Towards bright dysprosium emitters: Single and combined effects of environmental symmetry, deuteration, and gadolinium dilution

With the aim of creating new light emitting systems, two new dysprosium complexes of formula [DyQcy3(H2O)] (1-Dy) and [H3O][DyQcy4] (2-Dy) (where HQcy = 1-phenyl-3-methyl-4-cyclohexylcarbonyl-pyrazol-5-one) have been synthesized and characterized by spectroscopy. The reaction conditions to address the synthesis toward these tris-(diketonate)dysprosium or tetrakis(diketonate)dysprosium complexes have been optimized. The Qcy ligand provides effective sensitization of the luminescence of Dy3+ ion. 1-Dy and 2-Dy have been investigated by single crystal X-ray diffraction analysis, both species being packed via a system of hydrogen bonds. The dependence of quantum yield and lifetime of the excited state of Dy3+ ions have been examined by implementing two common approaches: replacing protons with deuterium in the coordinated H2O or in cation H3O+ and diluting Dy3+ cations with Gd3+ ions, to suppress vibrational and concentration quenching, respectively. It has been found that deuteration turns out to be very effective on both quantum yield and lifetime, but only in the case of replacement of the inner-sphere water molecules. The strategy of gadolinium dilution leads in all cases to an increase in lifetime. In addition, the possibility of a subtle tuning of the luminescence color has been discovered due to the change in the gadolinium content and deuteration, and a white light luminescent (CIE 0.31, 0.34) composition has been obtained.