Structure and Electronic Configuration of an Iron(II) Complex in a LIESST State : A Pump and Probe Method
Structure and Electronic Configuration of an Iron(II) Complex in a LIESST State : A Pump and Probe Method
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LIESST 态铁(II)配合物的结构和电子构型：泵浦和探针方法
DOI：
10.1002/chem.200802279
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Y.
中科院分区：
文献类型：
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作者：
Sheu;C.-F.; Chen;K.; Chen;S.-M.; Wen;Y.-S.; Lee;G.-H.; Chen;J.-M.; Lee;J.-F.; Cheng;B.-M.; Sheu;H.-S.; Yasuda;N.; Ozawa;Y.; Toriumi;K.; Wang;Y.
可转换分子：通过K边和L边X射线吸收和磁性测量证实了反式[Fe（tzpy）2（NCS）2]中Fe中心在低自旋、高自旋和LIESST态（LIESST=光致激发自旋态俘获）下的电子构型。在40 K下，辐照前后的分子结构叠加在图中，表明辐照导致了单晶到单晶的转变。分离并表征了单核六配位铁（II）自旋交叉配合物trans-[Fe（tzpy）2（NCS）2]（tzpy=3-（2-pyridyl）[1，2，3] triazole [1，5-a]pyridine）（1）的两种多晶型。 根据热相关磁性测量，多晶型A经历从高于200 K的顺磁性高自旋状态（5 T2，S=2，HS-1）到低于120 K的抗磁性低自旋状态（1A 1，S=0，LS-1）的逐渐自旋转变，而多晶型B显示出在102 K具有T1/2的突然自旋转变。 分别在300和40 K下研究了HS-1和LS-1态的多晶型A的分子和晶体结构。正如预期的那样，在两种自旋状态之间发现Fe的N-Fe距离和配位几何结构的显着差异。在40 K下用532 nm激光照射晶体时观察到光诱导激发自旋态捕获（LIESST），由此形成亚稳态高自旋态（HS-2）;由于其相对快速的弛豫，通过泵浦和探测方法研究了该亚稳态的分子和晶体结构。 Fe中心在HS-1、LS-1和LIESST（HS-2）态的电子构型通过Fe K-和L-边吸收光谱进一步确认。此外，配体上的C N伸缩频率也可以通过自旋跃迁来跟踪。在15-55 K和5-80 K温度范围内，分别测量了亚稳态的激发和弛豫过程中的C → N伸缩频率和磁化率. 通过X射线衍射、X射线吸收、红外吸收和磁性测量确定了多晶型A的LIEST态的结构和电子构型。通过辐照证实了单晶到单晶的转变。自旋跃迁导致的结构和电子组态的变化被认为是同时发生的。
Switchable molecules: The electronic configurations of the Fe center intrans‐[Fe(tzpy)2(NCS)2] in low‐spin, high‐spin, and LIESST states (LIESST=light‐induced excited spin‐state trapping) were confirmed by K‐ and L‐edge X‐ray absorption and magnetic measurements. The molecular structures at 40 K before and after irradiation are superimposed in the picture, which demonstrates a single‐crystal‐to‐single‐crystal transition by irradiation.Two polymorphs of mononuclear six‐coordinate iron(II) spin‐crossover complextrans‐[Fe(tzpy)2(NCS)2] (tzpy=3‐(2‐pyridyl)[1,2,3]triazolo[1,5‐a]pyridine) (1) were isolated and structurally characterized. According to the thermally dependent magnetic measurements, polymorphAundergoes a gradual spin transition from a paramagnetic high‐spin state (5T2,S=2, HS‐1) above 200 K to a diamagnetic low‐spin state (1A1,S=0, LS‐1) below 120 K, whereas polymorphBshows an abrupt spin transition withT1/2at 102 K. Molecular and crystal structures of polymorphAin the HS‐1 and LS‐1 states were studied at 300 and 40 K, respectively. Significant differences in FeN distances and coordination geometries of Fe were found between the two spin states, as expected. Light‐induced excited spin state trapping (LIESST) was observed upon irradiating the crystal with 532 nm laser light at 40 K, whereupon a metastable high‐spin state (HS‐2) was formed; the molecular and crystal structure of this metastable state were investigated by a pump and probe method because of its relatively fast relaxation. The electronic configuration of the Fe center in the HS‐1, LS‐1, and LIESST (HS‐2) states were further confirmed by Fe K‐ and L‐edge absorption spectroscopy. In addition, the CN stretching frequency on the ligand can also be followed through the spin transition. The excitation and relaxation process concerning such metastable state were followed by the CN stretching frequency and magnetic susceptibility measurements in the temperature ranges 15–55 K and 5–80 K, respectively. The structure and electronic configuration of the LIESST state of polymorphAwere firmly established by X‐ray diffraction, X‐ray absorption, infrared absorption, and magnetic measurements. A single‐crystal‐to‐single‐crystal transition through irradiation was demonstrated. The changes in structure and electronic configuration as a result of the spin transition are believed to occur concurrently.