Placing a crown on DyIII – a dual property LnIII crown ether complex displaying optical properties and SMM behaviour.

Two mononuclear Dy^III crown ether complexes [Dy(15C5)(H₂O)₄](ClO₄)₃·(15C5)·H₂O (1) and [Dy(12C4)(H₂O)₅](ClO₄)₃·H₂O (2) have been prepared and characterized. X-ray diffraction studies show that both compounds crystallize as half sandwich type structures with muffin and pseudo-capped square antiprismatic geometries respectively. Despite the comparable local environments of the Dy^III ions they display remarkably different dynamic magnetic properties with only 1 displaying SMM properties in zero field. The solid state emission spectra for both 1 and 2 display sharp bands associated with f–f transitions. From the fine structure of the ⁴F_9/2→⁶H_15/2 band, the Stark splitting of the ⁶H_15/2 ground state permitted the energy difference between the ground and first excited state to be determined. For 1 this value (ΔE = 58.0 ± 3.0 cm⁻¹) is in excellent agreement with ab initio calculations and the experimentally observed SMM behaviour. For 2, the photoluminescence data and theoretical calculations support a less well isolated ground state (ΔE = 30 ± 3.0 cm⁻¹) in which a rapid relaxation process affords no SMM behaviour in zero-field. [ABSTRACT FROM AUTHOR]