End-to-End Azido-Bridged Lanthanide Chain Complexes (Dy, Er, Gd, and Y) with a Pentadentate Schiff-Base [NO] Ligand: Synthesis, Structure, and Magnetism.

The syntheses, structure and magnetic properties are reported for five novel 1D polymeric azido-bridged lanthanide complexes with the general formula {[Ln(DAPMBH)(N)CHOH]CHOH} where HDAPMBH = 2,6-diacetylpyridine bis(4-methoxybenzoylhydrazone)-a new pentadentate pyridine-base [NO] ligand and Ln = Dy (), YDy (), Er (), YEr (), and Gd (). X-ray diffraction analysis of - show that the central lanthanide atoms are eight-coordinated with the NO donor set originating from the ligand DAPMBH, one coordinated ethanol molecule and two end-to-end type N bridges connecting the metal centers into infinite chain. The [LnNO] coordination polyhedron can be regarded as a distorted dodecahedron (). AC magnetic measurements revealed that compounds - show field-induced single-molecule magnet behavior, with estimated energy barriers ≈ 47-17 K. The experimental study of magnetic properties was complemented by theoretical analysis based on crystal-field calculations. Direct current magnetic susceptibility studies revealed marginally weak intrachain exchange interaction between Ln ions mediated by the end-to-end azide bridging groups ( ≈ -0.015 cm for ). Comparative analysis of static and dynamic magnetic properties of magnetically concentrated (, ) and diluted (, ) Dy and Er compounds showed that, despite fascinating 1D azido-bridged chain structure, compounds and are not single-chain magnets; their magnetic behavior is largely due to single-ion magnetic anisotropy of individual Ln ions.