Realizing Fluorescence-Valence-Tautomerism Synergy in Mononuclear Cobalt Compounds
Realizing Fluorescence-Valence-Tautomerism Synergy in Mononuclear Cobalt Compounds
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DOI：
10.1021/acs.cgd.2c00402
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
Yu-Qin Li;Jing-Wei Dai;Min Wang;M. Yamashita;Zhaoyang Li
中科院分区：
文献类型：
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作者：
Yu-Qin Li;Jing-Wei Dai;Min Wang;M. Yamashita;Zhaoyang Li
价互变异构体(VT)与其他物理或化学性质相结合，为构建双功能分子基磁性材料提供了一条非常有前途的途径，这类化合物有望有助于构建磁电或磁光器件。虽然已经报道了一些导电的VT络合物，但还没有将过渡金属与荧光团共价结合来提供荧光VT的例子。在本研究中，我们合成了一系列VT化合物，CoIII(3，5-DTCat2-)(3，5-DTSQ·-)(py-ph)2(1)，CoIII(3，5-DTCat2–)(3，5-DTSQ•–)(py-naph)2·CH3OH(2·MeOH)和CoIII(3，5-DTCat2–)(3，5-DTSQ•–)(py-an)2·CH3OH·H2O(3·MeOH·H2O)，并通过单晶X-射线衍射学、磁性测量、变温红外光谱、荧光光谱和漫反射光谱对其进行了系统的表征。1，2·MeOH和3·MeOH·H2O的磁性行为表明，电子从儿茶酸配体转移到Co(III)中心，随着芳香族吡啶配体π共轭的延长，VT转变温度从1增加到3·MeOH·H2O。首次在VT化合物中观察到固态荧光；因此，其他化学或物理性质可能被引入VT系统。此外，在VT转变的温度范围内，观察到3·MeOH·H2O的低色位移和增强的荧光发射。荧光-VT协同作用的机制似乎涉及中心金属和辅助配体之间的能量转移。这种同步性表明，双功能VT可以在单个分子系统中实现。
Valence tautomerism (VT) provides a very promising way of constructing bifunctional molecule-based magnetic materials when combined with other physical or chemical properties, and such complexes are expected to be conducive to the construction of magnetoelectric or magneto-optical devices. Although a few conductive VT complexes have been reported, there are no examples that covalently combine transition metals with fluorophores to provide fluorescent VT. In this study, we synthesized a series of VT compounds, CoIII(3,5-DTCat2–)(3,5-DTSQ•–)(py-ph)2(1), CoIII(3,5-DTCat2–)(3,5-DTSQ•–)(py-naph)2·CH3OH (2·MeOH), and CoIII(3,5-DTCat2–)(3,5-DTSQ•–)(py-an)2·CH3OH·H2O (3·MeOH·H2O), and systematically characterized them by single-crystal X-ray crystallography, magnetic measurements, variable-temperature infrared spectroscopy, fluorescence spectroscopy, and diffuse reflection spectroscopy. The magnetic behavior of1,2·MeOH, and3·MeOH·H2O reveals that electrons are transferred from the catecholate ligand to the Co(III) center; the VT transition temperature increased from1to3·MeOH·H2O when the π-conjugation of aromatic pyridyl ligand is extended. Solid-state fluorescence was observed for the first time in VT compounds; hence, other chemical or physical properties are potentially able to be introduced into VT systems. Moreover, a hypochromic shift and enhanced fluorescence emission were observed for3·MeOH·H2O within the temperature region of the VT transition. The mechanism responsible for fluorescence-VT synergy appears to involve the energy transfer between the central metal and the ancillary ligand. Such synchronization suggests that bifunctional VT can be realized in an individual molecular system.