [2+2] photocycloaddition of alpha-styrylpyrylium trifluoromethanesulfonate (TFMS) has been studied in great detail. During the photoreaction, optical and infrared spectroscopy confirms that crystals of alpha-styrylpyrylium change color. Since the reaction is reversible, it has been suggested to be used as an organic holographic storage device. The present photocrystallographic studies (with high spatial resolution) allow for an electron density analysis of the overall reaction kinetics, revealing the mechanism of bond-breaking and bond-formation. It could furthermore be proved how the reaction is influenced by the rearrangement of the surrounding moieties. Picosecond time-resolved X-ray diffraction studies allow for the monitoring the photoreaction in crystalline thin films under experimental conditions where the transformation times are greatly enhanced. These investigations are discussed in the context of the photocrystallographic results. It has been found that alpha-styrylpyrylium TFMS undergoes an ultrafast photoreaction to the dimer product state and back-reaction to the monomer reactant state which is temperature driven. The present experiments indicate that TFMS reacts on time scales which are the fundamental limiting ones of two-quantum systems and therefore has the potential to be used as an ultrafast organic molecular switcher.
KW  - Alkanesulfonates: chemistry
KW  - Crystallography, X-Ray
KW  - Dimerization
KW  - Electrons
KW  - Photochemical Processes
KW  - Pyrans: chemistry
KW  - Spectrophotometry, Infrared
KW  - Styrenes: chemistry
KW  - Temperature
KW  - Time Factors
KW  - Alkanesulfonates (NLM Chemicals)
KW  - Pyrans (NLM Chemicals)
KW  - Styrenes (NLM Chemicals)
KW  - alpha-styrylpyrylium (NLM Chemicals)
LB  - PUB:(DE-HGF)16
C6  - pmid:19824735
UR  - <Go to ISI:>//WOS:000271271800077
DO  - DOI:10.1021/ja905484u
UR  - https://bib-pubdb1.desy.de/record/89182
ER  -