Li-Zheng Cai,Wei Zhang,Zhao-Xia Zhu,Jing Ru,Min-Xia Yao
Three FeIII2LnIII2 tetranuclear heterometallic clusters, [H4LGd(H2O)Tp*Fe(CN)3]2·8H2O·2MeOH (1) and [H4LLn(MeOH)Tp*Fe(CN)3]2·6MeOH·2MeCN (Ln = Tb and Dy for 2 and 3, respectively, H6L = N,N′-(2,6-pyridine-dicarboxyl)-disalicylhydrazide, Tp* = hydridotris(3,5dimethylpyrazol-1-yl)-borate), were synthesized by use of the [(Tp*)Fe(CN)3]− unit as a metalloligand toward LnCl3 and H6L species. Structural analyses reveal that FeIII and LnIII ions in all complexes are connected to each other by one cyanide to form a heterobinuclear unit of [Ln(H4L)][(Tp*)Fe(CN)3], which is dimerized through Ln–N–C = O–Ln interaction. Magnetic susceptibility measurements show weak antiferromagnetic interactions between cyano-bridged FeIII and GdIII ions and amide-bridged GdIII ions are operative. Complex 1 displays the magnetocaloric effect with −ΔSmmax = 12.70 J·kg−1·K−1 at 4.0 K for ΔH = 7 T. No single-molecule magnetic properties are observed for 2 or 3 down to 1.8 K.
To address the inherent contradiction between adsorption/desorption energy barriers of intermediates in single-metal urea oxidation reaction (UOR) catalysts, this study developed a cyanide-bridged bimetallic catalyst , Ni 2 Fe(CN) 6 , via liquid-phase synthesis and plasma modification. Plasma modification enhances the structural stability of the three-dimensional framework and optimizes its electronic properties through selective metal ion substitution and framework reconstruction. In situ electrochemical Raman spectroscopy confirms that the cyanide bridge serves as an electron transport bridge, effectively linking Ni and Fe active centers and providing a stable electron transfer pathway for the Ni³ ⁺/Ni²⁺ redox cycle, leading to a 2.05-fold increase in cycling efficiency compared to untreated catalysts. Benefiting from the synergistic effect of the bimetallic centers, Ni 2 Fe(CN) 6 exhibits superior UOR electrocatalytic performance, achieving an overpotential of only 0.425 V（vs. Hg/HgO） at 10 mA cm −2 . Furthermore, theoretical calculations indicate that the protonation state of amino groups significantly influences the rate-determining step by modulating the reaction pathway. The presence of functionally distinct and diversified active sites enables a multi-pathway synergistic catalytic mechanism, effectively promoting key reaction steps, including amino proton transfer , C-N bond cleavage, and N-N coupling.
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