Slow magnetic relaxation of Ln(III)-nitronyl nitroxide radical complexes with shortest non-covalent O⋯O contacts

• Published in: Journal of molecular structure 2019-12, Vol.1197, p.666-671
• Main Authors: Yin, Xiao-Ying, Shi, Dan-Hua, Wang, Huan, Wang, Shu-Ping, Zhang, Jian-Jun, Geng, Li-Na, Shi, Shi-Kao, Liu, Zhong-Yi
• Format: Article
• Language: English
• Subjects: Complex; Magnetic relaxation; Nitronyl nitroxide radical; Non-covalent contact; Pseudo-one-dimensional chain
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2019.07.092

Two new complexes, Ln(hfac)3(NITPhOA)2 (Ln = Tb(1), Dy(2); NITPhOA = 2-(4′-amyloxyphenyl)−4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate) have been synthesized and characterized. Single crystal X-ray diffraction analysis reveals that both complexes show mononuclear tri-spin structures. The central Ln(III) ion is eight-coordinated by three hfac anions and two NITPhOA molecules, in which the NITPhOA radical acts as monodentate ligand through the NO groups, and the Ln(III) center exhibits a dodecahedron environment. It's interesting that the mononuclear units form a pseudo-one-dimensional chain structure through intermolecular non-covalent N–O⋯O–N contacts of nitroxide groups for 1. Alternating current (ac) magnetic susceptibilities show a frequency-dependent characteristic for both 1 and 2, typical of slow relaxation of magnetization. It's the first time for a lanthanide–radical complex to form a pseudo one-dimensional structure through non-covalent O⋯O contacts. Two nitroxide radical-Ln(III) complexes have been studied. Both complexes exhibit slow relaxation of magnetization. Interestingly, the Tb(III) mononuclear units form a pseudo-1D structure through non-covalent O⋯O contacts. [Display omitted] •Two novel mononuclear tri-spin Ln(III)-radical complexes have been synthesized.•Complex Tb(1) forms a pseudo-1D chain through non-covalent N-O…O-N contacts.•Both complexes exhibit slow magnetic relaxation.