A series of triple-stranded lanthanide(III) helicates: Syntheses, structures and single molecular magnets

Bis-beta-diketones have been proven to be effective for the construction of multiple-stranded helicates, where there commonly are two distinct Ln(3+) centers with subtle geometric difference. In this Study, a series of triple-stranded helicates [Ln(2)(BTB)(3)(DME)(2)]center dot C6H14 have been prepared with the ligand H2BTB and trivalent metallic ions, respectively [Ln = La (1), Ce (2), Pr (3), Eu (4), Dy (5), Ho (6) and Yb (7), H2BTB = 4,4'-bis(4,4,4-trifluoro-1,3-dioxobutyl)biphenyl and DME = dimethoxyethane]. All products have been fully characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and single crystal X-ray diffraction analyses. Structural analysis reveals that 1-7 are isostructurally crystallized in the orthorhombic space group of Pna2(1) and each Ln(3+) ion is ligated to six O atoms of three BTB ligands and two 0 atoms of one DME molecule. Interestingly, DME molecule as a chelator to the Ln(3+) centers has played a unique role in the crystallization of the triple-stranded helicate 1-7. Magnetic Measurement shows that 5 displays significant single-molecule magnetic property, exhibiting magnetic slow relaxation. And the large separation between Dy3+ ions in the same helicates leads to two distinct magnetic relaxation processes. (C) 2017 Elsevier Ltd. All rights reserved.