Observation of slow magnetic relaxation in triple-stranded lanthanide helicatesElectronic supplementary information (ESI) available: Further structural and magnetic data for complexes 1and 2. CCDC reference numbers 772951and 772952. For ESI and crystallographic data in CIF or other electronic format, see DOI: 10.1039/c1dt10729a

Two dinuclear triple-stranded helicates [Ln2L3]3+(Ln = Dy and Tb) obtained viaself-assembly from the ligand HL (2,6-diformyl-4-methylphenol di(benzoylhydrazone)) and lanthanide perchlorate have been synthesized and characterized. The crystal structural analysis demonstrates that three ligand strands wrap around a pseudo-threefold axis defined by the two metal ions, leading to a ‘meso’-relation between the right- (Δ) and left-hand (Λ) configurations of [Ln2L3]3+in the crystal. Each LnIIIion is coordinated by nine donor atoms in a distorted tricapped trigonal-prismatic arrangement. Alternating current (ac) susceptibility measurements of [Dy2L3]3+reveal a frequency-dependent out-of-phase signal under a 700 Oe dc field, indicating the onset of the slow relaxation of magnetization with a roughly estimated activation energy of ∼5 K and τ0of 10−7s. [ABSTRACT FROM AUTHOR]