Boosting the mono-axial crystal field in stable high-coordinate Dy() single-ion magnets by substitution of the phenoxy axial ligand

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 52; no. 3; pp. 1465 - 1471
• Main Authors: Zhang, Ben, Zhou, Yang, Dong, Chang, Xiang, Yi, Shi, Yanbo, Zhang, Chennan, Yuan, Aihua, Zheng, Shaojun, Li, Zhao-Yang, Zhang, Yi-Quan, Yang, Yong, Chen, Lei
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.08.2023
• Subjects: Bonding strength; Chemical synthesis; Hysteresis; Ligands; Magnets; Quantum tunnelling; Substitutes
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/d3dt01318a

Synthesis of air-stable and high-performance single-molecule magnets (SMMs) is challenging. Here, a heptadentate pentapyridyldiamine (BPA-TPA) ligand and fine-tuned axial phenoxy ligands are used to synthesize two triangular dodecahedral Dy( iii ) complexes [Dy(BPA-TPA)(4-methoxy-PhO)](BPh 4 ) 2 ·3CH 2 Cl 2 ( 4 ) and [Dy(BPA-TPA)(2,4-dimethyl-PhO)](BPh 4 ) 2 ·0.85CH 2 Cl 2 ( 5 ). Both complexes have high effective barriers exceeding 400 K and magnetic hysteresis up to 8 K, which is ascribed to one strong and short Dy-O bond combined with seven weak Dy-N bonds. Ab initio calculations reveal the thermally activated quantum tunneling of magnetization through the first excited Kramers doublet, due to the presence of a strong axial Dy-O crystal ligand. Substitution of the phenoxy ligand leads to more constrained vibrations, improving the magnetic hysteresis behavior for 5 . Two air-stable eight-coordinate mononuclear Dy( iii ) SMMs with a triangular dodecahedron exhibit high energy barriers of 444 K and 478 K and magnetic hysteresis temperatures of up to 8 K, which is attributed to one strong and short Dy-O bond.