MX chains have been widely studied as a 1D mixed-valence system. Although there have been a large number of studies on the boundary between class II and III materials of the Robin–Day classification, there are few studies of compounds at the boundary between classes I and II. In this study, we synthesized a series of Pt- and Pd- MX-chain compounds with perrhenate counterions, [M(en)₂][M(en)₂X₂](ReO₄)₄ (X = Br for M = Pd and X = Cl, Br, and I for M = Pt). All compounds were isostructural, and the metal–metal distances within the chain exceed 6 Å, which is the longest among MX-chain compounds thus far reported. For [Pt(en)₂][Pt(en)₂Cl₂](ReO₄)₄ (PtCl), an intervalence charge transfer (IVCT) transition was observed in the UV region at 335 nm (3.7 eV), which is the shortest wavelength for the MX-chain compounds thus far reported, indicating that PtCl is the closest to the Robin–Day class I limit.

中文翻译：

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具有ReO ₄抗衡离子的MX链化合物：Robin-Day I-II类边界的探索

MX链已被广泛研究为一维混合价系统。尽管对Robin-Day分类的II类和III类材料之间的边界进行了大量研究，但在I类和II类之间的边界上对化合物的研究却很少。在这项研究中，我们合成了一系列具有高r酸抗衡离子[M（en）₂ ] [M（en）₂ X ₂ ]（ReO ₄）₄的Pt和Pd- MX链化合物（对于M = Pd和X = Cl，Br和I，M = Pt）。所有化合物都是同构的，链中的金属-金属距离超过6Å，这是迄今为止报道的MX链化合物中最长的。对于[Pt（en）₂ ] [Pt（en）₂ Cl ₂]（ReO ₄）₄（PtCl），在335 nm（3.7 eV）的UV区观察到间隔电荷转移（IVCT）跃迁，这是迄今为止报道的MX链化合物的最短波长，表明PtCl是我所限制的Robin-Day课程中最接近的课程。