Tuning white light emission using single-component tetrachroic Dy3+ metallacrowns: the role of chromophoric building blocks

Abstract

White light production is of major importance for ambient lighting and technological displays. White light can be obtained by several types of materials and their combinations, but single component emitters remain rare and desirable towards thinner devices that are, therefore, easier to control and that require fewer manufacturing steps. We have designed a series of dysprosium(III)-based luminescent metallacrowns (MCs) to achieve this goal. The synthesized MCs possess three main structural types LnGa₄(L′)₄(L′′)₄ (type A), Ln₂Ga₈(L′)₈(L′′′)₄ (type B) and LnGa₈(L′)₈(OH)₄ (type C) (H₃L′, HL′′ and H₂L′′′ derivatives of salicylhydroxamic, benzoic and isophthalic acids, respectively). The advantage of these MCs is that, within each structural type, the nature of the organic building blocks does not affect the symmetry around Dy³⁺. By detailed studies of the photophysical properties of these Dy³⁺-based MCs, we have demonstrated that CIE coordinates can be tuned from warm to neutral to cold white by (i) defining the symmetry about Dy³⁺, and (ii) choosing appropriate chromophoric building blocks. These organic building blocks, without altering the coordination geometry around Dy³⁺, influence the total emission profile through changing the probability of different energy transfer processes including the ³T₁ ← Dy³⁺* energy back transfer and/or by generating ligand-centered fluorescence in the blue range. This work opens new perspectives for the creation of white light emitting devices using single component tetrachroic molecular compounds.