Thermal and light induced valence tautomerism in a samarium-pyrazine polymer

Valence tautomerism is a stimulated intramolecular electron transfer which allows for switching between two distinct redox isomers. Such compounds,
incorporating a redox-active ligand and a redox-active metal, allow for the realisation of switchable optical and magnetic materials. The first lanthanide containing
coordination polymer to exhibit this behaviour, SmI2(pyz)3, exhibits an abrupt, hysteretic transition between {Sm(II)-pyz} and {Sm(III)-pyz.-} tautomers. Alloying with other halides allows for tuning of the valence tautomeric "switching" temperature. Herein, we will utilise XANES and XMCD at the L2,3 edges of Sm alongside Sm-149 Mössbauer spectroscopy to probe the Sm valency and electronic configuration of the various tautomers formed after temperature change and light irradiation.

价互变异构（Valence tautomerism）是一种受激分子内电子转移过程，可实现两种不同氧化还原异构体之间的切换。这类包含redox活性配体与redox活性金属的化合物，
为可切换光学及磁性材料的实现提供了可能。首个表现出该行为的含镧系元素（lanthanide）配位聚合物SmI₂(pyz)₃，在{Sm(II)-pyz}与{Sm(III)-pyz·⁻}两种互变异构体之间呈现出急剧的滞后转变。与其他卤化物合金化可调节价互变异构的“切换”温度。本文中，我们将利用Sm的L₂,₃边XANES与XMCD技术，结合Sm-149穆斯堡尔光谱（Mössbauer spectroscopy），探究温度变化及光辐照后形成的各类互变异构体的Sm价态与电子构型。