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Updated: May 14, 2025
Author Spotlight: Experimental Approaches for the Synthesis of Low-Valent Metal-Organic Frameworks from Multitopic Phosphine Linkers
Published on: May 12, 2023
Six-coordinate lanthanide complexes based on bidentate phosphine oxide ligands: synthesis, structure and magnetic
Xiao-Jun Wu1, Hong-Yao Guo2, Wei-Quan Lin2
1Anhui Provincial Key Laboratory of Advanced Catalysis and Energy Materials, Anqing Normal University, Anqing 246133, P. R. China. mengyan@aqnu.edu.cn.
Abstract:
Three six-coordinate mononuclear lanthanide complexes of the formula [Ln{(O = PPh2)2CH2}2Cl2]Cl·THF based on the Kramers ions Dy3+ (1), Er3+ (2) and Yb3+ (3) have been synthesized and structurally characterized. Single-crystal X-ray diffraction reveals that these complexes adopt an octahedral geometry with cis-arranged chloride ligands and four oxygen atoms from two bidentate phosphine oxide ligands. The octahedral coordination sphere generates a crystal field environment conducive to field-induced slow magnetic relaxation for lanthanide ions with both oblate (Dy3+) and prolate (Er3+, Yb3+) electron density distributions. Under optimized direct-current fields, complexes 1Dy and 2Er show Orbach relaxation processes with effective energy barriers of 28.0(5) and 16.2(5) cm-1, respectively. In contrast, complex 3Yb exhibits more complex relaxation dynamics involving a combination of quantum tunnelling, direct, and Raman processes. Ab initio calculations demonstrate that complexes 1Dy and 2Er undergo magnetic relaxation through their first excited Kramers doublets, while the higher-lying first excited state in complex 3Yb (177 cm-1) prevents thermal relaxation via this pathway.
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