Papanikolaou Dionisis, Margadonna Serena, Kosaka Wataru, Ohkoshi Shin-ichi, Brunelli Michela, Prassides Kosmas
Department of Chemistry, University of Durham, Durham DH1 3LE, UK.
J Am Chem Soc. 2006 Jun 28;128(25):8358-63. doi: 10.1021/ja061650r.
The effect of X-ray illumination on the structural properties of the mixed valence Prussian blue analogue CsFe(II)[Cr(III)(CN)6] has been studied by time-dependent high-resolution synchrotron X-ray diffraction. Abrupt isosymmetric phase transitions, accompanied by dramatic volume collapse, were found in the temperature range 245-265 K, induced by sudden Fe(II) spin transitions from the high spin (HS) (4t(2g)2e(g), S = 2) to the low spin (LS) (6t(2g)0e(g), S = 0) configuration. Absorption of X-ray photons generates photoexcited Fe(II)(LS) domains whose size rapidly grows with time until the percolation threshold is reached and the structure collapse is triggered. The persistent character of the optically excited spin crossover states derives from the strong electron-phonon coupling, associated with the large lattice relaxations, which accompany the internal spin rearrangements. It is thus possible to use X-ray light in a controllable and efficient way to induce photoswitching between the ground and hidden or inaccessible excited states in suitably selected multistable materials in the bulk.
通过时间分辨高分辨率同步辐射X射线衍射研究了X射线照射对混合价态普鲁士蓝类似物CsFe(II)[Cr(III)(CN)6]结构性质的影响。在245 - 265 K温度范围内发现了突然的等对称相变，并伴有显著的体积收缩，这是由Fe(II)从高自旋(HS)(4t(2g)2e(g), S = 2)到低自旋(LS)(6t(2g)0e(g), S = 0)构型的突然自旋转变引起的。X射线光子的吸收产生了光激发的Fe(II)(LS)畴，其尺寸随时间迅速增长，直到达到渗流阈值并引发结构崩塌。光激发自旋交叉态的持久特性源于与大晶格弛豫相关的强电子 - 声子耦合，这种耦合伴随着内部自旋重排。因此，有可能以可控且有效的方式使用X射线光，在块状的适当选择的多稳态材料中诱导基态与隐藏或难以接近的激发态之间的光开关。
