On the Nature of the Multiple Ground States of the MMX Mixed-Valence Chain Compound, [PtII/III2(n-PenCS2)4I]∞
On the Nature of the Multiple Ground States of the MMX Mixed-Valence Chain Compound, [PtII/III2(n-PenCS2)4I]∞
复制标题
关于MMX混合价链化合物的多重基态性质，[PtII/III2(n-PenCS2)4I]∞
DOI：
10.1021/ic102461z
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
M.Kurmoo
中科院分区：
文献类型：
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作者：
M.Mitsumi;T.Yamashita;Y.Aiga;K.Toriumi;H.Kitagawa;T.Mitani;M.Kurmoo
我们提出了一个全面的研究，使用单晶X射线衍射和漫散射的晶体结构的温度依赖性，以及在室温下的电输运和磁性能以及一些光学性质，以阐明的起源和形式的多个基态的MMX链化合物，[PtII/III 2（n-PenCS 2）4 I]∞的热容量在以前的研究中证明。本研究结果证实了存在两个相变，一个可逆的一阶在207 K和其他不可逆的monotropic在324 K，分离的低温（LT），室温（RT），和高温（HT）相。由于属于中心双铂单元的二硫代羧基和戊基所表现出的结构紊乱，晶胞在RT和HT相中显示出3倍周期性的−Pt−Pt−I−。此外，对于HT-相，所有的二聚体显示这种无序。该化合物在TM −S= 235 K时发生金属-半导体转变。HT相和RT相中存在对应于2倍− Pt-Pt −I−周期性的弥散条纹，表明了-Pt 2 +-Pt 2 +-I−-Pt 3 +-Pt 3 +-I−-或-Pt 2 +− Pt 3 +-I−-Pt 3 +− Pt 2 +-I−-的动态价序。对于LT相，漫散射被压缩成清晰的布拉格衍射峰，同时保持3倍周期性。这一事实表明，通过电荷和自旋的二聚化进一步定位，证实了磁化率中的抗磁性状态和低于207 K的低电导率。本文的结果与前人对同系物[PtII/III 2（RCS 2）4 I]∞（R =甲基、乙基、正丙基和正丁基）的研究结果作了进一步的讨论。
We present a comprehensive study of the temperature dependence of the crystal structure using single-crystal X-ray diffraction and diffuse scattering, and electrical transport and magnetic properties as well as some optical properties at room temperature to elucidate the origin and the form of multiple ground states demonstrated in a previous study of the heat-capacity of the MMX chain compound, [PtII/III2(n-PenCS2)4I]∞. The present results confirm the presence of the two phase transitions, one reversible of first order at 207 K and the other nonreversible monotropic at 324 K, separating the low temperature (LT), room temperature (RT), and high temperature (HT) phases. The unit cell displays a 3-fold periodicity of −Pt−Pt−I− in the RT and HT phases because of the structural disorder which is exhibited by the dithiocarboxylato groups and then-pentyl groups belonging to the central diplatinum unit. In addition, for the HT-phase all the dimers show this disorder. This compound undergoes a metal−semiconductor transition atTM−S= 235 K. The presence of diffuse streaks corresponding to 2-fold −Pt−Pt−I− periodicity in the HT and RT phases indicates dynamic valence ordering of the type —Pt2+—Pt2+—I−-Pt3+-Pt3+-I−—or—Pt2+−Pt3+-I−-Pt3+−Pt2+—I−—. For the LT-phase the diffuse scattering is condensed into clear Bragg diffraction peaks while keeping the 3-fold periodicity. This fact suggests further localization through dimerization of charges and spins confirming the diamagnetic state in the magnetic susceptibility and the low electrical conduction below 207 K. The present results are further discussed in relation to those of previous studies on the homologues, [PtII/III2(RCS2)4I]∞, R = methyl, ethyl,n-propyl, andn-butyl.