Achieving white light emission and increased magnetic anisotropy by transition metal substitution in functional materials based on dinuclear DyIII(4-pyridone)[MIII(CN)6]3− (M = Co, Rh) molecules

Abstract

A building block approach has led to the construction of two unique bifunctional magneto-luminescent molecular materials, {[Dy^III(4-pyridone)₄(H₂O)₂][M^III(CN)₆]}·nH₂O (M = Co, n = 2, 1; M = Rh, n = 4, 2), incorporating the cyanido-bridged dinuclear {Dy^IIICo^III} (1) or {Dy^IIIRh^III} (2) molecules, that crystallize within the supramolecular network in the attractive non-centrosymmetric Cmc2₁ space group. Both compounds reveal dual physical properties of colour-tunable photoluminescence and slow relaxation of magnetization. While 1 exhibits multi-coloured photoluminescence ranging from yellow to blue, tuned by the excitation wavelength, 2 additionally reveals nearly white light emission under 336 nm excitation at room temperature. 1 and 2 show 4f-metal-centered strong magnetic anisotropy presenting Single-Molecule Magnet (SMM) behaviour with the large anisotropic energy barriers of 187(6) K for 1, and 214(4) K for 2. We have shown and discussed that the replacement of [Co^III(CN)₆]³⁻ by the heavier [Rh^III(CN)₆]³⁻ analogue in {[Dy^III(4-pyridone)₄(H₂O)₂][M^III(CN)₆]}·2H₂O crystalline materials is an efficient route towards white light emissive solid state matrices composed of Single-Molecule Magnets with enhanced magnetic anisotropy. Such extraordinary photoluminescent molecule-based magnets can become good prerequisites for future application in bifunctional optical and magnetic devices.