Luminescent, magnetic and ferroelectric properties of noncentrosymmetric chain-like complexes composed of nine-coordinate lanthanide ions

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 42; no. 43; pp. 15317 - 15325
• Main Authors: Li, Xi-Li, Chen, Chun-Lai, Xiao, Hong-Ping, Wang, Ai-Ling, Liu, Cai-Ming, Zheng, Xianjun, Gao, Li-Jun, Yang, Xiao-Gang, Fang, Shao-Ming
• Format: Journal Article
• Language: English
• Published: England 21.11.2013
• Subjects: Chains; Diffraction; Emission analysis; Ferroelectric materials; Ferroelectricity; Lanthanides; Magnetic properties; Methyl alcohol
• ISSN: 1477-9226; 1477-9234; 1477-9234
• DOI: 10.1039/c3dt51743h

Reaction of the chiral ligand (-)-4,5-pinenepyridyl-2-pyrazine (L) with Ln(hfac)3·2H2O precursors [hfac(-) = 1,1,1,5,5,5-hexafluoroacetylacetonate, Ln = Sm(3+) (1), Eu(3+) (2), Tb(3+) (3) and Dy(3+) (4)] in methanol solution led to the formation of four noncentrosymmetric lanthanide complexes with the general formula [Ln(hfac)3L]n·H2O. The single-crystal X-ray diffraction analyses revealed that they are isostructural and take a one-dimensional (1D) chain structure based on the Ln(hfac)3L repeating units, in which the nine-coordinate Ln(3+) ions reside in a tricapped trigonal prism (TTP) environment never reported in previous 1D chain lanthanide complexes. The investigations of their photophysical properties showed that complexes 1, and 3 exhibit characteristic emissions of Sm(3+), Eu(3+) and Tb(3+) ions with respective luminescent lifetime values of 0.065, 1.066 and 0.129 ms, while complex 4 does not display any emission. The different luminescent intensities and lifetimes among them were further discussed in detail. Moreover, the magnetic properties of complexes 1-4 were assessed with a special emphasis on the Dy(3+) complex 4. Alternating-current (ac) magnetic susceptibility measurements indicated that field-induced two-step slow magnetic relaxation processes were observed in 4, indicating the single-molecule magnet (SMM) behavior of 4. In addition, the noncentrosymmetric complexes 1-4 crystallizing in the same polar point group (Cs) exhibit both ferroelectric and nonlinear optical properties at room temperature. All these features make them multifunctional crystalline molecule materials.