Placing a crown on DyIII – a dual property LnIII crown ether complex displaying optical properties and SMM behaviour†
Two mononuclear DyIII 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 DyIII 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 4F9/2→6H15/2 band, the Stark splitting of the 6H15/2 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.