期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 18, 期 7, 页码 2051-2055出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201103048
关键词
excited state structures; nonequilibrium processes; phase transitions; photocrystallography; spin crossover
资金
- Institut Universitaire de France
- ANR [ANR-09-BLAN-0212]
- Europe (FEDER)
- Region Bretagne [CREATE 4146]
- Rennes Metropole
- Agence Nationale de la Recherche (ANR) [ANR-09-BLAN-0212] Funding Source: Agence Nationale de la Recherche (ANR)
We study by 100 picosecond X-ray diffraction the photo-switching dynamics of single crystal of the orthorhombic polymorph of the spin-crossover complex [(TPA)Fe(TCC)]PF6, in which TPA=tris(2-pyridyl methyl)amine, TCC2-=3,4,5,6-Cl4-Catecholate2-. In the frame of the emerging field of dynamical structural science, this is made possible by using optical pump/X-ray probe techniques, which allow following in real time structural reorganization at intra- and intermolecular levels associated with the change of spin state in the crystal. We use here the time structure of the synchrotron radiation generating 100 picosecond X-ray pulses, coupled to 100 fs laser excitation. This study has revealed a rich variety of structural reorganizations, associated with the different steps of the dynamical process. Three consecutive regimes are evidenced in the time domain: 1) local molecular photo-switching with structural reorganization at constant volume, 2) volume relaxation with inhomogeneous distribution of local temperatures, 3) homogenization of the crystal in the transient state 100 mu s after laser excitation. These findings are fundamentally different from those of conventional diffraction studies of long-lived photoinduced high spin states. The time-resolution used here with picosecond X-ray diffraction probes different physical quantities on their intrinsic time-scale, shedding new light on the successive processes driving macroscopic switching in a functionalized material. These results pave the way for structural studies away from equilibrium and represent a first step toward femtosecond crystallography.
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