A newly synthesized photomagnet based on a cyanido-bridged Co–W assembly, [{Co(isoquinoline)₄}₃{W(CN)₈}₂]·2EtOH (CoWisoq), exhibits a controllable photoinduced (PI) phase with a metamagnetic behavior. The PI phase shows a transition from paramagnetic to ferromagnetic with a coercive field of 550 Oe at 2 K. It has a monoclinic (P2₁/n) crystal structure and is comprised of two-dimensional cyanido-bridged Co–W coordination layers with two crystallographically independent Co sites (Co1, Co2) and one W site. Both Co sites adopt a pseudo-octahedral six-coordinated geometry involving four isoquinoline and two cyanide ligands. π–π interactions are induced at half of the isoquinoline ligands in Co1 and all of those in Co2 sites, suggesting that the coordination environment at the Co1 site has structural flexibility. CoWisoq displays a thermal phase transition around 140 K with a small thermal hysteresis due to the charge transfer–induced spin transition between Co^II–W^V of the high temperature (HT) phase and Co^III–W^IV of the low temperature (LT) phase. This charge transfer, which is also responsible for a drastic color change between purple (HT) and yellow (LT), involves only the structurally flexible Co1 sites. The ligand field, which is composed of four isoquinoline and two cyanide ligands, contributes to a unique metal-to-metal charge transfer absorption band of the LT phase at 1025 nm. Irradiation of the LT phase with near–infrared light produces a PI phase with the Co^II–W^V state.

中文翻译：

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基于具有 π-π 相互作用的层状氰基桥联 Co-W 组件的近红外光致超磁体

一种基于氰基桥联 Co-W 组装体的新合成光磁体 [{Co(isoquinoline) ₄ } ₃ {W(CN) ₈ } ₂ ]·2EtOH ( CoWisoq )，表现出具有变磁性的可控光致 (PI) 相行为。 PI 相表现出从顺磁到铁磁的转变，2 K 时矫顽磁场为 550 Oe。它具有单斜晶 ( P 2 ₁ / n ) 晶体结构，由二维氰基桥联 Co-W 配位层组成两个晶体学上独立的 Co 位点（Co1、Co2）和一个 W 位点。两个Co位点均采用伪八面体六配位几何形状，涉及四个异喹啉和两个氰化物配体。 Co1 位点的一半异喹啉配体和 Co2 位点的所有异喹啉配体都诱导了 π-π 相互作用，这表明 Co1 位点的配位环境具有结构灵活性。CoWisoq在 140 K 左右表现出热相变，由于高温 (HT) 相的Co ^II –W ^V和低温 (LT) 相的Co ^III –W ^IV之间的电荷转移引起的自旋转变，具有较小的热滞后阶段。这种电荷转移也导致紫色 (HT) 和黄色 (LT) 之间的剧烈颜色变化，仅涉及结构灵活的 Co1 位点。配体场由四个异喹啉和两个氰化物配体组成，在 1025 nm 处形成了 LT 相独特的金属间电荷转移吸收带。用近红外光照射 LT 相产生具有 Co ^II –W ^V态的 PI 相。