Gao Yu-Jing, Luo Ji-Peng, Yin Nan, Shi Quan, Meng Yin-Shan, Liu Tao
State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, No. 2 Linggong Road, Dalian 116024, P. R. China.
Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian Technology Innovation Center for Energy Materials Thermodynamics, Liaoning Province Key Laboratory of Thermochemistry for Energy and Materials, Dalian 116023, P. R. China.
Dalton Trans. 2025 Jul 29;54(30):11542-11550. doi: 10.1039/d5dt01187f.
The investigation of magnetic materials featuring unconventional magnetic topologies represents a forefront research area in the interdisciplinary fields of physics, chemistry, and materials science. Such systems hold considerable promise for applications in strongly correlated electron systems, spintronic devices, magnetic memory technologies, and magnetocaloric applications. Among them, cyano-bridged Prussian blue analogues (PBAs) have emerged as a prominent class of molecular magnetic materials, offering a versatile platform for the systematic modulation of magnetic interactions and topological architectures through the rational selection of paramagnetic metal centers and auxiliary ligands. Herein, we report two heterometallic molecular magnets based on tricyanoferrate bridges, namely, [(PzTp)Fe(CN)][Co(dypu)]·HO (1) and (Tp*)[Fe(CN)][Co(dypu)]·HO (2) (dypu = 1,3-di(pyridin-4-yl)urea), which exhibit field-induced magnetic phase transition. Structural characterization shows that compounds 1 and 2 exhibit one-dimensional double-zigzag chains, further connected into a two-dimensional network by the ditopic dypu ligand. Magnetic analysis reveals ferromagnetic coupling between the cyano-bridged Fe and Co centers in compound 1, whereas antiferromagnetic coupling occurs in 2. Interestingly, variable-temperature and variable-field magnetic susceptibility measurements reveal notable magnetic structure transitions in compound 1: (i) from spin-canted antiferromagnetism (AFM) to nearly collinear AFM at a critical field () of 3.5 kOe, followed by (ii) a transition to a nearly ferromagnetic (FM) alignment at a second critical field () of 18 kOe. Notably, a significant magnetocaloric effect is observed during the phase transition, with the change in entropy (Δ) reaching 23.22 J K kg. This study underscores that the rational modulation of auxiliary ligands enables the tuning of diverse magnetic interactions and structural topologies and advances the understanding of magneto-structural correlations in molecular magnetic systems.
对具有非常规磁拓扑结构的磁性材料的研究是物理、化学和材料科学等跨学科领域的前沿研究领域。这类体系在强关联电子体系、自旋电子器件、磁存储技术和磁热应用方面具有巨大的应用潜力。其中，氰基桥联普鲁士蓝类似物（PBAs）已成为一类重要的分子磁性材料，通过合理选择顺磁性金属中心和辅助配体，为系统调节磁相互作用和拓扑结构提供了一个通用平台。在此，我们报道了两种基于铁氰酸根桥联的异金属分子磁体，即[(PzTp)Fe(CN)][Co(dypu)]·H₂O (1) 和 (Tp*)[Fe(CN)][Co(dypu)]·H₂O (2)（dypu = 1,3 - 二（吡啶 - 4 - 基）脲）），它们表现出场诱导磁相变。结构表征表明，化合物1和2呈现一维双锯齿链状结构，并通过双齿dypu配体进一步连接成二维网络。磁性分析表明，化合物1中氰基桥联的Fe和Co中心之间存在铁磁耦合，而化合物2中则发生反铁磁耦合。有趣的是，变温和变场磁化率测量揭示了化合物1中显著的磁结构转变：（i）在3.5 kOe的临界场（）下从自旋倾斜反铁磁（AFM）转变为近共线AFM，随后（ii）在18 kOe的第二个临界场（）下转变为近铁磁（FM）排列。值得注意的是，在相变过程中观察到显著的磁热效应，熵变（Δ）达到23.22 J K⁻¹ kg⁻¹。这项研究强调，辅助配体的合理调控能够调节多种磁相互作用和结构拓扑，推动了对分子磁体系统中磁结构相关性的理解。
