Luminescent Er³⁺ based single molecule magnets with fluorinated alkoxide or aryloxide ligands

We report the synthesis, structures, and magnetic and luminescence properties of a series of new mono- and dinuclear Er3+ complexes derived from sterically demanding aryloxide and fluorinated alkoxide ligands: [4-tBu-2,6-(Ph2CH)(2)C6H2O](3)Er(THF) (1), [(C6F5)(3)CO](3)Er(Me3SiOH) (2), [(C6F5)(3)CO](3)Er[(Me3Si)(2)NH] (3), [(C6F5)(3)CO](3)Er(C6H5CH3) (4), [(C6F5)(3)CO](3)Er(o-Me2NC6H4CH3) (5) and {[Ph(CF3)(2)CO](2)Er(mu(2)-OC(CF3)(2)Ph)}(2) (6). In compounds 1, 2, and 4, the Er3+ ion is four-coordinated and adopts a distorted trigonal pyramidal geometry, while in 3, 5, and 6, the coordination geometry of Er3+ is impacted by the presence of several relatively short Er & ctdot;F distances, making them rather 6-coordinated. All compounds behave as field-induced Single Molecule Magnets (SMMs) and exhibit an Er3+ characteristic near infrared (NIR) emission associated with the I-4(13/2) -> I-4(15/2) transition with a remarkably long lifetime going up to 73 mu s, which makes them multifunctional luminescent SMMs. The deconvolution of the NIR emission spectra allowed us to provide a direct probe of the crystal field splitting in these compounds, which was correlated with magnetic data.