Powder XRD data were obtained on small batches of microcrystalline 2-Yb that were suspended in Fomblin ® oil to prevent sample decomposition from oxygen and water. These samples were mounted on a Micromount TM and placed on a goniometer head under a cryostream to cool the sample to 100 K, freezing the Fomblin ® to suspend the crystallites for the duration of the experiment. The PXRD data were measured on a Rigaku FR-X diffractometer, operating in powder diffraction mode using Cu Kα radiation (λ = 1.5418 Å) with a Hypix-6000HE detector and an Oxford Cryosystems nitrogen flow gas system. Data were collected between 3-70 °θ, with a detector distance of 150 mm and a beam divergence of 1.0 mRad. 78 Xray data were collected using CrysAlisPro. For data processing the instrument was calibrated using LaB6 as standard. Then, X-ray data were reduced and integrated using CrysAlisPro. Steady state and time resolved emission spectra were recorded at room temperature from 300-800 Continuous Wave (CW) X-band (ca. 9.4 GHz) spectra were recorded with a Bruker EMX spectrometer fitted with a Super High Q X-band resonator and at Q-band (ca. 33.9 GHz) microwave frequency using a Bruker EMX300 spectrometer. Polycrystalline and frozen solution (9 : 1 toluene : hexane, 10mM) samples of 1-Eu, 3-Eu, and 4-Eu were sealed in quartz X-band and Q-band EPR tubes in vacuo;