Rhodamine 6G-Labeled Pyridyl Aroylhydrazone Fe(II) Complex Exhibiting Synergetic Spin Crossover and Fluorescence

Here, we use a pyridinecarbaldehyde rhodamine 6G hydrazone ligand (L) to synthesize an Fe­(II) complex 1 for the search of new fluorescent-spin crossover (SCO) materials. Single-crystal structural determinations suggest that the Fe­(II) ion is chelated by two ring-opened ligands (L-o) to form a FeN4O2 coordination environment, and intermolecular π---π contacts of the xanthene groups connect the adjacent molecules to form a supramolecular one-dimensional chain. Magnetic susceptibility measurements on complex 1 show that three-step SCO takes place in the temperature range of 120–350 K, and its desolvated form 1-d exhibits SCO around room temperature (Tc↑ = 343 K and Tc↓ = 303 K) with a wide hysteresis loop of 40 K. Moreover, complex 1-d displays light-induced excited spin-state trapping phenomenon. Intriguingly, the fluorescence intensity of the maximum emission at 560 nm for complex 1-d displays discontinuous variation in the range of 250–400 K, indicative of the occurrence of synergetic fluorescence and SCO.本研究采用吡啶甲醛罗丹明6G腙配体（pyridinecarbaldehyde rhodamine 6G hydrazone ligand，记为L）合成了铁(II)配合物1，以探索新型荧光自旋交叉（SCO）材料。单晶结构解析结果显示，该Fe(II)离子被两个开环配体（L-o）螯合，形成FeN4O2配位环境；氧杂蒽基团的分子间π-π接触作用将相邻分子连接为超分子一维链。对配合物1的磁化率测试表明，其在120~350 K温度区间内发生三步自旋交叉行为；其脱溶剂产物1-d在室温附近展现出自旋交叉特性，升温临界转变温度Tc↑为343 K，降温临界转变温度Tc↓为303 K，伴随40 K的宽磁滞回线。此外，配合物1-d还表现出光诱导激发自旋态俘获现象。值得关注的是，1-d在250~400 K范围内，560 nm处的最大发射峰荧光强度呈现不连续变化，证明其实现了荧光与自旋交叉的协同效应。