Dinuclear and trinuclear cyano-bridged {DyM} (M = W, Mo) single-ion magnets supported by pentadentate Schiff-base ligands

• Published in: CrystEngComm 2023-11, Vol.25 (43), p.63-638
• Main Authors: Mao, Pan-Dong, Sun, Hui-Ying, Yan, Fei-Fei, Zhang, Shi-Hui, Li, Xin-Feng, Zhou, Ren-He, Zhang, Yi-Quan, Meng, Yin-Shan, Liu, Tao
• Format: Article
• Language: English
• Subjects: Imines; Ligands; Magnetic induction; Magnetic properties; Magnetic relaxation; Magnets; Modular construction; Protonation
• ISSN: 1466-8033; 1466-8033
• DOI: 10.1039/d3ce00720k

The modular construction method provides a feasible way to construct pre-designed cyano-bridged {Ln III M IV/V } systems with more attractive structures and adjustable interactions between 4d/5d and 4f ions. In this work, the pentadentate Schiff-base ligands H 2 L n (H 2 L 1 : 2,6-diacetylpyridine bis(nicotinoylhydrazone); H 2 L 2 : 2,6-diacetylpyridine bis(isonicotinoylhydrazone)) with multiple coordination sites were designed to coordinate with Dy III ions firstly, and then combined with K 4 M(CN) 8 ·2H 2 O (M = W, Mo) by a liquid-liquid diffusion method to successfully synthesize two trinuclear structures {Dy[M IV (CN) 8 ] 0.5 (HL 1 )(H 2 O) 3 } 2 ·8H 2 O ( 1 : M = W; 2 : M = Mo), and two dinuclear structures {[Dy[M IV (CN) 8 ](H 3 L 2 )(H 2 O) 3 ]}·sol ( 3 : M = W, sol = 11.5H 2 O; 4 : M = Mo, sol = 2CH 3 OH·9.5H 2 O). Interestingly, deprotonation occurs in ligand H 2 L 1 during the formation of complexes 1 and 2 , while deprotonation/protonation processes both occur in ligand H 2 L 2 during the synthesis of complexes 3 and 4 . Magnetic analyses reveal that complexes 1-4 are all field-induced single-ion magnets (SIMs). The energy barriers ( U eff / k B ) of complexes 1 and 2 are 92.83 K and 101.08 K, respectively, which are nearly three-fold higher than those of complexes 3 (30.19 K) and 4 (32.77 K). Ab initio calculations were performed on these series of {Ln III M IV } heteronuclear complexes to provide more insights into the magnetic relaxation properties. This work provides another example of improving the SMM behaviors of cyano-bridged {Ln III M IV } systems by deprotonation/protonation at different sites in the ligands. Four cyano-bridged {Dy III M IV } complexes 1-4 , with various structures and magnetic behaviors, were obtained by adjusting the pyridyl N-sites of the pentadentate Schiff-base ligands.